Have a 5 year old WB combi that is regularly serviced and works fine (I
believe).

In the last two days we experienced two problems:

1. The hot water cutting off during a shower. Turning the water off,
waiting for a few seconds and turning it back on resumes hot water
(until the next time...).

2. Heating that cuts off at random times, and does not seem to respons
to demand signal from the programmable room thermostat.

We are using one of these:
https://www.wolseley.co.uk/product/c...om-thermostat/
which I believe is a rebadged Honeywell basic(ish) version. I fitted it
2 years ago to replaced a failed Honeywell 927.

Earlier today I tried to create artifical demand for the heating/boiler
by setting the target temp to 30c, but the relay failed to turn itself
on (led stayed off). Pressing the manual/override button on the relay
box turned the led on and the boiler started.

A few hours later the heating was once again not working as expected, so
I repeated the above. This time the relay failed to start - the override
button does not seem to do anything.

The display on the controller is bright and clear, and there is no
indication that the batteries are low (there is usually a message).

- My gut feeling is that the relay box is dead. Any thoughts?
- Why would the hot water keep on cutting off then? because the boiler
receives random requests for heating from the faulty relay during a shower?
- Any other suggestions as to the cause?

Many thanks in advance.

On 29/12/2018 21:37, JoeJoe wrote:
Have a 5 year old WB combi that is regularly serviced and works fine (I
believe).

In the last two days we experienced two problems:

1. The hot water cutting off during a shower. Turning the water off,
waiting for a few seconds and turning it back on resumes hot water
(until the next time...).

2. Heating that cuts off at random times, and does not seem to respons
to demand signal from the programmable room thermostat.

We are using one of these:
https://www.wolseley.co.uk/product/c...om-thermostat/

which I believe is a rebadged Honeywell basic(ish) version. I fitted it
2 years ago to replaced a failed Honeywell 927.

Earlier today I tried to create artifical demand for the heating/boiler
by setting the target temp to 30c, but the relay failed to turn itself
on (led stayed off). Pressing the manual/override button on the relay
box turned the led on and the boiler started.

A few hours later the heating was once again not working as expected, so
I repeated the above. This time the relay failed to start - the override
button does not seem to do anything.

The display on the controller is bright and clear, and there is no
indication that the batteries are low (there is usually a message).

- My gut feeling is that the relay box is dead. Any thoughts?
- Why would the hot water keep on cutting off then? because the boiler
receives random requests for heating from the faulty relay during a shower?
- Any other suggestions as to the cause?

Many thanks in advance.

Just a quick update:

Just checked, and the relay box seems to have come back to life. Tried
is again after a few hours (both by creating demand by setting very high
target temp and by pressing the override button on the box), and it
works as it should, and the boiler is turned on.

The faults described above have now happened at least a couple fo times
over the last few days, but then, on occassion, everyting seems to work
as it should.

On 29/12/2018 21:37, JoeJoe wrote:
Have a 5 year old WB combi that is regularly serviced and works fine (I
believe).

In the last two days we experienced two problems:

1. The hot water cutting off during a shower. Turning the water off,
waiting for a few seconds and turning it back on resumes hot water
(until the next time...).

2. Heating that cuts off at random times, and does not seem to respons
to demand signal from the programmable room thermostat.

We are using one of these:
https://www.wolseley.co.uk/product/c...om-thermostat/

which I believe is a rebadged Honeywell basic(ish) version. I fitted it
2 years ago to replaced a failed Honeywell 927.

Earlier today I tried to create artifical demand for the heating/boiler
by setting the target temp to 30c, but the relay failed to turn itself
on (led stayed off). Pressing the manual/override button on the relay
box turned the led on and the boiler started.

A few hours later the heating was once again not working as expected, so
I repeated the above. This time the relay failed to start - the override
button does not seem to do anything.

The display on the controller is bright and clear, and there is no
indication that the batteries are low (there is usually a message).

- My gut feeling is that the relay box is dead. Any thoughts?
- Why would the hot water keep on cutting off then? because the boiler
receives random requests for heating from the faulty relay during a shower?
- Any other suggestions as to the cause?


Does the boiler have a local indicator that shows "heating demand"? Some
WB's do and some don't in my very limited experience.

Either way - the hot water is independent of any heating controls
assuming the boiler is getting power. A sudden cutout suggests a problem
in the boiler more than in any external(?) controller.

Are you in a position to safety test the output of the
roomstat/controller when it claims to be asking for heat (ie is the wire
to the boiler live?)

--
Email does not work

On 29/12/2018 21:37, JoeJoe wrote:


A few hours later the heating was once again not working as expected, so
I repeated the above. This time the relay failed to start - the override
button does not seem to do anything.

The display on the controller is bright and clear, and there is no
indication that the batteries are low (there is usually a message).

- My gut feeling is that the relay box is dead. Any thoughts?

A multimeter on the end of the relay box will tell you.

- Why would the hot water keep on cutting off then? because the boiler
receives random requests for heating from the faulty relay during a shower?

No normally the DHW will take priority over any heating demands.

- Any other suggestions as to the cause?

This sounds more like a over temperature on the primary CH circuit.
Could be an obstruction in the boiler (or on the primary side of its
plate heat exchanger). Possibly a dodgy flow switch.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 29/12/2018 22:43, Tim Watts wrote:
On 29/12/2018 21:37, JoeJoe wrote:
Have a 5 year old WB combi that is regularly serviced and works fine
(I believe).

In the last two days we experienced two problems:

1. The hot water cutting off during a shower. Turning the water off,
waiting for a few seconds and turning it back on resumes hot water
(until the next time...).

2. Heating that cuts off at random times, and does not seem to respons
to demand signal from the programmable room thermostat.

We are using one of these:
https://www.wolseley.co.uk/product/c...om-thermostat/

which I believe is a rebadged Honeywell basic(ish) version. I fitted
it 2 years ago to replaced a failed Honeywell 927.

Earlier today I tried to create artifical demand for the
heating/boiler by setting the target temp to 30c, but the relay failed
to turn itself on (led stayed off). Pressing the manual/override
button on the relay box turned the led on and the boiler started.

A few hours later the heating was once again not working as expected,
so I repeated the above. This time the relay failed to start - the
override button does not seem to do anything.

The display on the controller is bright and clear, and there is no
indication that the batteries are low (there is usually a message).

- My gut feeling is that the relay box is dead. Any thoughts?
- Why would the hot water keep on cutting off then? because the boiler
receives random requests for heating from the faulty relay during a
shower?
- Any other suggestions as to the cause?


