DIY Doctor

Air in cental heating system

Postby johnwilkinson » Fri Dec 14, 2007 1:20 pm

I am having some building work done, and in the process, I wanted to change my microbore system to a 15mm system. This has to be done in two stages. The first is to add 4 new rediators, on 15mm system, in a new extension to the house. Then, when we have moved all our clutter, replace the remaining 6 rads.

The heating engineer moved my boiler into the loft, and converted it to a sealed system. All went OK, and while we were all microbore, no problems.

Since we have had the new rads on the system, there seems to be a large amount of air when the valve turns to hot water.

The engineer fixed this the other day, and last night, I decided to go look at the pressure... it was 0. So I opened the fill valves, but could only raise the pressure to 1 Bar max, even if I opened the valves fully.

Ok, so 1 Bar is workable, but then outside the vent pipe was dripping water, and yet the meter still shows 1 Bar.

Then the hot water started to heat up, and air was back in the system again.

Does anyone have any ideas.
Surely if there was a leak in the new system, we should have seen a lot of water by now?

I am so worried that the new floors will be laid, and that there is a fault beneath the boards.

Best regards,
John :?
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Simply Build It

Postby htg engineer » Mon Dec 17, 2007 5:19 pm

If the pressure is dropping then yes there may be a leak, but it also could just be when the air escapes. Your boiler will have a automatic airvent, when air is released from here the pressure gauge will drop.

You should be able to get the boiler pressure to above 1.0bar, as long as the mains water pressure is greater than 1.0bar.

Another problem could be that the pressure relief valve is passing, this would drop the pressure and also prevent the pressure rising if not closing fully. If you have paid someone to move the boiler etc - get him to sort it out, after all you paid to have a working heating system - there shouldn't be any additional charge if only leaks - but he may charge abit more if it's due to faulty parts.
htg engineer
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