Hydronic towel warmer: run it with a 2 g. water heater or as a zone of the floor heat

Shortfinger

In new construction happening now, the walk-out basement level of a two level house will be heated with pex in the slab and one or two zones, the condensing boiler propane-fired. The owner wants a hydronic towel warmer in the bathroom immediately above the mechanical room.

How best to run that towel warmer / radiator? The simple way might be to do a 2 gallon electric water heater with a small circulator in a single circuit, 145 deg. F. water, no mixing valve needed, a simple on-off-timer switch controlling the circulator.

The other might be to pipe it to the floor heating system somehow, a single zone to the unit, but what would that entail, control-wise? The warmer would be run often in the summer when no heat is needed downstairs.

Suggestions and advice are appreciated. Thanks.

dko

If you were going to put a 2 gallon electric water heater you are better off just getting the electric towel warmer instead.

Is this just for warm/dry towels or to actually heat the space as well?

For example
https://runtalnorthamerica.com/residential-electric-towel-radiators/

Shortfinger

Cannot do electric. The warmer is in the shower room and code says no.

Shortfinger

The "room" is the tiled walls tiled floor shower plus soaking tub space, wet, and the towel warmer will provide some heat besides warming towels.

STEVEusaPA

Pipe it with the floor at the end of the run

Dave Carpentier

STEVEusaPA said:

Pipe it with the floor at the end of the run

Might not be using the floor heat in the summertime, but still would like warm/dry towels.
Imho, the small water heater would work.

hot_rod

Do you have a domestic hot water recirculation loop? Some radiator brands are made with potable water approval. Runtal for one.
A TRV could control it also.

dko

Towel warmers are usually installed on the other side of the glass..





If they take a nice steamy shower, they're going to wipe with a damp towel?

GroundUp

Can you just tie it into the existing DHW tank, if applicable? Unless you find something else to add to that towel warmer zone or employ a buffer tank, the boiler is going to short cycle like crazy if you try to run the towel warmer by itself. Obviously the floor heat will not be active in the summer nor would there be any control over the towel warmer if you piped it in with one of the radiant loops, so also a no-go. If tying into an existing DHW tank isn't an option, then yes you're looking at a small electric standalone WH.

GGross

Certainly seems strange to keep the towel in the shower, but to each their own. I say use the water heater, or tie to an existing water heater. No need to add complexity to the boiler system just for a towel warmer.

Shortfinger

They want the towel warmer/radiator in the wet "room," it's way on opposite side of shower head in an 8'6" width room, there are lots of installs seen in pics on web of these hydronic units above baths and in shower/tub rooms. There is no domestic hw recirc and hw heating is via a propane fired on-demand without the capacity to produce 145 deg. F water, which we want for the towel thing.

These things need hot water, hotter than what's going on in the in-slab floor heat for the floor 0 spaces, and if we were to want that as the water source, we'd want to dedicate a zone, so there's complexity there, circulator pump, t-stat or on off or whatever.

Running it as a loop from the domestic hot water means we'd be running the unit with 120 F. water, which greatly reduces the effectiveness of the rack as either a towel warmer, or a space heater. We want it in the shower room to add a little extra heating particularly because of large window over the soaking tub.

Myson makes a lot of these hydronic towel warmer/radiators, and offers this schematic for running one with a water heater.

We think maybe we can do one of the small water heaters capable of topping out at 145 F., an inexpensive recirc pump, and control the pump with a Honeywell programmable timer switch on the wall outside the glass wall room, to go On/Off or timed.

hot_rod

A small 6 gallon electric tank is what I have used on micro load systems. typically a 1300W element 4,400 BTU/hr.
And you can upsize the element if you need more power. 140F or so is possible in a small electric tank, should be plenty for that application as it is not heating the entire space. I hope.

dko

I would recommend the mini-boiler from electro industries for your use.

https://electromn.com/electric-mini-boiler/

Made in USA, great company to support, perfect for your application.

I never recommend the small 2-6 gallon tanks to anyone unless it was for personal use or a small office sink used under the cabinet. Those small tanks never seem to last and leak.

hot_rod

Water heaters are glass lined vessels tested to 300 psi. In closed loop 12 psi systems they should last as long as a plain steel tank boiler

The only drawback to electric wh tanks is they are not ASME listed
Although not all electric hydronic heaters are either