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New Central Heating Controls Pack-Problem


DJH

Question

Hi, I hope someone can help me with this one. I have fitted a Danfoss controls pack to my existing Potterton Prima C boiler. It only had a basic timed on /off before. Everything works as it should except that the boiler does not switch off when the central heating side has been on and is turned off either by room stat or timer. The programmer says it is off, with no lights on, but the boiler keeps firing up until the direct power to it is turned off. I am getting advice from Danfoss who seem to think that the boiler is being kept live by back voltage from the three way valve (some 50-100 volts). The boiler has pump over run and the system is fully pumped. Potterton refuse to tell me if the boiler(it's quite old) is compatible with a sprung 3port valve. I can't afford to get someone in and don't know where to go from here. Help please.

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14 answers to this question

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try using a honey wiring centre you dont even have to think about the connections.

Made especially for plumbers :D

ROTFWL

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are we still struggling here ? if so we have some links to pdfs that show the complete wiring for the y plan. i would start from the beginning and rewire it totally, it sounds a task but al lthe cable is there it just need re terminating ... 1 hr tops..

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are we still struggling here ? if so we have some links to pdfs that show the complete wiring for the y plan. i would start from the beginning and rewire it totally, it sounds a task but al lthe cable is there it just need re terminating ... 1 hr tops..

My thoughts to John.

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Thanks Guys

Yes I still have the problem, not been able to look at it for a few days. I have already rewired it from scratch, or a mate has, so that I did not repeat any mistakes. Convinced the wiring is as the Danfoss diagram. Sparkyrj sent a very useful pdf to me and it looks as if the wiring is correct but there are some differences. A pdf of a Y plan would be useful and if the offer still stands, I will pm my email address.

Thanks to everyone.

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Hi, I suspect that it is something to do with the pump over-run. The Danfoss help desk asked me to get some info from Potterton(my boiler), they refused to help. When I told Danfoss this they just abandoned me. I can make the system work including boiler shut down, by disconnecting the supply to the boiler SwL. However this also stops the pump over run.

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Hi All,

I am happy to say that I (well my brother actually) have solved the problem. The Danfoss diagram showed a link between the pump and the wiring centre that was not needed with pump over run. This wire was allowing back feed live to the boiler .In the end all that was required was disconnecting this wire and everything is fine.

Thanks again for the help and advice.

Cheers

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Hi. Make sure that the supply to the microswitch is wired from the feed side of the thermostat and not from the switched side as i have seen in some cases, as this causes the valve to remain permanantly energised once it has first opened due to backfeed from the boiler.

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this sounds very similar to a problem i had a while back....

3 port valve, ST699 programmer, cant remember boiler. once something was turned off, it would stay on. spent ages trying to get it working. iirc, the pump over-run link was cut, and i swapped a few wires round in the boiler. cant remember exactly what i done (since i kept changing things until i got it working). i think i eventually colved it by swapping some of the connections to the boiler

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Thanks Sparkyrj. Sorry to be a pain but I have no experience with these systems. Can you tell me which microswitch you mean and also which stat, room or cylinder. Cheers

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How is the valve wired ? ie does the grey wire at the valve have a permanent feed and the brown a timed live, I have seen systems wired using the timed live to also feed the grey wire which can be back fed from the boiler down the orange switch wire, through the grey hence then to the brown which then keeps feeding the valve as though the timed live was calling for heat hope this makes sense CJS

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Do you have the cylinder stats satisfied terminal wired back to the HW off terminal, as this effects the correct operation of the valve.Also could the pump overun be causing this problem .I think there are some links to S and Y plan diagrammes in another thread on here somewhere.

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Hi DJH . if you can pm me your email address, i can send you a pdf from danfoss that has a wiring diagram and an explanation on the workings of the three way valve.

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Hi all.

I have an update on my original problem. I have received some very useful advice and pdf's from sparkrj and jl-heating for which I am very grateful. I have tried wiring it up in different (to Danfoss) ways and there was no change.ie the boiler did not switch off when the programmer shut down. I have now semi solved the problem by disconnecting the permanent live to the over run thermostat. This leaves the Swt live and supply to the pump on the O/R thermostat. Everything works as it should except the pump over run. This is OK for a temporary fix but I do not want to leave it like this.

So my question is does anyone know how I can provide a live feed to the over run valve without causing my boiler problem, as well. The boiler is a Potterton PrimaC, yes I know,but I can't afford a new boiler yet.

Cheers

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