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Electric baseboard — mounting questions

laughswithcrows | Posted in Mechanicals on

I am converting to electric “baseboard” heaters in preparation for a solar install in a year. I live in a cold winter climate, Detroit. Conventional practice is to mount them low, preferably under a window.

However, mini-splits are mounted high. Here, ceiling fans are uncommon, especially with reverse cycle winter use. All of my rooms will have fans. I want to mount them high. This seems to make sense, given the fan and mini-split efficacy.

I am wondering if anyone has a definitive reason why this would NOT work, or perhaps, why it SHOULD work just fine. My reasoning is to avoid blockage from furniture, as these are small units with few options for furniture placement, and I do not want to further limit that or reduce efficiency with flow problems.

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Replies

  1. charlie_sullivan | | #1

    You can get "cove heaters" that are meant to mount high, and are meant to deliver more of their heat by radiation, and less by convection, compared to baseboard heaters which rely primarily on convection. I think that's a better choice for a high mounting position, and could give you more comfort at a lower room temperature, especially compared to using a fan.

    There have been reports that high mounting for mini-splits can substantially degrade their efficiency. Straight electric heating isn't subject to the same degradation, because the efficiency is always 100%, but the heat distribution through the room could be less uniform, if you used regular baseboard heaters. The products meant for mounting high should not have that problem.

    How good is your insulation? Good insulation leads to more uniform temperature throughout the room.

  2. laughswithcrows | | #2

    Thanks, that's useful. I'll Google under cove heaters, but is there any other term I should key into?

    I am working to improve my insulation. The building is double brick, so for the exterior walls, the majority in the controversy seem to feel that I should not put insulation along those walls. However, for the ceiling, floor and interior walls along the halls, I am using a high-R Roxul, both for temp and sound. These are also very small spaces, generally, ranging from 200-400 sf.

  3. GBA Editor
    Martin Holladay | | #3

    Marlena,
    If I were installing electric baseboard units, I would definitely install them low -- near the floor, as designed. Temperature stratification is a real problem in many buildings, and you can make a temperature stratification problem worse by mounting your electric heaters near the ceiling.

    Temperature stratification can be lessened by building an impeccable thermal envelope -- one with very low levels of air leakage and very high levels of insulation. But not every builder can achieve an impeccable envelope, even when the builder tries.

    I don't advocate using ceiling fans to try to reduce temperature stratification in winter, even when the rotational direction of the fan is reversed, for at least three reasons: (1) Fans use energy, raising your electric bill, (2) Moving air will make your skin feel cooler, causing you to turn up the thermostat, thereby raising your electric bill still more, and (3) Researchers who have looked into the issue haven't been able to find any benefits -- either energy-saving benefits or comfort benefits -- to the practice of operating a ceiling fan during the winter. For more information on this issue, see Using Ceiling Fans To Keep Cool Without AC.

  4. Expert Member
    MALCOLM TAYLOR | | #4

    Marlena,
    Baseboard heaters are manufactured on the assumption that they will be mounted at floor level. Many aren't even painted on the underside and the electrical connection plates would be visible. As Charlie said there are Cove Heaters designed to be mounted near the ceiling. Regular baseboard heaters would look odd.

  5. laughswithcrows | | #5

    Ok, Martin, I hear your feedback. I lived in Tucson for a decade, where ceiling fans were ubiquitous. Winter temps there also get quite chilly, around 20F (though it's a dry cold ;-)) I found the fans to be very effective in combination with typical gas or elec forced air mechanicals typical there, but that is anecdotal.

    I am very interested in the radiant cove heaters suggested, but I have read that radiant heaters do not work well with the delta needed in this zone, and I am wondering what the experience of others has been with this?

    My primary question was why mini-splits are successful - even if, as Charlie mentions, less efficient - mounted up, yet no one seems to consider this at all for baseboards?

  6. GBA Editor
    Martin Holladay | | #6

    Marlena,
    Ductless minisplits started out as air conditioners, and were mounted high because that's where they belong. Later, manufacturers designed reversible heat pumps that operated as heaters as well as air conditioners, and these units were still mounted high because they were first marketed in hot climates, and that's what people were used to.

