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Sten
Re: how seal floor boots
RJordan wrote:

Heating equipment and cooling equipment, whether properly sized or undersized, will shut off when the thermostat is satisfied.

You can put a Nascar engine in a Volkswagen and not exceed the speed limit by taking your foot off the accelerator.

You can put a furnace that will heat a supermarket in a house and it will. It will turnoff at whatever the thermostat is set at. Doesn't mean the house will be comfortable or good for the equipment.

Manual J says to design for the conditions that happen 99% of the time. If exactly designed, 1% of the time the heating equipment would be undersized. This isn't opinion. This is accepted engineering practice and required by the building code.

What is opinion (or maybe fear is the better word) by heating contractors is that Manual J will undersize the equipment. So the assumptions they put into Manual J will oversize equipment. A perfectly sized piece of equipment will be slightly undersized on the coldest day of the year, when sized by Manual J. In reality, the heating contractor will most likely end up oversizing because he won't be able to find a furnace of the exact capacity determined by Manual J.

There are a lot of other factors that affect the functioning and efficiency of the heating system. Like the ductwork and the tightness and insulation in the building. The new energy code will make this more predictable and enable heating contractors to size equipment correctly.

This has turned the original post upside down. Sorry. I live in a heating climate and think more about heating than cooling. The priciples are the same in the South, but reversed.

You know what, whatever, I'm not going to go back and forth with someone that thinks that on the coldest day of the year your furnace should run constantly as you said in a previous post. I'm not trying to offend you but that is wrong, Sorry

canuk
Re: how seal floor boots
Sten wrote:

To be honest with the both of you I don't care, I don't know where RJordan got his info on a furnace running constantly on the coldest day of the year, believe what you want.

Sten old buddy,
I don't believe the HVAC system should be running 24/7 either --- but rather it should be sized properly instead of going the way larger route ---- that's what I was agreeing on. ;)

canuk
Re: how seal floor boots
deadshort wrote:

Seems to give a whole new meaning to blue balls.

black and blue

RJordan
Re: how seal floor boots

I never said it should run 24/7. Manual J says to design for the temperature that is exceeded 1% of the time. In my Boston climate I should design heating for 2 degrees. If equipment was sized by Manual J, the furnace would run continously when the temperature was 2 degrees. At all temperatures warmer than 2 degrees, it would not run continuously. It is unlikely the temperature would be at the design temperature for more than a couple hours and most likely in the middle of the night.

The same procedure is done for AC. It is particularly importamt for AC because the AC removes humidity by blowing air over the coil. If the blower fan is not running, as is the case when the AC is oversized, there will be no dehumidification. In the worst case, the coil will freeze up.

Bob Gabrilson
Re: how seal floor boots

I'm going to risk it here and give my two cents worth. I would rather have a A/C too small verse to big so that it will dehumidify. That's why they make 2-speed A/Cs (so they run more). Lets assume his A/C is properly sized. With the high humidity in the south, I think a stand alone 90 plus pint dehumidifier is in order. The little space (gaps) between his register boots I don't believe are the problem.

RJordan
Re: how seal floor boots

I would bet a lot of money the AC is oversized by a lot, and I don't gamble.

Bob Gabrilson
Re: how seal floor boots
RJordan wrote:

I would bet a lot of money the AC is oversized by a lot, and I don't gamble.

Most A/C units are oversized (as are furnaces) because they need to take care of the (2%)extreme weather scenrios. That's why the manufactures have developed 2-speed and 2-stage equipment to get them to run more.
This improves efficiency and comfort.

Sten
Re: how seal floor boots
Sten wrote:

The insulation on the Boots should go all the way to Sub Floor with no gaps. Have you had this problem in the past?? You could shop for a Crawl Space Dehumidifier, just Key word the same. How old is your A/C System?? They are made to take the Humidity out of the Air, Bryant for one will run on Low Speed and after the Humidity is out of the Air it ramps up to High Speed, excellent system. If your A/C is oversized it will Run, Stop, Run, Stop, continually called short cycling. I'm not sure but if this is happening it could just be redistributing Air without Dehumidifying it. Good Luck!!! :)

We've pretty much gone full circle here, as for the unit being oversized.

Sten
Re: how seal floor boots
RJordan wrote:

Sten is right. It should work the same as the heating system.

However,on the coldest day of the year the heating system should run continuously also.

Heating systems and cooling systems that only run part of the time on the hottest day of the yaer or the coldest day are seriously oversized on more moderate days.

Oversized systems are inefficient and cause discomfort. Equipment is designed to run for extended periods. Stopping and starting, as oversized equipment does, shortens their life. Oversized heating equipment puts out a blast of hot air, satisfies the thermostat, and shuts off, repeating the cycle over and over. Hot, cold, hot, cold. Properly sized equipment puts out a more uniform heat and is more comfortable. As I said in the earlier post, oversized cooling equipment does not dehumidify the air sufficiently as there is not enough flow over the coil to remove the humidity. This is a major cuase of mold in the South.

Building codes call for a manual J calculation and manual J calls for matching the equipment to the load.

Sorry.

Your heating system should not run continuously on the coldest day of the year and your A/C should not run continuously on the hottest day of the year

RJordan
Re: how seal floor boots

You should set ASHRAE, ACCA and the ICC staight on this as they have it wrong too. At least according to you.

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