Baxi Solo 2 40 PF Luke Warm Water

[DaveAustin]

Hi Guys,

Firstly apologies, someone else calling on all your years of experience for free. I understand that this is a crime punishable by death on a lot of forums.

I have a Baxi Solo 2 40 PF - 13 years old.

The HW is luke warm, and so are the rads.

The boiler has been recently serviced, and fitted with a new stat and pump.

Everything was running fine until last week.

Hall thermostat calls for heat but the boiler only comes on for ten minutes or so then knocks off, then comes on a bit later, then off, and so on.

The potentiometer is currently set at half way and this makes no difference even when turned on full.


Your thoughts are appreciated, her indoors has ditched the Ann Summers gear in favour of fleeces and jogging pants.

 

[DaveAustin]

Forgot to mention, the fan appears to be working.

 

[Agile]

It sounds as if the pump is not working or the system is sludged up.

Set pump speed to "2" and make sure both pump valves are fully open.

Tony

 

[expertgasman]

It sounds as if the pump is not working or the system is sludged up.

Set pump speed to "2" and make sure both pump valves are fully open.

Tony

Why would valves be closed?

Could be faulty potentiometer, gas valve, motorised valve. Much more info needed.

 

[Agile]

Hi Guys,

The boiler has been recently serviced, and fitted with a new stat and pump.

Sometimes those fitting new pumps forget to fully open the valves.

Thye can work for a few days and then get blocked by circulating dirt!

 

[DaveAustin]

Thanks for the speedy replies.

Pump is definitely running, valves either side are fully open. I replaced them recently with gate valves.

Will turn the pump down to two and see how I get on. Will also test the potentiometer and report back.

I have removed actuator from 3 port valve and tried it in various positions manually, this didn't make any difference (pipes leading to the 3 port still Lukewarm). Valve operated by hand quite easily and I could audibly hear the "flow diversion".

 

[expertgasman]

We are getting dangerously close to "gas advice", which is not allowed, but it is neccesary to ascertain which control or device is closing down. As an RGI, I would be testing the gas valve to ensure that there is no voltage at the valve when the boiler closes down after the stated ten minutes. Also , you "think" the fan is running. If the fan is sticking when it gets warm, closedown will occur.

 

[namsag]

Could be the gas valve solenoid breaking down under use.
When the boiler shuts down when it should be on check the solenoid for 240v if its there then that is your problem if its not follow it back
Do you have 240v leaving the motorised valve some of these have a small circuit board in them which fail when hot

 

[expertgasman]

Could be the gas valve solenoid breaking down under use.
When the boiler shuts down when it should be on check the solenoid for 240v if its there then that is your problem if its not follow it back
Do you have 240v leaving the motorised valve some of these have a small circuit board in them which fail when hot

My point entirely.

 

[Foobix]

I had Solo 2 a few months back with the same symptoms which was a faulty air pressure switch.
The switch was making on initial fire up,then run for 5 minutes then would drop off.If the fan continues to run during the on/off cycle then this could be the same problem?But then again,it could be one of the solenoids on the gas valve as already mentioned.

 

[DaveAustin]

It sounds as if the pump is not working or the system is sludged up.

Set pump speed to "2" and make sure both pump valves are fully open.

Tony

Cheers Tony, turned the pump on setting 2 this morning to no avail. Sludge is still a contender but last Summer I drained and refilled at least 3 times and had clear running water - perhaps it has settled in the heat exchanger?

Sometimes those fitting new pumps forget to fully open the valves.

Thye can work for a few days and then get blocked by circulating dirt!

Righty "Tighty" Lefty "Loosey"? Yep, they are open.

We are getting dangerously close to "gas advice", which is not allowed, but it is neccesary to ascertain which control or device is closing down. As an RGI, I would be testing the gas valve to ensure that there is no voltage at the valve when the boiler closes down after the stated ten minutes. Also , you "think" the fan is running. If the fan is sticking when it gets warm, closedown will occur.

I agree entirely and an RGI will be performing the work. As a valve engineer, I appreciate when its time to call in an expert and I'm not afraid to do so!.
However, I would like to reduce the time the RGI has to spend checking (if I can).

Could be the gas valve solenoid breaking down under use.
When the boiler shuts down when it should be on check the solenoid for 240v if its there then that is your problem if its not follow it back
Do you have 240v leaving the motorised valve some of these have a small circuit board in them which fail when hot

The control valve has two live feeds, both are live when the boiler is running. When its shut down prematurely, the one on the left remains live, then one on the right shows zero volts.

I had Solo 2 a few months back with the same symptoms which was a faulty air pressure switch.
The switch was making on initial fire up,then run for 5 minutes then would drop off.If the fan continues to run during the on/off cycle then this could be the same problem?But then again,it could be one of the solenoids on the gas valve as already mentioned.

Thanks Foobix, the fan does continue to run. How can I can check the pressure switch or is this time to call in the man who can?

One thing I have just noticed is that the spark is visible through the combustion chamber window when the boiler cuts off....

 

[Foobix]

If the spark continues during shut down then it must be the pilot solenoid on the gas valve.

 

[DaveAustin]

If the spark continues during shut down then it must be the pilot solenoid on the gas valve.

EDIT: Removed all my crap about the pressure switch.

That sounds logical. Any one else concur?

Cheers Foobix.

 

[poolebybirth]

what a load of rubbish

sounds like either a) system sludged up/needs a clean b) pump is on way out or possibly pump valves furred up or c) gas pressures/gas rate incorrect (RGI jobs)

if fan is at fault - test resistance of coil and free running of fan (gently)

motorised valves - can stick

gas valves if borken usually won't work at all (high resistance of coil/infinity)


if you suspect a faulty pilot solenoid check the resistance of the coil...

 

[DaveAustin]

System been flushed (Not power flushed) but resultant water is very clear. Tank in loft is also clear.

Not sure about the fan, but it does continue to run even when the main burner knocks off.

Pump is new, so are the valves.

I have removed the actuator from the 3 port and manually moved the valve, which it does easily. This had no effect.

So, in summary. Boiler runs, after a few minutes the PCB shuts of power to the main gas solenoid, whilst the pilot solenoid still has power but no flame, just a healthy continuous spark.
Its like this for ten minutes, then it fires back up again.

As poolebybirth suggests I would have expected total failure of a solenoid, rather than intermittent.

RGI time?