How to remove one in-wall heater from a Hydronic system

[joshmeseattle]

Photos here: Hydronic heater photos

I'm doing a remodel project in my 2005 townhome in the Pacific Northwest and adding some cabinets along a wall that currently has an in-wall hydronic heater. I'm hoping to remove the heater (there's a second one in this room which is sufficient to provide heat), but I'm not exactly sure how to go about doing this. I might need to call a professional, but hoping this forum can give me the advice I need to DIY this.

The Turbonics in-wall heater receives hot water from the domestic water heater via a PEX tube. That runs over some copper tubing with fins and a ran blows over that to warm the air. It's attached to a 120V thermostat (King Electric HWPT120). The thermostat controls the fan in the wall heater as well as a pump that moves water to all of the heaters in the house. Note that the thermostat in this room controls two separate in-wall heaters which have separate PEX supply/return lines.

In the first image below you can see the heater on the wall after I removed the cover.


Second image shows the garage setup. Water flows from the domestic water heater (off to the right) to the series of PEX tubes that go to each hydronic heater. Then there's an equal number of return PEX tubes which bring back the cooled water which is deposited back into the water heater. You can see I actually turned off the valves for the water to/from the heater I want to remove. Also in the photo you can see the pump which moves water through this closed loop, and there's also a spigot along the bottom pipe on the return to the water heater.



So here's what I think needs to be done:

1. Turn off circuit breakers for the heating system.
2. Turn off the valves connecting the closed loop of hydronic heater water in the garage from the water heater.
3. Open the spigot and drain all water from the hydronic loop.
4. Remove the PEX tubes in the garage that go to/from the heater in question, and cap those off somehow (not exactly sure how - help appreciated!)
5. Go upstairs and disconnect the PEX tubes from the in-wall unit, disconnect the electrical, and remove the heater from the wall.
6. Put some wire nuts on the exposed electrical wires ( see potential issue below!)
7. Patch the drywall.
8. Re-open the valves connecting the hydronic pipes to the water heater so water refills the system and all the other heaters function as normal. ( is it that simple, or will I need to somehow purge the air from the tubes, aka bleed it?)
9. Turn circuit breakers back on.

One potential issue I see in step 6 is that there's one thermostat for two heaters in this room. I believe the wiring is in series, so after removing this heater I need to reconnect those wires together in the wall or the remaining heater won't work (it'll never have a closed electrical circuit). If that's the case what can I use inside the wall to connect the wires that would be up to code? There won't be any access to this since I'm installing cabinets in front of this.

Other than the potential issue noted above, does my list seem correct and complete? What potential pitfalls do you foresee that I'm missing?

Thanks in advance!

 

[TomFOhio]

If you can valve off the supply and the return from the bank of valves for just that heater only then all you have
to do is get a couple caps for the tubing. Leave the valves off.

 

[joshmeseattle]

If you can valve off the supply and the return from the bank of valves for just that heater only then all you have
to do is get a couple caps for the tubing. Leave the valves off.

Yep, I think that's my step 4.

 

[TomFOhio]

So if it's pex you can either use pex caps with the clamps or use sharkbite caps.

 

[joshmeseattle]

Thanks @TomFOhio, I looked up those caps on the Lowe's site and I think I see how they work! Would love any insights on steps 6 and 8 if you have expertise in those areas.

 

[TomFOhio]

On #6 I am not an electrician so I'm not sure about wire nutting off wires in the wall but I've seen it done. Maybe putting a
junction box in the wall with a cover over the wired off wires. Maybe someone else might know. On #8 you can turn it on to check
your caps for any leaks. Don't understand your comment about getting water back on so the system functions as normal.

 

[joshmeseattle]

Thanks.

On #6 I am not an electrician so I'm not sure about wire nutting off wires in the wall but I've seen it done. Maybe putting a
junction box in the wall with a cover over the wired off wires. Maybe someone else might know. On #8 you can turn it on to check
your caps for any leaks. Don't understand your comment about getting water back on so the system functions as normal.

To clarify, my concern is that in draining the system to remove the one heater I will introduce air into the pipes, and I may need to purge that air from the system. I've read that this is a common issue with hydronic systems if they're not purged/bled after installation.

 

[TomFOhio]

Josh, you said that you had a supply and a return for that heater only. If this is correct you won't be interfereing with the
system. You'll be valving off the supply and valving off the return to that heater only so you don't have to drain the rest of
the system. If the piping continues on to another heater then that's a different story.

 

[TomFOhio]

If I'm not understanding this guy correctly please chime in with better comments

 

[joshmeseattle]

Josh, you said that you had a supply and a return for that heater only. If this is correct you won't be interfereing with the
system. You'll be valving off the supply and valving off the return.

