no hot water


Postby pikey » Thu May 28, 2009 6:11 am

I have just drained down my system to remove a radiator to move to a new site (needed to cut pipes and re-route).

Have refilled system and boiler is boiling hot water (pipes coming out of boiler all get hot) and the water in the rads is hot, but there is no hot water in the tank and the hot water taps run cold. It feels like the hot water pipe under the bathroom floor above the boiler is hot for a short distance from the boiler (a meter or two) but then goes cold before the hot water tank so pipes going in to side of tank are cold.

There is no bleeder valve between the boiler and the hot water tank, and I can't get the nut on the top pipe undone to see if any water is getting through i.e. whether there is an airlock between boiler and tank (it must have been on there for about 30 years!).

Any suggestions?

ps. system is gravity fed with conventional boiler in kitchen and hot water tank in airing cupboard upstairs.
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Postby bd3cc » Thu May 28, 2009 8:57 pm

Did you drain the cylinder(tank) in the airing cupboard?
If it may be that the H/W tank in the loft has the ball valve stuck, and therefore there is no water in the cylinder, therefore no H/W.
This is where I would look.
HTH
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Postby htg engineer » Fri May 29, 2009 2:18 pm

bd3cc - pikey has said he is getting water it's just not hot - so the cylinder, tank are full and the ball valve is working correctly.

The problem is there's an airlock in the primaries between the boiler and the cylinder, I would try draining and refilling - it may fill up properly this time.


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Postby bd3cc » Fri May 29, 2009 9:06 pm

Yes, thanks for that HTG.Read Tank, no mention of cylinder, but didn't notice that there was water, but not hot.
In the absence of any other post was just trying to help.
There is often a problem with terminology, eg I have a customer who refers to their ground floor ceiling as their roof, very confusing 1st time.
Anyway, bow to your superior experience in these matters.
Cheers
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Postby pikey » Sat May 30, 2009 7:31 am

Thanks for the replies.

When I "drained system", I only drained water from a radiator pipe. I'm not sure if this drains radiaor circuit only or whether it would drain water from coil in tank too. Will draining from radiator again drain water between boiler and coil inlet on the tank? If not, how do I drain this part of system?
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Postby htg engineer » Sat May 30, 2009 5:27 pm

You would have drained the primaries too, it's all part of the heating, all the water in the radiators, boiler, primaries and cylinder coil all circulate around the whole system, with the primaries going to the highest point of the (central heating) system and no airvents fitted they are prone to becoming airlocked.

Drain as you did before and refill.

bd3cc - i'm not having a go or trying to make out I am more superior than anyone else on here, just explaining how I got to the conclusion of the airlock as there was water from the taps then the tank is full of water etc. Just trying to make it clear for everyone who reads the posts - It may help pikey and may even help you in the future.
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Postby bd3cc » Sat May 30, 2009 10:15 pm

Thanks for that HTG, understand completely.
Cheers
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Postby pikey » Sun May 31, 2009 10:22 pm

Thanks for your help. I have drained and refilled and it worked! Now have hot water again :-)
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Postby Daaan100 » Thu Aug 06, 2009 10:46 am

I have the exact same problem as pikey. And same system by the sounds of it.

I drained down the system in order to remove a radiator to do some tiling over the tails. I mistakenly left the timer on the boiler which came on for a short while before tripping out the overheat switch. I refilled the system, bled the rads, but now only have cold water coming from the hot taps. I reset the overheat switch and turned on the hot water and the boiler gets hot. Unfortunately the water from the taps doesn't.

Should I just try a simple drain down and refill, or have I knackered something by turning on an empty boiler.
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Postby londonmark » Thu Oct 15, 2009 4:08 pm

[quote="htg engineer"]You would have drained the primaries too, it's all part of the heating, all the water in the radiators, boiler, primaries and cylinder coil all circulate around the whole system, with the primaries going to the highest point of the (central heating) system and no airvents fitted they are prone to becoming airlocked.

Drain as you did before and refill.


Hi everyone, I was led to this forum after googling the same problem. I drained the central heating system in order to fit new radiator valves. Refilled and bled the radiators and everything seemed fine, untill I realised there was no hot water. Cold water from the hot taps and the cylinder is cold. The boiler is downstairs in the kitchen and I can feel that the [u]"hot water"[/u] pipe from the boiler is hot up untill about 2 foot below the ceiling, where it then becomes warm, then cool. My questions before I go ahead and drain/refill the system again (as htg engineer has advised) is: Do I need to drain the system completly? There is a feed pipe from the water tank in the loft to the hot water cylinder in the airing cupboard. This pipe has a stopcock and a drain-tap. could this be any help in solving my problem?? Many thanks. Mark :?: :)
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Postby wimiu012uk » Fri Oct 16, 2009 4:39 am

Had a similar problem with my system a while back and found that my chipboard wooden cover on expansion tank in loft had partially disintegrated and the particles of wood had found thier way into the indirect heating coils in tank after draining to remove a radiator.

Had to drain and backflush coils in tank, worked o.k after.
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