Firebird Boiler Problem

monseiur

Hi all, just looking for advise on the following

My auntie (who's living alone) has an indoor Firebird 90 Boiler - fitted about 15 years ago. House was built back in 1950. The analogue clock on front is set to come on at intervals for a few hours during day/night. There are no wall stats or motorised valves etc. on the system. Since the weekend it's overheating and not knocking off even when the temperature knob on front is turned down to low. It's now set temporarily to come on for just 15 minutes every 30 minutes to let the water cool down, in other word every second pin on clock is pushed in (If I'm making any sense!) Is this problem an easy fix ? She's worried that the boiler might break down completely with a cold spell on the way.

Thanks.

Kimbot

https://www.boards.ie/discussion/2058287356/firebird-boiler-problem

When was the last time the boiler was serviced? It may need one.

listermint

Get it serviced. Could be a safety problem here.

monseiur

https://www.boards.ie/discussion/comment/120328902#Comment_120328902

Not sure about service history but a new burner was fitted last year and it did get a good clean out at the time. She contacted same plumber last Monday but is very busy, he is to call in 4 or 5 days.

monseiur

https://www.boards.ie/discussion/2058287356/firebird-boiler-problem

Apologies, the boiler is a Firebird Super Q (not 90)

Wearb

Boiler thermostat needs checking and possible replacement.

Thing that confusing me is that when boiler stat fails, the hi limit usually trips.

monseiur

https://www.boards.ie/discussion/comment/120329267#Comment_120329267

Thanks Werab. Can I ask is replacing the thermostat a major job, where exactly is it located. I googled it but no joy. The reason I ask is that one of here neighbours has a similar boiler and she's would be OK with exchanging part to see if it's faulty. It would also help the plumber by ruling it in/out - assuming he shows up at the weekend. As the boiler is fairly old chances are parts to suit may no longer be available but plumber may be able to get his hands on a used one on an old boiler.

Wearb

"the temperature knob on front is turned down to low" That knob is part of it. Wiring can be fiddly enough and you are dealing with mains power unless properly isolated.

youtheman

If you boiler is overheating then I would suspect the 'pump overrun thermostat'. This is designed to trip your boiler if the temp in the return line is too high (indicating that the boiler is putting heat into the system but the radiators and hw cylinder is not taking the temp out of the system). See the white box in this photo. Very simple to replace (as long as you electrically isolate the system). Note that I installed cheap dial thermometers on the supply and return lines to keep and eye on how my boiler was performing. Well worth it in my opinion!.

monseiur

https://www.boards.ie/discussion/comment/120329712#Comment_120329712

Thanks yutheman. The indoor Super Q boiler is different to the one in your photo, it is clad in white metal casing with soundproofing. The temperature control knob is on the front but I assume the same principal - I guess the actual thermostat is located in more or less in the same position. Is this what you call the ''pump overrun thermostat'' or is there a second one. In your opinion is it OK to use boiler 15 minutes on followed by 15 minutes off until plumber calls, which will be at the weekend hopefully. There's loads of info on Google about Firebird boilers re. repairs, service etc. but nothing about this particular thermostat.

youtheman

15 minutes on then 15 minutes off is o.k. as long as the return temp does not get too high. You need to get a feel for how high this is. Can you get your hands on a cheap thermometer?.

jimf

the stats for these boilers are no longer available

but you can wire a new imit dual stat into the supply

the probes may be an issue as they can be thicker than whats fitted originally

John.G

I would look at "water" and the circ pump as a start.

Is the system gravity fed from a small tank in the attic?, if so check the water level. If its a sealed system what is the system pressure?

Does the circ pump run when the boiler fires up?.

jimf

if it was low in water or pressure and no problem with the stat it should turn off boiler once it reaches lowest setting on stat

John.G

Yes, should have read the first post properly.

jimf

https://www.boards.ie/discussion/comment/120332673#Comment_120332673

your more an early morning man john 😀

John.G

I ran my own 18 year old Firebird 90S for a few weeks last winter at ~ 35/45C, a neighbour was/is thinking of installing a ASHP and wanted to see what kind of heat his rads would produce at these low temperatures. I used a EPH pipe stat wired in series with the hilimit stat. If a suitable stat/probes cannot be located for the above, the pipestat wired in place of the control stat, should do the job except Wearb/jimf have any specific safety concerns?. If the boiler only has a switched live then the stat can be wired into this supply since the control stat has failed on.

Wearb

Any modification would have to ensure that the boiler and hi limit stats would still read boiler temperature even in the event of the circulation pump failing or a low water situation.

The trouble with a technician stepping outside the MI's is the responsibility he bears if anything goes wrong. There isn't the same burden on the householder as he would not be held to the same level of technical expectation.

