Overheat problem - Baxi Solo 3

[Malc C]

Hi, first post so please be gentile !

5 years ago we moved in to our home, and withing weeks the old Wickes Bolier packed up. We got a guy in (it was just before christmas) and he quoted over £2K to rip out the old boiler and install a new one. Regretfully I was not around whilst the work was done and the job wasn't done very well (running pipework at ceiling level rather than under floors etc) - The system necer worked well and about three years ago I purchased an new pump, valve, HW cylinder, controller and room stats, and after consultation with a really nice plumber re-did the lot and moved a few rads at the same time.

Things were fine for 18 months or so and then the boiler wouldn't light and the plumber came and replaced the gas valve and all was fine up until now. The past few days I've notice that the rads were cold and I didn't hear the boiler clicking in and out. On inspection the overheat light was lit. Resetting the boiler worked for a few times, but now this fails. The following comments might help anyone come up with suggestions as to what needs to be replaced or checked.

1) - The pump still over-runs, and hot water can be felt advancing through the pipes until the boiler goes in to overheat

2) - Turning on the room stat activates the bolier on light, but on some occasions when the boiler has been on, the fan and other lights don't come on and the boiler fails to ignight.

3) - Reset the boiler and had the knob set to low settings had no affect - it still overheats

4) - Setting the pump to run faster (speed III) - still overheated.

Heating just HW or CH or both has no affect - it still overheats.

Suggestions welcome

Thanks,

Malcolm

 

[Malc C]

OK an further update.

The boiler has been off for two hours, pressed the advance button on the controller to turn the CH on. Moved the room-stat so it called for heat, boiler on light came on, as did the fan etc and the boiler ran for about 30 - 45 seconds before it stopped and just the boiler on lamp was illuminated !

Why do these things happen in the winter time when it gets cold !!!

Malcolm

 

[Malc C]

Seems I'm the only one adding to this thread

Strange thing... the first radiator after the pump is the bathroom one. Because the cowboys who put the system in couldn't be bothered to move it, the only way I have of regulating this rad is to shut down the feed valve as the balance valve on the return is behind the bath panel. The boiler had just done a 20 second run and shut down (but with the boiler on light as the room stat was calling for heat). I fully opened the valve on the feed pipe to the bathroom rad and the pump made a whooshing sound and the boiler lit !

Could shutting down this rad cause a back pressure, which means the boiler overheats ?

 

[ollski]

It could be that the rad is plumbed in as a bypass which would certainly contribute to an overheat. A few of your other problems sound like a fairly typical pcb failure.

 

[Malc C]

Thanks for the reply,

Strange this is that last week we had an un-related problem with the gas cooker and called transco out to check the pressure.. the guy said then that these were prone to PCB failure... wish he had kept his mouth shut !!

Anyone have any links (apart from e-bay) for cheap PCB's, as even opening this rad the boiler has gone back into "on" mode (but no overheat light) after a few seconds !

 

[gas4you]

Yes they are prone to pcb failure but there are other things to check first.

If fan is running it could be aps, the little black elbow on the tops of these are prone to cracking.

check aps tubes, if all these are ok then it is pointing to pcb.

 

[Malc C]

Dave,

I've also notived that the room-stat is acting strange, often it has to be moved up to max before there is a click, and this morning both the neon on on the stat and the boiler ON light was flickering (boiler wasn't running either)

Can you elaborate "aps" I have no idea what you are referring to

I'm fairly practical minded, is replacing a PCB an easy thing to do on these boilers ?

 

[gas4you]

You need to get your system electrics checked first before lashing out lots of money on a pcb

Could be a faulty zone valve or as you say the room stat.

If all else fails changing a pcb is a easy job, but make a note of where each connector goes and above all make sure you keep earthing yourself before touchubg the pcb.

Static from your body could blow the new one

APS = air pressure switch

 

[Malc C]

Dave, thanks for the tips.

I've just been out and purchased a new digital room stat, and whist I'm not getting overheat problems the system still seems to be working in a strange way. Can you tell me if this is the correct operation

I've set the boiler temperature dial to approx half way (opposit the 0 mark).

