Heated Wall and TRV Remote Control Questions

AlaskaDick

I am progressing with the installation of my mod-con boiler and in-floor heat, which in most parts of the house will be installed from above in routed grooves with thin heat transfer plates in the 1-1/8” plywood subfloor. This will be covered with ¼” plywood and vinyl plank flooring. The boiler and near boiler piping and manifolds for the secondary loop is now in place.

The new boiler is a Navian NKC199n with a 10:1 turndown ratio and will have outdoor reset. , I am using an indirect water heater. There is one 0018e delta P system circulator. Most zones with be controlled with Taco Zone Sentry valves.

Some areas don’t lend themselves to in floor-heating, for those I am looking at in-wall heating. The smallest loads are two rooms at about 1,000 BTU/H each. One of those is an entryway which has never been heated. It gets cool, but not unbearably so. In those rooms the heating will be with ½” PEX, and thin heat transfer plates backed by 1” EPS foam and R15 fiberglass.

I plan on doing some or all of the heated walls as micro zones using TRVs. I have a couple of NOS Danfoss TRVs with remote controllers with 16 foot capillary tubes that will work, but wonder if there is another way to control them? Once the wall is sealed up it would be extremely difficult to replace the controller and capillary tube if it ever failed. Are there wired or wireless TRV remote controllers/thermostats that don’t require an app on a phone? They don’t need to be “smart”.

Two of the rooms that will have heated walls share the wall with a laundry room. I would much rather install the radiant heating from the laundry room side of the shared wall where the access is better and the appearance of the reinstalled drywall is less critical. After removing the drywall in the laundry, the PEX loops and thin aluminum heat transfer plates will be attached to the back side of 5/8” drywall in the stud cavities. 1” EPS foam will be used against the wall between the PEX runs. This will be backed by R-15 fiberglass batts the drywall installed in the laundry room. I am thinking that the heat transfer plates can be glued to the inside of the drywall with construction adhesive. Just a couple of spots at the center so they aren’t restricted from expanding when heated. The EPS insulation will be glued to the drywall and heat transfer plates with an adhesive appropriate for EPS. Can anyone who has heated a wall from the back side comment on this plan?

Kaos

A heated wall is pretty much an oversized panel rad, what's wrong with using a regular TRV mounted near the bottom of the wall? This would keep the bits that might need to be replaced outside the wall for easy access.

If you are installing the radiant heat in an inside wall, you don't need insulation. Laundry room and plumbing would still need heat, no point it keeping it cold. Instead of heat spreaders, either a simple pex loop through the middle of the studs and maybe add on some Ultra fins for extra output. Bonus of this setup is it keeps the piping away from the drywall.

AlaskaDick

Kaos, Thanks for the comments. Some additional information -

Using a remote control for the TRV lets me locate the valve in the nearby boiler room and allows the control to be in a location where it better sees the temperature in the main part of the room above the floor and away from potential drafts and from the emitter.

The laundry room is an inside room and doesn't currently get or need any heat from the heating system. It's also adjacent to the boiler room and picks up some heat through that wall. I expect it would get uncomfortably warm on a sub-zero day without insulation as the two adjacent rooms being heated have considerably higher heating loads than the laundry. I already have insulation in the interior walls that I added 20 years ago for sound deadening purposes so I will just reuse what I have.

I am working to keep the water temperatures low. The heat transfer plates will allow me to more effectively direct the heat into the rooms where it needs to go and improve conduction from the PEX through the dry wall so it is a more effective emitter. I did some testing with a couple of styles of heat transfer plates as well as no plates using a FLIR which convinced me of their value. I posted the FLIR photos a few months ago.

Kaos

In that case, I don't see the need for the rigid. I would hold up the transfer plates with construction adhesive and tack it in place with some shorty staples till the glue sets. The fluffy in the wall cavity is all you need after that. Adding some horizontal blocking notched about 5/8" to allow the pipe to pass would not hurt either. For a 1000BTU you don't need all that much area.

If you want the TRV in the boiler room, one option is to run it up inside ENT flexible conduit. You can put a gland on the end of the conduit to hold the bulb or a device box with a perforated cover. This would let you pull the whole thing back if you ever need to replace it without needing to get into drywall.

AlaskaDick

ENT is an option, although nails have played hell with my spade bits and enlarging the holes to fit it would do more of the same. Another option, assuming that the capillary tube is intact, to use it as a pull wire. I just wanted to see what options there were before I complete the installation.

hot_rod

I use Pex as a sensor tube, a copper stub on the end for better conduction. Push it in with a stiff wire or fish tape so it can be removed.

AlaskaDick

A bit of an update and a clarification. I'm using the type of remote thermostat that has the sensor and control combined in a wall unit with a capillary to the valve.

I'm having to put the valves behind a panel in the wall. I have 16 foot capillary tubes and would need 17 feet to reach the utility room. No big thing as the wall panel opening will be in the laundry room.

I've shuffled the washer and dryer out of the way without disabling them and moved a couple of wall cabinets and I'm in the process of removing the drywall.

Mark Eatherton

What HR said. We used 5/8" alumaPEX for cap tube conduit. We'd then use a vacuum to suck a string (nylon chalk line works well) with a big wad of cotton tied to the string to act as a mouse and then use the string to pull the cap tube back to the valve. Works like a champ. Old electricians trick.

bryanbdp

I used 1/4 inch plywood over my tubes & spreader plates, but I wish I had gone at least 3/8. The 1/4" is too flexible and telegraphs the unevenness of the plates through to the other side. I'd use a dense pattern of PL premium adhesive and just enough fasteners to hold the plywood down as needed until the glue sets to keep panel as flat as possible

AlaskaDick

Thanks for all the suggestions.

There was still just a little bit more to do before I started buttoning up the wall. The section left of the corner heats an entry, the right side heats my shop. The TRVs are near the floor. I used construction adhesive to attach the plates to the drywall for about the first six inches near the bends in the PEX. Otherwise the plates are held in place by 1/2" staples into the 5/8" drywall. I was going to use strips of EPS insulation between the studs and tubes and between tubes to support the plates, but decided not to. The layer of fiberglass will apply a bit of pressure to the plates to hold them against the drywall.

Although the calculations seemed to support using a fair amount of tubing to heat the shop, what I have is probably overkill and I probably underestimated the amount of insulation I have in that room when I did the calculations. I haven't had any heat in the shop for a couple of months and it has never been cold, even at 10 F outside. What heat it gets come through the open door to the adjacent garage (which I use as additional shop space) and the adjacent boiler room where the door usually stays open.