Chimney Height

Tony Mongeluzzi

I had my house done over about 7 Years ago. Three times over the years I had a problem with the sensor for the down draft. Recently I had a problem with it again. I changed the sensor and it was okay for about a month. Last night my boiler shut off a number of times and I had a down draft coming out of my chimney the bioler would stay on for a short period and shut down when I reset the sensor it would come on again. Today I reset it and it stayed on.It was not very windy either time. I was told that My chimney is not high enough although it has been like that for several years could this be the cause of the problem. It is about 1.5' above the peak of my house and several feet above the roof where it comes up.

Mark Hunt_6

You may have

a depressurization issue.

You state that you had the house "done over" so I take that to mean you made the house tighter.

It is quite common for something like this to happen after improvements are made to a structure. The house was leakier before and now all it may take to stop your boiler from drafting is an exhaust fan running in the bathroom, a clothes dryer, anything that sucks air OUT of the house. That air HAS to be replaced and a chimney makes a heck of a straw. If this is what is happening in your house, making the chimney higher WILL NOT solve the issue.

I'm sure I do not have to tell you this but, no matter HOW TEMPTING it is to jump that spill switch, DO NOT DO IT. That flue gas coming back into your house is carrying Carbon Monoxide(CO) and Carbon Dioxide(CO2). The CO2 will displace the oxygen your burner needs to burn correctly and the CO number will get high enough to kill anyone in the house.(If it isn't already) And it WILL BE in your house.

If you can, find someone in your area that can perform a "worst case depressurization" test. This requires a manometer with dual inputs so that the pressure in the boiler area can be tested in relation to atmospheric pressure.

This is serious and needs to be looked into quickly.

Mark H

Howard Emerson

Perhaps an outside air supply?

Hi Mark,
He doesn't state if his boiler is using oil, but if he is using oil, could he get past this problem with an outdoor air tube supply, and the 'box' burner cover such as the ones typically used on the EK systems like we have here?

HE

Mark Hunt_6

Well

I do not know of any oil appliance equipped with a spill switch so I assume it is a gas boiler.

Bringing combustion air from the outside directly to a burner will reduce the negative effect that combustion causes, but it will not negate depressurization caused by other appliances and the draft would still be effected.

Keep in mind that he is not experiencing problems with getting the equipment to burn, his issue is what is happening to the combustion by-product.

I was in a home several years ago where a customer did a major remodel on his kitchen. He had a small commercial gas stove/oven installed complete with the manufacturer recommended exhaust hood. The exhaust fan removed 1200cfm from the house when it ran. That 1200cfm needed to be replaced and the chimney became a straw. His boiler and water heater vented into the house every time he ran that exhaust fan AND those flue gases were sucked right up the basement stairs into his house.

I've seen the same thing happen with clothes dryers, bathroom exhaust fans, kitchen exhausts etc....

Any time we make a change to the structure, there is an effect on every mechanical aspect of the structure.

It is SO important to check these things when we are in customers houses. Only takes a few minutes.

I hope the original poster has this checked out and soon.

Mark H

Tony Mongeluzzi

Chimney Height

Since I posted my first message I have had a chimney company look at my boiler which by the way is gas. I have a clay and brick chimney on the outside of my house. They told me I needed to sleeve my boiler with stainless steal. That what is happening is I am building up condensation which is causing a downdraft I assume when the temp.drops below freezing. This condition will cause acid rain type substance to build up and eventually rot out the chimney. Can you shed any light on this subject.This problem has only happened about a 1/2 a dozen times over the 7 years that my house has been redone

Mark Hunt_6

Tony


You have been given two different opinions now. The first was the chimney was too short and now the chimney needs to be lined. Lining the chimney does not change the height.

Condensation does not cause downdraft. Downdraft causes condensation.

Try this link and see if you can locate a contractor in your area to do an analysis on your system.

Mark H

Unknown

Tony what is your location?

I may be able to get someone to help you out if your are close to me.