    Minisplit manufacturers design their indoor units so that the air flow has good "throw" characteristics and tends to mix well with indoor air. The vanes are adjustable, and different modes can be used to change the way the air is propelled. By all accounts, these design efforts work -- these units produce high levels of comfort and user satisfaction during the heating season.

    Needless to say, an electric baseboard heater don't have a fan. It's just a toaster element in a metal housing. It works by convection -- meaning that as the element heats the air, warm air tends to rise and leave the top of the baseboard unit. This subtle air movement draws in air at the base of the unit.

  7. laughswithcrows | | #7

    @Martin Right, and that's why I was thinking the combo of the heaters and the fans would work well, but you were not convinced by this logic ;-)

  8. laughswithcrows | | #8

    I appreciate this feedback. If anyone can now speak to the viability of the radiants as primary heating for the zone, I would value it.

    This building is a historic one, and so we are doing what we can to preserve original materials. However, we are also integrating a green retrofit. Whatever we do, we want to do it right , the first time, if we can. If the radiants really are that much cheaper to run over regular electric as they claim, that would be fantastic for our co-op tenants.

  9. Dana1 | | #9

    Mini-splits are still pretty efficient in heating mode if mounted a foot or more below ceiling height rather than at the manufacturers' specified minimum clearance.

    You don't have to mount the high or even use air conditioning style air coils. The floor mount versions are not a huge premium in up front and work just fine in both heating & cooling modes. The floor mount units don't protrude as much into the room as the standard wall-coils, and can usually fit under windows if desire.

    https://www.greenbuildingadvisor.com/sites/default/files/Floor-mounted%20indoor%20unit.jpg

    http://www.fujitsugeneral.com/PDF_06/Submittals/12RLFFSubmittal.pdf

    https://www.greenbuildingadvisor.com/sites/default/files/Green_Room.jpg

    https://meus.mylinkdrive.com/files/MFZ-KA12NA_For_MXZ_MULTI-ZONE_SYSTEMS_Submittal.pdf

    In a Detroit climate a floor unit type mini-split would use less than 1/3 the amount of electricity in heating mode than electric baseboards (more than 65% savings in heating energy use), AND they air condition at high efficiency.

  10. Yamayagi1 | | #10

    Marlena,
    You might want to re-read Martin's first post (#3) as he did address why your proposal is less than optimal.

  11. laughswithcrows | | #11

    I am compelled by the mini-splits, but the initial capital costs are astounding for 20 units. I used them on another project in 2007, when they were still $350-500, but now they are running 1.5x or more, especially for ones that can go to 5F. Plus, this is a multi-level, and so I would have to figure out a way to mount the compressor to the building for the "1st" floor, which is too far from the roof, I think, and would likely run afoul of historic pres people. 1st floor is not on the ground, but even if so, ground mounting is a risky venture in Detroit for the likelihood of theft.

  12. laughswithcrows | | #12

    @James I read it, and addressed it back. It does not fully explain to me WHY, however, especially if mini-splits work relatively well because of the "throw," which I would think the fans might mimic. Nevertheless, I understand that, in general, there are better options for my conception, and that's useful. I was not previously aware of the cove heaters, and they might be a good interim option - still feel uncertain about their ability to handle primary heating, even though their specs tout it.

  13. GBA Editor
    Martin Holladay | | #13

    Marlena,
    I don't doubt that cove heaters can be connected to a wall thermostat and can be used to meet the primary space heating load of the building. All the usual caveats for electric-resistance space heating apply: electricity is an expensive fuel, so make sure that your building has a very good thermal envelope to keep operating costs under control.

    There is also an aesthetic issue to consider. Cove heaters look fine to some people; to others, they look odd. A good installation can be fairly unobtrusive, but some installations look like they belong in a garage or warehouse.

    .

  14. laughswithcrows | | #14

    LOL. Yeah, for sure that bottom pick is a "DON'T." This season might be tough on tenants for cost, but next year when the solar is installed, it should be reasonable. Thanks!

