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LOFT small tank overheating?

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lostatplumbing

Happy new year.....

Little issue with central heating...When we put the central heating and water on, my small tank in the loft all gets steamed up and the water gets hot in the expansion tank and starts dripping. The boiler is a potterton suprema. The gas man has just recently changed the 3 way valve and the timer and this problem is still occurring. We do not know what the issue is, please could you advise us?:confused:
 
Well you do get expansion in the tank,so maybe water level when cold requires reducing
Is any water coming out open vent pipework above tank into tank
 
I am not sure where it was coming but the water was red hot and it was dripping on the floor.
 
Firstly I can't understand why you haven't called the Gas Man again. The problem is called pumping over which will happen (hopefully) only at start up or turn off. This would be either a blocked / restricted cold feed or poor configuration. If it is happening constantly you will need to address the configuration . Sometimes turning the pump speed down c an help
 
Try simple things first like turn your boiler stat down a little. Are your rads getting hotter than they used to? your boiler stat could be faulty
 
The issue is pumping over, turning the stat down may alleviate the problem but the problem is still there and not right. If it continues to pump over that system will sludge up in no time.
 
I did call the gas man and he came this morning. He turned down the down the pump and the boiler thermostat but the water is still going thru the expansion tank and to the overflow pipe outside and it is still hot. We had a power flush only a few weeks ago through a private company so I am shocked that there could be a blockage, the company is also saying it is highly unlikely to be a blockage. Never had this problem before and the gas man wants to charge 250quid plus for the blockage which he is not even sure is even there in the first place.. he is still unsure of what is causing the problem.
Thanks rory, but I do not understand what does configuration mean? Is there anything else that I can do meanwhile?
 
Unlikely to be a blockage but could be an airlock in the system after the powerflush. This may be preventing the water from circulating properly. Bleed all vents and rads (including at the top of the cylinder coil, with the pump off) and report back to us.

Check the setting on the pump. If it is on speed 3, try speed 2, ditto for 2, try 1.

Are all rads heating up and does your water cylinder work OK? Can you hear any air gurgling about?
 
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If the ch tank is getting red hot i wouldn't rule the boiler stat out (out of calibration), be careful because i think a couple of years back a couple died in bed when there boiler stat broke and the dhw tank melted and came through the ceiling and burnt them to death!! or was it an immersion stat i cant remember??
 
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Hi WHPES thanks for that, we did bleed the system, no airlock.. and its still continuing...we did the temperature low of boiler and water and the pump setting is on number 1. water cyclinder is working fine, and radiators all heating up with no problems.
 
WEll frankly I have had to advise (successfully) reflushes after 3rd parties many times. The other issue could actually be the pump itself, The vent is the excessive temperature and expansion pipe. If it ain't working properly your prob could happen; however I'd expect a bit of noise. A blockage is a possibility but there is a 'pecking order' with how the pipes are laid out as it were. This is the configuration aspect i mentioned and is more probable. The vent should be first in the flow followed by the cold feed (within 150 mm) and then the pump - all within a metre. I do hope you get it sorted mate
 
I totally understand what your talking about rory, the pipes are not right in the house but we were living in that house for last 15 years and never had this problem, it only arisen after that power flush! Do you think I will have to rer-plumb it all? What would you suggest, paying out another 250 to find the blockage and then any other extras.. or should i just scrap it all, and fit in a combi boiler? i just recently fitted the bathroom and the kitchen which makes me bit upset because I could have just re-plumbed everything b4 hand...

I dnt suppose rory by any luck you are in the hayes/middlesex area or nearby? I would rather call a professional than any cowboy any day.
 
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The company who did the power flushing most probably had to cut your vent pipe to cap it. Maybe it wasn`t replaced properly if your stat is ok i would check the hight of the vent pipe over the tank. there is a calculation you can do to check the correct hight
 
hi gavin
what is the calculation? He assurred me it was fine.
 
check where the cold feed joins the flow (or wherever it does) with a magnet. If it sticks, there's a good chance the blockage wasn't cleared. If that is the case I would do the following to check / clear a blockage. Drain the feed / expansion tank (somehow) & isolate cold water supply to there. Then drain the system and cut the pipe just above where it joins the main flow. There will be water in the pipe!! using some 10mm / 8 mm pipe..bash the life down thru the cold feed. It may feel like there's concrete in there, but u'll feel it give way. Then pour some x800 down there and refill - after about a cpla weeks drain off and refill. If someone comes up with a beter idea..then..all this was..... a waste of time....!! good luck

If you can't find a good heating guy why not try BG?
 
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Had a similar problem in my house. Ifound that the vent was only about 200mm above the expansion tank water level. The boiler instructions quoted a minimum of 450mm! Increasing the vent height has cured the pump over problem.
Hope this helps
 
payney1974 said:
If the ch tank is getting red hot i wouldn't rule the boiler stat out (out of calibration), be careful because i think a couple of years back a couple died in bed when there boiler stat broke and the dhw tank melted and came through the ceiling and burnt them to death!! or was it an immersion stat i cant remember??
Click to expand...

It was an immersion without a thermostat, which was on, along with the ch boiler, it scalded the baby in the cot below the room..it's happened twice recently
 
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