Horizontal furnace in the foundation crawlspace

[Keith Swift, PhD.]

I have a built-in narrative about the necessity of doors being undercut. Don't always use it, but it's there when I want it.

[Keith Swift, PhD.]

P.S. This "design" thread got interesting. Just when I think I'm close to an appreciation of how things work, someone throws in their two cents, and I'm left wondering. Take the temp split thread, for instance, I take temperature splits religiously, at every register, and find it difficult to understand that it's not valid. I hope spomeone at the NACHI conference will undertake an HVAC workshop, and clear up some of the mystery.

[Russel Ray]

Originally Posted by kswift

P.S. This "design" thread got interesting. Just when I think I'm close to an appreciation of how things work, someone throws in their two cents, and I'm left wondering. Take the temp split thread, for instance, I take temperature splits religiously, at every register, and find it difficult to understand that it's not valid. I hope spomeone at the NACHI conference will undertake an HVAC workshop, and clear up some of the mystery.

What would you tell me about these splits:

1 - 14° split, 64° and 78°
2 - 14° split, 70° and 84°
3 - 14° split, 76° and 90°

They all are 14° splits. In the first one, I suspect that my Client who likes it 80° or warmer during the winter ain't gonna be too happy. In the third one, I suspect that my Client who likes it 74° or colder during the summer ain't gonna be too happy.

That's why I don't use splits. They are kind of like percentages. Which company would you rather own:

Company 1 - 1000% growth between year one and year two
Company 2 - 10% growth between year one and year two

Better seek additional information. Company one increased from one sale to ten sales. Company two increased from 1,000 sales to 1,100 sales.

Now if standards required that the bottom end of the split be between, say, 60° and 70° and the high end of the split between, say, 85° and 90°, then I could possibly see value in determining the split.

[Robert J. OConnor]

Originally Posted by kswift

Remember, what I said about its return-air grill location, not simply being under the house but at one end of it. The air-conditioning was working nicely in the living room, kitchen, and laundry room, but the volume of air in the bedrooms on the opposite side was weak, and the rooms was decidely warm.

Originally Posted by kswift

P.S.Oops. The return-air grill was not under the house. It was at one end of the house, above the unit, and close to the floor. It was also limited in size, about ten-by-ten-inches.

Now you are talking about some issues with the mechanical system that can be reported on, and would further support the call for evaluation.

Much warmer rooms may indicate an installation problem (I don't like using the word "design" for home inspections, just to avoid even the appearance of reviewing that). That could just mean the system needs to be balanced, or there really are layout/sizing problems ... but leave that up to specialists.

For the typical single return residential system, the return grille should be more centrally located as it's difficult to draw warmer return air all the way across a house, particularly with any closed doors without a sufficient bottom gap. It's also more difficult to effectively get conditioned air to the end of a long trunk run (especially if it doesn't step down correctly), or a system with a lot of flex duct. And the return size does seem unusually small, which could restrict flow and also be noisy.

P.S. One clarification on a previous comment. While I usually think of moisture penetration as a separate issue from mechanical systems, excessive moisture over time may reduce the useful life of many things ... including mechanical systems nearby.

JMO & 2-nickels ...

[David A. Andersen]

Take the temp split thread, for instance, I take temperature splits religiously, at every register, and find it difficult to understand that it's not valid. I hope someone at the NACHI conference will undertake an HVAC workshop, and clear up some of the mystery.

Even though I disagree with the "Split", I also take them!

BUT, you can not use the information to determine the PERFORMANCE of the equipment. Your using the wrong tool for the job.

There is a workshop in CO.

The problem with some of this HVAC information is that so many are trying to do too much with too little.

Air duct design is another whole area in the HVAC world. It also has a direct effect of "Comfort" in the house. There are many reasons for low air flow, long straight runs from one side of the house to the other is not necessarily one of them! Did you know, you get more air pressure at the end of a 60 foot straight duct run than at the first takeoff at the unit? Why? Air (like water) does not like to change directions. Remember "things in motion want to stay in motion"? Before air will turn at the first takeoff, the air must hit the end of the 60 foot duct and build up "static" pressure, which forces the air sideways.

Turning the air flow results in a Dynamic Loss which results in this low air flow at the first takeoff. The air flow through the straight run of the main trunk line has less resistance, therefor the air passes towards the path of least resistance and does not readily change direction.

