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John Adrian Sopher
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« on: November 14, 2009, 09:15:17 AM » |
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Does anyone have any literature on HVAC differentials? I am looking for something on AC and Furnaces, for med and high efficiency units. I know that AC should be between 15-20ºF and cant remember the range for furnaces. Also I was thinking that high efficiency units were different also. Karma points may be awarded!!! lol  Thanks |
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HLC Home Inspections LLC www.OklahomaHomeInspector.bizWe are a licensed inspector for the state of Oklahoma. Our focus is Oklahoma City, Moore, Mustang, Yukon, Tuttle, and many other areas surrounding OKC. HLC-Home-Inspections-Oklahoma-City HLC Home Inspections LLC www.NormanHomeInspections.bizWe are a licensed inspector for the state of Oklahoma. Our focus is Norman, Oklahoma City, Moore, Blanchard, Newcastle, and many other areas surrounding OKC. HLC-Home-Inspections-Norman I am licensed Realtor with Keller Williams. Office Phone # 405-691-2708 www.OklahomaCityHomesForSale.bizFacebook: www.facebook.com/jasopher |
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Casey Patten
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« Reply #1 on: November 14, 2009, 05:43:10 PM » |
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John,
I thought the differential for AC was 10, heat was 20 or greater?
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Title: Root River Inspections URL: www.arochestermnhomeinspector.comBody: Root River Inspections serves Rochester, Winona, Red Wing, Austin, Albert Lea and surrounding Minnesota areas. Meta Key: Rochester home inspector, Winona home inspector, Red Wing home inspector, Albert Lea home inspector, Austin home inspector Meta Description: Home Inspections for Rochester, Austin, Winona, Albert Lea, Red Wing, and other Minnesota areas. URL Path: home-inspector-rochester-winona-red-wing-albert-lea-austin-minnesota.html |
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John Adrian Sopher
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« Reply #2 on: November 15, 2009, 12:21:21 AM » |
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John,
I thought the differential for AC was 10, heat was 20 or greater?
I think that is for high efficiency units, which is why I was asking for that also. As for heat, I couldn't remember if it was anything over 20 or if it had a range too. But now that you mentioned it, I think it is anything over 20. |
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HLC Home Inspections LLC www.OklahomaHomeInspector.bizWe are a licensed inspector for the state of Oklahoma. Our focus is Oklahoma City, Moore, Mustang, Yukon, Tuttle, and many other areas surrounding OKC. HLC-Home-Inspections-Oklahoma-City HLC Home Inspections LLC www.NormanHomeInspections.bizWe are a licensed inspector for the state of Oklahoma. Our focus is Norman, Oklahoma City, Moore, Blanchard, Newcastle, and many other areas surrounding OKC. HLC-Home-Inspections-Norman I am licensed Realtor with Keller Williams. Office Phone # 405-691-2708 www.OklahomaCityHomesForSale.bizFacebook: www.facebook.com/jasopher |
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Casey Patten
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« Reply #3 on: November 15, 2009, 12:44:41 AM » |
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John: http://www.nachi.org/forum/f11/c-temperature-differential-6394/Google turned up this nugget...with the links and such, I just figured it'd be better to let you wade through, and enlighten us all!  You da MAN!   |
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Title: Root River Inspections URL: www.arochestermnhomeinspector.comBody: Root River Inspections serves Rochester, Winona, Red Wing, Austin, Albert Lea and surrounding Minnesota areas. Meta Key: Rochester home inspector, Winona home inspector, Red Wing home inspector, Albert Lea home inspector, Austin home inspector Meta Description: Home Inspections for Rochester, Austin, Winona, Albert Lea, Red Wing, and other Minnesota areas. URL Path: home-inspector-rochester-winona-red-wing-albert-lea-austin-minnesota.html |
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Charley Bottger
Location: North Central Oklahoma
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« Reply #4 on: November 16, 2009, 03:00:49 PM » |
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For an example if the return air for a furnace was 70 degrees and the supply discharge temp was only 90 degrees going to be some unhappy females in that home 90 degree air feels very cold in the winter months |
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Tim
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« Reply #5 on: November 16, 2009, 04:23:28 PM » |
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John you should be getting the 15 - 20 with the AC, however heat is going to depend on the source
Gas or Electric coiled forced hot air can be substantial and with a heat pump it can be as little as 5 degrees
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link: http://www.timshomeinspections.com/page title:TIMS HOME INSPECTIONS description: Maryland Home Inspector providing inspection services in western Maryland, and the surrounding ares which include Washington, Frederick, Allegheny counties and some areas of Pennsylvania keywords:licensed home inspector Maryland, construction inspections, radon, mold, home buy, real estate, consulting, project management,FEMA, HUD, water sampling, free inspection warranty URL: TIMS-HOME-INSPECTIONS.html Web Site Submission LInk: http://www.timshomeinspections.com/link-exchange-submission-form.html+ |
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Charley Bottger
Location: North Central Oklahoma
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« Reply #6 on: November 16, 2009, 06:05:23 PM » |
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John you should be getting the 15 - 20 with the AC, however heat is going to depend on the source
Gas or Electric coiled forced hot air can be substantial and with a heat pump it can be as little as 5 degrees
Gas & Oil furnace should operate 125 to 135 degrees output Electric furnace output 105 to 115 degrees and a heat pump with a 5 degree discharge has some problems should never be that low |
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Jay Markanich
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« Reply #7 on: November 16, 2009, 08:32:10 PM » |
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For AC on a humid day 13-16 differential is acceptable. When not humid 15-20 is ideal. More than 22 is a problem, as is less than 8.
