no hot water


Postby trevor123 » Sun May 04, 2008 12:26 pm

hi, hopefully somebody can help me with this one? ive recently ripped my bathroom out and im currently replacing it, i drained the central heating system down to remove the rad, its a vented system using a conventional gas boiler, not a combi. ive not refilled the the system yet as i need to adjust the pipework for the new towel rad as im changing the position, however, we no longer have any hot water and when the pump is on it sounds as though it is not pumping anything? the gate valve from the expansion tank in the loft is closed, would this affect the hot water supply? the cylinder is still filling as we are currently using the immersion although id rather get it sorted sooner than later as its going to cost a bomb to leave the immersion on? thanks in advance, trevor.
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Last edited by trevor123 on Sat Mar 19, 2011 8:44 am, edited 1 time in total.
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Postby rosebery » Sun May 04, 2008 9:57 pm

You've probably also drained the primary circuit which heats the water if you have an indirect cylinder. The pump will be on the primary so that's why it's just pushing air. Is there a motorised valve adjacent to the cylinder where the hot from the boiler is either routed to the cylinder coil or the CH or both depending on what the programmer is calling for?

You solution is to adjust your pipework for the new towel rad whilst you have the system drained. Fit the rad valves. Make sure they're both SHUT and refill the system. The you can run as normal until you are ready to hang the new rad and shouldn't need to dreain down again provided you have got the position correct.

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Postby trevor123 » Mon May 05, 2008 9:09 am

yes it has the 3 way motorised valve which is situated next to the cylinder. i thought that was what had happened but you just confirmed for me thanks very much.
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Last edited by trevor123 on Sat Mar 19, 2011 8:44 am, edited 1 time in total.
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Postby htg engineer » Mon May 05, 2008 2:09 pm

You've drained the heating system - which heats the hot water.

The system is empty, if completely empty you could cause damage to the boiler and burn out the pump by turning the boiler or pump on.

You cannot heat the hot water using the boiler until the whole system is refilled.

Using the immersion will be fine as you have said the cold supply to the cylinder is unaffected.
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Postby trevor123 » Mon May 05, 2008 5:02 pm

the whole system is turned off now apart from the immersion, if both water and heating are set to off then the boiler should no longer fire, correct? what sort of damage could arise please?
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Last edited by trevor123 on Fri Feb 04, 2011 12:34 am, edited 1 time in total.
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Postby rosebery » Mon May 05, 2008 11:11 pm

Correct and just to be sure turn off the volts to the boiler at the FCU.

Damage potential:

Pump runs dry = pump burns out.

Boiler fires up dry - heat exchanger has nothing to exchange heat with (no water) = need a new one.

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