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Thread: Hi, more electric baseboard heater questions.

  1. #1
    DIY Junior Member Danimale's Avatar
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    Default Hi, more electric baseboard heater questions.

    Greetings everyone,

    Let me start with my situation. I have a nursery (son's bedroom next year) upstairs. Size of the room is 172 sq/ft with 9ft ceiling and runs about 5-8 degrees cooler then downstairs. The house is on a forced air LP furnace but the duct work is primitive, we had to install a return air to the room. I would like to supplement the room with electric baseboard heat. My questions are as follows:

    1. Knowing the standard rule of thumb, sfx10 for wattage, but is this too much just to supplement the furnace heat? And if so how do I determine the correct wattage requirement?

    2. Again with the hydronic, for supplement heat is it a waist of money and are they more safe in a little kids room?

    3. I would like a double pole thermostat, does this determine if I get a 120v or 240v model?

    4. It would be on a dedicated circut, does that help me decide between a 120v or 240v model?

    5. Are electric baseboard heaters required to be under the window or not really a benefit if I'm just supplementing the furnace?

    6. Would I need to reduce or block off the return air?

    7. Just for my knowledge what is a 208v vs. 240v?

    Thank you so much for your time.

    Dan
    Last edited by Danimale; 10-01-2009 at 11:30 AM.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    In most places, electric is the most expensive way to heat. Before I did that, I think I'd look at a booster fan in the duct to provide more flow into that room.

    You don't see 208vac generally in a residential setting, you can get it many ways, but off of 3-phase power is (I think) the most common.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member Danimale's Avatar
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    Thank you for the quick response!

    The problem I have is that the house thermostat is going to be satisfied buy the first floor temperature. If I boosted the air flow i do believe it would heat the room, but the furnace will kick off when the thermostat is satisfied and the heat will dissipate quicker from the second floor room. I can imagine a steep warm/cool curve.

    Any thoughts greatly appreciated.

    Thanks again,

    Dan

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    Homeowner Thatguy's Avatar
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    With 1720w you might get by with a 15A 120v circuit, but you can't run anything else at the same time on that circuit. Try 20A @ 120v and get a little humidifier.

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    DIY Junior Member jlanger's Avatar
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    I too am looking to add baseboard heat in my new babies' room, things are a little different, my house was built in 1904 with stoves on each floor, it appears that the current ductwork was installed in the 70's but they are unable to run ductwork up to this room due to the way the walls were built.

    Room is 10x11 ft and I'm looking at getting a 2000w heater. It has been sheetrocked and insulated in the last 10 years or so. ceiling is the insulated floor of the attic.

    My biggest question is do I go with 120v or 240v? I have room in my circuit box for 240v.

    From what I researched about the hydronic systems, is that they really don't seem to be worth the cost, unless you really need moister air. I've been told that it's better to run a few humidifiers or a whole house humidifier in my situation.

  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    Hydronic systems just means they use hot water to provide the heat...the system is closed, so it doesn't add any moisture to the space. As opposed to a forced air system which may use indoor air for combustion, which pulls in drier outside air, it has no effect on the humidity. If it uses outside air for combustion, it would have the same net zero effect. The big difference between radiant (most hydronic systems are radiant) and forced air is moving air makes you feel cooler, and it gives you an easier upgrade to central a/c. Radiant is more comfortable to most people and moves less dust around.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member Danimale's Avatar
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    Great replies!

    Would the return air in that room disrupt the convection of the radiant heat? And would I need to install the baseboard unit under the window?

    Thank you,

    Dan

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    Plumber jimbo's Avatar
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    A starting point number for electric heat is 10 watts per square foot. Cold northern climate will need more. A room with more glass, northern or southern exposure, etc. all add up. In your case, since this is not the principal source of heat, the 10 watts per square foot is a reasonable number. You could use that 2000 watt heater comforably. The max watts you should put on a 120 volt 20 amp dedicated circuit is 1920, so I would opt for a 240 unit. Actually, as I look at some of the catalogs ( Cadet, King, etc) the biggest 120 volt units I see are 1500 watts. And I just feel more comfortable running on lower amps.....less heat and loose connection issues to worry about.

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    DIY Junior Member PistonDog's Avatar
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    Lightbulb

    Don't know how far you want to go, but if the house is insulated well & has good windows the 2nd floor should be warmer than the 1st (heat rises). Do you have access above the new nursery to check the insulation in the ceiling ? How tight are the windows.

    Adding more heat will cost you $$ every month, adding insulation or windows is a 1 time cost (& might qualify for a tax credit).

    These insulation levels seem a little excessive, but might give you some guidelines.
    http://www.energysavers.gov/tips/insulation_sealing.cfm

    208 is 3 phase in Wye (Think of the letter Y). Each leg measures 120 Vac referenced to neutral, the intersection of the 'Y' legs. The 208 measurement is between any 2 points at the ends of the 'Y'.


    PD
    Last edited by Terry; 07-17-2013 at 01:28 PM.

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    Homeowner Thatguy's Avatar
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    Quote Originally Posted by PistonDog View Post
    Adding more heat will cost you $$ every month, adding insulation or windows is a 1 time cost
    And here's how to equate them

    http://www.money-zine.com/Calculator...ty-Calculator/

    The monthly payments you make are an annuity for the utility company.