For heat the differential is not very relevant. The temps are - what Charley said above is good. Sometimes I get a little warmer than 135 for gas and oil. New heat pumps kick butt - over 120 typically.
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Charley Bottger
Location: North Central Oklahoma
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« Reply #8 on: November 16, 2009, 09:44:30 PM » |
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Jay at 120+ degrees for a heat pump I would think the strips had kicked in as additional heat unless you are seeing a blended higher temp refrigerant than R22. The R22 on my own home will only do 108 fined tuned without additional heat and this is the second season virtually new.
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Jay Markanich
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« Reply #9 on: November 17, 2009, 04:35:56 AM » |
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Perhaps Charley. On a cold day the air sure feels good. The new ones are more efficient down to lower temps right? For the real old ones they lost efficiency about 36 degrees, the newer ones are much better though. When are the strips kicking in on the new units?
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Charley Bottger
Location: North Central Oklahoma
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« Reply #10 on: November 17, 2009, 07:45:34 AM » |
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Perhaps Charley. On a cold day the air sure feels good. The new ones are more efficient down to lower temps right? For the real old ones they lost efficiency about 36 degrees, the newer ones are much better though. When are the strips kicking in on the new units?
Jay two things very critical concerning the efficiency of a heat pump and they are both dependent upon the installing contractor one being the amount of insulation on the refrigerant suction line between the outside condensing unit and the A-coil as a heat pump has less temp to work with than a conventional heat source thus any heat loss is very noticeable if the insulation is missing or poorly installed the bare copper line will transmit its heat very quickly before it ever gets to the A-coil. The second would be poorly installed insulation on the supply air duct for the same reason temp loss before the air arrives at its destination the interior of the home. Most present day contractors that I inspect the duct work have no clue how to properly insulate duct work they don't know sickum from cum-here about it, joints of insulation not sealed the flap not overlapping leaving bare metal just covered with plastic or foil the wyes with bare metal and the list goes on. As for when the strips kick in should be determined by an outdoor stat on the condensing unit normally set for the low 30's. I see a lot of heat pumps with no outdoor stats the strips come on with the compressor un-be known to the owner |
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Jay Markanich
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« Reply #11 on: November 17, 2009, 10:57:00 AM » |
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One thing I have noticed, Charley, is the copper line from a new condenser being much larger than the line that was attached to the previous unit. There is a company around here that does that all the time. It breaks a year later and they probably swap it out for a new one at the manufacturer's warranty expense.
Your first comment (concern) above - is that when an older oil or gas furnace is replaced with a newer heat pump unit? Can't the old, and smaller, ducts be just as big a problem? Heat pumps require more air than those older units. When I call that out on an inspection, the sellers just get some HVAC guy to say that I am all wet and they go from there. I have no juice in that circumstance. I also call out bad insulation all the time. Good point from you.
You are welcome to come by my house any time for an evaluation of my two systems. Got a nice sofa bed downstairs in the Cuchihuasi (Redskin Room). Lemmino!
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Charley Bottger
Location: North Central Oklahoma
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« Reply #12 on: November 17, 2009, 11:22:12 AM » |
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One thing I have noticed, Charley, is the copper line from a new condenser being much larger than the line that was attached to the previous unit. There is a company around here that does that all the time. It breaks a year later and they probably swap it out for a new one at the manufacturer's warranty expense.
Your first comment (concern) above - is that when an older oil or gas furnace is replaced with a newer heat pump unit? Can't the old, and smaller, ducts be just as big a problem? Heat pumps require more air than those older units. When I call that out on an inspection, the sellers just get some HVAC guy to say that I am all wet and they go from there. I have no juice in that circumstance. I also call out bad insulation all the time. Good point from you.
You are welcome to come by my house any time for an evaluation of my two systems. Got a nice sofa bed downstairs in the Cuchihuasi (Redskin Room). Lemmino!
Not necessarily on the duct work if it was properly sized for the tonnage of the previous unit yes a heat pump requires a little more CFM from the air handler than conventional heat. Most air handlers of the modern times are multiple speed lower speed for a gas or oil furnace high speed for A/C and most just use the higher speed for heat on a heat pump so in essence the duct should have been sized for cooling to begin with. How do you spell Redskins I think Favre. My Mother in Law lives in VA and have not been there in years-)-) |
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Jay Markanich
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« Reply #13 on: November 17, 2009, 11:42:17 AM » |
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I spell it E-I-G-H-T-I-E-S-T-O-E-A-R-L-Y-9-0-'-S
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