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)

 

[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)

quick up date - by removing the wire from terminal 1 on the relay tank stat i get the system to operate "correctly" -- that is the CH works in response to the room stat / timer -- and i get hot water on demand -- both pumps operate only when they should ---- the relay tank stat has a permanent live feed to terminals C an 1 --- (term 1 has the wire that i disconnected) --- if term 1 should not have a permanent live then it must be faulty -- anyone know if this is so ? -- dont want to chase a fault just by fitting expensive new parts -- thanks

 

[SimonG]

You already have. Original fault is not the heat exchanger. But you'll find that out once it's running properly.

 

[wolbut]

You already have. Original fault is not the heat exchanger. But you'll find that out once it's running properly.

OK-so what would be the original fault?

 

[wolbut]

OK-so what would be the original fault?

so a bit more clarification -- the pressure gauge reads the CH circuit system pressure - with the boiler switched off i filled the system to 1 bar and disconnect filling loop - with boiler still off the gauge pressure then slowly built up to 3 bar until the safety blew - the only way the pressure could build up is from the incoming mains water which only feeds the heat exchanger and then the hot water pipework - as i understand it the mains water pressure can only increase the system pressure via an internal fault / leak inside the heat exchanger - changing the heat X stopped the abnormal increase of pressure in the system - now i can get both hot water and CH the system pressure does not increase above its normal running pressure of 2 to 2 1/2 bar

still need to find the fault

 

[Macca]

Me too.. Boiler runs ok,
Firebird Combi 90.
Pressure is fine, heating when required, piping hot water as required too.
DHW Pump just runs on?
I can hear this trickling noise through the pipe work in the dead of the night not long after a burn to replenish the heat store, i then go to the boiler and the white light on the pump is on? The pipework is hot both sides of said pump.
I have recently had this new pump fitted but plumber has no idea why this is running, and of course it doesn't do it on his arrival!
A switch off at mains for 5 mins stops this until the next burn
I have heard a relay type click when it starts but it will run until i switch it off?

 

[lame plumber]

get an oil technician in to sort it out, dont waste money on parts like the previous lad

 

[Gazzt]

You can download manual from firebird website for free. Is it a condensing combi or standard efficiency combi. The manual contains wiring diagram. To help your oil tech

 

[Macca]

get an oil technician in to sort it out, dont waste money on parts like the previous lad

Thanks, my Plumber is an oil tech but is lost to any solution to this, boiler is 10 years + as was in when i moved in so his advice is get a new one seems a bit of overkill as it runs fine but for this pump running.
I was just looking to see if there is an answer to this problem on here?
Thanks anyway i will keep an eye on this thread for any future responses.

 

[Gazzt]

A failed pressure vessel can cause pressure to rise to 3bar and blow off at the safety valve ,also a total loss of pre charge pressure can cause this.
The pump my be running on longer to satisfy the drop in temperature in the heat store. Get a boiler man in and phone firebird technical for advice.

 

[lame plumber]

get another technician, the better ones know how to fault find or where to get the answers, forums arent the answer if you have issues and your not a technician as it leads to all sorts of problems in my mind

 

[Gazzt]

Domestic Hot Water Operation
Hot water is available on demand by turning on a hot tap. This activates the flow switch which powers the domestic hot water pump ensuring that all boiler hot water is diverted to the domestic heat exchanger which heats the incoming mains water to give instant mains pressure hot water. Hot water is then mixed with mains cold water by a thermostatic mixing valve set to ensure that it does not exceed 65°C. This is shown in accompanying diagrams - Item No. 6.
The burner may continue to run after hot water draw off has ceased - to ensure the pre-set temperature is restored in the heat store. This may also occur at any time if the control system senses that there is a need to replenish the heat store, i.e. if there has been natural temperature drop in heat store during long periods of low demand for domestic hot water.
This is from firebird combi manual if it helps

 

[Macca]

Thanks for the response guy's
I already have a manual, my tech aquired it a while back to fault find a previous fault. Attached is a pic. My Combi is the one on the front cover, without the old control panel, mine is a separate lifestyle control panel.

(condensing combi or standard efficiency combi) ??
Standard i think.
Sorry i will have to ask the Tech!

He has followed said manual and all wiring diagrams are correct..
However, he has never seen any diagram as to the sequence of the stat phials and to which stat pocket they need to be positioned in?
There are 5 in all, i have 3 in the boiler and 2 in the tank.
His theory is,
*it could be the overheat stat calling for the DWH pump to circulate heat away from the boiler, as this is the only other stat that can control the DHW pump.
The phial for the overheat stat is positioned in the DHW tank stat pocket?