  15. laughswithcrows | | #15

    Ok, now that the cove heater is on my radar, anyone have brand experience? The King has gotten bad reviews. Comfort Cove at radiantsystemsinc.com certainly have done a good job making themselves look like a good buy.

    It looks like sizing for my zone and insulation is roughly 10 watts/sf. We're in the process of redoing electrical, so the 240 is no problem.

  16. charlie_sullivan | | #16

    Most people who look at electric heat with solar power conclude that it is overall cheaper to get mini-splits because the size of the solar array can be enough smaller to make up for the cost of the mini-splits.

    Mini-splits are widely used on high-rise apartment buildings, especially in Asia. The outside unit is mounted on the side of the building.

  17. Dana1 | | #17

    The notion that it would take 20 mini-split heads to deal with anything smaller than a 10,000 square foot house is a bit astounding. The individual room loads of many rooms are well below that of a mini-split, and unlikely to need direct heating 90% of the time. (And a 200-500 watt baseboard may make sense as backup in those rooms.) Mini-duct cassettes can manage the loads of 2-4 smaller load rooms.

    Without a room by room heat load calculation it's hard to do it right, but the cost of hiring a qualified third party (not an HVAC contractor) to run the numbers using aggressive rather than conservative assumptions (to reduce the chance of sub-optimally oversizing), will more than pay itself back on less equipment cost and higher comfort levels.

    In a tightened up older construction renovation with wall coils or floor units it's unlikely that you'll need as much as one cassette/head per 500' of conditioned space, but it'll probably be at least one head per 1000'. With mini-duct cassettes it can be as little as one per 1500'.

    Ground mounting is a lousy idea in Detroit even if there weren't any theft issues. Last time I looked it still snows in Detroit, sometimes even a lot. Wall mounting them on purpose-made brackets with the bottom at least a foot above the highest historical snow depth would be the lowest one should be considering. (In my area that's about 5 feet above grade.) But it's fine to mount them even higher. Mounted 8' above grade or above an exposed or less-accessible porch roof is a bit ambitious for the casual thief compared to ground mounted in a back yard or alley, less visible from the street.

    https://www.greenbuildingadvisor.com/sites/default/files/Fujitsu%20ducted%20minisplit%20-%20indoors%20and%20out%20-%202.jpg

    https://www.greenbuildingadvisor.com/sites/default/files/images/Samsung%20ductless%20minisplit%20outdoor%20unit.jpg

    http://limric.com/wp-content/uploads/2014/10/bigstock-Air-Conditioning-Heat-Pump-Mou-15040325.jpg

  18. charlie_sullivan | | #18

    I was interpreting "20 units" to mean this is a big building with 20 apartments, rather than a house that needs 20 mini-splits for a one-family living space. But perhaps Marlena can clarify. If it's 20 small apartments, it may be that the heat load for each is smaller than the smallest mini-splits, in which case electric heat starts to make more sense. One can also consider a hydronic heat pump solution (e.g. Chiltrix) to provide efficiency like a mini-split, with the ability to put in lower-heat-output "heads" which can be Chiltrix's fan coil units (as low as 3400 BTU/h) or panel radiators. The downside of that would be that you'd lose the ability to meter the electricity on a unit-by-unit basis, and it's nearly impossible to find an experienced installer, which means the installed cost could end up high.

  19. laughswithcrows | | #19

    @Charlie, that's right. 20 units. As I think I put in the beginning-ish, ranging from 200-400 sf only. In fact, depending on air flow, I might have to use a few more, because although the larger units are small, the rooms are offset so that the a unit may not be evenly cooled or heated even with the appropriate sized mini-split for the square footage. I notice that it's cheaper to buy individual ones rather than ones with multi-zone air handlers, weirdly.

    @Dorsett and @Charlie, the mounting issue is not a technical one, though I think it would be a pain and look crappy. It's also a factor of whether the historic preservation board would allow the building to be dotted with the wall mounts along the entire building. I would have to measure to see what the actual run would be to the roof, but then I might run into an issue with the solar panel config. In any case, I'm probably not willing to spend close to $20k on the solution, unless there's a reason that is so compelling, I can't get around it.