In this instance (as a service guy) I'd get guidance from Firebird, just to have some cover.

monseiur

https://www.boards.ie/discussion/comment/120332197#Comment_120332197

Hi John.G Yes it's a gravity fed system with tank in attic. House was built years before central heating was installed. Will check water level at weekend (I live 30 miles away) To the best of my recollection the circulating pump is wired separate to boiler - there's a pipe stat on the top pipe out of boiler, the pump is wired thru this stat (If that makes any sense!)

monseiur

https://www.boards.ie/discussion/comment/120332178#Comment_120332178

Hi jimf, This might be a stupid question...but here goes. Am I right in thinking that the Firebird Super Q is basically a Firebird Popular 90 with insulated panels ? If this is the case and as stats etc for Super Q are no longer available, would it be possible to remove the top panel of the Super Q and fit a Popular 90 stat on top, could an electrician modify wiring to suit ?

John.G

https://www.boards.ie/discussion/comment/120333809#Comment_120333809

Thats interesting, possibly installed for pump overrun?, or maybe the control stat failed a long time ago and the pipestat is being used as I described above and it too has failed "On", next time you visit see what its set to, note the setting and turn the setting knob up/down to hear it click, which is a reasonable indication that the contacts are opening/closing.

Wearb

I've come across over runs wired like described above. They seem to work well but can cause cooling of cylinder if not setup carefully. They also have the problem of bringing very cold water back to a very warm boiler on initial startup.

I personally haven't seen problems caused by that, but a lot of literature looks upon thermal shock as a bad thing.

jimf

https://www.boards.ie/discussion/comment/120333932#Comment_120333932

to a point yes but the pockets for the stat phials are different

the popular 90 goes in on top while the superq goes into the side and are pyramid shaped

monseiur

https://www.boards.ie/discussion/comment/120333966#Comment_120333966

Hi John, Had a good look at the set up yesterday. There's a twin socket on wall near boiler, the boiler is plugged into one and the pump is plugged into the other. The pump cable is wired thru the pipe stat and on to the pump. This stat is on the top pipe coming out of the boiler, it was set a 60 degrees and clicked when setting knob was turned as you suggested - I assume that once pipe cools down the stat knocks off the pump. I am of the opinion that the whole system would work better if pump was wired with boiler as the water would be circulating continuously instead stop start set up with stat.

The plumber called on Saturday - said he has to order some spare parts but told her it was safe to run boiler 15 minutes on then off for 15 minutes in the meantime.

John.G

A strange one, it would make a bit of sense if the stat was wired in series with the hilimit stat (if controlstat was knackered) and stopping starting the burner but not the circ pump which should run continuously once it or the boiler receives a switched live.

Wonder how long it has been wired like this and if so why was the boiler running normally and not tripping on the hilimit stat, maybe the control stat only failed (if it did) recently.

Wearb

https://www.boards.ie/discussion/comment/120353091#Comment_120353091

Wired that way, the pump only runns when the boiler is hot and stops when the boiler cools. Therefore the pump/pipe stat can be left permantly powered and the boiler is all that has to be switched on and off as needed or via a timer or room stat.

John.G

https://www.boards.ie/discussion/comment/120353285#Comment_120353285

Assume wired as you suggest and assuming a healthy boiler control stat with the same switching hysteresis as the pipestat of say 8C, the control stat must set lower than the pipestat to ensure continuous running of the circ pump?. if set it to say 58C (with pipestat set to 60C) then the burner will cycle on/off at 50C/58C, until boiler is programmed off but then the circ pump will never stop but will if (switched) wired the same as the boiler?.

We know the control stat has failed as turning the knob to minimum does not switch off the burner, the pump will cut out at 60C and even if it didn't the boiler will still reach the hilimit stat cut out at 113C or whatever as the burner output is far greater than the heat demand.

listermint

https://www.boards.ie/discussion/comment/120352758#Comment_120352758

Mines wired like this and has been since bought the house. Works perfectly fine so left it as is.

Pump knocks on when needs to and knocks off when it needs to. Burner has its own stat in the hall and trvs on each rad.

Fairly economical tbh for an old system I think the burners 6 years old just before we bought house. Reillo.

Wearb

https://www.boards.ie/discussion/comment/120354004#Comment_120354004

We'd want the circulation pump to run all the time that there's a call for heat (on initial start it will not run). The pipe stat will be wired to close in temperature rise. So a while after the heat demand switches off the boiler will cool enough to switch off the pump.

John.G

So wired to maybe also provide pump overrun if permanent supply?

Wearb

https://www.boards.ie/discussion/comment/120354391#Comment_120354391

Yes. That was the original idea...to have them as a pump overrun. Some of the boilers were prone to tripping the hi limit after shutdown, especially if the top pipe dropped immediately and there was no natural thermal circulation.