Does the boiler have a local indicator that shows "heating demand"? Some
WB's do and some don't in my very limited experience.

Sorry, I am not sure.

Either way - the hot water is independent of any heating controls
assuming the boiler is getting power. A sudden cutout suggests a problem
in the boiler more than in any external(?) controller.

Good to know - thanks for that!
I already phoned WB and arranged for them to send someone to have a look
at the boiler on Monday (it is still under warranty).

I later noticed that the relay/controller were misbehaving (as described
above) and thought that perhaps they were the cause, rather than the
boiler itself.

Are you in a position to safety test the output of the
roomstat/controller when it claims to be asking for heat (ie is the wire
to the boiler live?)

I can, but see above - I would probably leave it to the guy coming to
look at it.

The wolseley 10 minute drive away has the controller/relay in stock, so
I can always get them later if they prove the be the cause.

On 29/12/2018 23:03, John Rumm wrote:
On 29/12/2018 21:37, JoeJoe wrote:


A few hours later the heating was once again not working as expected,
so I repeated the above. This time the relay failed to start - the
override button does not seem to do anything.

The display on the controller is bright and clear, and there is no
indication that the batteries are low (there is usually a message).

- My gut feeling is that the relay box is dead. Any thoughts?

A multimeter on the end of the relay box will tell you.

See my subsequent message - there is clearly something strange with the
controller/relay box...

- Why would the hot water keep on cutting off then? because the boiler
receives random requests for heating from the faulty relay during a
shower?

No normally the DHW will take priority over any heating demands.

That is what I thought.
- Any other suggestions as to the cause?

This sounds more like a over temperature on theÂ* primary CH circuit.
Could be an obstruction in the boiler (or on the primary side of its
plate heat exchanger). Possibly a dodgy flow switch.

So most likely boiler problem then? Good, as WB are sending someone on
Monday to have a look (still under warranty).

I just wanted a quick sanity check that it was not 100% the
controller/relay that I can easily replace myself.

On 29/12/2018 23:08, JoeJoe wrote:
On 29/12/2018 22:43, Tim Watts wrote:
On 29/12/2018 21:37, JoeJoe wrote:
Have a 5 year old WB combi that is regularly serviced and works fine
(I believe).

In the last two days we experienced two problems:

1. The hot water cutting off during a shower. Turning the water off,
waiting for a few seconds and turning it back on resumes hot water
(until the next time...).

2. Heating that cuts off at random times, and does not seem to
respons to demand signal from the programmable room thermostat.

We are using one of these:
https://www.wolseley.co.uk/product/c...om-thermostat/

which I believe is a rebadged Honeywell basic(ish) version. I fitted
it 2 years ago to replaced a failed Honeywell 927.

Earlier today I tried to create artifical demand for the
heating/boiler by setting the target temp to 30c, but the relay
failed to turn itself on (led stayed off). Pressing the
manual/override button on the relay box turned the led on and the
boiler started.

A few hours later the heating was once again not working as expected,
so I repeated the above. This time the relay failed to start - the
override button does not seem to do anything.

The display on the controller is bright and clear, and there is no
indication that the batteries are low (there is usually a message).

- My gut feeling is that the relay box is dead. Any thoughts?
- Why would the hot water keep on cutting off then? because the
boiler receives random requests for heating from the faulty relay
during a shower?
- Any other suggestions as to the cause?


Does the boiler have a local indicator that shows "heating demand"?
Some WB's do and some don't in my very limited experience.

Sorry, I am not sure.

Could be worth wiring a neon to the output at a convenient time (like a
grid module in a single gang box) - very handy for debugging problems.

Either way - the hot water is independent of any heating controls
assuming the boiler is getting power. A sudden cutout suggests a
problem in the boiler more than in any external(?) controller.

Good to know - thanks for that!
I already phoned WB and arranged for them to send someone to have a look
at the boiler on Monday (it is still under warranty).

Good luck - hope it gets fixed

--
Email does not work

John Rumm used his keyboard to write :
A multimeter on the end of the relay box will tell you.

- Why would the hot water keep on cutting off then? because the boiler
receives random requests for heating from the faulty relay during a shower?

No normally the DHW will take priority over any heating demands.

- Any other suggestions as to the cause?

This sounds more like a over temperature on the primary CH circuit. Could be
an obstruction in the boiler (or on the primary side of its plate heat
exchanger). Possibly a dodgy flow switch.

These problems are precisely the reason I put together a row of LED's
permanently wired to terminals in my heating system's joint box. I can
tell at a glance exactly what is happening. Power on, pump running,
call for heating, call for hot water, call for boiler to fire up.

It took a while to make it up, but when there is an issue, I can see
what is happening with just a glance.

On 29/12/2018 23:39, Harry Bloomfield wrote:
John Rumm used his keyboard to write :
A multimeter on the end of the relay box will tell you.

- Why would the hot water keep on cutting off then? because the
boiler receives random requests for heating from the faulty relay
during a shower?

No normally the DHW will take priority over any heating demands.

- Any other suggestions as to the cause?

This sounds more like a over temperature on the* primary CH circuit.
Could be an obstruction in the boiler (or on the primary side of its
plate heat exchanger). Possibly a dodgy flow switch.

These problems are precisely the reason I put together a row of LED's
permanently wired to terminals in my heating system's joint box. I can
tell at a glance exactly what is happening. Power on, pump running, call
for heating, call for hot water, call for boiler to fire up.

It took a while to make it up, but when there is an issue, I can see
what is happening with just a glance.

There is a lashup you can do with the normal Y plan system and some
relays and neons that will achieve this as well (it also saves
continuously powering the valve when all calls for heat are satisfied)

http://wiki.diyfaq.org.uk/index.php/...h_ indicators



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

It happens that John Rumm formulated :
There is a lashup you can do with the normal Y plan system and some relays
and neons that will achieve this as well (it also saves continuously powering
the valve when all calls for heat are satisfied)

http://wiki.diyfaq.org.uk/index.php/...h_ indicators

My LED's give more detail and I would expect them to last rather longer
than neons, which in time will dim.

It might be an idea to check all electrical connections for loose screws
etc, and also see if the relay is merely sticking.
Other than that I guess there could be some odd dry joint somewhere in the
electronics, but it would be a swine to find it.
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"JoeJoe" wrote in message
news
On 29/12/2018 21:37, JoeJoe wrote:
Have a 5 year old WB combi that is regularly serviced and works fine (I
believe).

In the last two days we experienced two problems:

1. The hot water cutting off during a shower. Turning the water off,
waiting for a few seconds and turning it back on resumes hot water (until
the next time...).

