Turning off water supply but leaving the boiler on?

Discussion in 'Boiler Forum' started by bentz69, Nov 23, 2018.

  1. bentz69

    bentz69 New Member

    Joined:
    Nov 14, 2018
    Location:
    New York
    As a new homeowner Im still learning quite a few things. The family and I will be away for 7 days and the tempertures over here are dropping just below freezing at night time now. My home is well insulated.

    I have a burnham v84 oil boiler for baseboard heating and hot water. I understand there is no perfect solution but I would like to minimize the potential damage if a pipe were to burst/leak while away if possible. I was curious if I could turn off the main water supply to the house but keep the boiler on. Obvioubly no one would be using the sink/shower/toilet and I will flush the toilets and open up the sinks to let any remaining water out before heading out. I would be leaving the thermostats set to roughly 50-55F so its possible baseboard heating could come on. Is that ok?
     
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    Unless you blow the lines out, there will likely be some pockets of water in the supply pipes. Also, there will be water in the traps that could freeze. If any of those traps are blown out, they'll provide an open path for sewer gasses to get inside of the home. If you were really worried about it, you can buy some RV antifreeze and pour some in each of the traps. This differs from automotive style in that it isn't toxic.

    65 might be a safer temperature. Also, open the kitchen cabinet doors under the sink and the same on a vanity if it's on the outside wall to allow some room heat to circulate.

    The boiler itself likely has a fill valve that may be fed with an autofill valve. If you don't have any leaks in the boiler and heating system, you can shut that fill valve off. If there is a slow leak, the volume and therefore boiler pressure may drop enough to force the safety circuit to shut it down. This is a situation where an internet attached thermostat or home monitoring system can give you some peace of mind since you can monitor what's going on in your home. On some, you can set it to automatically e-mail you if the temperature drops below a certain level.
     
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  4. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    In a "...well insulated..." house in weather where the temperature is only "... dropping just below freezing..." at night there is effectively 0% chance of freeze-up damage even if you turned the power off and walked away. The solar gains during the day will exceed the overnight losses. Freeze-up is only a concern if it's it's going to STAY below freezing for a week at an average outdoor temp less than 25F or cooler, or a few consecutive days where it dwells in the teens.

    Turning the water off is fine. Unless your heating system has leaks the water to the boiler never needs to be turned on once it's been properly filled & pressurized. Even if it has minor seepage at the vents or something it won't lose enough in a week to matter.
     
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  5. bentz69

    bentz69 New Member

    Joined:
    Nov 14, 2018
    Location:
    New York
    That's what I wanted to know.

    I was very curious to see how long it would take before the house itself would come down to freezing temperatures with no heat based on weather conditions.
     
  6. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    The critical aspect is what is meant by "well insulated". Air tightness of the house is as important as R-value, particularly for pipes near potential air leak points such as the foundation sill & band joists.

    A 20F night in a stiff 50mph wind might freeze up a section of pipe near big air leak, but in most of NY the basement floor starts emitting quite a bit of heat once the room temperatures drop below 45 F. With an insulated air sealed basement the bigger freeze up risk will be upstairs.

    Shading factors and window orientation can make a difference in how quickly it hits the freeze point on upper floors.
     
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