furnace too big

**oilie hands** · 03-23-2005, 05:21 AM

is there any way to make a furnace work right in a house if it is about 50,000 BTUs oversized?-- need some more professional opinions for a homeowner.

**Gunnery Sergeant Hartman** · 03-23-2005, 07:39 AM

Tear it out and install the correct size.

**drcustom** · 03-23-2005, 08:06 AM

Put an addition on...

**t527ed** · 03-23-2005, 08:08 AM

leave the windows open

**rimek** · 03-23-2005, 08:09 AM

MORE as in number or in quality of opinions?
This is a loaded post- Who has determined the oversized condition? What, if it is so, is the correct size relationship(in other words, is 50K a 50% oversizing or a 25% oversizing or what?) Why is the unit oversized? Why isn't the first thought to replace with the correct size, will there be expansion in building? If this is a new install, why not get the installer by the short ones, and get satisfaction? If these factors don't concern you, then just load that sucker up-open all the windows, punch holes in the roof, etc.

**oilie hands** · 03-23-2005, 10:45 AM

well, a 90000 would suit his needs perfectly. He bought this and installed it. thought bigger was better,I went there to see why it was recycling all the time, burner shutting off and then the blower running for about 6 min, then off, then on and so on until the exchanger cooled, I just told him that the unit was grossly oversized for his needs. He would have to pipe hot air to the outside and cold air in side to equalize the thing, they don't believe me. this unit would easly heat 2 houses like theirs.

**casturbo** · 03-23-2005, 12:05 PM

Is this an oil furnace by chance? If so, downfire the nozzle size and run the blower on low speed. You could even adjust the fan and limit settings to accomodate less cycling. Don't go to low on nozzle size or consumption will likely skyrocket and exhaust temps will be too low.

**oilie hands** · 03-23-2005, 03:48 PM

yes oil burner, i slowed the fan and set the limits to 90 and 130, from 120 and 150.. I did suggest changing nozzels from 1.00-80B to 85-80B.They also need more- larger ducts, hot and cold. it's just hard to get it through to them.

**tinner73** · 03-23-2005, 03:53 PM

Originally posted by oilie hands
yes oil burner, i slowed the fan and set the limits to 90 and 130, from 120 and 150.. I did suggest changing nozzels from 1.00-80B to 85-80B.They also need more- larger ducts, hot and cold. it's just hard to get it through to them.

tell them what it needs and walk away. you don't need the headache.

**beenthere** · 03-23-2005, 07:30 PM

Down fire it to .75, and adjust the blower to the middle of the units rated temp rise.

Other then that, they screwed themselves.

**GradyWhite244** · 03-23-2005, 08:09 PM

Be careful in downsizing the nozzle. Don't drop below the minimum for the installed end cone if it is a Beckett burner.

**beenthere** · 03-23-2005, 08:19 PM

Originally posted by GradyWhite244
Be careful in downsizing the nozzle. Don't drop below the minimum for the installed end cone if it is a Beckett burner.

Hate when I forget those details.

Thanks Grady.

**casturbo** · 03-23-2005, 11:04 PM

Originally posted by oilie hands
.... i slowed the fan and set the limits to 90 and 130, from 120 and 150..

I would have reset the limits to 100, 170, 200 instead. With these settings you'll have 70° of limit span which will reduce fan cycling. Brief rundown of each setting has 170° being the fan turn-on temp, 200° being the max plenum temperature (burner high limit) and 100° being the blowdown temperature after the thermostat is satisfied. I usually use these settings on all units, including new installations, since HO (including myself) hate short fan cycling.

Thread: furnace too big

Thread Tools

Search Thread

Display

Posting Permissions