Pump does not stop running

[stepfaul]

Hi everyone,

This is my first time posting and as an amateur I hope you will excuse my non technical terms.

I have a Baxi solo 3 PFL controlled by a Drayton Lifestye LP112 with a HTS3 cylinder thermostat all pumped through by a Grundfoss pump.

We have our hot water heating set to constant controlled by the cylinder thermostat, every time I entered our bathroom I noticed that the boiler seemed to be fired up and heating and upon further investigation, I noticed that the cylinder thermostat had come away from the cylinder, NICE... This had been the case for a month or two and as I work for one of the large utility companies I braced myself for a large gas bill during that quarter.

I have since re-seated the cylinder thermostat but have noticed that the pump runs all the time, regardless of the timer settings and regardless of what temparature the cylinder thermostat is set too. The only way I can stop the pump is to isolate the mains.

I fear that because the whole system was running for 8 weeks or so I have melted something.

My initial thoughts where that the cylinder thermostat was faulty but after turning the HW and CH to off via the timer, I noticed the pump was still running and I mean all the time and not just the usual few minutes due to pump overun.


Any suggestions or help are very welcome.

Steve

 

[Agile]

You seem to have a better understanding of heating systems than some CORGI registered people I come across!

The pump over run is provided by the PCB IF the pump has been wired to the boiler as it should be.

If it used to be OK with the pump going off then it sounds as if the PCB has become faulty.

Bearing in mind though that you seem to have been oblivious of the boiler running all the time HW was selected for a month or two then are you quite sure that the pump was really shutting off before?

Tony

 

[stepfaul]

Thanks for your quick reply Agile,

Yeah, the system had been running OK for about 6 months, about a week after the install I had to call the guys who fitted it in again becuase they had not wired up the pump correctly!

Basically the system had been running OK for about 6 months, the cylinder thermostat became dislodged from the cylinder, the thermostat was re-seated and I then noticed the pump problems.

Naively enouth, when I entered the bathroom and heard the boiler I thought that my timing was perfect and that the water had just dropped below a ceratin temparature and the boiler was firing up to heat the water again

Then I thought 'hold on old boy' every time I enter the bathrooom, the boiler is running. Something odd here.

A faulty pcb sounds expensive though

I am a computer engineer by trade, is there not a switch or a check box I can tick to resolve the issue?

 

[ollski]

S plan system (2 x 2 port valves) or y plan (1 x 3 port) ?

 

[stepfaul]

Hey ollski, getting technical now.

I have a 3 port 'mid postion valve' all that from memory ehh

 

[Agile]

It could just be the boiler stat setting is not compatible with the cylinder stat.

The cylinder should open at 55 C and the boiler should give a flow of 65 C.

Try setting the cylinder correctly and turn up the boiler if necessary.

Tony

 

[stepfaul]

Thanks Agile,

I did think something along the same lines as well. I have got the cylinder thermostat set to around 55-60 and the boiler set to almost max.

Any problems with running the boiler at max?

I will try keeping the boiler on max and setting the cylinder thermostat temp to around 50, waiting a little while and seeing what happens.

 

[stepfaul]

Oh well,

The pump is still running. I have now got my boiler set to max and the cylinder thermostat set to 50.

 

[stem]

I've got a solo 3 and I had this problem, I disconnected the switched live pump wire from terminal at the boiler and then connected a multimeter. The terminal was permanently live with CH and HW set to off. Infact it was live the instant the power was turned on without a live from the heating controls being present. A new PCB sorted it.

If your system used to work properly it would suggest that the wiring is correct. I understand that the PCB on the Solo 3 is notoriously unreliable. (Search the posts on this site and you will see) My boiler is 6 years old now and I'm on my 3rd PCB, but the other faults had nothing to do with the Pump. I keep a second hand PCB I bought from a website as spare now! (Solo 2 uses same PCB)

 

[stepfaul]

Thanks stem,

It is looking like a new pcb ££££££'s

Shafted by Mr C**p Product & Co again. The boiler is only a year and a half old.

 

[stepfaul]

Here we go, dodgy question time now

I am an average B&Q type DIY guy who is familiar with circuit boards and such from my job as a computer repairer. I have browsed sites where you can buy new pcb's. Is this something I can replace myself?

I do appreciate that some jobs require a specialist but am just interested in your opinions.

 

[Agile]

If you can replace computer pcbs then you should be able to deal with the Solo pcb as long as you take care to fully isolate the possibly different mains supplies.

Its a rather fiddly pcb to change but not a problem to an electronics expert.

Tony

 

[Elwood38]

The pump over run is provided by the PCB IF the pump has been wired to the boiler as it should be.

If it used to be OK with the pump going off then it sounds as if the PCB has become faulty.

I'm having the same problem with my CH pump in that it never stops running even when the programmer is switched off and the HW & CH thermostats are turned down to off.

When you refer to the PCB, I take it you mean Printed Circuit Board. Is this to be found inside the programmer? If this is the case then replacing the programmer is the same as replacing the PCB. Is this correct?

OR

Is the PCB to be found elsewhere in the system? Although I can't think where it might be.

I'd be grateful if you would clear this up for me, please.

 

[philgee]

On the pcb in the valve there should be a micro switch. Switch off the mains to the whole system, remove the cover to the valve, locate the switch and press it until you hear it click. Then replace the cover and power up again and see if the pump is now silent (provided that no heat is being called for). Just remember to shut down the power first due to live parts etc!

 

[geoff@cetltd]

Hi everyone,

This is my first time posting and as an amateur I hope you will excuse my non technical terms.

I have a Baxi solo 3 PFL controlled by a Drayton Lifestye LP112 with a HTS3 cylinder thermostat all pumped through by a Grundfoss pump.

pump not turning off is a fairly common problem on the bax solo 2 / 3 pcb