Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Condensing furnace in cool basement

pfrasier Member Posts: 1
What are your thoughts on installing a condensing furnace in a basement in northern Wisconsin where it has just a plennum supply and the temp is about 48 degrees?   the current 80% furnace is sweating throughout the class B venting and it is crumbling.    Wouldn't a condensin furnace be better and keep the temp at about 50 degrees in this vacation home?  Nobody is here most of the winter.


  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Space must be maintained above 40 degrees F...

    And I found out the hard way this last weekend...

    Went to ye old mountain resort/cabin (Hydronicahh) and when I left the last time, I shut all water systems down and drained them "just in case", including the thermostats serving the home being turned to the OFF position.

    I forgot that there is an internal sensor on the boiler that if the control gets below 40 degrees F, it will fire the boiler to keep the boiler from freezing. There is no way to over ride this function on this particular (Munchkin) boiler. Well, guess what happens to condensate below 32 degrees F. You got it, a solid block of ice half way up the inside of the combustion chamber.

    I have glycol on the hydronic side of the system, but never even thought about the condensate.

    Now I have to replace the refractory, and have installed an electric heater in the mechanical room to keep the condensate from freezing.

    I was just trying to save energy...


    So long as you can keep the space above 40 degrees F, it should not be a problem, although, I also saw something else this weekend with my modcon that I had never seen before.

    After I got the acid ice cube thawed out, when the boiler went to fire, it missed the first three times, causing it to lock out. I reset the lock out, and it caught, for a minute. As soon as it started to ramp up, it flamed out and tried to restart to no avail.

    I walked outside to inspect the vent termination, and saw that the 2" vent pipe was completely blocked with hoar frost. I rammed a pipe into the vent, and cleared the frost, and the boiler finally caught and took off like it was supposed to.

    I suppose a person could put heat tape on the condensate trap and vent and avoid this problem, but again, WHOODA THUNK?

    I guess it is impossible to anticipate every condition you will run into in the field.

    Have also heard that I could put a 60 watt light bulb into the control vestibule to defeat the internal sensor.

    Oh well, live and learn :-)

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Gene Davis_3
    Gene Davis_3 Member Posts: 51
    Does such a sensor work to fire the boiler . .

    . . if all power in the house is switched off?  As in, flipping the main breaker in the panel, or doing some other form of main service disconnect?

    Just curious.  I'm asking because many of the "summer camp" homes we have here get drained and shut down for winter, with the power turned off as well.

    I had to deal with something akin to that freeze-up in a badly-built house we once owned.  The natural-gas-fired forced-air furnace used to heat the upstairs, was installed in a badly-insulated attic space, and the condensate line would freeze solid all the way up, shutting down the furnace.  I had to heat-tape the thing.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    No power, no function....

    But, if they ever plan to show up in the middle of the winter and expect to be able to flip the switch ON and go, then as a part of their fall winterization program, they will want to use a shop vac and suck the condensate out of the condensate trap on the appliance, or there will be no warm cabins...

    And then, when they initially start the appliance, there WILL be some spillage of products of combustion until which time the trap refills with condensate (5 to 10 minutes). Keep the structure well ventilated for the initial restart.

    And then when THEY leave, THEY must also suck the condensate trap dry, or plan on replacing it the next time they go to fire the appliance.

    It is just another step in the winterization program that MUST be followed, that most people don't take into consideration. I didn't obviously. Had I not been as skilled and tooled as I was, I would have had to call in extra troops for support, and sometimes (New Years Day) troops are hard to come by....

    Proceed with caution and proper knowledge.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
This discussion has been closed.