Firebird 90 - hot water pump runs continuous

[wolbut]

Had a problem with the water pressure in the system rising over 3 bar and blowing the safety - fitted a new heat exchanger and fixed that -- then i had no heating but had hot water - found that the hot water pump was running continuously -- checked the flow switch and that was working correctly - realised that hot water demand over rides heating - found that the relay that switches for the hot water pump to run is fed by the flow switch and also the "relay tank thermostat" --- by disconnecting the wire from the stat de-energises the relay coil (flow switch still in circuit) and the hot water pump stops and the central heating will operate (CH pump runs OK) -- any advice on where the problem lies ? - it appears to be the relay tank stat unless that is being fed by another faulty part/stat ---- prior to the heat exchanger failure all appeared ok - hot water on demand and CH as required -- could the over pressure caused a component failure or would it be just coincidence (the multi pin relay works ok and a substitute operated the same)

 

[Gazzt]

If you read the part of the manual you posted it tells you the location of each stat eg boiler or tank. I think Kevin got it wrong. The overheat and early alert stat take heat away from the boiler to the tank.

 

[Macca]

The early alert stat should be at the boiler not the tank, the tank can reach higher temps than boiler, that could be running the pump. Also turn the control stat down to reduce heat in the boiler it could be faulty letting the boiler over heat, causing the over heat stat to run the pump to dissipate the heat from the boiler.

The Control stat is on minimum setting, which does work as this slows down the burn times while the heating is on. If I turn it up it burns for longer and hotter..

 

[Macca]

If you read the part of the manual you posted it tells you the location of each stat eg boiler or tank. I think Kevin got it wrong. The overheat and early alert stat take heat away from the boiler to the tank.

The information I posted was what my tech aquired for the Enviromax condensing combi, that has two different sized stat pockets,
1 will accommodate 4 phials and the other takes 1.
The parts section explains these different sized pockets for this particular boiler.
Although it makes sense my stat pockets will only hold 3 phials maximum. He has tried to set them as described in that information manual but he just can't fit 4 phials in either of the Boiler/Tank stat pockets.

 

[tridimnaw]

Could be the relay sticking, ive had it happen on a grant boiler, not many firebirds round here

 

[Macca]

Many Thanks Tridimnaw, sorry for the late reply. The latest update is,
I have suggested this sticking relay theory to my tech who asked if i would leave my boiler running until he arrived, when he did arrive the pump was running as it always is.
He opened the electrics panel and tapped the relay!!
This immediately stopped the pump!!
He then suggested i do the same as and when it runs on for a while.
This is what i have been doing since last Wednesday and every time i tap the relay it stops the pump..
I am now waiting for a new Overheat stat/relay to arrive for my tech to fit.
Fingers crossed this will sort it..
I will post the results ASAP in anticipation it will have cured the problem.
Many thanks for all the suggestions.

 

[Macca]

Sorry it's been a while,
Update on the boiler as follows.
New stat fitted, pump now runs all the time as before! Tapping this stat does nothing.
Removing the copper phail from the boiler stat pocket stops the pump so it is sensing an overheat in the boiler which triggers the stat to run the pump.?

On the up side my Tech wants to find the problem and is willing to do it for free!
The saga continues.....