Pipe stat

22 Feb 2006
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United Kingdom
When the room stat turns off on my oil-burning Firebird S90 boiler, it cuts the pump, too. Had a pipe stat fitted by an electrician, then had an extension and the boiler was moved and the stat refitted by another electrician. Just looked at his handiwork and currently it's spliced into a permanent live (the only one at the boiler control box), but doesn't redirect to a pump live, so it doesn't do anything.

Is it a case of me tracing the pump feed in the boiler's control pack and sticking a branch off the live feed to it? Ie live into pipe stat, live out of pipe stat into existing pump feed.

Reason for wanting to get it operational is boiler heat build-up. When the boiler's turned off, excessive heat trips the safety cut out.
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All depends on how your installation is piped & wired.

If the room stat is now controlling the pump and boiler simultaneously, that suggests to me that they are wired together. If so and you feed a live from the pipe stat back to the pump, the boiler will be kept running as well.

On the other hand, if you just connect the pump directly to the pipestat, you may find that the boiler heats up, but because the pump is not running yet the boiler will overheat and trip before the heat reaches the pipestat and starts the pump.

I'm not familiar with oil fired boilers, but gas boilers that require an overrun facility have a feature built in to their circuit boards with a terminal to connect the pump to in order to keep it running after the boiler goes off.

There are many ways of wiring boilers and their associated controls, you really need to speak to the person that wired it up to know what they have done.
Thanks for that. Firing up the pump and the boiler wouldn't be too clever.

Contacting installer isn't an option, sadly, and two sparkies have had goes at it, so it isn't looking too rosy, although Firebird do mention in their literature about wiring in a pipe stat to rid the boiler of heat build up.
What system do you have, is it fully pumped hot water and central heating, with one or two valves (S Plan or Y-Plan).

Is it gravity hot water and pumped central heating.

Do you have TRV's fitted to all radiators, at least one upstairs should not have a TRV, usually the bathroom, this then allows the hot water to dissipate from the boiler.

Although I understand the Firebird does suffer with overheat problems.

They do recommend a pipe stat but what system have you got.
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Fully pressurised indirect (I think...) system (in bungalow), all radiators TRV'd except one, which is fully open at both ends. Two motorised valves fitted.

System has a basic bypass but heatsoak build-up problems will occur at 75C or above on boiler unless programmer's set to auto, so pump stays on all the time and boiler thermostat shuts off boiler when it's at temp, and refires it up when it has dropped again. This is fine if we're in all day. Problems start if the timer shuts it down while its mid cycle.

I can run it cooler than 75C and there's no problem. But the building's cold, especially at the far end.
That's helpful, and different from my paperwork. Will see if it rates exactly to my setup when I'm home this evening.

* Unless I'm misreading this, the facility for an overrun is already standard on some models of the same boiler...
As you can see, pump is connected to the common terminal, then you have the switched boiler supply and a permanent supply.

Under normal conditions the pump is supplied along with the boiler, but on temperature rise the state of the stat changes and puts a direct supply onto the pump until the temperature drops and the stat goes back to it's original state.

Hope this helps.
Hi Steve3948

The data looks like it covers my boiler model, thank you, but I'm going to bottle attempting a DIY cure, as I don't feel comfortable making these changes.

Thank you very much again for all your help.

* Edit to say three sparkies have had a go previously, not two.
Print off page 16, hand it to any decent spark and they should be able to connect up your pipe stat with no problem.

Glad to be of some help.


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