Fall and Winter

Q: When I light my wood burning fireplace, my gas furnace pilot light on the other side of the house blows out. How do I stop this? – ST

A: Dear ST, Well without actually seeing this particular situation in action it is hard to tell. Two major questions are: How old is the furnace, is this an open fireplace or enclosed fireplace?

If I had to take an educated guess…I would say that the stack effect in your home is rather strong, and the draft is accelerated through your furnace when you light the fireplace and this is blowing out the furnace pilot light.

When you open your fireplace damper there is heated inside air immediately rising out of the chimney. As you light and stoke a fire the volume of air escaping your house through the chimney is higher and higher. That is why heating with an open fireplace is a losing battle. Since your home has to take in air in other areas to replace the air it is loosing out the flue, your normal drafts in your house (around baseboards, outlets, doors, windows & furnace flues) are under pressure to allow in more and colder outside air. This type of increased draft could be what is blowing out your furnace pilot light.

This has the potential to be a dangerous situation so you will want to have an HVAC tech over to check the furnace draw during the fireplace use. – Jason