Nowhere in the manual states the position of these phials?
This is his next trail of elimination along with calling firebird..

 

[Macca]

Attached are 2 item he has seen which relate to the position of the phials only these are the enviromax model..

 

[Gazzt]

I think your tech could be correct its very possible the overrun stat is the problem. You should phone firebird technical for further info.

 

[Macca]

At least it seems we are heading in the right direction.
Is an Overrun Stat,
The same as an Overheat Stat?
I'm looking for prices of the stat in the firebird parts section.
I have a part code of FC 03154 which is called an over run stat in the book but relates to the over heat stat in the illustration code?

Thanks for your time everyone it been a challenge .

 

[ShaunCorbs]

totally different stats best advice has already been given sorry to say

get a different oftec engy or ask firebird do they have an engineer available

 

[Macca]

Hi All,
Just an update, we have hit a wall with this as no information exists for the location of these Thermostat Phial's on the Firebird Combi 90/120 Standard Efficiency Boiler??
Neither Firebird Technical, or any Oil Tech's out there know which stat pocket these belong in??
All the advice I am getting is fit a new boiler !!
Great Advice @£2500.00!! For a pump running problem...
Thanks for any help.

 

[Gazzt]

Over run stat vial go to boiler, early warning stat go to boiler high limit to boiler, the only vial goes to heat store is tank thermistat. The three i have mentioned go to the boiler should be located on top of the boiler heat exchanger. The other on the heat store tank is located on the top of it.
By tbe way are you talking about the overrun stat

 

[lame plumber]

could be air in your system affecting stats working in heat store, needs bleedin out

 

[Macca]

Thanks Gazzt,
For info To clarify, i have 5 Thermostat phials:-
1, Control stat, in the Boiler pocket
2, High limit Stat, in the Boiler pocket
3, Early alert Stat, in the Tank pocket
4, Over Heat Stat, in the Boiler pocket
5, Tank Relay Stat, in the Tank pocket

Each of the 2 pockets will only accommodate 3 phials maximum.
As you say the
(OVER HEAT / OVER RUN) are the same thing as Firebird tech confirmed this too.
Also this is the only stat which controls the DHW pump without running the burner so the problem lies with it.
I have An Email from a firebird tech with the position of these phials.
I have set out the Phials exactly as described but the pump runs on..
As advised, i removed the Over heat phial from the boiler pocket (this stopped the pump running immediately!)
and inserted it in the Tank pocket
and away it went again.
My tech still insists the pump is dispersing heat away from the Boiler to stop the limit stat from activating.
This makes sense, so it must go to the boiler pocket to prevent it from over heating. As its name suggests,
over heat stat.
Either way the sensor is detecting high temperatures in both boiler and tank pockets which will cause the pump to start circulation to dissipate the heat.

As a foot note, if i flick the heating on for 1 minute which pumps the hot water out from the boiler, the DHW pump stops..
The mind boggles.

 

[Macca]

could be air in your system affecting stats working in heat store, needs bleedin out

All the bleeding points have been checked numerous times over weeks of running the system. And no air has been found at any of the bleed valves.

 

[Macca]

Thanks Gazzt,
For info To clarify, i have 5 Thermostat phials:-
1, Control stat, in the Boiler pocket
2, High limit Stat, in the Boiler pocket
3, Early alert Stat, in the Tank pocket
4, Over Heat Stat, in the Boiler pocket
5, Tank Relay Stat, in the Tank pocket

Each of the 2 pockets will only accommodate 3 phials maximum.
As you say the
(OVER HEAT / OVER RUN) are the same thing as Firebird tech confirmed this too.
Also this is the only stat which controls the DHW pump without running the burner so the problem lies with it.
I have An Email from a firebird tech with the position of these phials.
I have set out the Phials exactly as described but the pump runs on..
As advised, i removed the Over heat phial from the boiler pocket (this stopped the pump running immediately!)
and inserted it in the Tank pocket
and away it went again.
My tech still insists the pump is dispersing heat away from the Boiler to stop the limit stat from activating.
This makes sense, so it must go to the boiler pocket to prevent it from over heating. As its name suggests,
over heat stat.
Either way the sensor is detecting high temperatures in both boiler and tank pockets which will cause the pump to start circulation to dissipate the heat.

As a foot note, if i flick the heating on for 1 minute which pumps the hot water out from the boiler, the DHW pump stops..
The mind boggles.

To add to this my boiler is the standard efficiency combi 90 with no thirmistors.
These are only on the updated boiler.

 

[Gazzt]

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.

 

[Macca]

See attached,
This is what information i have received from Firebird,
Although it was a Tech's best guess as no information is available for my Boiler.