Boiler fires up but after 2 or 3 minutes shuts down


Postby Jonestom » Tue Jan 15, 2008 8:39 pm

Just replaced rad's after decorating, didn't flush them when putting them back (stupid I know) heating worked fine for a day, now the boiler fires up after a couple of minutes the pipes in the boiler make a hammering noise and the boiler shuts itself down. I reset it and it goes thro the same process, I can't feel the pump running and I suspect, I have a blockage from the dirty rad's and water is not getting to the bolier, I intend stripping the pump out to check lines etc are there any checks I can make on the pump while I have it out or am I completely on the wrong track, I didn't do anything to fill the system after replacing the rad's other than just turning the water on and bleeding each rad thro. The boiler is a baxi solo 2 40 pf.
I have put a flushing agent in the CH header tank, but of course it hasn't gone anywhere yet.
Any advice would be appreciated.
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Postby htg engineer » Tue Jan 15, 2008 8:57 pm

have you vented the pump ?
made sure auto airvent is open (if there is one)
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Postby rosebery » Tue Jan 15, 2008 9:32 pm

"I didn't do anything to fill the system after replacing the rad's" and

"pipes in the boiler make a hammering noise and the boiler shuts itself down"

Boiler got air in it rather than water methinks and the overheat stat is shutting it down. If you don't have an auto air vent as Htg Engineer suggests or one of those clever little airtraps that releases air into the vent then you'll have to spend some time purging the system of air and getting it properly full of water again.

Cheers
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Postby Jonestom » Tue Jan 15, 2008 9:57 pm

Blimey,
I wasn't expecting a reply so quickly, thanks a lot guys.
I don't know if there is an auto vent on it, but I'll certainly try venting the pump and purging all air out of the system before I try anything more drastic. I have bled the boiler line.
It's odd that the system worked fine then started playing up isn't it? What does this back filling entail.
Is it just filling up from the drain point? and do you think it would help bleed the system through, getting rid of the air?
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Postby frogger » Wed Jan 16, 2008 11:04 pm

Take the screw out of the center of the pump and vent
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Postby Jonestom » Thu Jan 17, 2008 7:34 pm

Hi all,
thanks for your advice, re-my boiler cutting out shortly after firing up.

I tried bleeding the pump and two bleed points that were either side of the pump, no difference, I removed the cover from the pump power cables and there was no power present,

Flicked the power isolation off, held the tester on the pump cables, switched the power back on and the lights lit up on the tester for a split second, then off again.

I did this with the boiler on and off, same result.

So the pump is not being powered up for some reason. I removed the pump, rigged power to it on the bench and it run ok (just flicked it on and off) so as not to dry run it for too long.

The pump is back in now, any suggestions where I might look now,
Thanks in anticipation of positive replies
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Postby htg engineer » Thu Jan 17, 2008 9:58 pm

Room stat calling for heat ?

Possible PCB fault.
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Postby frogger » Thu Jan 17, 2008 10:35 pm

Have you reset the boiler after it over heated ?
You can do this by turning the thermostat to 0 for about 10 15 seconds to re set.
If its the older model the reset button (red) is on the side of the thermostat
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Postby rosebery » Fri Jan 18, 2008 7:36 am

I'm going to ask this boring question again. Are you sure you have all the air out of the system - particularly the boiler?

Cheers
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Postby dcc » Fri Jan 18, 2008 5:26 pm

sounds like the boiler is 'kettling' which can be caused by the pump not kicking in to take away the heat, or trapped air. since youve just taking off a radiator, im guessing its trapped air
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Postby Jonestom » Fri Jan 18, 2008 11:30 pm

Thanks for the comments once again.
Yes I have vented the boiler and the pump and also there were high point vents in the copper pipe on the feed and return lines of the pump, and I vented those too.
The pump etc is all in the loft next to the cold water tanks. There is a fused spur feeding a honeywell junction box with 10 terminal blocks inside of it. I have tested these wires with the fused spur switched on and they're live, but the pump does not get a signal from wherever it's supposed to get one and therefore cannot run and acts like a blockage in the line, thus I guess the boiler doesn't get a water supply and 'Kettles' as has been pointed out.
Does the signal for the pump to run come from the boiler PCB? if so then I think HTG engineer has hit the nail on the head and I will have to fork out for a new PCB.
The room thermostat does work, because the boiler won't start unless I put it into a high temp position. So in summary, everything seems to work except whatever gives the signal to the pump to run.
If it is the PCB, where is the cheapest place to buy one and while I'm waiting for it coming, would it harm anything and would it work, if I took the pump out of the auto system and switched it on independantly?
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Postby Jonestom » Sun Jan 20, 2008 1:26 pm

Rigged the pump up independently, started it running, then switched the boiler on, bled the full system, the boiler fired up, I could hear water going through the boiler, but boiler still tripped after a few minutes running, I guess there must be more than just the pump that is waiting for a signal from the PCB....am I right?
I've found addresses for local suppliers for pcb's so will just pop down and purchase a reconditioned one if I can, if it doesn't rsolve the problem, I'll be back for more advice.
Regards to all
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Postby Jonestom » Sun Jan 20, 2008 4:12 pm

With the water/CH switched off on the control box, and the boiler set at zero, there is a constant ticking coming from the box on the boiler this is the box with that is used for resetting the boiler. Does that give any better clues as to the fault?
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Postby htg engineer » Sun Jan 20, 2008 7:13 pm

Would it not be better to get a Heating Engineer in to take a look - you can check everything but we're pretty limited to what advice we can give with the info provided.

If you're not getting power to the pump - then yes this is the problem. But why is there no power there ?

Check all connections in the junction box - possibly a loose connection ?

I cannot find any instructions on the net for your boiler - how old is it ?
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Postby Jonestom » Sun Jan 20, 2008 9:42 pm

Thanks for that htg engineer.
my son has just bought the house,

Therefore I can't tell you the exact age of the boiler, my guess is about 10 years, but I do know the whole system was worked on 3 or 4 years ago. Also a new pump fitted, very recently because of evidence left in the loft with dates on boxes.

I've downloaded installation and operating instructions as well as a parts list, so the boiler must still be available, A Baxi SOLO 2 40pf

That clicking I mentioned in my last post, was actually evident even before the rads were removed, when everything was switched off but with just electrical power switched on.

I have had the system running well for over 24hrs until the episode with the pump and the boiler tripping.

I appreciate it's very difficult to diagnose things based on what is written on forums like this, therefore I think I'll call it a day and get an expert involved. But thanks for the support and advice offered, it's a great site.
Jonestom
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