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Adding underfloor heating

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(@scrchngwsl)
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1409 kWhs
Joined: 2 years ago
Posts: 88
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We currently have an ASHP installed, which was fitted with our existing radiators and one zone for both upstairs and downstairs. We are currently building a small extension (12 sq.m.), and we want to put underfloor heating in it. We also intend, at a later date, to replace the downstairs radiators with underfloor heating, possibly in the next 5 years.

My question is, how should the plumber add underfloor heating to the extension, given (a) the small area currently, and (b) the plan in the future to put UFH all through the downstairs? Is this something that any plumber can do, or do we need to go back to the original installers?

ASHP: Mitsubishi Ecodan 8.5kW
PV: 5.2kWp
Battery: 8.2kWh


   
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(@hughf)
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2918 kWhs
Joined: 2 years ago
Posts: 479
 

if your ashp has hydraulic schematics for these types of install (vaillant for example) then copy those exactly. Otherwise:

The plumber should use close coupled Ts on the return line to take a parallel circuit to the UFH mixer/pump station. They should use an Ivar unimix3 blending valve (unless your your rad sizing was done to a suitable ufh temperature such as 35 degrees) because these are suitable for blending down low flow temps.

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.


   
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(@scrchngwsl)
Estimable Member Member
1409 kWhs
Joined: 2 years ago
Posts: 88
Topic starter  

Posted by: @hughf

if your ashp has hydraulic schematics for these types of install (vaillant for example) then copy those exactly. Otherwise:

The plumber should use close coupled Ts on the return line to take a parallel circuit to the UFH mixer/pump station. They should use an Ivar unimix3 blending valve (unless your your rad sizing was done to a suitable ufh temperature such as 35 degrees) because these are suitable for blending down low flow temps.

Thanks so much, that's really helpful!

 

ASHP: Mitsubishi Ecodan 8.5kW
PV: 5.2kWp
Battery: 8.2kWh


   
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(@redzer_irl)
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509 kWhs
Joined: 1 year ago
Posts: 36
 

@scrchngwsl I can't advise you on the technical aspects of it but can give you my opinion after carrying out similar works. 

We were adding an extension and switching to a heat pump. We had specified ufh in the extension but mid works asked for a quote for the existing concrete floors to be removed, insulation and ufh to be retrofitted downstairs - approx 85sqm. The quote came back as €12k which was too much so just went for the kitchen and wetroom shower for €5k.

We are in about a year and recently switched electricity providers and went for a smart tariff with a cheap rate for 3 hours (2am - 5am). We now heat the ufh to 22 degrees overnight and those rooms don't need any more heat during the day. 

 


   
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