Johnny B Good laid this down on his screen :
Using a 220 ohm surge limiting resistor, it's no wonder you managed to
blow your test LED! :-)

No it didn't - during test the LED survived for a couple of days, since
I reduced the cap value to the ones I suggested, the entire set of
LED's have so far survived a couple of years in circuit with zero
failures.

I used so far as possible the components I had to hand, with only a
rough idea of the LED spec..

JoeJoe used his keyboard to write :
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.

I cannot remember what level sensing system they used, but as an
engineer, I would quite often come across similar automatic condensate
pumps in a/c systems, where the sensing systems would become choked
with dirt. The usual fix was to replace them with a peristaltic
condensate pump, which used a pair of temperature sensors, one in the
ambient air, the second one in the output of the a/c unit. As soon as
the cool sensor detected cool air from the a/c, the pump would be
triggered to run.

The point I am trying to make, is that I would ever just replace any
item, without examining the failed item to work out in what way it has
failed - even if that involves destroying the item and a thorough bench
test. It might be as simple a fix as cleaning out the collection tray
and the sensors.

Andy Burns has brought this to us :
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-

That is what I would expect - call for the boiler to run, will be via
the pumps 'safety circuit', which confirms that the condensate pump is
not flooded and working normally.

Bridging that connection across the pump, should enable the boiler to
run when called.

After serious thinking JoeJoe 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...)

Under the floor is probably one of the worse places for bacterial slime
to occur and build up, could you not find somewhere more accessible for
it to be installed?

If you do have it replaced, ask for the old unit and bench test it
after cleaning it out - bet it works perfectly.

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?

Could it be they have wired the pump in such a way that it can inhibit
the boiler (by removing power) should it fail in some way? There is a
certain "fail safe" logic that would stop a potentially damaging
condensate related leak.




--
Cheers,

John.

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

On Mon, 31 Dec 2018 22:35:42 +0000, Harry Bloomfield wrote:

Johnny B Good laid this down on his screen :
Using a 220 ohm surge limiting resistor, it's no wonder you managed to
blow your test LED! :-)

No it didn't - during test the LED survived for a couple of days, since
I reduced the cap value to the ones I suggested, the entire set of LED's
have so far survived a couple of years in circuit with zero failures.

I used so far as possible the components I had to hand, with only a
rough idea of the LED spec..

To be fair, I was only guessing that LEDs would have a lower average to
peak ratio current handling spec based on the larger forward volt drop
compared to an ordinary silicon rectifier diode. I may have under-
estimated their peak current handling abilities using 'faulty logic' -
I've never checked LED data sheets like I've checked out rectifier diode
data sheets.

It's good that you at least considered the potential risk of switch on
transients and added a surge limiting resistor even though, to my mind,
220 ohms seems a little on the low side to guarantee safe operation in a
worst case scenario. However, given a low enough C value, the virtue of
220 ohms versus 10K (or even 2K2) ohms is that it makes the switch on
transient mercifully brief.

With the use of "Super Bright" LEDs and a starting point of 470nF, I'd
have thought the motivation to try a 100nF cap would have been to reduce
the blinding glare rather than to stop them burning out. :-) Indeed, if
you'd decided to use those new funky blue LEDs, you'd have landed up
using 4.7nF caps for the same reason.

BTW, where I'd misremembered fitting a single gang "Protected Supply"
socket, it turns out that all three sockets I'd modified with indicator
LEDs were dual gang. Only one is now still in use in my office come
workshop. The other two are no longer serving IT kit so that gave me a
chance to check them out to verify the C and R values I'd actually used
in my LED indicator lamp circuit.

I've only been able to look at one of the two unused sockets so far and
the values used here (100nF and 2K2 ohms) aren't quite as I remembered
them but this socket may not be typical of the other two which may well
be using 47nF caps instead.

Even the surge limiting resistors might well prove to be different as
well - all three socket mods would have effectively been 'prototypes' so
no guarantee of 'consistency' (at least as far as the C values used). The
R values would probably have all been 2K2 but even here there may have
been some experimentation so 10K is still a possible maximum value.

Without undoing the other two sockets to examine the indicator lamp
components actually fitted, I can only speak for the one I've examined so
far and I'm not going to assume that I used the exact same component
values in all three cases (other than for the actual 1970s vintage 3mm
red LEDs themselves).

--
Johnny B Good