2. Heating that cuts off at random times, and does not seem to respons to
demand signal from the programmable room thermostat.

We are using one of these:
https://www.wolseley.co.uk/product/c...om-thermostat/
which I believe is a rebadged Honeywell basic(ish) version. I fitted it 2
years ago to replaced a failed Honeywell 927.

Earlier today I tried to create artifical demand for the heating/boiler
by setting the target temp to 30c, but the relay failed to turn itself on
(led stayed off). Pressing the manual/override button on the relay box
turned the led on and the boiler started.

A few hours later the heating was once again not working as expected, so
I repeated the above. This time the relay failed to start - the override
button does not seem to do anything.

The display on the controller is bright and clear, and there is no
indication that the batteries are low (there is usually a message).

- My gut feeling is that the relay box is dead. Any thoughts?
- Why would the hot water keep on cutting off then? because the boiler
receives random requests for heating from the faulty relay during a
shower?
- Any other suggestions as to the cause?

Many thanks in advance.

Just a quick update:

Just checked, and the relay box seems to have come back to life. Tried is
again after a few hours (both by creating demand by setting very high
target temp and by pressing the override button on the box), and it works
as it should, and the boiler is turned on.

The faults described above have now happened at least a couple fo times
over the last few days, but then, on occassion, everyting seems to work as
it should.

- Any other suggestions as to the cause?

This sounds more like a over temperature on the primary CH circuit.
Could be an obstruction in the boiler (or on the primary side of its
plate heat exchanger). Possibly a dodgy flow switch.



I was going to suggest that - the shower will be causing to to run flat out
and maybe it is overheating and shutting off a thermal switch.

On Sunday, 30 December 2018 08:06:06 UTC, Harry Bloomfield wrote:
It happens that John Rumm formulated :

There is a lashup you can do with the normal Y plan system and some relays
and neons that will achieve this as well (it also saves continuously powering
the valve when all calls for heat are satisfied)

http://wiki.diyfaq.org.uk/index.php/...h_ indicators

My LED's give more detail and I would expect them to last rather longer
than neons, which in time will dim.

They don't dim out if you halve run current with a series resistor. Neon life is generally inversely proportional to current to the power of 3. So half the current gets you 8x the usual life of decades.


NT

On Sun, 30 Dec 2018 08:05:58 GMT, Harry Bloomfield
wrote:

It happens that John Rumm formulated :
There is a lashup you can do with the normal Y plan system and some relays
and neons that will achieve this as well (it also saves continuously powering
the valve when all calls for heat are satisfied)

http://wiki.diyfaq.org.uk/index.php/...h_ indicators

My LED's give more detail and I would expect them to last rather longer
than neons, which in time will dim.
How are you powering the LEDs from the 240v ac points you are
monitoring? An individual "circuit" for each LED or something
cleverer?

On 30/12/2018 15:56, Davidm wrote:
On Sun, 30 Dec 2018 08:05:58 GMT, Harry Bloomfield
wrote:

It happens that John Rumm formulated :
There is a lashup you can do with the normal Y plan system and some relays
and neons that will achieve this as well (it also saves continuously powering
the valve when all calls for heat are satisfied)

http://wiki.diyfaq.org.uk/index.php/...h_ indicators

My LED's give more detail and I would expect them to last rather longer
than neons, which in time will dim.
How are you powering the LEDs from the 240v ac points you are
monitoring? An individual "circuit" for each LED or something
cleverer?

A diode and resistor in series, or capacitive dropper and a diode will
normally do it...


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Sunday, 30 December 2018 18:35:27 UTC, John Rumm wrote:
On 30/12/2018 15:56, Davidm wrote:
On Sun, 30 Dec 2018 08:05:58 GMT, Harry Bloomfield
wrote:
It happens that John Rumm formulated :

There is a lashup you can do with the normal Y plan system and some relays
and neons that will achieve this as well (it also saves continuously powering
the valve when all calls for heat are satisfied)

http://wiki.diyfaq.org.uk/index.php/...h_ indicators

My LED's give more detail and I would expect them to last rather longer
than neons, which in time will dim.
How are you powering the LEDs from the 240v ac points you are
monitoring? An individual "circuit" for each LED or something
cleverer?

A diode and resistor in series, or capacitive dropper and a diode will
normally do it...

capacitor needs a resistor as well.


NT

Davidm expressed precisely :
How are you powering the LEDs from the 240v ac points you are
monitoring? An individual "circuit" for each LED or something
cleverer?

An individual circuit per LED, it needs just a diode, 300v capacitor
and the LED. You can then connect them between test point and either of
neutral, or live - which ever way produces lit for active. I made it up
with 8x LED's. I posted full details of the circuit I used on here,
maybe a couple of years ago.

I built it up on a long strip of Veroboard, then mounted it in a two
gang surface socket box, with a two gang blanking plate, mounted next
to the heating joint box.

John Rumm presented the following explanation :
A diode and resistor in series, or capacitive dropper and a diode will
normally do it...

Using the resistor method, the resistor will have to dissipate a lot of
watts, much more efficient to use a capacitive dropper. I will see if I
can dig out my out circuit, the one I ended up with after a bit of
bench testing.

On Mon, 31 Dec 2018 08:56:12 GMT, Harry Bloomfield
wrote:

Davidm expressed precisely :
How are you powering the LEDs from the 240v ac points you are
monitoring? An individual "circuit" for each LED or something
cleverer?

An individual circuit per LED, it needs just a diode, 300v capacitor
and the LED. You can then connect them between test point and either of
neutral, or live - which ever way produces lit for active. I made it up
with 8x LED's. I posted full details of the circuit I used on here,
maybe a couple of years ago.

I built it up on a long strip of Veroboard, then mounted it in a two
gang surface socket box, with a two gang blanking plate, mounted next
to the heating joint box.
Thanks Harry

Harry Bloomfield expressed precisely :
An individual circuit per LED, it needs just a diode, 300v capacitor and the
LED. You can then connect them between test point and either of neutral, or
live - which ever way produces lit for active. I made it up with 8x LED's. I
posted full details of the circuit I used on here, maybe a couple of years
ago.

I built it up on a long strip of Veroboard, then mounted it in a two gang
surface socket box, with a two gang blanking plate, mounted next to the
heating joint box.

L ---- 220 -- 0.1 -- 4148 + LED (back to back) ---- N

That is a 220Ohm resistor, a 0.1uF 630v cap, then back to back a 1N4148
diode in parallel with a superbright 6mm LED.

I found the cap value by some trial and error, decrease its value if
you use with a lower current LED. 0.47uF blew my test LED after a
couple of days on test. With 0.1 they have so far survived 2 years
running.