  20. Expert Member
    Dana Dorsett | | #20

    200-400 square foot apartments are in the realm of half-ton ton PTHPs, not mini-splits. It'll use half the power of baseboards, and will delivery the luxury of air conditioning. It may not pass muster with a historical preservation board, but from a cost point of view it could still be pretty attractive if you're buying a score of them at a time. Most hotel rooms & small suites that size are heated & cooled with a single PTHP.

    Begging your pardon, but I don't see any reference (even in the beginning- ish) about this being a 20 unit rental. The statement: "My reasoning is to avoid blockage from furniture, as these are small units with few options for furniture placement, and I do not want to further limit that or reduce efficiency with flow problems." is ambiguous to this reader, especially with the lead lines being "I am converting to electric "baseboard" heaters in preparation for a solar install in a year. I live in a cold winter climate, Detroit." but maybe I need to keep working on my 'merican-ish? :-)

  21. laughswithcrows | | #21

    So, any brand suggestions for coves? @Dana, I find PTHPs aesthetically repugnant and many would require me to punch through the double brick, which I would not do. The coves seem a good bet. Comfort Cove looks good, but....

  22. Expert Member
    MALCOLM TAYLOR | | #22

    Marlena,
    I have specced coves for two projects I designed, although they only were installed in one. That owner is happy, but the reason the other declined to use them was the price. Although there appears to be a case for them being a bit cheaper to run than baseboard heaters as the radiant heat may allow occupants to keep rooms a couple of degrees colder, they aren't any more efficient, and in a residence with a few rooms, the cost of upgrading to coves begins to really add up. I'm not sure on what basis I would suggest them to a client again.

  23. Dana1 | | #23

    I hear you about the aesthetics of PTHPs, they're right up (down?) there with window air conditioners, though those with scroll compressors are noticeably quieter than those with reciprocating compressors.

    On other space heating possibilities, how is domestic hot water being supplied to the units?

  24. laughswithcrows | | #24

    @Malcolm, what brand did you use?

  25. Yamayagi1 | | #25

    Another approach worth considering that gives you the efficiency of a high performance heat pump and as well as summertime air conditioning is to go to a central variable refrigerant system such as the Mitsusubishi City Multi system. They have a Hyper-Heat cold climate system available, and they can be installed in banks to handle the entire heat or cooling load. I believe that they can serve up to 18 heads per system, so they might not cover all 20 units, but would certainly serve most. Check it out....

  26. charlie_sullivan | | #26

    I'm sure this has been said already somewhere in the 25 comments, but the first step in any case is to calculate the unit-by-unit heat load, to size whatever heating system you choose ... and to figure out what other options might be practical. VRF might be a good fit, and although it's surely more expensive than electric don't forget that it can save you money on the solar installation, which can then be smaller.

    Malcolm, is the second of Martin's two pictures your project? The industrial look of the switch mounted on the window mullion is a brilliant ironic statement.

  27. Expert Member
  28. Expert Member
    MALCOLM TAYLOR | | #28

    Charlie,
    No. I wish I could claim that level of intellectual sophistication in my designs, but usually fall well short :)

  29. Expert Member
    Dana Dorsett | | #29

    Is it one power bill for the whole building, or are there 20 separate meters?

    How are the utility rates structured? Is there time of use rates available, with a big discount for off-peak?

    James Kreyling: I can't imagine installing an 18 head City Multi for even 2x the proposed budget, described as:

    " I'm probably not willing to spend close to $20k on the solution, unless there's a reason that is so compelling, I can't get around it."

    On that kind of budget the only heat pump solutions would be PTHP.

    If the tenants are paying the bills there's nothing compelling about any heat pump solution. If off peak rates apply it may not be compelling even if she's paying the power bill. Only if she's paying the power bill at full retail would there be a possible rationale for mulit-split solutions.

