Ideal classic query

cubix

Lads
We are doing a house revamp at the moment. The boiler was giving issues were it was going into overheat mode Rads are heating fine and there is no kettling effect etc. New pump was installed and seemed to work for a number of weeks prior to Xmas but problem is back now. Since then we have tried the items below with little or no joy as the overheat issue still kicks in. I have been told these ideals are quite a good work horse with only possible fan issues, but thats about it. Is it possible the pcb is not telling the pump to run when it should, in saying that when it does run the rads all heat up.
The issue seems to arise mainly in the morning as the clock is set for two times. Comes on first thing then goes off, when its meant to come on again it doesnt and when checked it has gone into overheat. On the rare occassion it has happened in the evening but not alot. Is it possible that the time clock could be having an effect ? There is an expansion vessel externally to the boiler, I know these can play havoc with pressure jumping up and down but can they make a boiler go into overheat? Thanks

Overheat stat changed
Thermistor changed
Chemical cleaner applied

shane0007

Could be a partially blocked heat exchanger. New pump could have shifted a bit a crap to begin with but it usually comes back.
Check the system for sludge.

cubix

System did not seem over sludged, I have been told these boilers have cast iron heat exchangers and do not clog?. We stuck a magna clean on to confirm if anything large is floating around. Any electrical check we could be doing, the biggest problem we seem to be having is the inconsistency of the fault, as in it will work for a day or so that go back to its old form.

Thanks

sullzz

When it goes out on timer does the pump continue to run for a while or does it stop with the timer , you could have a volume of hot water lying in the boiler causing it to activate the stat

shane0007

If might not be sludge but lime scale within the heat exchanger. I found a pebble blocking one before.
Have you actually checked the expansion vessel pressure or just checked for air from the valve?

cubix

Cheers lads: Please bear in mind I am not a plumber regarding my answers below.
Sullzz: I have been lead to believe this model does not have pump over run which doesnt make sense as I presume cast iron exchangers hold more heat, more chance of overheat?

Shane: Our prob may be lime scale but not so bad it would casue a blockage as the heating seems to work, I am thinking it more of a case of the pump not running after the boiler goes off. Meant to say new vessel installed as existing unit was full of water. How did you find your peeble size block, cut it open?
Lads I have linked another post and would appreciate your feedback, what does gas pressure have to do with overheat issues.

http://www.diynot.com/forums/viewtopic.php?t=117695

Anyone with free tomorrow Sandyford area to look at this, feel free to pm me.

Thanks

shane0007

cubix wrote: »

Cheers lads: Please bear in mind I am not a plumber regarding my answers below.

Are you an RGI? I understand you do not seem to doing all this work, but if you are not an RGI, who is doing the works?

When I was taking out the HE, the pebble was lodged in the inlet of the HE. Have found them rattling around in circulating pumps also.

cubix

There was an RGI up at the job but need a second opion at this stage. Someone was obviously have a good laugh putting pebbles in the system.

shane0007

No, very common in houses fed from private wells.

cubix

Is there not a filter that goes on in those situation?

Milkman2012

You need to ensure that the boiler is wired correctly, it should have two supplies, a switched live and a permanent live, make sure the next RGII checks that. The switched live is your call for heat (i.e. when you want your radiators to get hot). The permanent live is a continuous live supply to the boiler that facilitates (among other things) pump overrun and stops boilers over-heating so that when the time clock switches off the boiler circulation pump will still run for a while longer ensuring that any excess heat is dissipated from the boiler. I should add that not all boilers have their wiring done this way but certainly all models manufactured in recent years are designed like this.

cubix

Milkman: My understanding is that this setup has been like this from day 1 and the issue only arose before Xmas. Thats not to say there is not a problem as you outline.
Thanks

shane0007

Milkman2012 wrote: »

You need to ensure that the boiler is wired correctly, it should have two supplies, a switched live and a permanent live, make sure the next RGII checks that. The switched live is your call for heat (i.e. when you want your radiators to get hot). The permanent live is a continuous live supply to the boiler that facilitates (among other things) pump overrun and stops boilers over-heating so that when the time clock switches off the boiler circulation pump will still run for a while longer ensuring that any excess heat is dissipated from the boiler. I should add that not all boilers have their wiring done this way but certainly all models manufactured in recent years are designed like this.

Not on an Ideal Classic. This boiler does not have pump over-run. Cast iron heat exchangers generally do not require it as they can take a lot more heat than a steel HE, etc.
So either it is a faulty HL stat, but that has been replaced or a faulty thermister but that was replaced. The PCB could be faulty or indeed the parts replaced could be faulty! Known to have happened. Or a partial HE blockage.
They are a fairly simple boiler & generally overheat issues are circulatory problems.
CI heat exchangers do have larger passage ways but they do block. There is a drain valve on the HE & when re over is a good indication of the amount of crud in it.

Milkman2012

Generally if there is an issue with restriction you will hear kettling, can assume no extraneous controls are causing the problem like the pump on a back boiler or motorised valves that are closed. I have regularly seen pumps that seize with heat which might explain why it happens in the morning when the boiler is switched on for the second time. About once a quarter I come across a boiler that malfunctions occasionally due to a loose wire. The problem you have may not be easy to fix unless someone can witness the fault first hand (such as pump not running due to seizure or loose wire). How did you confirm that the boiler is not working due to overheat, what diagnostics did it give you?

cubix

Shane: What part does the pcb play regarding the pump, is there anyway to check for intermitent issues from the PCB.

Milkman: A new pump was installed from the word go

shane0007

PCB controls everything. It tells the pump when to come on & off. It bases all the information upon all of the information it receives from thermistors, flow switches, pressure switches, APS, etc.
Can they be intermittent? They can be anything!
Can they be tested? Sure, with a new one!
Can they torment an RGI for the fun of it? I think they do it on purpose!
Can they make a grown man cry? Usually only on Friday evenings!
Can they work in kahoots with a new one? They live to a secret code!

sullzz

shane0007 wrote: »

Can they make a grown man cry? Usually only on Friday evenings!

Lol ! So true !!

K.Flyer

cubix wrote: »

A new pump was installed from the word go

Go back and double check your wiring connections onto the pump. Could be a new pump with a faulty capacitor, or just a faulty pump.