Combi boiler...does it have to be a 'circuit'?


Postby billybilly » Sat Mar 22, 2008 7:44 pm

This is difficult to explain without a diagram, but here goes.

Does a central heating system with a combi boiler have to be a complete 'circuit', as in, if all thermostas were closed, water could still flow around the whole circuit.

OR......can I have one pipe for flow, one for return with the rads branched off at their various poitns. This would mean at the 'end of the line' as it were, the main pipes would be blanked off.
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Postby andy2510 » Sat Mar 22, 2008 10:54 pm

I'm not an engineer, but I was reading the installation instructions of my combi boiler not half an hour ago for a problem I have. Seems if you want thermostatic valves on all your radiators you'd need a bypass point (looking at the diagram given it looks like a joining pipe between the other 2) to make a circuit.

An engineer will know more though.
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Postby htg engineer » Sun Mar 23, 2008 8:45 am

Normally and a simple solution for this - is fit TRV's (thermostatic radiator valves) to all radiators apart from one - normally the bathroom one or the radiator in the same room as the room thermostat would be fitted with normal radiator valves.
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Postby billybilly » Mon Mar 24, 2008 5:34 pm

Could I put TRV's on all radiators and then just connect up the flow and return pipes at the end of the line?
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Postby ericmark » Mon Mar 24, 2008 10:58 pm

Read your boiler info some have bypass valves built in and since you want hot water to return to boiler fast if all radiator valves are closed normally fitted close to boiler.
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Postby billybilly » Tue Mar 25, 2008 8:43 am

Thanks guys. Much appreciated.

But what would you choose........if my boiler has no auto valve fitted, would you go for the option of fitting one OR, having one radiator without TRV's and normal valves?

Cheers.
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Postby stevenc1603 » Tue Mar 25, 2008 11:09 am

In our house the radiator in the hall only has 2 lock shield valves which would make it the bypass.

I guess you could do it on the pipework but wouldn't it end up with that being the easiest route for the water to flow, thus the flow through each radiator would be limited?
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Postby ericmark » Tue Mar 25, 2008 6:42 pm

My TRV's came with a replacement top to convert them into standard valve. looking at one now they unscrew to turn on so just removing the head on one radiator should do the job?
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Postby rosebery » Tue Mar 25, 2008 7:06 pm

Off topic probably but, just for info, the "replacement top" is known as a "decorators cap".

It allows you to shut off the valve completely for painting purposes.

Cheers
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