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[pscocoa]

Boiler has worked fine for 5 years but last 2 days boiler is running but no heating being delivered consistently - thought it may have been pump or room stat.

My wife called in a heating engineer different to the plumber installer who says that it is not wired correctly. Bascially pump is supposed to be wired in directly by running additional cable from airing cupboard to pump. This was never done but boiler as said has been working.

Proposal is to change pcb to see if that corrects problem. Has anyone come across the issues of the need for this extra pair of wires - is this likely to be part of the problem?

[Marks DTM Calib]

Pump should be powered from the boiler to support pump overrun (protects the boiler from flash boiling).

You say the boiler fires, do you get hot water, heating or both?

Is the pump running?

[henri]

  Thought Omegas were either petrol or diesel,must be an old model,serioously google in plumbing forums and you'll get loads of info on your problem

[TheBoy]

That particular boiler must be about one of the least reliable ones out there!

As MDTM says, that boiler (like virtually all modern boilers) controls the pump itself, and will run the pump for a while after the boiler has switched off.

The pump should be wired directly to the boiler's pump control.

[Marks DTM Calib]

The thing I struggle with is....although the PCB is knows to be about as reliable as an MP at election time, if the boiler is firing and the pump is running.....something should be getting hot....either water or heating

[pscocoa]

Pump should be powered from the boiler to support pump overrun (protects the boiler from flash boiling).

You say the boiler fires, do you get hot water, heating or both?

Is the pump running?

Boiler is firing no problem, heat is not circulating consistently so I presume if the pump was directly wired it would shut down the fans. If you switch boiler off and on everything starts to work - heating and hot water - for a time.

[pscocoa]

The thing I struggle with is....although the PCB is knows to be about as reliable as an MP at election time, if the boiler is firing and the pump is running.....something should be getting hot....either water or heating

Yes this is my dilemma - my first reaction was pump not working - fiddled with room stat and everything fired up and ran last night very well.

I suppose I will have to change pcb to rule that out but why has it run fine for 5 years? Has the lack of direct wiring to pump caused pcb to blow I wonder?

[pscocoa]

Thought Omegas were either petrol or diesel,must be an old model,serioously google in plumbing forums and you'll get loads of info on your problem

Henri - I did indeed investigate boiler/Potterton sources but nothing similar to this problem seems to be out there - loads of stuff on pcb failures which this may turn out to be - but the OOF sometimes brings solutions in this General Discussion area

[Marks DTM Calib]

The basic flow should be:

Timer demands heating

Stat says heat required

Valve opens (or moves position if a Y plan), switch in valve then calls for the boiler to fire

Boiler starts pump

Boiler fires


Key thing is that the boiler does not know if the pump is running. It will have an internal trip which kicks in if the water temp in the heat exchanger gets to high (on a Suprema I think the light flashes when this happens)

[pscocoa]

The basic flow should be:

Timer demands heating

Stat says heat required

Valve opens (or moves position if a Y plan), switch in valve then calls for the boiler to fire

Boiler starts pump

Boiler fires


Key thing is that the boiler does not know if the pump is running. It will have an internal trip which kicks in if the water temp in the heat exchanger gets to high (on a Suprema I think the light flashes when this happens)

So logically if pump not wired to boiler then if pump working spasmodically boiler will continue to fire until internal trip comes in. The light sequence is off,off, flashing which means "Burner Off".

Only other issue is why turning boiler off and on seems to get everything working. Will change pcb and report back but not convinced on this.

[Marks DTM Calib]

The basic flow should be:

Timer demands heating

Stat says heat required

Valve opens (or moves position if a Y plan), switch in valve then calls for the boiler to fire

Boiler starts pump

Boiler fires


Key thing is that the boiler does not know if the pump is running. It will have an internal trip which kicks in if the water temp in the heat exchanger gets to high (on a Suprema I think the light flashes when this happens)

So logically if pump not wired to boiler then if pump working spasmodically boiler will continue to fire until internal trip comes in. The light sequence is off,off, flashing which means "Burner Off".

Only other issue is why turning boiler off and on seems to get everything working. Will change pcb and report back but not convinced on this.

Correct, turning the boiler off will reset the trip on these micro controlled units (cant recall if pressing the reset button on them does the same). 

PCB is F-expensive on these by the way.....so be ABSOLUTELY sure before doing it!

[PhilRich]

If it locks out in the morning it may be the spark electrode that gets damp overnight if it has a hairline crack in it, it will usually recover once it has some voltage put through it, hence it lighting on the second attempt, and sometimes the gas control valve sticks. If it is overheating then I would usually check the system and bypass first, and I would replace the overheat and boiler stat sensors before shelling out for a costly pcb.  :-/



edit: Do a e-bay search for Potterton Suprema PCB, there are a plethera of new & recon pcb's with guarantees for far less than the usual cost 

I have no knowledge or affilliation with these people but
these guys have a good reputation & are apparently very helpfull to talk to. This link is NOT for your particular PCB but gives you all the info to get in touch with them & how they operate. I hope it helps 

http://cgi.ebay.co.uk/Ideal-Isar-Icos-Istor-173534-PCB-Exchange-Service-/200544221826?pt=UK_Home_Garden_Hearing_Cooling_Air&hash=item2eb15dfa82

[pscocoa]

just got back home and everything has been working for several hours without a pcb change.

Pump is red hot though - not sure I recall it being so hot previously - is this normal - does not appear to be stuck as heating and water working fine

[Marks DTM Calib]

just gtot back home and everything has been working for several hours without a pcb change.

Pump is red hot though - not sure I recall it being so hot previously - is this normal - does not appear to be stuck as heating and water working fine

They do get hot, certainly 60+ degC.

[Marks DTM Calib]

Do you have thermostatic valves on most or all the rads?