Electrics on a central heating system

[EFLImpudence]

Its an old permanent pilot/thermocouple Baxi solo probably about 15-20 years old. There is a small PCB about the size of a playing card with one connection to it that sends power to the pump. Im assuming as there is no cylinder stat that the boiler stat controls the water temperature.

That's not the problem is it?

You, and we if you want any help, need to know where there is voltage and where there is not voltage where there should be.

 

[matt1e]

have you tested the pump?
as its more than likely that the pcb you describe is an overrun timer, which presumably was somehow damaged since you decided to replace it
are you sure this is a baxi solo BTW....... the GC number would be useful
if there is no cylinder stat then the hot water will overheat ... you really should know this and for the price of a stat you should be fitting one, the system will never work correctly without one
does the valve motor over with hotwater off and central heating on selected at the programmer?
do you have a multimeter?
some photos of the valve and connections would be useful

Matt

 

[ericmark]

I do seem to remember a Y plan with supply to pump from boiler something like this.

I seem to remember it was to allow the boiler to cool before the pump turned off and of course it also has to hold open the motorised valve while it cools.

I will admit I had a lot of problems with my daughters Y plan as the diagram shows one micro switch but in fact there are around three micro switches inside the motorised valve so trying to test gets results which reading the diagram seem impossible.

In the end I replace the whole valve as I could not find a supplier for the micro switches on the Sunday I was doing the job. Lucky Screwfix was open. She also at another time had problems with the PCB and my son replaced that for her.

To my understanding the thermostat does not control the boiler but it controls the motorised valve which once open then in turn works the boiler.

She has now moved house so I know no one with a Y plan any more. And am glad of that. However there is no connection to lights and no fault with a boiler should effect any lights.

What I have seen is people using three core cable to the cylinder thermostat and using the earth marked core for a non earth connection. This could result in a fault if the thermostat was changed from a double insulated to one requiring an earth and the miss marked cable was earthed.

The diagram shown is not mine can't remember where I got it from so can't really answer too many questions but it does show the pump connected separate to main boiler supply.

 

[Eyebrowes80]

have you tested the pump?
as its more than likely that the pcb you describe is an overrun timer, which presumably was somehow damaged since you decided to replace it
are you sure this is a baxi solo BTW....... the GC number would be useful
if there is no cylinder stat then the hot water will overheat ... you really should know this and for the price of a stat you should be fitting one, the system will never work correctly without one
does the valve motor over with hotwater off and central heating on selected at the programmer?
do you have a multimeter?
some photos of the valve and connections would be useful

Matt

Matt give me some credit please its a baxi solo GC number 47-077-78. I havent damaged any board as it was dead before I replaced it. The original fault was no hot water as the valve was stuck in heating. The boiler was kettling and the pump was sticking so I decided to replace the pump. By the time I went back the whole thing had gone down. In all honesty they should take the thing out and put a combi in.

 

[matt1e]

Matt give me some credit please its a baxi solo GC number 47-077-78. I havent damaged any board as it was dead before I replaced it. The original fault was no hot water as the valve was stuck in heating. The boiler was kettling and the pump was sticking so I decided to replace the pump. By the time I went back the whole thing had gone down. In all honesty they should take the thing out and put a combi in.

Hi eyebrowes
the GC no you have given is not a baxi solo (typo?), I think you most likely have a Baxi solo 2 GC 41-477-78 please confirm

If so how the system is wired will depend on

whether it is gravity hot water/pumped central heating
fully pumped open vented
fully pumped sealed

first thing to do is look at the control box
is there a connection to the P/L terminal?
Is the pump connected directly to the boiler or elsewhere externally?

Matt

 

[bhm1712]

that is the problem here, its supposed to be a Y plan but it has no cylinder stat, we cant guess at how its wired we need to know for sure! I doubt very much its a Y plan as the cylinder stat is kinda central to the control of a Y plan.

Like i said before...check the output from the programmer to see if 240volt is coming from it!!!!!! presumably this system worked before the PCB went down and you replaced it. So maybe the programmer got screwed as well!!!

Like i asked before, is the MV wired EXACTLY the same as it was originally? what type of motorised valve is it? honeywell? part number please?