using wired valves for wall-mounted radiators

[pocock]

I have a lot of radiators and I'm not keen to have battery operated TRVs on all of them.

I looked at the 2-wire actuators, most of them are promoted for underfloor heating manifolds but I'm told they fit regular radiators too.

It appears they can be controlled easily using a smart socket or inline relay.

However, they can only be fully open or fully closed (on / off) whereas the wireless battery operated TRVs can also partially open the valve to help maintain the temperature after a target is reached.

The specs also say that the wired actuators take 3-5 minutes to fully open or close.

Has anybody tried using wired valves like this on wall mounted radiators or under floor heating?

Does the software need to compensate for the opening/closing delay?

Are there any full TRVs that can be connected to a power supply all the time, even if it is with a USB charger?

[keepitsimple]

Bit late in replying !

I've done this on only one radiator in my house. They all have conventional TRV's, but when remodelling that room, it meant that a desk would be directly in front of and above part of the radiator. The heat output is handled by slots in the desk above it, so the convected heat can rise, but it also meant the TRV wouldn't be accessible to change the setting, and also would be in a confined space.

I used a standard underfloor valve fitted in place of the TRV head, and switched by a plug in module.

Some valves will screw directly on: others like mine (a Danfoss model) need a collar type adaptor. If you need one of those, get a metal one not plastic - they take quite a bit of stress.

Most if not all use a wax motor, so very very reliable, but as you say a bit slow. I think 2-3 minutes to open fully, but longer to close as there's heat from the radiator and pipe work delaying the cooling.

You're right that the degree of control isn't very granular. To achieve very close control would be very difficult given the latency of the valve, and it would need some sort of PID algorithm - which is far far beyond me - that takes into account the rate of heat dissipation/room cooling when the valve is switched to close, and the delay in reheating when open. Very tricky.

For what I need though, it works very well, and it has one big advantage being that you can site the controlling thermostat at the best place in the room as opposed to it being directly next to the heat source as is the case with a TRV. I've never found the conventional TRV's to be that precise and don't see how they can be given their location. I presume, but don't know, that the more sophisticated electronic TRV's have some sort of learning/PID function built into them, but they're still right next to the heat source !

The setup uses a simple set of rules checking what the required temperature is, which depends on the time of day and whether the house is occupied or not, and switching appropriately. I use a selector switch with "off/20/21/22/on" options so the required temperature can also be manually set or over-ridden at any time. Those are all the options I need. It does undershoot - waiting for the switch to open, and overshoot once it's closed, but from my log today, in real life has had a delta around the set temperature of .5 of a degree.

The rest of the heating system is purely conventionally controlled from a main house programmer, so obviously this radiator can only demand heat when the boiler is firing anyway. To do it properly, you'd need full boiler control as well, and that needs to account for proper boiler firing management some of which may be built into the boiler firmware itself, such as over-run times, frequent firing prevention etc..

If you've already done any of this, would like to know how you got on.