Low profile Floor Box to replace radiator where new sliding door going

[b gordo]

We're putting in a sliding door, but there is a baseboard radiator there. I'm guessing a floor box would be the best replacement, but SlantFin's is almost 9" tall, and we've only got about 5" to a slab.

Any suggestions as far as a low profile floor box, or other approaches, are appreciated.

 

[Dana]

Trench heaters pretty much suck, they don't convect well, fill up with dust dirt & debris, basically a PITA. You'd be better off installing radiant floor there, or maybe a small convecting panel radiator.

How much baseboard are you replacing, and how much wall area is being replaced by glass? Increased glass area increases the heat load and the amount of radiation required- we just need to get a handle on just how much larger the heat load is going to be to size the replacement heat emitters appropriately.

 

[Sponsor]

 

[b gordo]

Hi Dana, currently it's four windows about 8 feet, long to be replaced by an 8 foot sliding door. The baseboard heater is 12'. Note, this area had been a separate room but a wall was taken down. So the new room dimensions are 18 by 24, with 18' of baseboard remaining at the other end of the room.

Yellow is where windows will be replaced by sliding door, and the red baseboard in front must be removed, and maybe replaced somehow. Note, it is fully open to the kitchen. The green line is where there used to be a wall before the previous owner's modification. So, I'm not 100% sure we need to replace it but since we are redoing the floor as well, now is the time to do something. The other option is a portion of the floor getting electric radiant, perhaps not used very often.

There will be new porcelain tile going down in all of the areas in the diagram.

 

[Dana]

How many square feet are the windows that are going away (including the sash, but not the trim)?

Ceramic tile floors are VERY amenable to low temperature radiant heating due to a much higher thermal conductivity than hardwood or carpet. It's expensive to do the whole thing that way.

How much wall distance do you have between the sliding door trim and the fireplace, and how much between the slider trim and the partition to the breakfast nook?

 

[b gordo]

Hi Dana,
I'm not at the new house, but can answer some questions now. First, the Breakfast nook will no longer be divided by the short walls. We are going to have porcelain tile for the entire floor area depicted, so we are wondering what Replacement heat source, if any, is needed once the 12' baseboard is removed (shown in red in front of the 3 bay window highlighted in yellow). That Yellow Window has two normal sliding windows on each end, with a large fixed pane between. The length is about 8.5'. Sliders will increase the height by about 2 feet. The fireplace is an efficient insert with a blower and is only in the middle of the diagonal. I'd say there is about 1.5' from the to be installed slider to the corner of the fireplace wall. There is also about 1.5' from the other end of the slider to the old breakfast nook wall, which is going to be removed. Thus, we could extend the breakfast nook baseboard about 3.5' maybe 4'.

One other complexity, the portion of the room currently has a sunken floor. We'll be raising it to match the rest of the house. That is why my original question was about a low profile floor box, because we only have about 5" to raise.

Electric Radiant is another option.

We're not sure if we really need to replace the baseboard to be removed, as it was placed there when the green wall existed. Can something like a Suncor 30" electric matt do the trick, or maybe two of them?

Would we have a problem with a tile floor that is only heated in one section?

We think we'd have a thermostat set pretty low, except when we have big family over and the kitchen table would be doubled out towards the fireplace, in the winter.

o

Here's another diagram, the tan section is the sunken section. Those short white walls shown in the picture above between the sunken section and the living room will be gone.

I could get exact measurements of the weekend if that would help.

 

[Dana]

You could do the electric radiant, but at NY utility pricing it's very expensive to operate if it's supplying the proportionate amount of heat that 12' of baseboard was delivering. If you do that, run it off a floor thermostat, not a room thermostat, and keep it under 75F.

If the half-wall partition is going away you have plenty of room to add a thin panel radiator with equivalent (or slightly greater) output than 12' of baseboard. This would improve comfort by quite a bit relative to baseboard, since it counterbalances the lower radiant temperature of the window with a higher radiation temp, increasing the average radiant temperature of the room. When it's cold out the glass might be 50F, detectible on your face with eyes closed from a handful of feet away, but if it's next to a 140F (surface temp) panel radiator it balances pretty well, feels great! The average radiant temperature is far more relevant to human comfort than air temperature. The heat transfer from fin-tube baseboards is nearly entirely air convection, not radiation.

With 180F entering water temperature typical baseboard puts out about 500 BTU/hr per running foot, and at 180F average water temp it puts out about 600 BTU/ft-hr. So a 12 footer is good for about 6000-7200 BTU/hr when the heating duty cycle is high and the baseboard is at full temp. There are many panel radiators good for more than 7200 BTU/hr @ 180F AWT that will likely fit. A 30"H x ~48W x 3"D Myson SX70 120VN is good for about 7600 BTU/hr @ 180F AWT, and the front face would be about 3.5-4" from the wall. If that's too tall for your liking the 20"H x 40W x 4.5"D A Myson T622-5-10 delivers about 7200 BTU/hr @ 180F AWT and if 48" is too wide the 24"H x 36" W x 4.5" deep T622-6-92 is good for ~7400 BTU/hr @ 180F AWT.

A slightly deeper (formerly Biasi) Ecostyle B-24.40 ECO (24" H, 40" W, 5" deep) puts out about 7600 BTU/hr @ 180F AWT and the narrower but taller B-36.32 ECO (36" H x 24"W x 5"D) delivers about 8500 BTU/hr @ 180F AWT.

Any of those would be a reasonable and more comfortable upgrade to the baseboard. There are others, some with designer aesthetics (for a price) but the Ecostyle rads in that range run about $400 or less (delivered, internet pricing), the Myson SX70 120VN would run about $200 or less, the T622 series about $300 for the T622-5-10, and ~$225 for the T622-6-92.

There are prettier versions (multiple vendors) if the Euro-basic radiator look feels like it would crash. Basic flat panel looks like this:

But there are others with aesthetics along the lines of this:

...or this:

...and convecting bi-metal rads like this:

 

[b gordo]

Thanks, we didn't know of those options

 

[b gordo]

Do these radiators have an adjustment that controls how much heat they project into the room versus what they pass through? My thought is that the existing baseboard works at one level and we'd be introducing a different technology into the same circuit. So perhaps we might need to cut back the heat given off slightly.

 

[Dana]

At boiler output temperatures above 120F there is nothing mysterious about mixing panel rads with fin tube baseboard. BTUs are BTUs and the output of both radiators and fin tube grows linearly with average water temperature. There really is a "equivalent baseboard" metric that can be applied. At average water temps of 110-115F or lower panel radiator output is still pretty linear, whereas the low convector height of fin-tube baseboards results in ever lower output in a non-linear fashion. This is only relevant if you're trying to run a modulating condensing boiler with primarily fin-tube baseboard as the heat emitters.

Most panel radiators are designed with the ability to take a radiator thermostat for tweaking a particular radiator's flow & output to tweak the room-to-room temperature balance within a zone. It would stick a few inches out the side, adding to the overall width, which may be of concern if the available space is a bit tight.

The particulars on how they are set up vary- you would have to consult the manuals to be sure no exterior plumbing such or valves are needed to work with the radiator thermostat when plumbed in series with the baseboard.