Eric, I just leave the bath towels on the warmer all the time. It would be a bit of a hassle remembering to move them back and forth. Smaller hand towels and the bath mat hang on other towel bars or rings. I have the Runtal automatic controller. It allows you to program different on and off cycles for each day of the week, multiple on and off cycles per day, and to control the temperature setting. Since I'm a creature of habit, the week days are all programmed the same, but at the weekend, the warmer comes on later and goes off later, as I tend to get moving later on those days. If my schedule deviates from normal, I can easily override the programming. The warmers in my guest rooms are programmed to be on in the mornings and again in the evenings, but off during the middle of the day. When I don't have guests, I simply set the temperature to "0", and they don't come on at all. The controllers are hidden away in cupboards or closets, where they're out of sight, but easily accessible, so their appearance wasn't a consideration. If you choose to go with a Lutron timer, be sure it's one rated for a heating appliance, and be aware that it probably won't provide as much flexibility or allow you to control the temperature level. I usually don't operate my warmers at their highest setting, and I appreciate being able to lower the settings on them during the warmer seasons. I've been totally happy with Runtal and recommend them.

Does it really need to be enclosed? Some of them are really good looking, it would be almost a shame to hide them. The cab would make it harder to build, and less likely to be used in day to day life. But if you really have to hide it, I think what you need to find is a heater with a maximum heat that's a known quantity. IIRC, many have a preset max around 110 degrees because anything higher could make a towel stored there [as in, not used for several weeks] hot enough to burn human skin. If the heater can't get higher than 110, the inside of the cab can't either. If all the materials are capable of constant exposure to that heat, you should be fine. Still, I'd allow at least a foot of space in front of the towels for air circulation, and a similar gap bottom and top to let the warm air create a chimney effect. But this sort of 'off label' adaptation could be problematic in all sorts of ways-- bet your insurance company wouldn't be thrilled, for instance. So I'd get a big, whole room heater size, display it proudly, and put it on a timer so it ran for a couple hours before and after your normal shower time.

I have a hydronic Runtal, not an electric, however my understanding is that Runtal makes radiators... yes towel bars, but their function is actually as radiators. That is why they have BTU ratings, so one can calculate the heat requirements and choose an appropriately sized unit. As stated on their website referring to both electric and hydronic, "Runtal towel radiators offer comfortable radiant heat in the bathroom while at the same time providing the luxury of warm, dry towels and bathrobes." BTW, my hydronic one is even a little too warm!! There is a way to calculate how many BTU's one needs... but it can be complicated.

In your case when you are installing a 1/2" S&R radiator on a 3/4" series loop, a monoflo tee system should be used. Similar to a hydronic kickspace heater, many pros will use 2 - 3/4 x 1/2 x 1/2 tees to connect. The reducing tees create a throttling effect taking the 3/4" flow and diverting 1/2 to the branch (Side) and up to the radiator and the rest through to the other side where it joins the return of the radiator and increasing back up to 3/4" (Like a bypass) When access is available and depending on supply and return distance of the radiator between TÂs, some will add a ½" SS ball valve to balance flow by closing that which will force more through the radiator.