Each floor as a separate zone?

[Olf]

Downstairs 70sqm UFH (40sqm house, 30sqm extension), upstairs 40sqm now rads (though running at 40C only), but UFH happening probably next year.

The plumber insist each floor should be a separate zone (so together with UVC that would make 3 zones/S+ plan) which I think is overkill and unnecessary installation and maintenance burden.

When would you split space heating circuit into zones?

[Marvin]

55 minutes ago, Olf said:

When would you split space heating circuit into zones?

I don't know lots about UFH, however different areas of a house require different amounts of heat to reach the same temperature so zoning sounds sensible. Extension and original house may have different thermal resistance so different amount of heat required to reach the same temperature. Definetly upstairs will be warmer because the upstairs floor is warm.

[Olf]

13 hours ago, Marvin said:

different areas of a house require different amounts of heat to reach the same temperature

Yes, but they draw from the same source of heat. My thinking is that UFH is zoned anyway, so the delivery of the heat to specific areas will be controlled at manifolds (one for each floor)

 

[Marvin]

Confused between zoning and zones, so sorry @Olf I can think of no further reasoning, and you will have to wait for an expert. 

Perhaps just needing 3 separate runs to rads, ufh and uvc.

 

[Nickfromwales]

15 hours ago, Olf said:

Downstairs 70sqm UFH (40sqm house, 30sqm extension), upstairs 40sqm now rads (though running at 40C only), but UFH happening probably next year.

The plumber insist each floor should be a separate zone (so together with UVC that would make 3 zones/S+ plan) which I think is overkill and unnecessary installation and maintenance burden.

When would you split space heating circuit into zones?

If you have at least one bypass radiator ( towel rad or back of airing cupboard ) plus each radiator has its own TRV, I would say there is a definite benefit to having the rad circuit left open, without a zone valve, so the UFH gains some additional system volume which should help with short-cycling when only one or two UFH zones are calling for heat.

The UFH deffo needs a zone valve so the manifold and TMV don't act as a bypass for the radiator circuit, eg when the rads are selected on their own the UFH ZV stays shut.

With 2 lots of heating and with them both adding their own percentages of bypass, I would seriously consider W-plan ( DHW priority ), unless this is an ASHP install which would give you that anyway. If it is an ASHP then you 100% need a 3-port ZV ( diverter, not mid-position ) or 3x 2-port to facilitate isolation for the heating circuits during the higher temp DHW cycle.   

What is the heat source?

Edited November 8, 2021 by Nickfromwales

[Olf]

17 minutes ago, Nickfromwales said:

What is the heat source?

28kW Combi, but with addition of UVC to be reduced to kind-of-system (no DHW calls). Everything planned with ASHP in mind, though no timeline on that.

 

24 minutes ago, Nickfromwales said:

I would seriously consider W-plan ( DHW priority )

 

Will research, many thanks!

 

23 minutes ago, Nickfromwales said:

If you have at least one bypass radiator ( towel rad or back of airing cupboard ) plus each radiator has its own TRV, I would say there is a definite benefit to having the rad circuit left open, without a zone valve, so the UFH gains some additional system volume which should help with short-cycling when only one or two UFH zones are calling for heat.

The UFH deffo needs a zone valve so the manifold and TMV don't act as a bypass for the radiator circuit,

That will be exactly the situation for the next few months. I'm ok with separate leg for the rads, without fitting the valve on it.