The 220Ohm is intended to limit the inrush current as the cap charges.
Almost any small diode with do for the 4148.

On 29/12/2018 21:37, JoeJoe wrote:
Have a 5 year old WB combi that is regularly serviced and works fine (I
believe).

In the last two days we experienced two problems:

1. The hot water cutting off during a shower. Turning the water off,
waiting for a few seconds and turning it back on resumes hot water
(until the next time...).

2. Heating that cuts off at random times, and does not seem to respons
to demand signal from the programmable room thermostat.

We are using one of these:
https://www.wolseley.co.uk/product/c...om-thermostat/

which I believe is a rebadged Honeywell basic(ish) version. I fitted it
2 years ago to replaced a failed Honeywell 927.

Earlier today I tried to create artifical demand for the heating/boiler
by setting the target temp to 30c, but the relay failed to turn itself
on (led stayed off). Pressing the manual/override button on the relay
box turned the led on and the boiler started.

A few hours later the heating was once again not working as expected, so
I repeated the above. This time the relay failed to start - the override
button does not seem to do anything.

The display on the controller is bright and clear, and there is no
indication that the batteries are low (there is usually a message).

- My gut feeling is that the relay box is dead. Any thoughts?
- Why would the hot water keep on cutting off then? because the boiler
receives random requests for heating from the faulty relay during a shower?
- Any other suggestions as to the cause?

Many thanks in advance.

A quick update:

WB engineer just been and gone.

After spending quite some time trying to work out what was going on he
concluded that it was the condensate pump that was the culprit.

What he showed me:
- The boiler is fed from the main (240v) by a flex.
- Every time the pump is called into action the 240v to the boiler goes
down to 0v.
- The controller relay, which gets its power from the boiler, then stops
working as its (the boiler's) power is cut off (see my original message).
- Once there is no demand any more for the pump (after a few minutes)
the power to the boiler is restored and it goes through the "boot" cycle
and starts again until the next time the pump is called.

He thinks that the pump causes some sort of a short on the power feed to
the boiler.

Makes sense to me... What do the experts think?

PS: I have already replaced the pump once since it was fitted 5 years
ago. Unfortunately it is located under the house with quite tricky
access, and since I just had a minor operation I will have to get
someone in to replace.

On Sunday, 30 December 2018 15:56:06 UTC, Davidm wrote:
On Sun, 30 Dec 2018 08:05:58 GMT, Harry Bloomfield

My LED's give more detail and I would expect them to last rather longer
than neons, which in time will dim.

How are you powering the LEDs from the 240v ac points you are
monitoring? An individual "circuit" for each LED or something
cleverer?

How to design a suitable RC power supply.

First you size the C for the wanted i.
2mA would require 120kΩ, which at 50Hz is 0.0266μF. 0.022μF is the NPV. Modern LEDs don't need more current for indicator use.

Then you size your R for the peak current under any circumstances. If we allow 0.33A at a peak of 330v we need 1kΩ.

Next: capacitor ratings. A mains capacitor requires a 250v ac X2 rating. 400v caps were formerly used but fail too often on mains, and lack safety features.

Now resistor ratings. 1kΩ at 2mA rms drops 2v rms & dissipates 4mW, so power rating is no issue. A 400v rating is a minimum, and typical through hole parts are rated to 200v, so 2x 470 ohm in series will do the job.

Finally the diode that goes back to back across the LED. It must cope with 0.33A peak and a few volts in reverse - not a demanding spec, but germaniums & some small signal diodes are unsuitable.


NT

On Monday, 31 December 2018 10:49:10 UTC, JoeJoe wrote:
On 29/12/2018 21:37, JoeJoe wrote:
Have a 5 year old WB combi that is regularly serviced and works fine (I
believe).

In the last two days we experienced two problems:

1. The hot water cutting off during a shower. Turning the water off,
waiting for a few seconds and turning it back on resumes hot water
(until the next time...).

2. Heating that cuts off at random times, and does not seem to respons
to demand signal from the programmable room thermostat.

We are using one of these:
https://www.wolseley.co.uk/product/c...om-thermostat/

which I believe is a rebadged Honeywell basic(ish) version. I fitted it
2 years ago to replaced a failed Honeywell 927.

Earlier today I tried to create artifical demand for the heating/boiler
by setting the target temp to 30c, but the relay failed to turn itself
on (led stayed off). Pressing the manual/override button on the relay
box turned the led on and the boiler started.

A few hours later the heating was once again not working as expected, so
I repeated the above. This time the relay failed to start - the override
button does not seem to do anything.

The display on the controller is bright and clear, and there is no
indication that the batteries are low (there is usually a message).

- My gut feeling is that the relay box is dead. Any thoughts?
- Why would the hot water keep on cutting off then? because the boiler
receives random requests for heating from the faulty relay during a shower?
- Any other suggestions as to the cause?

Many thanks in advance.

A quick update:

WB engineer just been and gone.

After spending quite some time trying to work out what was going on he
concluded that it was the condensate pump that was the culprit.

What he showed me:
- The boiler is fed from the main (240v) by a flex.
- Every time the pump is called into action the 240v to the boiler goes
down to 0v.
- The controller relay, which gets its power from the boiler, then stops
working as its (the boiler's) power is cut off (see my original message).
- Once there is no demand any more for the pump (after a few minutes)
the power to the boiler is restored and it goes through the "boot" cycle
and starts again until the next time the pump is called.

He thinks that the pump causes some sort of a short on the power feed to
the boiler.

Makes sense to me... What do the experts think?

PS: I have already replaced the pump once since it was fitted 5 years
ago. Unfortunately it is located under the house with quite tricky
access, and since I just had a minor operation I will have to get
someone in to replace.

That raises an obvious question or 2. Why is the power feed of high enough resistance for it to drop to 0v? Why has no fuse blown as a result?


NT

JoeJoe wrote:

He thinks that the pump causes some sort of a short on the power feed to
the boiler.

Makes sense to me... What do the experts think?

Fuses would be going BANG! if that were true.

Sounds like the flex feeding the boiler isn't direct from the mains, but
from some other relay, thermostat, multi-port valve, whatever that he
hasn't understood ...

On 31/12/2018 11:05, Andy Burns wrote:
JoeJoe wrote:

He thinks that the pump causes some sort of a short on the power feed
to the boiler.

Makes sense to me... What do the experts think?

Fuses would be going BANG! if that were true.

Sounds like the flex feeding the boiler isn't direct from the mains, but
from some other relay, thermostat, multi-port valve, whatever that he
hasn't understood ...

