Baxi Solo control problem
 

I could do with some help re a Baxi Solo 50pf. Some mornings we are
getting up to a cool house :( The boiler has come on the time clock
an obviously run for a while but then stopped working: The "boiler
on" light is on and the pump running but nothing more. It almost seems
as if it is in "cool down" before going off. Various options to get
it going again: Turn off the power to the boiler and then back on -
reset the overheat and off it goes. Or turn down the room stat till
it clicks off and the change over valve operates sometimes restarts it
as does turning down the boiler stat potentiometer until off; pause;
back on.

Also secondary simptoms: sometimes when cycling correctly, on the
boiler stat, the boiler fires up and immediately shuts off, fires up
again,off, fires up and runs.

From my own electrical/electronic experience over many years I suspect
a pcb problem, a relay or poor contact somewhere but would welcome
others thoughts.

Pete

In an earlier contribution to this discussion,
Peter Dron wrote:

I could do with some help re a Baxi Solo 50pf. Some mornings we are
getting up to a cool house :( The boiler has come on the time clock
an obviously run for a while but then stopped working: The "boiler
on" light is on and the pump running but nothing more. It almost seems
as if it is in "cool down" before going off. Various options to get
it going again: Turn off the power to the boiler and then back on -
reset the overheat and off it goes. Or turn down the room stat till
it clicks off and the change over valve operates sometimes restarts it
as does turning down the boiler stat potentiometer until off; pause;
back on.

Also secondary simptoms: sometimes when cycling correctly, on the
boiler stat, the boiler fires up and immediately shuts off, fires up
again,off, fires up and runs.

From my own electrical/electronic experience over many years I suspect
a pcb problem, a relay or poor contact somewhere but would welcome
others thoughts.

Pete

What vintage of Solo is it? - there's a Solo (effectively Mk1 but not called
that) and subsequently a Solo 2 and Solo 3. They're all different in their
PCBs etc. - so it's important to identify the correct model.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

"Peter Dron" wrote in message
om...
I could do with some help re a Baxi Solo 50pf. Some mornings we are
getting up to a cool house :( The boiler has come on the time clock
an obviously run for a while but then stopped working: The "boiler
on" light is on and the pump running but nothing more. It almost seems
as if it is in "cool down" before going off. Various options to get
it going again: Turn off the power to the boiler and then back on -
reset the overheat and off it goes. Or turn down the room stat till
it clicks off and the change over valve operates sometimes restarts it
as does turning down the boiler stat potentiometer until off; pause;
back on.

Also secondary simptoms: sometimes when cycling correctly, on the
boiler stat, the boiler fires up and immediately shuts off, fires up
again,off, fires up and runs.

From my own electrical/electronic experience over many years I suspect
a pcb problem, a relay or poor contact somewhere but would welcome
others thoughts.

Pete

Pete,

What Solo is it? And have you run through the Installation and servicing
guide, especially the faults section at the back? If you haven't got a copy
download one from baxi.com. One thing to look at if its a Solo 3 are the
small flexible sensing tubes to the pressure switch. They have a tendency to
collapse and this can cause cycling. They usually flatten near the pressure
switch so a quick repair is to cut off the last 5 - 10 mm and refit.

Andy

I would be looking at the sensors first and pcb last. Most sensors cost £10 or so. If you can get the data from BaxiPotterton you can prove them. They are thermisters which vary in resistance depending on heat. Heat yours in a pan with water and a thermometer and prove it follows the chart. I have the resistance data for just a few but not your Solo. A lynx for instance ranges from 0 deg c 33.6kohm through 50 deg 3k5 to 99 deg c 716 ohm. Make your own graph. The Myson Midas otoh ranges 64k at 10 deg through 10k at 50 deg to 3k at 80 deg. The Puma ranges from 7k (max temp) to 15k (minimum temp). So you see thermioster values are variable across boilers.

You could empirically test a boiler with a variable resistor and thermometer, see at which temperatures which resistance alters the modureg. Then test your Thermister from that data. With a combi most manufacturers use the same thermister for heating and hot water, so you just switch leads to prove that fault (don't forget to switch back or you'll have hot water and heating that doesn't modulate). A friend of mine did leave one in a house with the leads switched for a year until he next serviced it when he found his mistake. Householder hadn't noticed anything wrong.

Always prove all the little things are working right before you start to blame the pcb.

