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Thread: Back-up baseboard heaters

  1. #1
    DIY Junior Member Commonground's Avatar
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    Default Back-up baseboard heaters

    Hello!

    I want to install baseboard heaters as back-up to my wood range.
    At the moment I only have the range and it is more than enough to heat our 1 story 21'x32'x7' Cape Cod house. For a while I had installed a 15 kBTU (or was it kW?) propan space heater but it didn't see much use and was starting to rust. I sold it. Now to my question:
    The back-up heating will only be used when we leave the house for an extended period of time to keep the plumbing from freezing, in this case is it necessary to install the baseboard heaters under the windows? I might have room under the windows but the wiring is complicated by the very wide granite foundation supporting the sill. It would be much easier to mount the heaters on inside walls.
    Thanks for your answers

  2. #2
    Electrical Contractor/Instructor jwelectric's Avatar
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    They need to be on the outside wall but the bigger question is will your service handle the load

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    DIY Junior Member Commonground's Avatar
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    Thanks,

    can you explain why they should be on the outside walls?
    I am not planning more than 3 or 4 kW on a 240V circuit and there will be no other load except a 7cuft freezer in the cold cellar during the operation as the house will be empty. It's just to keep the house from freezing so around 5-7C.

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    DIY Senior Member Reach4's Avatar
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    Quote Originally Posted by Commonground View Post
    The back-up heating will only be used when we leave the house for an extended period of time to keep the plumbing from freezing, in this case is it necessary to install the baseboard heaters under the windows?
    If it is only to keep the plumbing from freezing, it could be located in a non-standard place with regard to where your plumbing is. Keeping the doors open under the kitchen sink could help.

    If the bathroom is near the kitchen, maybe you could have one of the heaters double as a bathroom heater. Maybe you could put the other in the kitchen. You will also need enough heat to keep the pipes under the house from freezing.

    Maybe you could use heater tape on pipes.

    Non-expert, non-pro.

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    DIY Senior Member Murphy625's Avatar
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    Quote Originally Posted by Commonground View Post
    Thanks,

    can you explain why they should be on the outside walls?
    I am not planning more than 3 or 4 kW on a 240V circuit and there will be no other load except a 7cuft freezer in the cold cellar during the operation as the house will be empty. It's just to keep the house from freezing so around 5-7C.
    If you're just trying to keep the pipes from freezing and running the temperature at bare minimum, it wouldn't matter where you put the heaters if you also turn on a small fan to circulate some air around. One of those oscillating fans pointed at a 45 degree angle up towards the ceiling will probably circulate enough air to keep the whole place at an even temperature no matter where the heater is. Or a ceiling fan on low speed would also work.

    Hope that helps,

  6. #6
    Electrical Contractor/Instructor jwelectric's Avatar
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    Well I hant no expert about this but I was always told heat rises, might be wrong but that is what I was told by someone a very long time ago and you know how all those old farts are.

    You will either have to do one of two things. 1- Install enough heat to heat the house and keep it warm or 2- direct your heat.
    With baseboard heat one has to keep in mind that it is radiant heat. In other words it will take it all day to raise the temperature in the room just a couple of degrees so unless you install enough then it is useless.

    If you live in Nova Scotia and I think that is what the NS in your profile stands for then it has been known to get down as low as minus 41 degrees Fahrenheit and I dont think that a small baseboard heater set close to a inside wall will be much benefit.

    Like I said, I hant no expert but I did stay at the Holiday Inn last night, that is why I am awake at 3 AM, and what you propose just will not work. I think I heard someone once say that to keep a 68 degree temperature Fahrenheit with ambient of 32 will require 10 watts per square foot.

    To take this and say all I want to do is keep it just above freezing so I will install 2 watts per square foot just dont work. You will still need a minimum of 10 watts per square foot and set the thermostats lower but the lower watts per square foot will not produce enough heat to accomplish what you propose.

    A little experiment you can try to see just how much I learned at the Holiday Inn last night is to light a bunch of candles on January first and dont build a fire cause the theory of just a little heat in the house will keep the pipes from freezing means that just a little fire in the house will keep you from freezing.

    Now before we talk anymore about where to place this baseboard heat lets talk about your service. How big is your service? Will it take the added load of baseboard heat? Maybe if the service will not handle the added load then there might be enough heat to keep the pipes from freezing but the heat wont be form the heaters but instead it will be from I think you get the idea.

  7. #7
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Commonground View Post
    Thanks,

    can you explain why they should be on the outside walls?
    For your little story and a half home you will need about 10kw heat at 240 volts this will equate to about 55 amps of added current to your service. Being that you are a human being there is no doubt that on real cold nights the heat will be on even with the heat you have now so your idea of it will be on when everything else is off goes out the window. If this is not enough to cause you to think about the added load then your homeowners insurance will help you to decide that you should consider the added load to the service.

    The laws of physics say that cold is a natural state and that heat goes to cold. In other words the baseboard heaters need to be on the outside of the envelope being heated. Ever build a fire on the outside on a real cold day? Standing close to the fire one side of your body was warm while the side away from the fire was cold. When the fire started dying did we not add more fuel to the fire? Now why did we do that? Maybe it was because there needs to be enough BTUs produced in order to make the fire warm enough to accomplish what we was desiring.

    These same principles apply to what you want to accomplish with your water pipes. If there are not enough BTUs being produced to heat the air around the pipes guess what, they will freeze. Trying to use a little heat to save the pipes is like having a blacksmith use a bic lighter to heat the metal that he is going to forge. Just won’t work because the bic lighter will not produce enough BTUs to heat the metal unless he stands there for days on end and somehow figures out how to stop the conduction of the heat away from the point he is trying to heat.