I just had a closer look inside the spur fuse/switch box feeding the boiler.

4 cables going in/out of it:

- A feed cable coming out of the wall behind and going into it (feed
from the ring main I believe)
- 1 x thick flex going to the boiler (240v from the box to the boiler I
believe)
- 2 x thin flexes going from the box to the cond. pump (feed and return?)

I am not 100% sure, but I am 99% certain that the wiring is as in this
diagram:

http://tinypic.com/r/2edqjc7/9

Based on that it looks as if his diagnosis is probably correct.

A fault in the pump causes it to cut off, resulting in breaking the live
feed to the boiler. After a while it "recovers" and the feed is resumed.

Not the behaviour I would expect from the pump (does it not have a
fuse?), but possible...

The penny dropped for him when, with no power to the boiler, he
disconnected the discharge pipe from the boiler to the pump, blew into
it (removing debris perhaps?), causing the pump to start working and the
boiler came back to life.

I saw the guy checking the fuse on the 240v feed inside the boiler,
which was fine.

Any thoughts?

On 31/12/2018 11:51, JoeJoe wrote:
On 31/12/2018 11:05, Andy Burns wrote:
JoeJoe wrote:

He thinks that the pump causes some sort of a short on the power feed
to the boiler.

Makes sense to me... What do the experts think?

Fuses would be going BANG! if that were true.

Sounds like the flex feeding the boiler isn't direct from the mains,
but from some other relay, thermostat, multi-port valve, whatever that
he hasn't understood ...

I just had a closer look inside the spur fuse/switch box feeding the
boiler.

4 cables going in/out of it:

- A feed cable coming out of the wall behind and going into it (feed
from the ring main I believe)
- 1 x thick flex going to the boiler (240v from the box to the boiler I
believe)
- 2 x thin flexes going from the box to the cond. pump (feed and return?)

I am not 100% sure, but I am 99% certain that the wiring is as in this
diagram:

http://tinypic.com/r/2edqjc7/9

Based on that it looks as if his diagnosis is probably correct.

A fault in the pump causes it to cut off, resulting in breaking the live
feed to the boiler. After a while it "recovers" and the feed is resumed.

Not the behaviour I would expect from the pump (does it not have a
fuse?), but possible...

The penny dropped for him when, with no power to the boiler, he
disconnected the discharge pipe from the boiler to the pump, blew into
it (removing debris perhaps?), causing the pump to start working and the
boiler came back to life.

I saw the guy checking the fuse on the 240v feed inside the boiler,
which was fine.

Any thoughts?


Also this one:

http://tinypic.com/r/feh3dt/9

See the 3 flexes in the bottom right of the photo. Also, the thick live
(to the boiler) connected to the thin cable coming from the pump using
the connector block.

On 31/12/2018 11:51, JoeJoe wrote:
A fault in the pump causes it to cut off, resulting in breaking the live
feed to the boiler. After a while it "recovers" and the feed is resumed.

Not the behaviour I would expect from the pump (does it not have a
fuse?), but possible...

The penny dropped for him when, with no power to the boiler, he
disconnected the discharge pipe from the boiler to the pump, blew into
it (removing debris perhaps?), causing the pump to start working and the
boiler came back to life.

I saw the guy checking the fuse on the 240v feed inside the boiler,
which was fine.

Any thoughts?



Well I guess its possible that the condensate pump has a switch in it
that discoinnects the boiler if it trips. Could be overtemeparytuer or
overcurrent.

Or this (wiki)

"Condensate pumps usually run intermittently and have a tank in which
condensate can accumulate. Eventually, the accumulating liquid raises a
float switch energizing the pump. The pump then runs until the level of
liquid in the tank is substantially lowered. *Some pumps contain a
two-stage switch*. As liquid rises to the trigger point of the first
stage, the pump is activated. If the liquid continues to rise (perhaps
because the pump has failed or its discharge is blocked), the *second
stage will be triggered*. *This stage may switch off the HVAC equipment
(preventing the production of further condensate), trigger an alarm, or
both*. "

Maybe time to say what the part number of the pump is and do some
reasearch on it.

What it looks like is that you have a second stage switch and it thinks
that the condensate is not getting punped out. And perhps it isn';t.

Personally life being increasingly too short, I'd get a whole new
assembly and replace the whole thing. Probably less than £100 and not
hard to do.


--
"Women actually are capable of being far more than the feminists will
let them."

On 31/12/2018 12:19, The Natural Philosopher wrote:
On 31/12/2018 11:51, JoeJoe wrote:
A fault in the pump causes it to cut off, resulting in breaking the
live feed to the boiler. After a while it "recovers" and the feed is
resumed.

Not the behaviour I would expect from the pump (does it not have a
fuse?), but possible...

The penny dropped for him when, with no power to the boiler, he
disconnected the discharge pipe from the boiler to the pump, blew into
it (removing debris perhaps?), causing the pump to start working and
the boiler came back to life.

I saw the guy checking the fuse on the 240v feed inside the boiler,
which was fine.

Any thoughts?



Well I guess its possible that the condensate pump has a switch in it
that discoinnects the boiler if it trips. Could be overtemeparytuer or
overcurrent.

Or this (wiki)

"Condensate pumps usually run intermittently and have a tank in which
condensate can accumulate. Eventually, the accumulating liquid raises a
float switch energizing the pump. The pump then runs until the level of
liquid in the tank is substantially lowered. *Some pumps contain a
two-stage switch*. As liquid rises to the trigger point of the first
stage, the pump is activated. If the liquid continues to rise (perhaps
because the pump has failed or its discharge is blocked), the *second
stage will be triggered*. *This stage may switch off the HVAC equipment
(preventing the production of further condensate), trigger an alarm, or
both*. "

Maybe time to say what the part number of the pump is and do some
reasearch on it.

What it looks like is that you have a second stage switch and it thinks
that the condensate is not getting punped out. And perhps it isn';t.

Personally life being increasingly too short, I'd get a whole new
assembly and replace the whole thing. Probably less than £100 and not
hard to do.

I agree 100%, life is too short, and am happy to replace.

Unfortunately I am unable to get to the pump at the moment as it
requires crawling under the house for 10m, and I am after a minor op...
I'll get a man in.

I did however manage to find the receipt from when I bought and replaced
it myself a couple of years ago (the float mechanism died after 3
years). All it says is Jet HighFlow (£60 at the time). I do remember
that it looked very much like these (most probably this is the one):
https://www.ebay.co.uk/itm/Jet-Range...y/173714956548
https://www.wolseley.co.uk/product/j...sate-pump-kit/

No much info online though (it looks as if it had been discontinued),
apart from a single sheet on the Wolseley website above.

