In Bitter Cold Weather, Never Use a Fireplace or Woodstove

by Charles Brand -

2/6/2019

In Bitter Cold Weather, Never Use a Fireplace or Woodstove

At the end of January we experienced some extreme cold weather in Northwest New Jersey. The average temperature on those days was as follows:

January 30, 2019 - 13 degrees

January 31, 2019 - 5 degrees

February 1, 2019 - 12 degrees

With relatively windy conditions, the wind chill on all three days was well below zero. Every time we experience extreme cold weather like this, a number of our customers end up with frozen heating pipes and loops. Frequently, this results from the use using a fireplace, wood stove or other form of supplemental heat. At first, this seems counter intuitive, but if you think about it makes perfect sense.

The way a hydronic (hot water based) heating system works is by heating water (which occurs in your boiler) and then circulating that hot water around the house through heating pipes and baseboard which is generally on the outside walls of the building. Even though the outside walls are insulated, on a bitter cold day, it doesn’t take much for the water in your heating pipes to get below 32 degrees and freeze. The main thing that keeps this from happening is the fact that the water is constantly being heated and circulated. Generally water that is moving will not freeze. That’s why lakes freeze but rivers don’t.

Now think about what happens, on a bitter cold day, if you fire up the wood stove or fireplace. The heat generated by this supplemental heat source will be sensed by your thermostat and cause your unit to run less often or not at all. As the water sits in the baseboard heating pipes on an outside wall, without being heated or circulated, it is very likely that it can get down to 32 degrees and freeze. Once that occurs lots of bad things can happen including the following:

  1. You will have no heat in that zone since the frozen pipe will prevent the hot water from circulating.

  2. It can easily break your heating pipes since when water freezes, it expands approximately 9% at a pressure of up to 30,000 pounds per square inch. In order to repair the broken pipe, the zone may have to be drained and refilled which can get very expensive.

  3. Eventually, the weather will get warmer and the frozen pipe will thaw out. If there is a broken pipe that was not repaired, the water feeder in your heating system will continue to feed more and more water. Particularly if you are not aware of the situation, this water can cause major damage in your home.

We’ve seen this unfortunate scenario play out many many times over the years. In bitter cold weather (particularly with a baseboard heating system) you would be wise to avoid using a fireplace, wood stove or any other form of supplemental heat.


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