I should add that it is symptomatic of thermister trouble. Another big cause of thermister trouble is sludge and scale . When the thermister is wet you can clean it directly, but some are in a dry pocket or surface mounted to a pipe. In these case the boiler can need descaling before it modulates properly again. Keep your system clean if you want your boiler to last.!

In message , Peter Dron
writes
I could do with some help re a Baxi Solo 50pf. Some mornings we are
getting up to a cool house :( The boiler has come on the time clock
an obviously run for a while but then stopped working: The "boiler
on" light is on and the pump running but nothing more. It almost seems
as if it is in "cool down" before going off. Various options to get
it going again: Turn off the power to the boiler and then back on -
reset the overheat and off it goes. Or turn down the room stat till
it clicks off and the change over valve operates sometimes restarts it
as does turning down the boiler stat potentiometer until off; pause;
back on.

Is it a Solo mk 1 or a Solo 2 (or 3)?

They're completely different animals

--
geoff

In message , Set Square
writes
In an earlier contribution to this discussion,
Peter Dron wrote:

I could do with some help re a Baxi Solo 50pf. Some mornings we are
getting up to a cool house :( The boiler has come on the time clock
an obviously run for a while but then stopped working: The "boiler
on" light is on and the pump running but nothing more. It almost seems
as if it is in "cool down" before going off. Various options to get
it going again: Turn off the power to the boiler and then back on -
reset the overheat and off it goes. Or turn down the room stat till
it clicks off and the change over valve operates sometimes restarts it
as does turning down the boiler stat potentiometer until off; pause;
back on.

Also secondary simptoms: sometimes when cycling correctly, on the
boiler stat, the boiler fires up and immediately shuts off, fires up
again,off, fires up and runs.

From my own electrical/electronic experience over many years I suspect
a pcb problem, a relay or poor contact somewhere but would welcome
others thoughts.

Pete

What vintage of Solo is it? - there's a Solo (effectively Mk1 but not called
that) and subsequently a Solo 2 and Solo 3. They're all different in their
PCBs etc. - so it's important to identify the correct model.

The Solo 2 and Solo 3 pcbs are the same and interchangeable

The Mk 1 pcb however is completely different

--
geoff

On Sat, 22 Jan 2005 02:43:49 -0800, Peter Dron wrote:

I could do with some help re a Baxi Solo 50pf. Some mornings we are
getting up to a cool house :( The boiler has come on the time clock
an obviously run for a while but then stopped working: The "boiler
on" light is on and the pump running but nothing more. It almost seems
as if it is in "cool down" before going off. Various options to get
it going again: Turn off the power to the boiler and then back on -
reset the overheat and off it goes. Or turn down the room stat till
it clicks off and the change over valve operates sometimes restarts it
as does turning down the boiler stat potentiometer until off; pause;
back on.

Also secondary simptoms: sometimes when cycling correctly, on the
boiler stat, the boiler fires up and immediately shuts off, fires up
again,off, fires up and runs.

From my own electrical/electronic experience over many years I suspect
a pcb problem, a relay or poor contact somewhere but would welcome
others thoughts.

These would typically be the symptoms of a failure of flame failure
sensing.

Either the gas is not really being lit and then the PCB doing its stuff
just fine, or the gas is lit but the flame sense probe and/or pcb is not
seeing the flames.

Check the ignition and flame sense wiring and electrode positions first
the pcb last.



--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

In message , Paul Barker
writes

I would be looking at the sensors first and pcb last.

.... ...


Always prove all the little things are working right before you start
to blame the pcb.


A qualified "well said, that man" to that

However, in certain cases, it's MUCH more likely to be the pcb

I include the Solo 2 in this but not the Solo mk 1

I'd also like to point out that I've come across a couple of cases
recently where people have bought new temp sensors which were faulty -
blaming my repaired pcb for the problem as "it can't be the sensor as
I've replaced it"

--
geoff

In message .uk, Ed
Sirett writes
On Sat, 22 Jan 2005 02:43:49 -0800, Peter Dron wrote:

I could do with some help re a Baxi Solo 50pf. Some mornings we are
getting up to a cool house :( The boiler has come on the time clock
an obviously run for a while but then stopped working: The "boiler
on" light is on and the pump running but nothing more. It almost seems
as if it is in "cool down" before going off. Various options to get
it going again: Turn off the power to the boiler and then back on -
reset the overheat and off it goes. Or turn down the room stat till
it clicks off and the change over valve operates sometimes restarts it
as does turning down the boiler stat potentiometer until off; pause;
back on.