PS: The WB guy suspected that it the pump that was the problem as soon
as I described the symptoms to him. However, after he went under the
house with a bottle of water he returned to say that it seemed to be
working fine.

Only when the boiler started to turn itself on and off for no apparent
reason whilst he was looking at it did he start investigating the power
feed and concluded that it looked as if it was the pump that was faulty
after all.

JoeJoe wrote:

On 29/12/2018 21:37, JoeJoe wrote:
Have a 5 year old WB combi that is regularly serviced and works fine (I
believe).

In the last two days we experienced two problems:

1. The hot water cutting off during a shower. Turning the water off,
waiting for a few seconds and turning it back on resumes hot water
(until the next time...).

2. Heating that cuts off at random times, and does not seem to respons
to demand signal from the programmable room thermostat.

We are using one of these:
https://www.wolseley.co.uk/product/c...programmable-r
oom-thermostat/

which I believe is a rebadged Honeywell basic(ish) version. I fitted it
2 years ago to replaced a failed Honeywell 927.

Earlier today I tried to create artifical demand for the heating/boiler
by setting the target temp to 30c, but the relay failed to turn itself
on (led stayed off). Pressing the manual/override button on the relay
box turned the led on and the boiler started.

A few hours later the heating was once again not working as expected, so
I repeated the above. This time the relay failed to start - the override
button does not seem to do anything.

The display on the controller is bright and clear, and there is no
indication that the batteries are low (there is usually a message).

- My gut feeling is that the relay box is dead. Any thoughts?
- Why would the hot water keep on cutting off then? because the boiler
receives random requests for heating from the faulty relay during a shower?
- Any other suggestions as to the cause?

Many thanks in advance.

A quick update:

WB engineer just been and gone.

After spending quite some time trying to work out what was going on he
concluded that it was the condensate pump that was the culprit.

What he showed me:
- The boiler is fed from the main (240v) by a flex.
- Every time the pump is called into action the 240v to the boiler goes
down to 0v.
- The controller relay, which gets its power from the boiler, then stops
working as its (the boiler's) power is cut off (see my original message).
- Once there is no demand any more for the pump (after a few minutes)
the power to the boiler is restored and it goes through the "boot" cycle
and starts again until the next time the pump is called.

He thinks that the pump causes some sort of a short on the power feed to
the boiler.

That's not credible. It could only cut off the boiler by a short if the
fuse blew/MCB tripped. However, the condensate pump may have an
additional NC level switch which is higher than the design maximum
level in the tank, so that if the pump fails the "overflow" level switch
opens and cuts off the boiler live feed which is wired in series with
it. The actual pump motor is wired in parallel with the boiler always
live supply (and in series with the normal level switch) and the issue
will then be failing to pump, either due to motor failure, level switch
failure or (my recent case) blockage of the pump with bacterial slime.
Blockage of the pump outflow would be another possible cause.




Makes sense to me... What do the experts think?

PS: I have already replaced the pump once since it was fitted 5 years
ago. Unfortunately it is located under the house with quite tricky
access, and since I just had a minor operation I will have to get
someone in to replace.


--

Roger Hayter

On 31/12/2018 13:04, Roger Hayter wrote:
JoeJoe wrote:

On 29/12/2018 21:37, JoeJoe wrote:
Have a 5 year old WB combi that is regularly serviced and works fine (I
believe).

In the last two days we experienced two problems:

1. The hot water cutting off during a shower. Turning the water off,
waiting for a few seconds and turning it back on resumes hot water
(until the next time...).

2. Heating that cuts off at random times, and does not seem to respons
to demand signal from the programmable room thermostat.

We are using one of these:
https://www.wolseley.co.uk/product/c...programmable-r
oom-thermostat/

which I believe is a rebadged Honeywell basic(ish) version. I fitted it
2 years ago to replaced a failed Honeywell 927.

Earlier today I tried to create artifical demand for the heating/boiler
by setting the target temp to 30c, but the relay failed to turn itself
on (led stayed off). Pressing the manual/override button on the relay
box turned the led on and the boiler started.

A few hours later the heating was once again not working as expected, so
I repeated the above. This time the relay failed to start - the override
button does not seem to do anything.

The display on the controller is bright and clear, and there is no
indication that the batteries are low (there is usually a message).

- My gut feeling is that the relay box is dead. Any thoughts?
- Why would the hot water keep on cutting off then? because the boiler
receives random requests for heating from the faulty relay during a shower?
- Any other suggestions as to the cause?

Many thanks in advance.

A quick update:

WB engineer just been and gone.

After spending quite some time trying to work out what was going on he
concluded that it was the condensate pump that was the culprit.

What he showed me:
- The boiler is fed from the main (240v) by a flex.
- Every time the pump is called into action the 240v to the boiler goes
down to 0v.
- The controller relay, which gets its power from the boiler, then stops
working as its (the boiler's) power is cut off (see my original message).
- Once there is no demand any more for the pump (after a few minutes)
the power to the boiler is restored and it goes through the "boot" cycle
and starts again until the next time the pump is called.

He thinks that the pump causes some sort of a short on the power feed to
the boiler.

That's not credible. It could only cut off the boiler by a short if the
fuse blew/MCB tripped. However, the condensate pump may have an
additional NC level switch which is higher than the design maximum
level in the tank, so that if the pump fails the "overflow" level switch
opens and cuts off the boiler live feed which is wired in series with
it. The actual pump motor is wired in parallel with the boiler always
live supply (and in series with the normal level switch) and the issue
will then be failing to pump, either due to motor failure, level switch
failure or (my recent case) blockage of the pump with bacterial slime.
Blockage of the pump outflow would be another possible cause.




Makes sense to me... What do the experts think?

PS: I have already replaced the pump once since it was fitted 5 years
ago. Unfortunately it is located under the house with quite tricky
access, and since I just had a minor operation I will have to get
someone in to replace.



Thanks for that.

Sounds as if I might have failed to explain the problem properly, but
you agree that a new pump is in order nonetheless?

JoeJoe wrote:

Any thoughts?

I don't know if wiring to condensate pumps varies, but this one shows
that the live is fed to the pump, and then via a "safety wire" to the
boiler, so the boiler depends on the pump being "happy"

http://sauermann.co.uk/sites/default/files/styles/paragraph_image/public/paragraph_image/wiring.jpg?itok=aH89sGa-

On 31/12/2018 13:43, Andy Burns wrote:
JoeJoe wrote:

Any thoughts?

