I drained my central heating system through the bottom draincock before fitting a new radiator in the same position as an old one with some minor alterations to pipe-work. Once the new rad was fitted I proceeded to turn the system back on however the boiler refuses to fire up even though the pump seems to be running, however the water level in the top expansion tank does not seem to alter. Could I have huge airlock preventing water flowing down through the system and if so how would I clear it. A colleague at work suggested connecting cold mains to the bottom draincock and filling system from bottom up, would this be the correct thing to do? I should mention that the hot water is also refusing to heat.
Central heating will not start - HELP
- Thread starter dazhaz
- Start date
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From previous post,
Sounds like you have a air-lock, as it was okay before you repairs the leaking radiator.I think you got to start again,turn off the main feed supply to the expansion tank,open up motorized valve to manual,drain down system again,when finish draining the water,shutdown your drain point then open the radiator bleed valve nearest to the drain point, then open up the water supply to expansion tank,but don't wait until the expansion water filling up,go down to the lowest radiator & bleed,hoping it will push the air out both way then bleed each radiator backward from the drain point,when finish put the motorized valve back to auto position.
Sounds like you have a air-lock, as it was okay before you repairs the leaking radiator.I think you got to start again,turn off the main feed supply to the expansion tank,open up motorized valve to manual,drain down system again,when finish draining the water,shutdown your drain point then open the radiator bleed valve nearest to the drain point, then open up the water supply to expansion tank,but don't wait until the expansion water filling up,go down to the lowest radiator & bleed,hoping it will push the air out both way then bleed each radiator backward from the drain point,when finish put the motorized valve back to auto position.
First of all thanks for the advice, however i still have a problem. I followed the instructions on the last post but the expansion tank in the loft is refusing to empty both during the drain and when i turn the system back on, although some more air was released. Could it be a blockage between the expansion tank and the pump? I would prefer not to remove the pump so any more advice would be appreciated.
somewhere near the highest point of the pipework there should be a vertical bit of pipe with a fitting on the end to release the air from the system....normally find it in the airing cupboard or in the loft....have you released the air from here?
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dazhaz said:
A blockage in the feed pipe from the header tank is quite common. You will have to bung up the outlet from the tank, or pump out the contents, then cut the pipe just above where it joins the rest of the system and mechanically clear the blockage.
I now have re-drained the system as far as possible but the expansion tank was still not draining so i removed the pump and still no joy, it seems likely there is a blockage between the pump and the tank (the pump is in the airing cupboard about 2 ft below the level of the tank. Any handy tips on clearing the blockage would be welcome.
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