    Residential retail electricity is bumping on 15 cents/kwh, higher than the national average of 12.6 cents, and higher than what she had been paying in Tucson. Without more information it's hard to say just how much power it takes to heat a building with resistance electricity in a climate that sees ~6400-6500 heating degree days, compared to Tucson's ~1500-1600 HDD. It's one thing to heat electrically without heat pump leverage in the desert southwest (it's pretty common there), quite another in Detroit. If it's a double-brick with no wall insulation a ~6000 square foot building could easily have a design heat load of 150,000 BTU/hr @ +5F (Detroit's 99% outside design temp) , which is 44,000 watts, at a 65F temperature difference. A full day of that would be 24 hrs x 44kw= 1056 kwh and 65 degree-days, so for a 6500 HDD heating season it would be 100 x that, or 105,600 kwh of heat energy use. The solar is going to offset some of that, but it would take a gia-normous rooftop to have enough panel to deliver even half that.

    At 15 cents/kwh that would cost $15,840 /year of heating with baseboards.

    With PTHPs it would be $7920 /year

    With reasonably sized ductless, less than $5000 / year.

    If you're paying the power bills, not the tenant, the $10K+ per year difference in heating costs might be compelling enough to invest in better class heat pumps.

    But if you can get off peak power at 6 cents or something, maybe not, since most of the heating power use will fall into (or could be made to fall within) off peak rates.

  30. laughswithcrows | | #30

    @Dana, that's a detailed analysis.

    Currently, the units are separately metered. However, that's not to speak to my motivations, which include a broader picture than the net costs - although immediate cash flow is a limitation. In fact, MI has an asinine law which will require me to effect some change with the metering, because you cannot net meter more than you're billed. Therefore, I could not distribute a net meter credit to tenants unless I put them all under my bill and meter them myself. However, I am willing to do this if the solar will result in some significant off-set.

    Right now, projections are that the solar array would generate 11,600 kWh/yr. If your calculations are correct, that would be about an 11% benefit to the sum use. However, although our exterior walls are brick, we are insulating all interior walls and ceilings, and replacing windows, so we expect to greatly increase our efficiency. There are only 8 apts which have 2 exterior walls; the rest only have 1.

    I did not actually use electric in Tucson for heat or most months of cooling; I had a dual swamp cooler/AC system that provided good cooling in all but the most humid of the monsoon period. Electric seemed high, but I had been spoiled by the Bay Area, where heating/cooling is virtually unneeded and is heavily subsidized. In Detroit, there are several ways to meter, but the maximum is $.1324/kWh, which includes the distribution charge. Time of day use is almost .$.11/kWh, and that plan is only available to so many users per year, so it may not even be an option. I can get effectively the same rate by converting our building to a commercial account (running all apts through a central meter); the highest rate in that category is $.1144/kWh.

    FOR COVE HEATERS, does anyone have any brand experience?

  31. Dana1 | | #31

    In most states you have to be a regulated utility to sub-meter and charge tenants for power. I'd be surprised if that isn't also the case MI.

    In states wehre third party ownership of rooftop solar is allowed, the solar company owns & maintains the rooftop array, but is allowed contract with the property owner to establish a rate, which could be viewed as a micro-utility with one customer. But it's still a single meter, owned & operated by the local utility. I don't know of any states where sub-metering by the solar company is allowed.

    There are states where community solar is allowed, and the output of a solar array can be "virtually net metered" to multilple shareholders' or lease-holders meters. Michigan is one of those states that allows community solar but I don't know the details of the local regulations around that. You may be able to set your array up as a community solar array, with the output being apportioned only to the meters within the building, if that's legal under MI regulations.

    It is worth paying someone (a professional engineer or RESNET rating firm) to run the heat load calculations on a room by room basis, which would probably pay for itself up-front in reduced equipment costs, even if you're using inexpensive cove heaters to heat the place. Without the load numbers it's very easy to oversize by 3x "just to be sure", which increases the minimum size of the power service to the building necessary, and the total amount of heater installed. The load calculations would likely cost somewhere between $1-2K.

  32. laughswithcrows | | #32

    Any landlord can apportion utility costs to tenants, based on #s of occupants, square footage, or actual use. But that is off-topic.

    I hope someone can weigh in on brand experience with cove heaters. Thanks!

  33. Expert Member
    MALCOLM TAYLOR | | #33

    Marlena,
    Like baseboard heaters I think the biggest variable is their looks. They all seem to perform quite similarly and there really isn't too much in them to go wrong.

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