Also secondary simptoms: sometimes when cycling correctly, on the
boiler stat, the boiler fires up and immediately shuts off, fires up
again,off, fires up and runs.

From my own electrical/electronic experience over many years I suspect
a pcb problem, a relay or poor contact somewhere but would welcome
others thoughts.

These would typically be the symptoms of a failure of flame failure
sensing.

Either the gas is not really being lit and then the PCB doing its stuff
just fine, or the gas is lit but the flame sense probe and/or pcb is not
seeing the flames.

Check the ignition and flame sense wiring and electrode positions first
the pcb last.

By which he means (in layman's terms)

Check that the HT lead is intact and has not broken, especially at one
of the connectors (the insulation is also crimped, so it's not always
obvious that it's broken

Check that the electrode is actually in the pilot flame and has not
corroded and burned away

lastly, I would add, ensure that the earthing is good - no resistance
(less than an ohm) from the electrode earth to the pcb and the main
earth
--
geoff

On Sun, 23 Jan 2005 00:02:07 +0000, raden wrote:

In message .uk, Ed
Sirett writes
On Sat, 22 Jan 2005 02:43:49 -0800, Peter Dron wrote:

I could do with some help re a Baxi Solo 50pf. Some mornings we are
getting up to a cool house :( The boiler has come on the time clock
an obviously run for a while but then stopped working: The "boiler
on" light is on and the pump running but nothing more. It almost seems
as if it is in "cool down" before going off. Various options to get
it going again: Turn off the power to the boiler and then back on -
reset the overheat and off it goes. Or turn down the room stat till
it clicks off and the change over valve operates sometimes restarts it
as does turning down the boiler stat potentiometer until off; pause;
back on.

Also secondary simptoms: sometimes when cycling correctly, on the
boiler stat, the boiler fires up and immediately shuts off, fires up
again,off, fires up and runs.

From my own electrical/electronic experience over many years I suspect
a pcb problem, a relay or poor contact somewhere but would welcome
others thoughts.

These would typically be the symptoms of a failure of flame failure
sensing.

Either the gas is not really being lit and then the PCB doing its stuff
just fine, or the gas is lit but the flame sense probe and/or pcb is not
seeing the flames.

Check the ignition and flame sense wiring and electrode positions first
the pcb last.

By which he means (in layman's terms)

Check that the HT lead is intact and has not broken, especially at one
of the connectors (the insulation is also crimped, so it's not always
obvious that it's broken

Check that the electrode is actually in the pilot flame and has not
corroded and burned away

lastly, I would add, ensure that the earthing is good - no resistance
(less than an ohm) from the electrode earth to the pcb and the main
earth

There is no cremated bumblebee sitting on the flame sense electrode.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

In message .uk, Ed
Sirett writes

By which he means (in layman's terms)

Check that the HT lead is intact and has not broken, especially at one
of the connectors (the insulation is also crimped, so it's not always
obvious that it's broken

Check that the electrode is actually in the pilot flame and has not
corroded and burned away

lastly, I would add, ensure that the earthing is good - no resistance
(less than an ohm) from the electrode earth to the pcb and the main
earth

There is no cremated bumblebee sitting on the flame sense electrode.

I knew there was something I'd forgotten

--
geoff

Good point Geaff, this is why we have to prove thermisters by geting the test data and proving it functions correctly.

I recently changed a Worcester 240 pcb for a customer because the relay was frequently making and breaking. Discussions with Worcester confirmed my choice of part. Now they've phoned me to say it's doing it again. Perhaps it was the thermister? I've bought one to take round. If I was wrong about the pcb I'll refund them in full and fit the correct part. I've also taken the precaution of purchasing for £2.50 a suitable relay from RS in case it's the relay. I hadn't learned from my own lesson. Relay clattering like mad, must be the relay, customer wants it fixed same day, can't get a relay in time round to hrpc for a pcb.

One bug bear, suppliers won't take pcb's back, so now that's another pcb in my stock.

Have you any take on this particular problem?

I had already checked that the thermistor resistance alters with temp
on this Solo 2. It certainly does that but I don't know what the range
should be. It seemed to give a sensible range over a few test with
nothing to indicate any reason for this intermitent fault

Pete

Just noticed my post yesterday to say it was a Solo 2 got lost in the
either!

In message , Paul Barker
writes

Good point Geaff, this is why we have to prove thermisters by geting
the test data and proving it functions correctly.

