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Propane Backup for Wood Boiler - Tankless or Conventional?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Medman, Jul 3, 2013.

  1. Medman

    Medman Feeling the Heat

    Joined:
    Jul 8, 2008
    Messages:
    438
    Loc:
    Sault Ste. Marie, Ontario
    Hi all. I know traffic is slow this time of year, but I'm hoping someone can answer my question.

    I'm currently using an EKO 25 to heat my house and DHW. I want to install a backup heat source to keep things hot while I'm away in winter, and I have been looking closely at propane because natural gas service is 2-3 years away in my area. When NG is put in I would convert the gas boiler from propane to NG.

    I have searched the archives but haven't seen anyone say that they are actually using a direct-vent gas appliance as backup. I want to avoid installing a flue for a gas appliance, and I think that given my relatively small heat load that a tankless heater would work well. Cost of direct-vent boilers is high.

    Can anyone provide more information about propane backup systems that are direct vent, either tankless or conventional boiler? I would be installing the backup in parallel with my EKO - I have read that I may need a larger circulator on a tankless heater to move heat, and also that tankless heaters don't work well when input temps are high (e.g. heating 140* water to 180*).

    Any input would be appreciated!

    Ryan

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  2. bmblank

    bmblank Minister of Fire

    Joined:
    Jan 17, 2013
    Messages:
    698
    Loc:
    Michigan
    I'm using a tankless propane boiler. The way its hooked up its only heating the house, not the tank (where my domestic coils are). Works like a charm. Mine is a hydro smart 115 from Menards. Got it for roughly $800.
  3. bmblank

    bmblank Minister of Fire

    Joined:
    Jan 17, 2013
    Messages:
    698
    Loc:
    Michigan
    I should point out that my backup is marketed for being the primary heat source in radiant floor heating. It only burns what it needs in order to heat the water to the set temperature. It is flow triggered. In general, when it is heating (and i have it set to 140) the return temp (going into the cold side of the boiler) is in the 135 area. Being made for what it is i can't imagine having low input temperatures.
  4. Medman

    Medman Feeling the Heat

    Joined:
    Jul 8, 2008
    Messages:
    438
    Loc:
    Sault Ste. Marie, Ontario
    Thanks for the reply. It looks like Menards no longer sells that unit, but it gives me a starting point.
  5. timberr

    timberr Member

    Joined:
    Sep 17, 2008
    Messages:
    228
    Loc:
    Hill, NH
    Ryan,

    I too run a EKO 25 for heating my house and installed a Munchkin Contender condensing boiler. It is direct vent. I have been very happy with the performance. During the summer we use it for DHW, I have a Superstore indirect hot water heater.
  6. bmblank

    bmblank Minister of Fire

    Joined:
    Jan 17, 2013
    Messages:
    698
    Loc:
    Michigan
    In hind sight i do wish i got a boiler with a separate coil for domestic. The problem i was running into is to do that the price pretty much doubles. I got a steal of a deal on mine too, straight from the manufacturer.
    In our case, the likelyhood of having a cold storage tank is low. Only time would be coming home from a vacation our something. I could probably get the tank back to shower temps in the matter of 5 or 6 hours (if its even that low to begin with).
  7. timberr

    timberr Member

    Joined:
    Sep 17, 2008
    Messages:
    228
    Loc:
    Hill, NH
    When we use the propane for vacation backup DHW isn't an issue, I through a switch to prevent the demand call for heat. Usually I do the same, when we get home fire the wood boiler and when storage is adequate I flip the switch and allow the DHW loop to energize. I have ben looking into solar for summer DHW. this is where we spend most of our propane dollars.
  8. bmblank

    bmblank Minister of Fire

    Joined:
    Jan 17, 2013
    Messages:
    698
    Loc:
    Michigan
    I would like a solar system to heat my storage also, but the return for me would take quite a while. Wood is free for me, short my labor. Eventually i think I'll build a drain back system, but for now it doesn't really make sense for me.

    I burn throughout the year as wood is my only choice for dhw right now. I've gone through half a face cord over the last two months or so.
  9. Medman

    Medman Feeling the Heat

    Joined:
    Jul 8, 2008
    Messages:
    438
    Loc:
    Sault Ste. Marie, Ontario
    I have found a Noritz tankless boiler (NH199-DV) that may fit the bill. I'm trying to stay in the $1500 ball park. Most options available are much higher than that. Any advice on this unit? Installation is not an issue - I can do the plumbing and my father is a licensed gasfitter.

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