Replacement for baseboard heater

[gvladybug]

This is for a cabin in Colorado at 8600 ft elevation where we shut the cabin down November - April and have no heat or water.

We have gutted our basement bathroom that is 5X7 in size. It had one 4' long baseboard heater with a wall thermostat.
As part of the remodeling we have enlarged the shower and now the baseboard heater has to be replaced, otherwise it would be in the shower. It was a 220v baseboard electric heater.

I have been looking at wall mounted heaters as we have enough room to put one on the wall in the bathroom away from the shower and use the existing wiring.
I was thinking of a smooth heater for ease of cleaning. But the the thought of a fan sounds appealing to circulate air and dry up moisture from showers (no exhaust fan but there is a small window).

Here are a couple I am considering:
https://www.homedepot.com/p/Stiebel-Eltron-Wall-Mounted-Electric-Fan-Heater-CK-20E/204091960
or
https://www.homedepot.com/p/Stiebel...unted-Convection-Heater-CNS-150-2-E/204493100
or
https://www.homelectrical.com/1500w...MjfPqRgQmckCNk93eVQ0pXVwXo4N-cHBoCqkkQAvD_BwE

Anyone have advice or recommendations?

Thanks in advance!
Di

 

[Dana]

Run a heat load calculation on the room. A 5x7 bathroom in a mostly below-grade insulated conditioned basement probably doesn't call for more than 75-100 watts to keep it warm even when it's -10F outside. It's highly likely that the baseboard was way oversized for the actual needs of the room, and that a panel radiator or heated towel rack of a more appropriate wattage would be an improvement in comfort.

The CK 20E uses 2000 watts, probably more than 2x bigger than needed, and if running at a high duty cycle would cook the place. Same problem with the CNS 150-2-E. If it's running off a thermostat the fan won't be running a high enough duty cycle to provide much benefit.

While still LUDICROUSLY oversized for the heating load, the Stelpro convecting panel radiator would be more comfortable heat to bare skin, since a large fraction of the heat would be radiated, which provides nice sunny bare-skin comfort even when the room temperature is low. But a much lower wattage version would run longer duty cycles and have a more stable surface temperature.

A 100 watt heated towel rack or panel radiator is good for 340 BTU/hr which may be close to the actual heat load of the bathroom if it has a signficant sized window (yours is described as "small").

If you can give me the approximate dimensions of the exterior walls of the bathroom (not the partition walls to the basement), the insulation R value, and the size and type of window, as well as a ZIP code (for approximate outside design temp) I could come up with something better than a WAG on how many watts it really takes, but even if it were a corner room fully above grade with a 2x4/R13 type wall insulation and a 3 square foot clear glass (not low-E) double pane (like most basement windows) the heat load of an 8' tall room at -10F outside, +70F inside looks something like this.

Total wall area: (5 ' + 7') x 8'= 96 square feet, less 3 square feet of window is 93'. The heat loss per square foot of that type of wall is about 0.1 BTU/hr per square foot per degree F temperature difference. At -10F outside, 70F inside it's an 80F difference, so the wall losses are about...

93' x 0.1 x 80F= 744 BTU/hr.

A typical clear glass vinyl basement window runs about 0.5 BTU/hr per square foot per degree-F, so the window loss for a 3 square foot window is:

3' x 0.5 x 80F= 120 BTU/hr

Total losses: 964 BTU/hr.

Changing units to metric (watts), 1 watt is 3.412 BTU/hr, so you'd be looking at 964/3.412= 283 watts (not 1500 watts, not 2000 watts.) And that's for a sub-code fully above-grade room, with no lights on. For a mostly below grade basement the window losses would be the same, but most of the wall losses would be 1/3 that or less.

So, to dial it in,

1. How big IS that window, really?

2. How high is the ceiling?

3. How many horizontal feet of exterior wall?

4. What is the R-value of that wall?

5. How much of the wall is above-grade?

6. Where is the house located? (For outside design temperature purposes.)

 

[Sponsor]

 

[gvladybug]

1. How big IS that window, really? --- it is a 24x24 - this is not a low E fancy window and is really a cheaper window
https://www.lowes.com/pd/ThermaStar...4-in-x-24-in-Actual-23-5-in-x-23-5-in/3119739

2. How high is the ceiling? -- 7.5 ft ceiling

3. How many horizontal feet of exterior wall? -- exterior wall is 5 ft long

4. What is the R-value of that wall? - Rvalue is not sure what was put in but it is new bat insulation

5. How much of the wall is above-grade? -- 100% north facing wall

6. Where is the house located? (For outside design temperature purposes.) -- 81055 but we are about 1600 ft higher than the zip code

When I posed my question I was thinking:
* What is easiest to clean as those vents collect dust/grime and are hard to clean
* Would one type of heater versus another be better for drying the air of humidity after a shower since there is no fan in the room and typically it is too cold to open the window
* Comparing the types of heaters and given I have a wall thermostat; would one heater versus another heat up the room faster from an unheated state? We regularly will have the heaters off when the cabin is open (April - November) and it can be very chilly in the basement; so going from upper 50s to 70 quickly (not hours) is preferred.
* Longevity - the current baseboards were installed in the early 80s and are functioning with no issues; I would like to choose something that will last equally as long. I would not have changed this one if it were not too long for the room now that the shower is bigger.
* Are there any brands or types I should avoid and stay away from? I need something that is reliable as in the late spring/fall there is a significant amount time it will be in use when no one is there.