    5% a year is 0.41%/month.
    Last edited by Thatguy; 10-03-2009 at 08:12 AM.

  11. #11
    Jack of all trades frenchie's Avatar
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    Quote Originally Posted by Danimale View Post
    Thank you for the quick response!

    The problem I have is that the house thermostat is going to be satisfied buy the first floor temperature. If I boosted the air flow i do believe it would heat the room, but the furnace will kick off when the thermostat is satisfied and the heat will dissipate quicker from the second floor room. I can imagine a steep warm/cool curve.

    Any thoughts greatly appreciated.

    Thanks again,

    Dan

    It's about balance, then.

    Have you considered constricting the flow to the first floor rooms? A damper costs way less, and is way simpler, than anything else that's come up in this thread.
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    DIY Junior Member Danimale's Avatar
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    Great stuff!

    The house is far from energy efficient. I did my best to "wrap" the nursery with insulation. I have a few issues impeding my progress: the roof/ceiling slants though this room and the house is balloon framed. This room has the longest run and is buried behind lath and plaster, I suspect the duct is not very "tight" and assume it leaks all the way up. As far as the house goes all the returns are on outside walls and most of them use the framing as duct work. All the main supply runs do have dampeners though.

    Wife says "lose the space heater NOW!". I guess I'll install a standard baseboard heater. Now I'll ask, Sq/ft says I need at least 1700W unit, a 2000W unit is about 8ft. long, is this over board for the room to gain 5-10 degrees? Grandpa says no, think of the forced air system supplementing the electric heat for the room, not the other way around.


    This board has been a great resource for me.
    Thank you very much,
    Dan

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    Homeowner Thatguy's Avatar
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    Quote Originally Posted by Danimale View Post
    Wife says "lose the space heater NOW!".
    To find your wife's Utility Function for things other than space heaters, present alternatives along with their costs and benefits.
    I'd think appearance & comfort is high on her list, along with reliability and low noise.
    If your usefulness for appearance & comfort, reliability and quietness is low, there will be trouble. . .

    This link is a bit too technical but it's all I got
    http://www.google.com/search?client=...UTF-8&oe=UTF-8
    Last edited by Thatguy; 10-09-2009 at 12:15 PM.

  14. #14
    DIY Junior Member Danimale's Avatar
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    Indeed I see you point.

    She only spoke of safety concerns. Little one is walking now but still in crib. Her main reasons were not to have anything readily there hot to touch or drape things over. He already walks up to the heater and plays with the thermostat dial. Her second was that it plugs into the wall, she would rather have it be hard wired if it were to be electric. I am comfortable with the space heater she is not, I don't have a case to argue.

    Dan

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    In the trades Dana's Avatar
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    Quote Originally Posted by jadnashua View Post
    Hydronic systems just means they use hot water to provide the heat...the system is closed, so it doesn't add any moisture to the space. As opposed to a forced air system which may use indoor air for combustion, which pulls in drier outside air, it has no effect on the humidity. If it uses outside air for combustion, it would have the same net zero effect. The big difference between radiant (most hydronic systems are radiant) and forced air is moving air makes you feel cooler, and it gives you an easier upgrade to central a/c. Radiant is more comfortable to most people and moves less dust around.
    Even sealed combustion forced air has a drying effect, since it's relying on pressure differences to move the air, and the pressure differences between rooms get short-circuited via every conceivable infiltration path to the great outdoors. This happens even with perfectly-sealed perfectly-balanced Manual-D ductwork unless the building itself is EXCEPTIONALLY tight (as in well done insulated concrete form or SIP construction.)

    But even then, humidifiers tend to create more health problems than they ever solved. As long as the relative humidity is between 30-60%, removing or adding humidity is best avoided. (The humidifiers themselves become mold farms, complete with spore dispersion into the air.)

    Balloon framed structures with no wall insulation are common in some areas. If this is the case with yours, don't wait- get bids on blowing them full of cellulose- the comfort & sound abatement alone will make it worthwhile, but it'll cut your heating bill by more than 25%, and slow down the air infiltration by a large fraction, even if you still have some leaky windows.

    If you're an ambitions & talented DIYer, this isn't rocket science, but it can be labor intensive. The stuff itself is cheap. Start with the kid's room...


    As for kw sizing, there is no such thing as a good rule of thumb, and it's further complicated by the fact that you have another heat source. I'd bet you need no more than 500w of baseboard as supplement to any bedroom though. More baseboard just means more & more rapid cycling, possibly with temperature overshoots.

    A manual-J heat loss calc would tell you what the coldest hours of the year total heat load is, but this sounds more like a balancing issue with the rest of the house than a peak load issue, and 1.7-2kw is ~1/5 of what my entire house needs when it's 0F outside(!). That'd be one heluva lossy room to need that much in supplemental heat in less than VERY severe weather.

    An electric blanket on the floor under a thin quilt or heavy bedspread makes a comfortable play/sitting space for the toddlers if the room chills too much- it's something akin to having radiant floors- maintaining comfort even at lower room temps. (In Japan they sell family sized electric floor sitting mats for hangin' out in front of the TV etc.- they're quite comfy even in 60-65F rooms- much cushier than standard tatami flooring.)

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