Wood boiler Back up recommendations

rockwall Posted By rockwall, Dec 7, 2018 at 6:05 AM

  1. rockwall

    rockwall
    Member 2.
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    Dec 1, 2015
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    Loc:
    Central Maine
    I have a 1400 sq. ft. apartment in central Maine in a renovated barn with radiant floor heating. The floors downstairs are concrete and upstairs wood. A Tarm gasification boiler with 820 gallon storage tank is used to heat the floors and DHW. This system was designed by professionals and the total heat load is 40kBTUs/hr. It is a passive solar design so when the sun shines it helps but it doesn't shine a lot in the winter. I have been very happy with the system but I would like to leave for a week or two and I'm looking for a back up system, any recommendations would be appreciated.
     
  2. maple1

    maple1
    Minister of Fire 2.
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    Sep 15, 2011
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    I put in an electric boiler for backup when I did my system over. It is a cheap & easy install that takes up next to no room, as long as you have the space in your electric panel. It is quite expensive to run though - which might be OK for only infrequent backup. Mine is an 18kw. I could likely get by with one half that size, but I got a good deal on it.

    If you have time of day rates, you might check that out to go along with it.

    We just put 2 mini-splits in last month, those are our main backup now. Plus they will a/c in the summer. I figure they cost like 1/5 as much as the electric boiler to run for heat when it is cold out (like -15c). They won't heat your floors though. If I absolutely needed to heat the water in my system a lot during the winter with something other than wood, I would likely put an oil burner back in (uggh).

    You don't have propane already do you?
     
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  3. peakbagger

    peakbagger
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    Jul 11, 2008
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    Depending on your heat load, if you have a 200 AMP panel, a few electric radiators in the right places will keep a house from freezing up. Its cheap to install but depending on your distribution piping location you may want to put a timer on the circ loops to keep them running occasionally to avoid them freezing in cold spots. There are also electric boilers that could be plumbed into the same Tarm system. They are super reliable and only cost money to use if you need them. nI have also seen electric water heaters used for backup heat. If its plumbed into the heating system they work fine. but the controls ca get a little tricky.

    My wood boiler is backed up with a oil boiler. I havent bought oil for several years but have some left in the tanks. If I was going to be gone for a significant period of time, I would just break down and buy 50 gallons and run the storage up before I leave. My controls just switch over to oil boiler when the storage drops below 140F. Note I do have the oil boiler serviced so I know its reliable and its a cold start unit do no worry about the sections leaking.

    One of the reasons why banks will typically not write mortgages on home with only wood heat is they dont want to get stuck with a home that requires it to be heated if they end up with it. I think they grudgingly will now accept pellet boilers as long as there is bulk storage that can get fed from bulk truck.
     
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  4. rockwall

    rockwall
    Member 2.
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    Dec 1, 2015
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    Loc:
    Central Maine
    I do have propane to the house in the kitchen but not the boiler room. When you say the electric boiler is expensive, how expensive? I will think about the combo of mini splits and electric boiler. Mini splits are all the rage around these parts.
     
  5. Bad LP

    Bad LP
    Minister of Fire 2.
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    Nov 28, 2014
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    Loc:
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    I'm north of you now with a foot and a half of snow on the ground and if I did not have a back up generator I'd be very nervous about pex freezing in the floor. A small LP boiler would be my back up plan along with some antifreeze. I have no idea how your piping is done but I would not be heating the 820 storage with LP, just the heating loops.

    This past year my generator has run over 100 hours more than the last 13 years. CMP is not getting better.

    Mini splits are great but if the power goes out... Now what?
     
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  6. peakbagger

    peakbagger
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    Jul 11, 2008
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    How many levels of redundancy before someone just makes sure their insurance premiums are paid up ;).

    There are things like setting the heating loops up on glycol if someone is not home for extended periods during cold weather in an area with undependable power. I suppose it could be done with storage but the initial charge of glycol will be pretty costly. No autofill valves are allowed so a charge bucket and charge pump are needed. I know of folks with camps that use that method. Not so easy on potable water, although PEX really helps as when it freezes it rarely cracks but unfortunately that doesn't help the fixtures especially toilets and drains which have a water trap.

    If the owner is really paranoid the best option is winterize the house before heading out. Drain the heating system and blow out the loops, then drain the potable system and pour polypropylene glycol (the safe stuff) down all the traps including the toilet. There really is no need to heat the house in that mode except that it does raise havoc with drywall eventually and takes quite awhile to warm it back up.

    There few if any unattended heating devices that don't require power to run them. If the owner is not home and the power goes out for a long period they are effectively scr***d during cold temps unless they have a battery bank. About the only non powered units I am aware of are the old Kerosuns and think they only have limited fuel storage. If someone has 30K burning a hole in their pocket they can put in battery bank and some PV to supply some electric power to the house even if the utility fails. If they are just running a boiler the loads are low so the battery should be able to cover a few days Unfortunately along with the upfront cost there are battery replacement costs every 10 to 15 years if the batteries are treated well, far less if they aren't. Battery replacements will be about 2/3rd the cost of the original system.

    My solar hot water is a batteryless DC system so it runs when the sun is shining and actually has the option run through some fin tube but it doesn't put out anywhere near the amount of heat my house needs.
     
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  7. maple1

    maple1
    Minister of Fire 2.
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    Sep 15, 2011
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    Somewhere in the $20-30/day range.

    I would consider an LP boiler if you already have LP on site.
     
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  8. Bad LP

    Bad LP
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    Nov 28, 2014
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    Loc:
    Northern Maine
    There is a lot of truth in that statement.

    The pex might survive but my Gypcrete pour might not be very happy and I know my copper fintube, valves and shower heads will be ruined.

    I was in my old home from 13 years ago. New owner fell on hard times and the place has been taken over by the bank so a girl I know is trying to buy it and took me to see it for some answers on the wood furnace and other items.
    The long term cold has cupped all the maple floors but surprisingly the drywall has held up rather well.
     
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  9. Scott Pond

    Scott Pond
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    Nov 30, 2013
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    I have a similar question, but my time periods are a few days here and there, maybe a week. I do have someone to come and check/fill my boiler but I do have to pay for it. If there was a LP unit that I could plumb in that would act like an anti freeze, protecting both the house and the boiler and not run all the time, that would be my ideal.
     
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