    Trying to use just a little heat to keep the pipes from freezing will entail directing this heat at the pipes without having it conduct away as the battle between the heat and cold will be lost by the heat. One sure fired way to rest assured that water pipes will never freeze is to move to the equator where it doesn’t get cold enough to freeze.

    I have drank all the coffee that they left in this room so now I will apply the laws of physics of heat conduction as I stand in the shower for the next hour and a half waiting for the breakfast bar to open so I can get another cup of coffee and warm up a little as I will have drained all the hot water from the water heater and all the other guest will have to take a cold shower.

  8. #8
    Electrical Contractor/Instructor jwelectric's Avatar
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    As I am getting dressed and packing to leave a thought came to me that is so simple that I couldn’t think about for thinking about all those laws of physics concerning heat transfer. Why not do like I do at the barn and drain the lines when you are planning on being gone for a while or is this just for when you might get caught up in something and not make it back home in time.

    The reason I ask this is because you said the only current draw there would be is the freezer in the cellar which makes me believe that you are turning off the refrigerator and water heater.

  9. #9
    Moderator & Master Plumber hj's Avatar
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    Putting the heaters under the windows allows the "convection" currents to intercept the cold air flowing off the windows. The heaters main source of heat is radiation which does not require the heater to be under the windows, since it heats the surfaces that are exposed to it.
    Licensed residential and commercial plumber

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    DIY Junior Member Commonground's Avatar
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    Thanks for your answer,

    so putting the heaters away from the cold envelope of the building should mostly have an effect of air stratification.
    I am also wondering about the radiation effect of the heaters since they are encased and their outer surface is not hot.
    Do you think the main heating effect is radiating more than conductive?

    I read somewhere that installing too much capacity would induce the heaters in more cycling. It seems to make sense to me. If the capacity is small the heaters tend to be always on if it's get really cold.
    The question is how small can I go to achieve my aim of keeping the plumbing from freezing. It is obviously quite a different approach than trying to achieve 20C (68F) throughout the building with 10W/sqft.
    Is there a rule of thumb to apply with the variable being the ambient temperature to achieve, in my case 5C (41F)?
    Can someone answer that question?

  11. #11
    Electrical Contractor/Instructor jwelectric's Avatar
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    If you don’t size the heaters correctly they will over heat and the thermal will open and guess what, no heat at all. If they heat constantly they hit end of life real quick. When they die they have to be buried and can’t be revived.

    You want to size the heat just like it was going to be the sole source of heat in the house and control the temperature of the rooms by use of a thermostat. You want it to be 40 degrees F the set the thermostat at 40. You looking at 38 set it at 38. Invest in a good thermostat with a wide range of settings.

    When I started in this trade baseboard heat was just about the only heat installed so believe you me my experience in the stuff is not limited. Over the years I have watched it come and go.

    I have seen tried what you are attempting more times than you have fingers and toes carried to the tenth power and in every case it resulted in failure. These heaters are not designed to heat 24/7 and trying this will surly result in damaged heaters.

    Listen to me, I ain’t green. I have over 45 years in this field. It is all I have done my entire life. I am serious when I say what I say. What you are proposing is going to end up with froze pipes. Please listen to me before it is too late.

    If you don’t want to listen then all I have to say is a hard head makes for a soft a$$.

    Call the manufacturer of baseboard heaters and ask them about sizing them so the will only achieve your desired temperature and see what they say.
    Last edited by jwelectric; 10-08-2013 at 02:12 PM.

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    Moderator & Master Plumber hj's Avatar
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    quote; If you don’t size the heaters correctly they will over heat and the thermal will open and guess what,

    They have a device called a "thermostat" which is supposed to sense the "heat" and cycle the baseboard on and off. If the baseboard is too large, it will stay on for a shorter time if it is too small it will either run for a longer period, or forever if it is extremely undersized. The off period will be the same because that will be determined by the heat loss of the area after it is to temperature.
    Licensed residential and commercial plumber

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    DIY Senior Member Murphy625's Avatar
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    One other suggestion... (now that I realize you're in a very cold climate...

    Why bother spending big money to heat a place when you're not there? Wouldn't it be far safer and cheaper to just drain the water lines and add antifreeze to the waste traps? In short, prep the place to freeze?

  14. #14
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by hj View Post
    quote; If you don’t size the heaters correctly they will over heat and the thermal will open and guess what,

    They have a device called a "thermostat" which is supposed to sense the "heat" and cycle the baseboard on and off. If the baseboard is too large, it will stay on for a shorter time if it is too small it will either run for a longer period, or forever if it is extremely undersized. The off period will be the same because that will be determined by the heat loss of the area after it is to temperature.
    HJ, the problem he is facing is trying to just barely get by and using baseboard that when left on will heat continuously to keep the area just above freezing which will kill the heater in short period of time.

    The baseboard heaters are not designed to stay on continuously but instead they are designed to keep the temperature constant. Way back when baseboards was the way to fly I have seen complete systems burn out after a power failure trying to heat the house from low temperatures. This is the main reason that it fell by the way side over the years.

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    DIY Senior Member Reach4's Avatar
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    Quote Originally Posted by jwelectric View Post
    HJ, the problem he is facing is trying to just barely get by and using baseboard that when left on will heat continuously to keep the area just above freezing which will kill the heater in short period of time.
    Suppose he had used the word continually rather than continuously-- would that work for everybody?

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