Baxi Solo 3 PFL 50 S-plan pump runs forever! (overruns)

[Das]

Hi, i have an s-plan central heating system in my house, pump seems to run on indefinitely after water has been heated, only solution is to turn off power to the whole system. Have done some fault finding and think the problem lies with the boiler pcb (baxi solo 3 pfl 50). Is this the likely culprit?

 

[steptoe]

dunno,

you need to tell us how the clock/programmer/stat/boiler is wired,

S plan doesnt mean anything really, dozens of different ways of actually wiring it, if it is even wired correctly that is.

 

[sellers]

2 questions,

is this pump connected into a main wiring centre and is not supposed to over-run?

or

is it connected into the boiler and is supposed to over-run?

 

[PC Electrics]

Could be the switch in the valve(s) wired wrong.

There are a list of possible causes as long as two arms!

In all seriousness - get an electrician who knows heating plans (ask before you engage him). If you buy a PCB but don't actually need one it will cost you more than getting an electrician in probably.

Post up your area and we can see if anyone here is near you.

 

[Doc Hudson]

Hi, i have an s-plan central heating system in my house, pump seems to run on indefinitely after water has been heated, only solution is to turn off power to the whole system. Have done some fault finding and think the problem lies with the boiler pcb (baxi solo 3 pfl 50). Is this the likely culprit?

Welcome to the forum Das, without knowing what fault finding you have done and the results you got it is impossible to say what is the likely culprit. It is possible that the board you suggest could be a cause, but as suggested there are others. How have you proved the other items are working correctly?

Doc H.

(I shall move this thread to our heating section, I am sure you will understand why.)

 

[Das]

Ok mate, supply to time controller and boiler via switch fuse, cyl stat wired from controller, valve controlled by cyl stat, valve limit switch wired to switch live on boiler pcb, pump wired to 'pump L' on pcb.

 

[steptoe]

thanks Das,

but we need to know what actual 'wire' on what goes to what terminal on what other device, not just a general schematic.

sorry, but this really isnt a DIY fix, it does require a bit of knowledge,

a lot of electricians/plumbers/gasmen dont even understand how these systems work and simply follow diagrams, this is where/when problems occur.

it really doesnt matter if someone calls it S plan, Y plan, or something altogether different, it still needs connected up and wired to a set pattern of switching,.

 

[Das]

Thanks for your suggestion, to fault find set hot water to 'on' on controller, turned cylinder stat up til it changed state and noted the valve opened, measured voltage across valve limit switch to prove it had activated, boiler and pump both kicked in, turned stat back down and noted valve close and limit switch change state. Boiler turned off, pump still running, I'm aware pump should have run on time but this thing will run all night unless power turned off.

---------- Post Auto-Merged at 20:52 ---------- Previous post was made at 20:40 ----------

I appreciate that steptoe sorry to mess u about, am on the verge of calling Plummer anyway, just having quick look myself.

 

[Lannielectrical]

If the 3 port valve is faulty thus will cause a possible fault

 

[Doc Hudson]

Thanks for your suggestion, to fault find set hot water to 'on' on controller, turned cylinder stat up til it changed state and noted the valve opened, measured voltage across valve limit switch to prove it had activated, boiler and pump both kicked in, turned stat back down and noted valve close and limit switch change state. Boiler turned off, pump still running, I'm aware pump should have run on time but this thing will run all night unless power turned off.---------- Post Auto-Merged at 20:52 ---------- Previous post was made at 20:40 ----------

I appreciate that steptoe sorry to mess u about, am on the verge of calling Plummer anyway, just having quick look myself.

A lot of plumbers haven't got a clue about the electrical control wiring for a heating system. they often use a regular spark to do their heating wiring. Also as new central heating control wires are notifiable under part P, some plumbers have moved away from the wiring side all together.

Doc H.

 

[batty]

As the quack says sparks are a better bet than plumbers most plumbers don't even have a test meter they will use a neon screwdriver for testing.

 

[sellers]

This is a problem with the internals of the boiler, if you know what your doing and know the inner parts of the boiler you can ring up technical and over the phone they will go through what voltages you should expect on certain terminals, and what resistances you should find on certain valves and sensors, they will then diagnose the problem over the phone but will not be liable if it is a mis-diagnosis.

 

[rainydays]

Hi Das, have you always had this issue or has it just recently started happening?

 

[Barx]

If the 3 port valve is faulty thus will cause a possible fault

If the 3 port valve is faulty then its not a s-plan. Lol

But yes 1 of the 2 port valves could be faulty.

Sent from my Desire Z

 

[sellers]

If one of the valves were faulty the boiler would be on constantly too!

When it does this again, test inside the boiler at its switched live, if the switched live is dead then your valves have operated correctly. As when opening the micro switch gives the boiler 240v to fire up and when closing it switches it off.

 

[sparkytim]

If pump is wired FROM boiler it has Pump overrun control most likely. This means a Thermostat in the boiler keeps the pump running when the boiler turns off, so either your boiler is taking a long time to cool down or maybe the internal thermostat is faulty.

 

[kme]

No need for that mate.

The boiler PCB feeds the pump directly; if the wiring was wrong then the boiler itself would not work correctly. The circuitry controlling the over-run appears to have developed a fault; PCB replacement or internal wiring error are the only possible options, as far as I can see; having just read the boiler manufacturers fault-find & schematic.

HTH

KME

 

[a1]

As already asked...

... Are you sure it is wired correctly? Are you also sure that the pump did stop at an earlier date?

And as suggested, it could be for several reasons why this is happening.

But from research, it sounds like a very common fault with the PCB in the Baxi Solo 2 and Baxi Solo 3. The switched live has become a perminent live through a fault in the PCB.

I am not saying that this has happened to yours, but again, as suggested, you should call out an electrician. What area are you and we can see if there is an electrician on here that is local to you.

Apparently, the PCB are in the region of

 

[gordy71]

Baxi solos do not require a pump live even though there is a terminal for it. Like Sellers said it sounds like an internal problem with the boiler as the pump is not on to begin with. Just isolate the pump live in the boiler cable and put the pump live in with the orange wires on the valves.

 

[sellers]

Got to be careful, the over run is for a reason! I cannot remember why off the top of my head, but i recently wired 2 dommestic boilers combined for a commercial application. The existing pump was 300w where as the pump outputs were 150w max from the boiler, so had to put it through a contactor.