TRV, with remote sensor or no?

R. Kalia

Wondering if you find that thermostatic valves work OK without remote sensors. (When I think about it, it seems they can't possibly sense the room temperature, they must sense the radiator temperature, and that's not enough to determine the room temperature. But I am probably confused...)

Mike T., Swampeast MO

The illustrations provided with Danfoss TRVs show units WITHOUT remote sensing located ONLY on the top connection of a floor-standing radiator. If you are using bottom connections (again on a floor mounted rad) a remote-sensing device is suggested and to be located in a quite specific area.

Mark J Strawcutter

Mike and I disagree on this...

but my interpretation of Danfoss instructions are that integral sensor heads on what they call "side mount" valves are quite legal on bottom fed radiators. They even show an example in their literature.

What you want to avoid is having the operator head above any piping where convective currents would incorrectly influence it.

Honeywell TRV instructions agree with Danfoss in this regard.

That said, I used angle valves with remote-sensor operators because I thought the side-mounted ones would be prone to getting hit/damaged by furniture etc.

I do agree that the remote sensor would probably give slightly more accurate performance however.

Mark

Paul Pollets

My experience

I've used more than several hundred TRV's on radiators over the past 10 years. The remote actuator head is as accurate as floor mounting the TRV at the bottom radiator tappings. Never had any problems with the heads mounted vertically, either. I'm told that horizontal installation is more applicable to using the TRV's on a steam rad. I've had one head fail after 8 years, being on the radiator that was adjusted 2x daily. The capillary connection on the remote TRV sometimes requires some carpentry to conceal, and care is required not to damage the capillary.

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Mike T., Swampeast MO

Yea, I'm probably \"reading in\" a bit...

...but that integral sensor is supposed to be where free air can pass over and the illustrations I have where it appears to be on the bottom of a radiator doesn't show legs--like it's a wall-mount rad. All the rest show an integral sensor on top but NOT covered by drapes/etc.

The mounting illustrations for remote sensors specifically show them NOT near the floor and recommended 12" - 28" above the floor.

Using the bottom connections an integral sensor will only be about 4-5" off the floor and would seem to be more in line to be affected by either cool air or drafts near the floor...

I do know from experience that the sensors are HIGHLY sensitive to drafts! A slight draft seems to make it overheat just enough to make you turn down the valve a bit and while it still works, temp fluctuation seems to increase. A heavy draft will keep the thing running at nearly full-blast all of the time. Also, if installing a remote sensor on an outside wall that is not (or poorly) insulated make CERTAIN you install insulation behind the sensor--or perhaps drill a little hole and fill that area of the wall with expanding foam insulation...

Mike T., Swampeast MO

Glad to hear...

...confirmation that I'm being overly conservative!

HydronicRookie

Vertical still doable?

Hi Paul, Its been 10 years since this post and I just wanted to ask if its still the case, in your experience, that orienting a TRV vertically while mounted at the bottom inlet of a cast iron hot-water radiator can be done without the heat of the rad affecting the TRV too much.



You cited the precaution of using a 'side-mount' (horizontally oriented ) valve to be geared towards steam radiators mostly, which makes sense to me. I attached a picture from the Danfoss valve guide, but they fail to differentiate between usage in hot-water vs. steam rads - I guess they're being cautious?



I'm hoping this is still the case, as I am about to pull the trigger on buying a whole set of TRVs, but would prefer that they all oriented vertically if there isn't too much of a noticeable difference.

Paul Pollets

TRV's

10 years and still the same advice. I do use the remote actuator head when the radiator is covered by an enclosure. The room where the T-stat is located should not have a TRV.

ChrisJ

Remote

I have two TRVs in use and part of me wishes I could locate the sensors away from the outside walls.



The outside temperature as well as wind have a decent effect on mine. Problem is from what I've seen to use a remote sensor they don't give you much distance and I'd need to protect the capillary somehow.



It's a shame no one makes a wireless setup for this yet?

SWEI

The right answer here IMO

is proportional zone valves paired with modern controls.  Standard practice for DDC jobs, but unfortunately not available for off-the shelf residential and light commercial applications, at least in North America -- yet.



http://www.belimo.us/ishop/cms/sh/belimolibrary/cv/ccv/CCV.html if anyone is interested.