reduce output of my natural gas furnace

Peter Cascio

My furnace is oversized and cycles too fast. I was wondering if I could reduce the capicity of the furnace by changing the orifice's or pluging 1 or 2. The furnace is natural gas . is it safe and recommended. Thanks Pete

Unknown

peter

A few manufacturers check in here. If you provide the make and model number, your question may get a better response.

In short, that is not a good thing to do. It will shorten the life of the unit.

Noel

Unknown

Gas Furnace

I need Make, Model BTU input and what kind of controls do you have on furnace? How old is it? How do you know it is oversized? Cycling can be controlled without de-rating. De-rating is not always a good idea. Somtimes furnace can be set up by a professional who knows how to do Constant Air Circulation with a warm air furnace. How many returns do you have on the furnace? Is the blower direct drive (no belt) or belt drive? Any de-rating should be done by a professional. DO NOT PLUG ANY ORIFICES OFF THAT IS UNSAFE!!!
If the orifices are to be changed they need to be sized by a professional who knows what they are doing, that would not however be my solution.

Duncan_2

Within limits... maybe

You need to know what the heat rise across the heat exchanger is, and to stay within specs for that particular unit. Should be on the ratings nameplate. Heat rise is air temperature out minus air temperature in. Vent draft pressure and temperature needs to be OK after the downfiring, too (atmospheric draft?).

Is your air filter clean? AC coil? Got good, unblocked cold air returns? In other words, good air flow across the heat exchanger? Heat anticipator setting at the room thermostat OK? Lots of things can cause short cycling.

Most manufacturers don't like to kill one or two burners, because uneven heating could stress the heat exchanger. Some don't have a problem with a little derating, if it's done by qualified technicians. Some don't like it at all, because they think bad things will happen and they'll get sued for encouraging the modification.

No matter what else... if you don't follow manufacturer's recommendations, you're on your own if things go south.

Steve Levine

Reducing capacity

Many do it to furnaces and boilers. In most cases, without consulting the manufacturer, as they should. Generally, the appliance is approved (AGA, CSA,etc.)at a particular input, and varying that input becomes your sole responsibility. There are only a few that I know of that are approved for more than one input.

Steve Levine

Slant/Fin

c-rex

input too large?

do a heat loss calc. of the house. Then install the correct size furnce. Asumeing the duct is size correctlly? Hire a pro. There are guys who make a living burying folks who "re-size" their stuff in the basement.........