I don't know if wiring to condensate pumps varies, but this one shows
that the live is fed to the pump, and then via a "safety wire" to the
boiler, so the boiler depends on the pump being "happy"

http://sauermann.co.uk/sites/default/files/styles/paragraph_image/public/paragraph_image/wiring.jpg?itok=aH89sGa-



Thanks - looks very much like my setup.

On 31/12/2018 09:00, Harry Bloomfield wrote:
John Rumm presented the following explanation :
A diode and resistor in series, or capacitive dropper and a diode will
normally do it...

Using the resistor method, the resistor will have to dissipate a lot of
watts,

You can probably get enough light out of a modern LED at 2mA... that
would mean 0.5W dissipated in the R.

much more efficient to use a capacitive dropper. I will see if I
can dig out my out circuit, the one I ended up with after a bit of bench
testing.

You can also buy mains indicator LEDs that will do the job out of the
box with no extra components.

(i.e. they include the resistors/caps and shunt diodes in the same package)



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

JoeJoe wrote:

a new pump is in order

Yes, unless you can strip it down and see anything hampering any
microswitches?

On 31/12/2018 14:32, Andy Burns wrote:
JoeJoe wrote:

a new pump is in order

Yes, unless you can strip it down and see anything hampering any
microswitches?

Thanks (life too short for that...)

JoeJoe wrote:

On 31/12/2018 12:19, The Natural Philosopher wrote:
On 31/12/2018 11:51, JoeJoe wrote:
A fault in the pump causes it to cut off, resulting in breaking the
live feed to the boiler. After a while it "recovers" and the feed is
resumed.

Not the behaviour I would expect from the pump (does it not have a
fuse?), but possible...

The penny dropped for him when, with no power to the boiler, he
disconnected the discharge pipe from the boiler to the pump, blew into
it (removing debris perhaps?), causing the pump to start working and
the boiler came back to life.

I saw the guy checking the fuse on the 240v feed inside the boiler,
which was fine.

Any thoughts?



Well I guess its possible that the condensate pump has a switch in it
that discoinnects the boiler if it trips. Could be overtemeparytuer or
overcurrent.

Or this (wiki)

"Condensate pumps usually run intermittently and have a tank in which
condensate can accumulate. Eventually, the accumulating liquid raises a
float switch energizing the pump. The pump then runs until the level of
liquid in the tank is substantially lowered. *Some pumps contain a
two-stage switch*. As liquid rises to the trigger point of the first
stage, the pump is activated. If the liquid continues to rise (perhaps
because the pump has failed or its discharge is blocked), the *second
stage will be triggered*. *This stage may switch off the HVAC equipment
(preventing the production of further condensate), trigger an alarm, or
both*. "

Maybe time to say what the part number of the pump is and do some
reasearch on it.

What it looks like is that you have a second stage switch and it thinks
that the condensate is not getting punped out. And perhps it isn';t.

Personally life being increasingly too short, I'd get a whole new
assembly and replace the whole thing. Probably less than £100 and not
hard to do.

I agree 100%, life is too short, and am happy to replace.

Unfortunately I am unable to get to the pump at the moment as it
requires crawling under the house for 10m, and I am after a minor op...
I'll get a man in.

I did however manage to find the receipt from when I bought and replaced
it myself a couple of years ago (the float mechanism died after 3 years).
All it says is Jet HighFlow (£60 at the time). I do remember that it
looked very much like these (most probably this is the one):
https://www.ebay.co.uk/itm/Jet-Range...sate-Pump-only
/173714956548
https://www.wolseley.co.uk/product/j...sate-pump-kit/

No much info online though (it looks as if it had been discontinued),
apart from a single sheet on the Wolseley website above.

PS: The WB guy suspected that it the pump that was the problem as soon
as I described the symptoms to him. However, after he went under the
house with a bottle of water he returned to say that it seemed to be
working fine.

Only when the boiler started to turn itself on and off for no apparent
reason whilst he was looking at it did he start investigating the power
feed and concluded that it looked as if it was the pump that was faulty
after all.

If the pump is working well, it is beginning to sound like a loose
connection either at the pump or boiler end of the wires to the pump.
Other possibilities are an intermiittenly failing pump motor or float
switch, neither being likely. Or a blockage in the condensate pipe to
the pump. The latter is excluded if ithe technician demonstrated that
the live supply to the boiler from the pump was failing. Might be worth
checking the mains supply to the pump, which is probably not from the
boiler but might be, and the cable to the pump overflow switch. You can
check the terminals at the boiler end even if the other end is currently
inaccessible. Competent replacement of the pump will sort the
connections at that end, even if it wasn't the pump that failed!
--

Roger Hayter

JoeJoe wrote:

On 31/12/2018 14:32, Andy Burns wrote:
JoeJoe wrote:

a new pump is in order

Yes, unless you can strip it down and see anything hampering any
microswitches?

Thanks (life too short for that...)

And especially if you have to pay someone to do it it will be a lot
cheaper and quicker to replace the pump than to remove, repair and
replace it.

--

Roger Hayter

On Mon, 31 Dec 2018 14:30:42 +0000, John Rumm wrote:

On 31/12/2018 09:00, Harry Bloomfield wrote:
John Rumm presented the following explanation :
A diode and resistor in series, or capacitive dropper and a diode will
normally do it...

Using the resistor method, the resistor will have to dissipate a lot of
watts,

You can probably get enough light out of a modern LED at 2mA... that
would mean 0.5W dissipated in the R.

much more efficient to use a capacitive dropper. I will see if I can
dig out my out circuit, the one I ended up with after a bit of bench
testing.

You can also buy mains indicator LEDs that will do the job out of the
box with no extra components.

(i.e. they include the resistors/caps and shunt diodes in the same
package)

A purpose made LED analogue of a neon indicator lamp could be fabricated
using a pair of same colour LEDs mounted on the same header wired anti-
parallel[1] with a 10K resistor and a 2nF Y class cap in series. That
would draw 300 microampres or 0.3mA. Using a 10nF cap would draw 1.5mA
with the 10K 500v rated surge limiting resistor wasting all of 22mW with
the LEDs consuming a mere 4mW or so.

The 10K surge limiting resistor is required to limit the worst case
switch on transient (cap charged to -340v when switched back on at a
positive peak of 340v giving a total of 680v across the resistor) current
spike of 68mA.

Silicon rectifier diodes are usually specced to handle 1 microsecond
current surges around about a hundred times the average continuous
maximum current rating rating but this is with a Vf of only a quarter of
that of a LED so I'd expect a LED to only have such transient peak
ratings around 20 to 30 times their maximum average rating. For a small
indicator LED, which these days may only have a 25mA rating, this would
correspond to a circa 750mA 1 microsecond non-repetitive peak rating so a
1K surge limiting resistor could be utilised to reduce the waste energy
to a mere 2.2mW.