FYI, this is the only source of heat for this bathroom. In the basement, there are other baseboard heaters in the bedroom and laundry but no forced air.
Thank you in advance for your insight/information.

 

[Dana]

According to the spec for that window the U-factor is 0.34 BTU/hr per square foot per degree F (which is indeed a low-E window.) But it's 4 square feet.

Rounding up to 8' for height you're looking at 5' x 8' = 40 square feet, less 4 feet of window is 36 square feet.

Assuming it's 2x4 16" on center framing you're still looking at about U0.10 for the wall performance, if it's 2x6 it's about U0.07.

The 99% outside design temp at the the nearby Alamosa airport weather station at 7543' of altitude is -11F. Giving it a 3F per 1000' of adiabatic cooling fudge factor would put you at about -14F, which would be an 84F difference when it's 70F indoors.

So the window losses are roughly

U0.34 x 4' x 84F = 114 BTU/hr (not too different from the WAG)

The wall losses are roughly:

U0.1 x 36' x 84F= 302 BTU/hr

Total 416 BTU/hr, which in watts is (/3.412=) 122 watts. If it's a 2x6 wall you'd be looking at 85 watts.

So a 150 Watt heater operated by a wall thermostat would have you covered down to below -20F even if it's a 2x4 wall/

If it's a 2x6 wall 100 Watts would do it.

Throwing at 1500-2000 watt heater at it makes no sense. If heating it up quickly from 50F to 70F is a primary goal, 300 watts would do it. At 500 watts it would heat even faster but would be less comfortable, delivering hot flash followed by a chill every time the thing cycled. Since you're not there in the dead of winter you don't necessarily need even the 100 watts, but if you want fast response, 250-300W wouldn't be terrible, even though it means a fairly low duty cycle when it's in the +20sF. (If the specs for the heater product are in BTU/hr, keep it under 1000 BTU/hr, which would be ~3x your design load, and already complete overkill.)

No heater is going to remove humidity from the room after a shower. Heat doesn't move moisture, it can only cause the moisture to change state from liquid to water vapor. The most a heater will do is to evaporate surface liquid moisture into the room air, which would only condense once the room cool enough. The only humidity solution is dilution aka "ventilation" with less-humid air. If it often stays humid enough to get moldy in there, a tiny through the wall bath fan might be in order. Panasonic makes some very efficient & quiet bath fans- the 70 cfm through-the-wall FV-08WQ1 is about right for a bath that size. Put it on a timer or occupancy/vacancy sensor switch so you don't forget to turn it off (it's pretty quiet.)

My own preference for this application would be a heated ladder type towel rack, since they're practically self-cleaning (even easier than flat panel radiators) , and provide another useful function: A heated towel rack dries off the towels pretty fast (even though it doesn't dry out the bathroom) compared to hanging them in the bathroom with a fan type heater running an extremely low duty cycle of only a few percent. From a reliability point of view it should have as long or even better longevity as electric baseboards, unlike heaters fans which have bearings to rust up and grilles to dust-up. Most small electric heated towel racks in the US run off 120VAC, and can use a line voltage thermostat. It's more likely that your 4' baseboard was a 240VAC unit- the thermostat might be made to work with your lower wattage towel rack, but brand new line voltage thermostats for <1000 W loads are pretty cheap.

There are lots of variations on the theme, but electric resistance heaters are a mature technology, and the one that suits your decor that has the right wattage range should last pretty much forever. This 150 watter would cover your heating load without any problem. I haven't really specified or inspected very many electric towel rack heaters- I suspect even the box stored have something to offer. Just measure the available wall space carefully to make sure it fits.

An alternative or addition (for faster heating time) to a heated towel rack would be to install some electric mesh radiant floor, which is pretty cushy. That would improve the drying time of the floor, but since it lowers the duty cycle of the towel rack, would slow the drying time of the towels if both are in use.

 

[gvladybug]

Thanks for all the detailed info. As a novice I just think about ascetics and utilization costs as electricity costs are high there so the shorter the run cycle and the longer between cycles seems in my mind to be optimal.

I had thought since the air is so dry in the mountains that the fan might move the air around and have it absorb some of the moisture thus eliminate the steaminess after a shower.

FWIW, I thought the 4' baseboard heater didn't do a great job keeping the room toasty-- but that could be because I am from Texas where it is MUCH warmer and in Colorado where it's MUCH colder. Right now there is a 30 degree temperature difference.
Alamosa is a high desert so it is much warmer during the day and likely close to the same at night -- but that is hear nor there.
It could also be because the door to the bathroom is open 99% of the time when we are there unless it is in use, so the heater is likely heating the hallway area as well.

I will look into a hardwired towel heater . I have used one in Europe before and it is nice to have a warm towel. Just not sure since the baseboard heater didn't really warm the room toasty warm for me.

 

[Dana]

If toasty warm is a requirement it's hard to beat the radiant floor + heated towel rack combination.

Even the same heat output finned baseboard convectors are at the very low end of the comfort scale compared to any radiator, including a warm towel rack. Even if it's keeping the room at temperature it's not delivering any kind of warm-glow feel.

A radiant floor is at the high end, since close to 100% of the heat transfer is radiated, not convected, and feels really great on bare feet when getting out of the shower compared to a cold slab. If you do some radiant floor, be sure to give some clearance around the toilet drain, lest it melt out the wax seal.