No heat and hot tank overflowing....help!!!


Postby gsxr-jon » Wed Dec 12, 2007 3:06 pm

Hello

New to this Forum, but had a look around and it looks good!!

Basically I'm here for some advice.

My central heating system is playing up.

Worked fine a couple of week ago and then started to get noisy (water hammer/etc). and the rads have stopped working.

Then the small hot water expansion tank periodically started to overflow. The water is hot and a bit steamy and coming from the pipe that sits above the tank (ie not actually screwed to the tank). This only happens in bursts of about 10 second every 30 mins or so. It's as if the system is overpressurising and there is a relief lifting or something (I cannot find one on that line).
I have changed the pump and have closed every rad in the house and opened one up at a time to check if it is getting water. They all are individually. When I try to open up the whole system (even opening up 1/2 turn on each rad, the rads won't get hot and the overflow starts again.

Have tried all this with the hot water set to off and the Central Heating set to constant with the room stat at 30 degrees.

I have a Baxi WM 50/4 RS boiler in the garage with it's stat set to MAX.
Hot water and cold water tanks in the loft.

I have tried to add all relevant info but if you need more, just ask.

Like I mentioned earlier the system worked fine a couple of weeks ago.

It's getting pretty cold here....help please!!!
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Postby peter the plumber » Thu Dec 13, 2007 5:42 pm

You need to call someone out for this.

It’s the boiler.

Your pressure expansion unit in the boiler has gone or is cracked.

It’s not the kind of work you can do yourself.
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Postby marrtin » Thu Dec 13, 2007 8:49 pm

When you say the header tank is overflowing, do you mean the overflow is running outside the house or do you mean the heating water is running from the expansion pipe into the tank?

Look here at central heating types and explain. [url]http://www.diydoctor.org.uk/projects/central_heating.htm[/url]

Closing all rad valves could actually cause damage, so is not a good idea.

Are you saying that with most rads closed off, the others get hot?
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Postby gsxr-jon » Sat Dec 15, 2007 8:22 am

marrtin

Basically the expansion tank for the heating (the small one in the loft) has a pipe that comes from the suction side of the pump and into the top of the tank. This is spitting water out at irregular intervals and that causes the tank to fill up and overflow through the normal overflow lins and out of the house (well, actually down the side and in this weather it turns to ice!!).

With regards to the rads, I closed all but one rad, and it got hot (not very hot just a bit warm!! Opened the next one up and closed the last, etc, etc. I wanted to proove each rad clear and although it did this, the heat was not what it should be.

Pete

Are you sure about this as it's gonna cost me an arm and a leg to get someone in this time of year!!!

Cheers for the comments guys.......

jon
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Postby marrtin » Mon Dec 17, 2007 8:52 am

My first thoughts would be to check that the pump is working correctly. Change the speed setting. Does it sound quiet, and do you hear the speed change?

By your description, it sounds as if the system is boiling caused by a lack of flow, but this doesn't explain the overflowing tank which is probably caused by a faulty hot water cylinder.

This is not necessarily going to be an easy fix. How proficient are you with electrics and plumbing?
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