Alternatively, with the ultra high efficiency LEDs we have today, a half
milliamp of drive current would likely suffice and the 1 or 2 nF cap
could be dispensed with and a single 300v rated 470K resistor used in
place of the cap and surge limiting resistor.

The total dissipation would rise to 122.5mW (1/8 th of a watt), mostly
in the dropper resistor. Though a magnitude larger energy consumption
compared to the capacitor dropper circuit, it's still less than the 200mW
or more consumed by the classic neon with 220K/180K ballast resistor
mains voltage driven indicator lamp.

Fun Fact: The neon lamp in a recently purchased three way switched mains
socket extension adapter draws some 200 to 250mW which is noticeably more
than the 100mW or less standby consumption of a "Pound"land 2.1A USB
charging wallwart I recently purchased for 2 quid.

Such USB wallwart chargers with sub 100mW standby consumption have been
available for a decade or so now, rendering the advice to switch off or
unplug such chargers when not actually in use, in order to reduce the
UK's energy demand, rather *more* pointless than it was at the turn of
the century.

[1] If such LED based indicator lamps are ever put into production (for
all I know, seeing as how this is such an obvious application, they may
well be available right now), the 'no-brainer' improvement to efficiency
would be to integrate a string of 4 or 5 such LED pairs to convert a
larger fraction of the mains voltage into light, allowing even lower lamp
current requirements such that a 5M ohm ballast resistor will both
simplify and reduce the manufacturing (and running) costs of such modern
day replacements for the humble neon indicator lamp.

--
Johnny B Good

On Mon, 31 Dec 2018 10:23:13 +0000, Harry Bloomfield wrote:

Harry Bloomfield expressed precisely :
An individual circuit per LED, it needs just a diode, 300v capacitor
and the LED. You can then connect them between test point and either of
neutral, or live - which ever way produces lit for active. I made it up
with 8x LED's. I posted full details of the circuit I used on here,
maybe a couple of years ago.

I built it up on a long strip of Veroboard, then mounted it in a two
gang surface socket box, with a two gang blanking plate, mounted next
to the heating joint box.

L ---- 220 -- 0.1 -- 4148 + LED (back to back) ---- N

That is a 220Ohm resistor, a 0.1uF 630v cap, then back to back a 1N4148
diode in parallel with a superbright 6mm LED.

I found the cap value by some trial and error, decrease its value if you
use with a lower current LED. 0.47uF blew my test LED after a couple of
days on test. With 0.1 they have so far survived 2 years running.

The 220Ohm is intended to limit the inrush current as the cap charges.
Almost any small diode with do for the 4148.

Using a 220 ohm surge limiting resistor, it's no wonder you managed to
blow your test LED! :-)

That's a worst case scenario of 2.49 amps spike current through an LED
probably rated for a maximum average current of 25mA with a possible non-
repetitive 1 microsecond surge rating as high as 1 amp. You should have
chosen a 1 to 10 K ohm surge limiting resistor to protect against such
extreme switch on surge transients.

When I wanted to modify a couple of two gang and a single gang 13A mains
sockets with LED indicator lamps for use on a dedicated 2KVA UPS
protected supply nine years ago, I did give the surge current limiting
resistor value some thought. I think I chose 10K (possibly just 1K - it
was almost a decade ago!) with 47nF caps and 1N4000 series diodes in anti-
parallel with 3mm red LEDs recovered from 70s vintage IT kit (no such
thing as "super bright" LEDs back then).

They're still going strong after nine years of continuous service. To be
fair, they haven't had to withstand many transient switching events in
all that time compared to other mains powered kit that gets switched on
and off on a daily basis. However, they must have gone through scores of
switching events just the same in all of that time so ample opportunity
to succumb to any miscalculation on my part wrt my choice of surge
limiting resistor value.

If I'd been prepared to accept blue LEDs for this job, I'd have probably
used just a 470K resistor sans capacitor (with a 1N4000 series diode
wired anti-parallel across the blue LED).

--
Johnny B Good

On Mon, 31 Dec 2018 02:51:21 -0800, tabbypurr wrote:

On Sunday, 30 December 2018 15:56:06 UTC, Davidm wrote:
On Sun, 30 Dec 2018 08:05:58 GMT, Harry Bloomfield

My LED's give more detail and I would expect them to last rather
longer than neons, which in time will dim.

How are you powering the LEDs from the 240v ac points you are
monitoring? An individual "circuit" for each LED or something cleverer?

How to design a suitable RC power supply.

First you size the C for the wanted i.
2mA would require 120kΩ, which at 50Hz is 0.0266μF. 0.022μF is the NPV.
Modern LEDs don't need more current for indicator use.

Then you size your R for the peak current under any circumstances. If we
allow 0.33A at a peak of 330v we need 1kΩ.

That's not under *any* circumstances otherwise you'd have used a peak
(worst possible case value) of 680v (2 times root 2 of the nominal rms
mains voltage) so, for a non-repetitive peak of 330mA, you should have
chosen a 2K2 resistor, ideally with a 600v rating but a pair of 1K1 200v
rated resistors in series would have sufficed in practice.

Next: capacitor ratings. A mains capacitor requires a 250v ac X2 rating.
400v caps were formerly used but fail too often on mains, and lack
safety features.

Now resistor ratings. 1kΩ at 2mA rms drops 2v rms & dissipates 4mW, so
power rating is no issue. A 400v rating is a minimum, and typical
through hole parts are rated to 200v, so 2x 470 ohm in series will do
the job.

Finally the diode that goes back to back across the LED. It must cope
with 0.33A peak and a few volts in reverse - not a demanding spec, but
germaniums & some small signal diodes are unsuitable.


The 1N4000 series of any PIV rating (50 through to 1000 volts iirc) are
*the* go to choice of diode for this job. Its rated average forward
current is an amp with a peak around 2 orders of magnitude greater for 1
microsecond non-repetitive transients (typical of all silicon rectifier
diodes).

An LED with four times the Vf is unlikely to have more than 1 1/2 orders
of magnitude peak to average ratio, plus in this case, we're not
discussing the sort of LEDs used in GLS typically rated for 350mA average
current. Indicator LED lamps are typically rated between 20 and 50 mA
average forward currents so you might see peak transient values somewhere
from 330 to 1000 mA - 330mA is a safe conservative choice but, imo, you
underestimated the *worst case* scenario by a factor of two. :-)

--
Johnny B Good