Oversized furnace

Damper Dan

I have an old house that a contractor replaced the 30 year old furnace with a 100,000 BTU. The house is old and drafty, but the heat is a 'cool heat' and always feels kind of clammy.
I was told the furnace may have been over-sized for the sq. footage of the house (2100 sq. ft). Would adding a humidifier help with the cold, clammy feeling?

Brad White_202

Ugh.

First off, was a heat loss calculated for the house as it is? If 100 MBH (presumed input), that works out to 80 MBH if 80% efficient and if high efficiency, maybe 90 to 92 MBH available to heat your house. That is between 38 and 44 BTUH per SF, a little on the high side if in a zero or single-digit design temperature area, maybe OK for some parts of Canada.

I am not sure what you mean by "Cool Heat" except that it might be a higher efficiency unit than the old one (I should hope so!) but those in the 90%+ range move more air, hence it comes out at a lower temperature.

I am cautious regarding adding a humidifier. It can only make you feel warmer if it is so dry that your skin chills by evaporation; the other side is, added humidity can cause damage to the structure in some cases. I would not recommend it without knowing a lot more.

klaus

No

"Would adding a humidifier help with the cold, clammy feeling?"

My interpetation of "clammy" would be cool and damp. Adding a humidifier would only add to that. Get yourself a simple hygrometer to see what your humidity level is actually at. Generally speaking (very generally!) 40 - 50% relative indoor humidity is comfortable in the heating season. If you're above that and your house is cool it can feel "clammy".

Lastly, make sure it's vented properly. If for instance it's improperly vented some of the flue gasses could spill back into the house and give high moisture levels. If that were the case it could also kill you. Do you have a carbon monoxide detector in your house? That's always a good idea to have regardless. Not trying to scare you, but check that out.

Good luck.

Damper Dan

I think heat loss calculations were done to some extent, windows and doors were measured, etc. The cold air returns are gigantic left over from the coal furnace days, but only exist on the first floor. Air flow on the second floor is not great, but works. The old furnace used to make the register hot to the touch. Now, the air coming out is of a higher velocity, but feels cooler. I was told this was normal.
The furnance does not seem to run too little as would be the case (as I am told) if it were too big, but according to my gas bills in the winter, it does run too much!! The house is old, the windows are in need of replacement and most of the outer walls have some form of insulation.

mark ransley

Im no pro but to me clammy means turn up the temp unil you are comfortable, Your thermometers, thyroid,and who knows may be off. Get an acurate thermometer and humidistat, digital are best.

Damper Dan

The problem lies in turning up the heat until we are comfortable means going broke. There are times when turning up from 68 to 73 still does not feel warm. Thats why I suspected the humidity. Where can I get a humiditstat?

klaus

Hygrometer

A humidistat controls the operation of a humidifier. A hygrometer measures the relative humidity of an area. I'm not trying to split hairs, just want you to get the right thing

Check out: Radio Shack hygrometer

Jim Franklin

Propane or NG?

What size line feeds the unit?

Anything else being fed off the line?

What?

Damper Dan

Hey Thanks!

Damper Dan

Hi Jim,
The furnace is a forced air NG, 1/2" black pipe line. The only other thing feeding off the NG line is a 40 Gallon H20 heater which is a power vent. I installed this three years ago after the new hi eff. furnace was installed. No other gas appliances.
Thanks!

seabee570

air temp

Just as brad said,because this is a newer high efficiency furnace,the discharge air at the register is cooler.Most new furnaces have a multi-speed blower,this speed setting can be changed to get you a warmer air discharge,but this must be done according to manufacturers specifications. The temperature rise across the furnace heat exchanger must be checked,and possibly adjusted to get you warmer air.It should be on the furnace nameplate.normally,the blower could be adjusted to a lower speed to acomplish this,if it remains within the specified 'temperature rise'

martin

Oversized

Usually oversized to me means short cycling, when its cold out say 0 it should be cranking a good % of the time