Thermoelectric actuators on radiators

[endecotp]

Dear Experts,

Does anyone have any experience of using thermoelectric actuators on radiators?

I'm thinking of products like this Honeywell one: http://www.honeywelluk.com/products/Underfloor-Heating/MT8/
and this Danfoss one: http://products.danfoss.com/product...s/thermal-actuators/twa-standard-actuators/#/

My understanding is that these have a wax cylinder, like a traditional TRV, and a heating element that causes it to expand when power is applied. This is in contrast to the battery-operated "smart" or wireless TRVs which contain motors (at least, mine do); I don't think the heating element + wax approach could be used in a battery-powered device because of the power requirement.

I find that battery-operated TRVs with motors are noisy - too noisy for my bedroom - and I guess that these thermoelectric ones should be silent.

I note that the Honeywell one linked above claims to work at intermediate positions under PWM control, which the others I've looked at don't mention.

I believe these are most often used with UFH, but they should also work as zone valves for CH or on radiators.

Does anyone have any recommendations or experience to share?

 

[Dan Robinson]

They will work fine, but not sure how you plan to control them.

I have installed hundreds and hundreds of Honeywell HR82 and HR92 head sand never had a complaint about noise.

PWM control is not something you will be able to make use of unless you are an electronic nerd. No domestic controller on the market will utilise it.

 

[endecotp]

Thanks Dan.

PWM control is not something you will be able to make use of unless you are an electronic nerd .

That's me . Nerdy light sleeper.

I'm thinking about this now because I'm fitting some new radiators and I'm wondering about (a) what brand of TRV base I should fit and (b) installing some sort of wiring outlet near the valve.

 

[Dan Robinson]

Honeywell Valencia valves will work fine on Honeywell MT4 actuators and probably the John Guest ones too.

Problem being you'd need to power them.

Depending on the number of rads we're talking about you could wire them back to an HCC80R and control through evohome. I have plumbed all my rads back to a UFH manifold and control them this way. Each rad just has a lockshield valve on each end fully opened.

The number of actuators wired directly into the HCC80 is limited (11 or 12 I think), but easily overcome with a relay if you had mahoosive numbers.

You can then sub zone the house into 5 zones out of the box or 8 zones by fitting the expansion board.

 

[endecotp]

Honeywell Valencia valves will work fine on Honeywell MT4 actuators and probably the John Guest ones too.

Thanks. Do Evohome (etc.) expect normally-open or normally-closed actuators? I presume 240 rather than 24 V. I'm thinking about how I'll retrofit a conventional control system when I get bored with my nerdy DIY control project.

I have plumbed all my rads back to a UFH manifold and control them this way. Each rad just has a lockshield valve on each end fully opened.

I may end up with a combination of on-rad valves and remote vales due to pipe routing.

 

[Dan Robinson]

expect normally-open or normally-closed actuators

It can do either as long as they're all the same.

 

[MeldrewsMate]

PWM will regulate the power absorbed by the actuator, but to what end? The main reason that TRVs can cause noise is by the high velocity of heating water passing the valve when it is nearly closed, and the reason it is nearly closed is because the mechanical TRV head has an 'analogue' output. In a simple radiator application surely the radiator, under the control of a local thermostat, can be either ON or OFF to regulate the room temperature to a satisfactory level. So having ON-OFF relay control of the actuator (which takes about 3 minutes to fully modulate) will be adequate and will almost eliminate velocity noise. Now to the problem of feedback. How do you 'tell' the boiler to supply heat to that single room when the thermostat calls? You can either provide hardwired feedback (from each thermostat) to provide (in heating parlance) boiler interlock or, if using something like the Honeywell Evohome, the Single Zone Thermostat pack which will communicate the room temp to the main Evohome control panel and also provide ON-OFF control of your actuator via its relay (called a BDR91 boiler relay).....and communicate with your smarty-pants phone too, if you wish.

In short....ON-OFF control of your radiator is adequate, trying to position control the valve (TRV position) by PWM (or any other power modulation method) is a waste of time and effort to no benefit, and potentially to reproducing the mechanical TRV noise, and possibly generating electrical/RF noise in the process.

I hope this helps.
MM

 

[endecotp]

The main reason that TRVs can cause noise is by the high velocity of heating water passing the valve when it is nearly closed

Well, in my case the most disturbing noise is the motor in the battery-operated TRV. It's disturbing because it's a short burst of noise, whereas the water flow noises tend to be more or less continuous and easier to sleep through.

When I do hear noise from high-velocity water in valves, I believe it's because only one or two TRVs are open in the system and my pump doesn't reduce its speed in that case.

In a simple radiator application surely the radiator, under the control of a local thermostat, can be either ON or OFF to regulate the room temperature to a satisfactory level. So having ON-OFF relay control of the actuator (which takes about 3 minutes to fully modulate) will be adequate and will almost eliminate velocity noise.

All true, though I think there may be uses for PWM when you're trying to heat more than one room, but not all of them - i.e. you use intermediate valve positions to share the boiler output between rooms in some way. Or perhaps lockshield valve balancing and correct radiator sizing are sufficient. I only mentioned PWM because I noticed that some actuators claim to have it and others don't, and clearly a PWM actuator can be used as on/off but not vice-versa.