Adding underfloor heating to existing system

[stevelup]

Hi

First of all, thanks for everyone's contributions here. I've been lurking for years in 'read-only' mode

At the moment I have an EvoHome system with six zones. I'm refurbishing one end of my home and intend on installing underfloor heating.

The current system is Y-Plan. The boiler is downstairs in the utility room right next to where the UFH manifold is going to go. The pump and existing three port valve are upstairs in the airing cupboard.

My (almost certainly flawed) logic tells me that the best way of dealing with this would be the following:-

1) Remove the three port valve and replace with a pair of 2 port valves - that deals with DHW and the existing radiators
2) Move the pump downstairs next to the boiler
3) Add a third two port valve feeding the UFH connected in parallel with the UFH pump which will be controlled by the HCC80

It this right?

Cheers,

Steve

[bruce_miranda]

Unless your UFH is going to comprise of many zones, you don't need the HCC80. A single BDR91 + TR87RF will be fine. The UFH zone will need it's own flow and return and valve. The BDR91 will switch on the valve, the valve will switch on the UFL heating pump.

[jdp80]

On the assumption you could run any number of UFH zones with BDR91s and temperature sensors, what advantage does the UFH controller bring? I guess after a point it’s cheaper than multiple BDRs, but does it have different runtime settings, cycles etc?

[bruce_miranda]

The HCC is needed if you want to zone a single manifold into multiple zones. if you have a manifold per zone then a BDR91 is just as good.

[mtmcgavock]

The HCC is needed if you want to zone a single manifold into multiple zones. if you have a manifold per zone then a BDR91 is just as good.

You can still do it using multiple BDR91s with single zone manifold and multiple zones. We have two zones off our manifold each controlled by a BDR91.

[stevelup]

I have one manifold serving four zones, so I think the HCC makes sense?

[mtmcgavock]

I have one manifold serving four zones, so I think the HCC makes sense?

I make it about £200 cheaper using 4 BDR91s and TR87RF?

[stevelup]

Leaving the thermostats out of the equation (as I'd need them for either solution), I don't see how you come to that conclusion.

The HCC80 is £280. Four BDR91s would be £220. That's a saving of just £60, not £200.

I'm obviously missing something here though!

[bruce_miranda]

and make sure the zones are definitely independent I.e. you can close the doors etc. No point zoning if open plan or doors are not normally closed....which often happens downstairs.

[mtmcgavock]

Leaving the thermostats out of the equation (as I'd need them for either solution), I don't see how you come to that conclusion.

The HCC80 is £280. Four BDR91s would be £220. That's a saving of just £60, not £200.

I'm obviously missing something here though!

Yeah but you can buy the T87RF with a BDR91 for around £20 more. So @ £92 each * 4 = £368

If you use the HCC80, then that's £280, plus the stats at £74 each, so = £576 making a £208 difference between the two.

That's going on that fact that you already don't have the stats though....

[stevelup]

There's a shower room and a utility room both with 'normally closed' doors, there's a study which does have a door, but it's usually left open and finally an open plan hallway / kitchen / diner. So I'd say three zones minimum.

If I went for three, then going for the BDR91s probably does make sense at almost half the price of the HCC. Presumably, I'd just parallel up all the auxiliary contacts on the actuators and use them to operate the pump.

The HCC is still a bit more elegant though I think. It'll make for a tidier install.

[stevelup]

Yeah but you can buy the T87RF with a BDR91 for around £20 more. So @ £92 each * 4 = £368

If you use the HCC80, then that's £280, plus the stats at £74 each, so = £576 making a £208 difference between the two.

That's going on that fact that you already don't have the stats though....

Ah, got you now. Yes, that makes sense, and no, I don't already have the stats.

[mtmcgavock]

There's a shower room and a utility room both with 'normally closed' doors, there's a study which does have a door, but it's usually left open and finally an open plan hallway / kitchen / diner. So I'd say three zones minimum.

If I went for three, then going for the BDR91s probably does make sense at almost half the price of the HCC. Presumably, I'd just parallel up all the auxiliary contacts on the actuators and use them to operate the pump.

The HCC is still a bit more elegant though I think. It'll make for a tidier install.

Assuming you've already got existing stats in place (Wired ones) you'd just wire the A and B ports to what would be the existing stat (So it makes and breaks the circuit). But yes the HCC80 would make for a better install.

[stevelup]

Ok, back to the 'integration' question.

Existing Y-plan system stays exactly as it is
Manifold added on the flow and return of the heating system (no valve needed?)
3 (or 4) BDR91s driving the actuators on the manifold. Aux contacts on the actuators driving the UFH pump

That's it? Will this still trigger the existing BDR91 to activate the boiler?

[bruce_miranda]

The Y87RF kits (T87RF + BDR91) can be had for less than 70 a pack. However I am intrigued as to how you can use multiple BDR91s on a single manifold to zone without any actuator heads?