Evohome, combi boiler + rads + UFH

[thecarfixer]

I currently run evohome, and like it a great deal. I am wanting to optimise my heating system which consists of a Worcester Bosch Greenstar 35CDi combi boiler, 7 radiators and a UFH system containing 3 loops for three rooms. I am using an evohome system with HR92s on all of the radiators, and a BDR91 as the boiler/appliance relay.

I then have a HCC80R controlling a two port zone valve and pump for the UFH manifold – the UFH system is just teed off the flow and return pipes near the boiler which means when the UFH zone valve is open the radiators are basically bypassed which is not optimal at all. It's not hydraulically neutral, either, so I can hear all sorts of pump noise. I want to change to run the UFH off close coupled tees, following a neat design by Worcester Bosch and proposed by Andrew Millward (YouTube - https://www.youtube.com/watch?v=7_qLBqpqqZQ), however I need to power a 3 port valve when the radiators are calling for heat as the diagram below. This 3 port valve would be sprung ‘closed’ to ensure primary flow when only the UFH loop is running.



I know I can set up a zone valve under zone configuration, but this would not allow me to continue using the HR92 radiator valves, which I do not want to lose. Is there a way to achieve this configuration with evohome?

(I've sent resideo tech support an email, to this effect, also)

[thecarfixer]

Can close this topic if required - resideo confirmed it's not possible without losing the HR92s, as a zone is either a HR92, or a zone valve, you can't have HR92's 'under' a zone valve. (Which is a shame).

I'm unsure what I'll do to fix this challenge, short of ditching the whole lot.

[Richard]

Just for clarity, neither Andrew nor Worcester Bosch invented Closely Spaced Tees (I'm not sure why we call them 'Close Coupled Tees' in the UK either, as this is a way we connect toilets not heating systems! ).

CST's come from the hydronic designers in America. Both Andrew and Worcester have been reading Caleffi Idronics guides (page 68 - https://www.caleffi.com/sites/default/f ... a_2019.pdf), which is where I learnt my knowledge about them from.

As for your evohome system, I believe there is a way to do this. Have you purchased the system from us?

[thecarfixer]

Just for clarity, neither Andrew nor Worcester Bosch invented Closely Spaced Tees (I'm not sure why we call them 'Close Coupled Tees' in the UK either, as this is a way we connect toilets not heating systems! ).

CST's come from the hydronic designers in America. Both Andrew and Worcester have been reading Caleffi Idronics guides (page 68 - https://www.caleffi.com/sites/default/f ... a_2019.pdf), which is where I learnt my knowledge about them from.

As for your evohome system, I believe there is a way to do this. Have you purchased the system from us?

I did buy from you, albeit nearly three years ago..

Would be interested to know how we can do this, as Resideo suggest it can't be done with evohome!