Digital readout on the room thermostat showing 21C.

CH turned on via the controller - with the room thermostat set point set below the current room temperature none of the indication lights on the boiler were lit.

Set the room thermostat set point to 23C - it clicked and indicated HEAT - Boiler ON lamp lit, and pump could be heard running - seconds later the FAN, PILOT and BURNER indicators light and the boiler burst into life.

However it then runs for between 40 - 45 seconds then shuts down with just the BOILER ON lindicator lit - the room thermostat still indicating HEAT and is still below the set point.

The Boiler remains in this state for three mins and then runs again for 40-45 seconds before shutting down again for three mins.

The pump is running hot, as are the FEED pipe running off to the rads. The first rad in the bathroom is glowing (as I have it fully open), the other two rads upstairs are warm to touch - all rads downstairs are stone cold.

The fan is running, but i'll take the cover off and have a look at the aps as directed. We have recently (three months ago) boxed the pipes in, but there is still plenty of ventilation, and the heating was working OK after this was done so I wouldn't of thought that was the cause ?

Comments please

Malcolm

 

[ollski]

Malcolm you have checked the pump is spinning haven't you?

 

[Malc C]

Malcolm you have checked the pump is spinning haven't you?

Yes, last night I could feel the hot water progressing through the pipes when I turned it on, and if I undo the large "nut" in the middle the impeller can be heard rubbing the casing.

I've also removed the cover and checked that nothing is broken (by that I mean physically hanging off or cracked)

Interestingly, now I've turned on the power and set both HW and CH to come on the boiler is running for a couple of mins, then turns off for 60 - 180 seconds, then runs again for two to three mins, etc etc. I've also closed the first rad down to almost off to see if I can still get the pipes and rads down stairs warm !

This is beginning to do my head in..

 

[gas4you]

Sounds like a lack of flow .

Does the pump sound like it is still spinning when the boiler shuts down?

The pump is controlled via the boiler pcb.

Pumps can 'spin' but not circulate. I would be tempted to replace the pump if there are no blockages or valves shut off anywhere else.

 

[Malc C]

Dave, thanks for your continuine support.

I've been round trying my best to check for circulation by closing off lockshields where I can get to them or just opening the rad valves where the lockshields are not accessable (like behind the bath panel). I've also tried bleeding them and all I got was water - no air ! On most the feed pipe is hot, but the rad the other side of the valve is cold. I have managed to get one rad at the end of one "spur" warm, but with the boiler only coming on for short spirts it's taken hours to get some heat to the lower floor

How long should pumps last... this one is less than two years old. The pump does indeed spin when the poiler is shut down (ie with the boiler on light lit) - its also has overrun which lasts for about 10 mins when it finally shuts down when the controller turns off the CH

I do suspect a blockage somewhere in the system. The pump that was fitted two years ago was because it was making a lot of noise. I removed was was a perfectly good pump as when I fitted the one in the system now it still made the noise, which turned out to be gunk in the air seperator which blocked the feed to the pump. I'm not sure, but I may still have the old pump in the shed, but we could of disposed of it when we cleared the shed out a few months back !

Also, as all the pipework up to the first rad is new (well less than 5 years old, some 2 years), but the remainder could be decades old, I'm inclied to re-do all the rad circuit and install new rads to boot.

At least its not as cold in the house now as it was last night as the boiler is running and not locking up in overheat !

Thanks for your continued support.

Malc

 

[gas4you]

The valve you mention, is it a 3 port? Set it to manually open and see if rads heat up.

This is beginning to sound like a problem that needs someone there to look at

I think that re-piping the system is very extreme thoughts at this moment

Try turning off all rads except one.

At worst it may just need a professional power flush.

 

[Malc C]

Dave, thanks again for your comments

Yes the valve is three way, and works fine as this afternoon I tested the system by selecting just the HW and felt the pipework to see if it was being pumped correctly. It was as the feed to the rads was cold by comparison. I then selected CH/HW and the motorised valve was heard moving and the feed to the rads became hot (I couldn't keep my hand on it !)

The thing is, the price for a powerflush is about the same as a bundle of new copper and a few rads from B&Q

Malcolm