CH - UFH manifolds

[Tim Watts]

I will have 2 UFH circuits. The conservatory which must be controllable and a tiny 3m2 one in a rear shower room (that does not exist yet).

Obviously need a blender.

I notice these tend to come as an assembly with X thermo-actuators and a pump. However, I cannot find out whether they tend to have any control built in (eg either actuator operating calls the local pump into action) or not.

Anyone had any experience? I'm assuming I should provide a box of relays to handle this - and also the call-for-heat to the boiler?

[Roger Mills]

I don't think they have any electrics - they're just blender valves which mix some of the returning water with 'new' hot water in order to achieve the desired flow temperature.

I've got wet UFH in my kitchen, and that's implemented as a separate zone on the (S+ plan) CH system. The wireless room stat opens a zone valve in the airing cupboard which, in turn, tells the boiler and main pump to run - and also switches on the UFH's dedicated circulation pump. No relays needed.

[Tim Watts]

I was thinking of made up blocks that contain their own pump and blender valve and array of actuators (these are available down to 2 UFH circuits). Seemed neater to have a block assembly. But it is very unclear where they contain any basic logic or are just mechanicals only.

I see how yours works.

Mine would not have a zone valve but would run in conjunction with the rest of the CH - so I'd have

UFH-A-Actuator--| OR UFH-B-Actuator--|------> UFH pump ---| OR Main CH control----------------------|------> Boiler call for heat (inc boiler pump)

So 4 relays (OK could do 3 if we assumed Main CH Control has volt-free contacts but I'd rather not assume).

Not hard - but was wondering whether I needed to plan for this...

[Roger Mills]

I'm not sure that that will work very well. The UFH is likely to have much longer time constants than the radiator zones so, for example, you may wish to start it up earlier in the morning than the rest of the system.

I'm not sure what you mean by "UFH Actuator". What kind of device are you referring to? Are the UFH areas going to have their own timers and room stats?

If I understand correctly, your solution will enable you to heat the radiators without heating the UFH areas at the same time - but not the other way round. Is that correct - and, if so, is that what you really want?

[Tim Watts]

Yes indeed Roger - nothing in that prevents this, in fact it is there specifcially to enable separate UFH control (which is not shown there - assume UFH-A and UFH-B are both separate zones under their own control).

Electric valve basically. Most UFH systems do not use traditional zine valves (motorised) - but use electro-thermal wax valve actuators (basically a TRV head with a small heater in). One per UFH circuit off a common manifold with a common blender valve and pump.

No - the control is full independent. The relays are needed to logical-OR the UFH demand signals with the demand for the radiators, whilst allowing the UFH control lines to operated the UFH-A/B circuit valves and operate the blender pump.

We assume that the main CH pump is in the boiler.

This is the sort of thing:

[Roger Mills]

OK, I see - so presumably the radiator zones do have zone valves - with the auxiliary contacts switching the boiler and pump? And your relays will generate similar logic for the UFH - with the addition of having 2 UFH zones share a single pump? That should work ok. I guess that if you

*did* use zone valves instead of actuators, you'd still need to devise some pump sharing logic.

In my case, the main pump is in the airing cupboard - followed by 3 zone valves for the DHW, radiator-CH and UFH respectively.

[Tim Watts]

No zone valves.

I'm planning on a "smart" system with some TRVs under direct RF control (bedrooms mostly as these need to be on less) and a main RF thermostat sorting out the rest of the house. Manual TRVs on the rest of the rads will trim the temperature of the rest of the rooms.

The signal to the boiler will be a single RF enabled boiler relay (Horstmann HRT4-ZW)

[Roger Mills]

So what does the "main RF thermostat sorting out the rest of the house" actually switch?

And do the RF-controlled TRVs send an "I am open" message somewhere, to interact with the boiler switching logic?

[Tim Watts]

It provides a call for heat that needs to be OR'ed with any call for heat from the UFH circuits.

I've just installed a simple HeatGenius system at a relative's flat (2 RF TRVs, 2 room sensors - guinea pigs are wonderful!)

I'm actually studying that aspect.

There's a sensor in one bedroom with an RF TRV. The other bedroom has the other RF TRV but is slaved to the first bedroom for timing.

The other sensor is in the main room with only the original TRVs.

There is an RF boiler relay. So the bedroom with the sensor+TRV - it knows the temperature of the room (with a little chart to prove it).

It is giving a chart for the slave bedroom too - so I guess the Danfoss ZWave TRV must be feeding data back.

It's not totally easy to see all the interactions as the battery devices (most of the sensors and TRVs) have long (like 10 minute) sleep periods so you kinda have to poke the settings, then wait to see what happens.

But I must say, it seems very polished.

[Chris French]

I've been looking at the HG system, among other things.

AIUI the room sensor are occupancy sensors? does it use those to switch the heating on and off directly, or is more of a learning process so it can predict when you might be using the room?

[Tim Watts]

More a learning process - but those devices also contain temp sensors.

[Chris French]

Ah thanks, that wasn't clear from the website

[Tim Watts]

I can correct this - the Danfoss does NOT feed back temperature data - the engineers at HeatGenius confirmed that for me over the weekend.

I am impressed - I reported a couple of very edge case bugs (the sort only I would find and not stability related) and they have fixed one in a couple of days, and are looking at the other and have asked if I'd like to join the beta test programme!

I think their system is going to become the ultimate domestic/small office CH control system over the next year or two - it is already equal in functionality to the best out their now, though lacking in a fancy wall panel (eg compared to the Honeywell - though HG has an app, so you could nail that to a wall in theory on a cheapy or old phone/pad) and they are very actively developing it. I admire their engineering - start simple, get it solid and work up from there.