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How to extend an existing central heating and hot water system for underfloor heating?

Postby FrankRSC » Wed Dec 11, 2019 8:34 pm

I have a conventional oil-fired boiler system providing hot water and central heating. It is controlled by a "Y" plan, incorporating a motorised mid-position valve.
I wish to add wet under-floor (UF)heating in the bathroom and I understand that the conventional way of incorporating this would be to remove the existing valve and convert the system to a three zone-valve "S" plan, which sounds rather wasteful. Could I instead add a second mid-position valve in series in the existing system, so that the first provides UF heating and/or everything else and the second provides CH and/or hot water?
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Simply Build It

Postby ericmark » Thu Dec 12, 2019 9:53 am

There is no reason the underfloor heating can't be supplied from the Y plan system, main reason for Y plan is default is DHW and the old pump will allow water to pass even when off, so when the central heating turns off, any heat in the boiler can be dissipated into the DHW so no need for run on to allow boiler to cool.

UFH uses a second pump, and recirculates the water to keep the temperature down to below 27 deg C. There is a bank of controls, and it is really not a DIY job, I fitted electric UFH to wet room in mothers house, it was a waste of money, hardly ever used as it took so long to heat up.
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