I recently changed a Worcester 240 pcb for a customer because the relay
was frequently making and breaking. Discussions with Worcester
confirmed
my choice of part. Now they've phoned me to say it's doing it again.
Perhaps it was the thermister? I've bought one to take round. If I was
wrong about the pcb I'll refund them in full and fit the correct part.
I've also taken the precaution of purchasing for £2.50 a suitable relay
from RS in case it's the relay. I hadn't learned from my own lesson.
Relay clattering like mad, must be the relay, customer wants it fixed
same day, can't get a relay in time round to hrpc for a pcb.

One bug bear, suppliers won't take pcb's back, so now that's another
pcb in my stock.

Have you any take on this particular problem?


Yes - relays don't normally chatter because they're faulty, they chatter
because there's a fault in what's driving them




--
geoff

In message , raden
writes
In message , Paul Barker
writes

Good point Geaff, this is why we have to prove thermisters by geting
the test data and proving it functions correctly.

I recently changed a Worcester 240 pcb for a customer because the relay
was frequently making and breaking. Discussions with Worcester
confirmed
my choice of part. Now they've phoned me to say it's doing it again.
Perhaps it was the thermister? I've bought one to take round. If I was
wrong about the pcb I'll refund them in full and fit the correct part.
I've also taken the precaution of purchasing for £2.50 a suitable relay
from RS in case it's the relay. I hadn't learned from my own lesson.
Relay clattering like mad, must be the relay, customer wants it fixed
same day, can't get a relay in time round to hrpc for a pcb.

One bug bear, suppliers won't take pcb's back, so now that's another
pcb in my stock.

Have you any take on this particular problem?


Yes - relays don't normally chatter because they're faulty, they
chatter because there's a fault in what's driving them

Also ... look at my website www.cetltd.com

--
geoff

Thanks for all the comments, although I'm not sure I'm much further
forward.
A few points relating to the comments. I started by cleaning out the
insides getting rid of the incinerated bugs etc. There no sign of an
electronic flame failure device or any sensor listed for the Solo2. I
had already tested the thermistor by immersion in hot water and got a
range of values that seemed reasonable (but I don't have any data on
the correct values). I orginally suspected the thermistor from the
fault finding chart. I must say I am still a bit suspicious of this
part of the circuit.
As far I can tell there is no obvious relay chatter - nothing audible
anyway. The ignition fires fine when called on to do so - the problem
is that it isn't being called on (i.e. the pilot warning lamp is off)
Now the weather has turned colder there is some evidence of the the
boiler going out/switching off soon after firing up i.e. very short
cycling times. From the outset it has seemed that the problem was
usually seen when the boiler had had to work hard - on stating in the
morning, etc.

Pete

In message .com,
sixVolt writes
Thanks for all the comments, although I'm not sure I'm much further
forward.
A few points relating to the comments. I started by cleaning out the
insides getting rid of the incinerated bugs etc. There no sign of an
electronic flame failure device or any sensor listed for the Solo2.

It's the spark electrode, the same lead which conducts the spark to the
electrode is used for sensing the flame

I
had already tested the thermistor by immersion in hot water and got a
range of values that seemed reasonable (but I don't have any data on
the correct values). I orginally suspected the thermistor from the
fault finding chart. I must say I am still a bit suspicious of this
part of the circuit.
As far I can tell there is no obvious relay chatter - nothing audible
anyway. The ignition fires fine when called on to do so - the problem
is that it isn't being called on (i.e. the pilot warning lamp is off)

So, is the pcb generating a spark ?

Now the weather has turned colder there is some evidence of the the
boiler going out/switching off soon after firing up i.e. very short
cycling times. From the outset it has seemed that the problem was
usually seen when the boiler had had to work hard - on stating in the
morning, etc.

If there's no spark, given that the temp sensor is OK, then it is either
the pcb, the pressure switch or the fan bearings

to test 2, you need to test the resistance of the microswitch on the APS
in each position. You need to test between common and normally closed,
then, removing one of the tubes on the APS blow or suck GENTLY to change
to the normally open contacts (to common) and test again. You should
find the connections in your manual

if 1 or 3, look at my site - www.cetltd.com


--
geoff

Thanks Geoff

I had already checked the ignition lead to make sure it wasn't loose

If the fan runs, then it sparks - as it should. However when its not
working, the fan (and indicator light) is off too.

I will test the pressure switch as you suggest. I can sort out the
connections

You supplied me with a fan when the bearings did go! (A year or so
ago) But anyway the fan is not being switched on.

Pete