I see the confusion . I've added a few more details to this photo below. The valves in the red squares are indeed only for this one heater, so that's the part I need to drain. However, I don't see an easy way to drain that loop without making a big mess (i.e. I could cut that PEX and let water go all over). So my plan for draining it (steps 2-3 in my original post) was to use the spigot in the blue circle. Even if I close off all the other valves so that there's no impact on the other heating loops, I think I'd end up with air in these pipes I highlighted in yellow.

Maybe the answer is really simple, I just don't know the best way to purge that air, or avoid it in the first place, other than making a mess.

 

[Mitchell-DIY-Guy]

If you want to drain just that zone—yes you may lose a little HTF. (Heat transfer fluid). Have a bucket and towels at the ready.

You indicated that the the heat supply is a domestic hot water heater? Is it also supplying hot water for use at fixtures? (Faucets etc.) If so (unless you’re going through a fluid-fluid heat exchanger) your hydronic heat system is not closed loop but open loop. You will always have the possibility of air being introduced into the system, more so on an open loop than closed.

Regardless of open vs. closed loop, proper design would have included an air eliminator. Is there one in the system?

https://www.supplyhouse.com/Spirotherm-VJR125-1-1-4-Spirovent-Jr-Air-Eliminator-Threaded-3561000-p
That’s just one brand and style. There are others…

 

[joshmeseattle]

Thanks @Mitchell-DIY-Guy! Yes, the water heater splits out to domestic fixtures with a mixing valve for cold water so the heating water can be hotter than the showers, sinks, etc. So I suppose you're right, that it really is an open loop.

I looked into air eliminators and learned that they're usually installed between the boiler (water heater in my case) and the circulator pump. I don't see one in my system. I did find some valves I can't identify in the return pipe that deposits the cooled water back into the heater (at least I'm pretty sure that's what this pipe does). Not sure what these are for, but they don't appear to be air eliminators. You had me excited that maybe there was a built-in solution for my problem .

 

[Mitchell-DIY-Guy]

Your first photo is a screen filter I believe. Second photo looks like a drain valve w/o the handle.

 

[Twowaxhack]

First valve is a swing check

the second is a screwdriver ball valve drain found on water heaters, rheem in particular, possibly others.

 

[joshmeseattle]

OK, so my system doesn't appear to have an air eliminator, which leads me back to the original question about bleeding the air.

• Is the best option to just disconnect the PEX for the one zone without draining first and thus let all the water pour out into a bucket, probably making a bit of a mess as I disconnect it? Not sure how much water will be in the pipes, but probably a decent amount.
• Or is the better option to drain the larger loop (yellow highlights in my previous photo) with the valves for the unwanted zone open so it all drains from the spigot (blue circle in photo), and if that's the cleaner option how do I purge air once I'm done?

I've also still got the electrical issue, which maybe is better answered on another forum, but I need some solution for connecting the wires in the wall after removing the in-wall heater. Would love a solution that's up to code without requiring a junction box with access panel.

Thank you all for the guidance!

 

[Mitchell-DIY-Guy]

I've also still got the electrical issue, which maybe is better answered on another forum, but I need some solution for connecting the wires in the wall after removing the in-wall heater. Would love a solution that's up to code without requiring a junction box with access panel.

I've run into this in a remodel in the past, and I used both solutions depending on the specifics of the situation.

The first time, in order to prevent a termination, I was able to bring the wire back to where it originated and remove it. Was not exactly easy, but I did it; it was maybe like 6-8' of NM cable.
The second situation was actually easier; I simply placed a J-Box and added an outlet, rather than a blanking plate. At least it proved useful now and then.

You probably want to look up "hydronic system design" and take a good look at the various schemes used and all the parts necessary...my experience in hydronic systems was from the car wash I owned, and the de-icing and snow melt system I had in place. I then did the same thing for my home, and did a lot of research before settling on a system plan. I've attached the preliminary plan; after we installed that, we had to make field modifications. That plan is, by the way, a "primary loop - secondary loop" design where the total flow requirements of the entire system cannot be met by a limitation; in this case, the limit was the flow through the heater. The field mods after the first season of use were the Takagi TK-Jr was changed out for a TK-3 which was larger, and the pre-made SS manifolds were swapped out for custom manifolds with full flow valves. Hydronic heating has some different requirements that snow-melt and de-icing, but I think if you do a bit of research you'll find out what you may need pretty easily.

 

[joshmeseattle]

I've run into this in a remodel in the past, and I used both solutions depending on the specifics of the situation.

The first time, in order to prevent a termination, I was able to bring the wire back to where it originated and remove it. Was not exactly easy, but I did it; it was maybe like 6-8' of NM cable.
The second situation was actually easier; I simply placed a J-Box and added an outlet, rather than a blanking plate. At least it proved useful now and then.

In my case since the heaters are wired in series I need to connect the wires and not add an outlet (I think it could overload the circuit that powers all 6 remaining heaters in the house). I think a junction box and some twist-together wire connectors is my best option, and then I need to cut a hole in the back of the cabinet that will be going on this wall.