Have any of you seen the ranch house with an attached garage on one side of the house that was converted to a family room? Often a supply register is installed off of the end of the main trunk line. The result is a massive amount of air flow into that room and a resulting drop in the rest of the house.

Return duct as well as supply ducts must be balanced! Not a 10 x 10" !

[Charley L. Bottger]

Originally Posted by rray

What would you tell me about these splits:

1 - 14° split, 64° and 78°
2 - 14° split, 70° and 84°
3 - 14° split, 76° and 90°

They all are 14° splits. In the first one, I suspect that my Client who likes it 80° or warmer during the winter ain't gonna be too happy. In the third one, I suspect that my Client who likes it 74° or colder during the summer ain't gonna be too happy.

That's why I don't use splits. They are kind of like percentages. Which company would you rather own:

Company 1 - 1000% growth between year one and year two
Company 2 - 10% growth between year one and year two

Better seek additional information. Company one increased from one sale to ten sales. Company two increased from 1,000 sales to 1,100 sales.

Now if standards required that the bottom end of the split be between, say, 60° and 70° and the high end of the split between, say, 85° and 90°, then I could possibly see value in determining the split.

RR

What I would tell you about the three splits you have listed is that you have 3 identical systems 14 degree split. All three units are transferring exactly the same temperature from the air circulated across the A-coil to the freon being circulated in the A-coil. The return temps you listed as 78 84 & 90 and the supply temps of 64 70 & 76 simply means nothing or that someone just started the A/C unit on a hot house. What means something is that you have 14 degrees of capability of transferring or removing heat from the home to the exterior and if you set the thermostat on 70 degrees it will eventually reach set point just takes a longer run time to get there

[Charley L. Bottger]

Ok guys here we go I am going to spell out what I do as an Hi to inspect a A/C system and why I do what I do. I am not a PE or anything close but I have been working in this field since mobey dick was a minnow.

With the unit running I take the temperature from the registers and the return air temp as my very first item. Why because I don't care what the temp at the discharge from the A-coil is at this point I want to know what the temp is that is available for cooling the home. Its called duct loss between the coil and the registers more duct loss in the attic than in the floor due to extreme temperatures makes sense to me. I check for air volume at the registers and if I have a good TD between the supply registers and the return air 16 to 20 with good air volume I store this in the memory bank until we view the furnace and ducts if they are in the attic or in the crawl space.

I check visible wiring in the furnace for evidence of burnt wires. I view what ever part of the heat exchanger usually just the bottom for rust build up and I check the flame in heat mode for color and roll out on the older type of open burners. I check the blower wheel for lint build up as this will tell me if the A-coil is matted over with lint. I perform a CO test on the heat exchanger if present.
In this area with ducts in the slab I look for signs of water in the ducts. With ducts in the attic or the crawl space I want no bare metal showing and If flex is used I want to see no inner lining. I Check for air loss where the ducts connect to the plenum and for separated duct any where between the plenum and the registers. The return ducts if used should be completely sealed I do not want to draw in any un-conditioned air. The suction line should be insulated especially above a finished wall.

The condensate drain line should not be hard piped to the sewer main (air gap required) and it does not matter if there is a P-trap installed or not if it is hard piped to the sewer line you will get sewer gas into the air stream on a up flow furnace because the water will evaporate from the trap in the heat cycle. If the furnace is installed in a attic it is required to have a secondary drain pan under the coil with a secondary drain that enters a visible area from the ground level.

On electrical furnaces and strip heat on heat pumps I use a amp meter to ensure all of the multiple strips have amperage draw with the stat in the high position just in case there is a two stage stat for bringing on all of the strips.

I check the name plate data for tonage and age and the MFG's recommended breaker size and ensure that the breaker size has not been exceeded or undersized. I check the condenser fins for lint build up and physically touch the suction and liquid lines at the unit while casually checking the size of these lines.

I do not consider this as an in depth or micro evaluation of the system. Checking TD at the registers has served me well as a HAVC person and as a HI I don't think I will be changing my mind in the near future.

RR you need to close all of the windows and doors if you are getting TD's as described above




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[Keith Swift, PhD.]

Well said, Sir, clear and succinct, and I thank you for it. Glad I started the thread.

[Russel Ray]

Originally Posted by kswift

Well said, Sir, clear and succinct, and I thank you for it. Glad I started the thread.

Ah-ha! So you're the culprit! No margaritas for you this weekend.

[trausch]

Re. the kitchen faucet leak escalade - that has got to be the funniest thing I have read all day - Russel, you have GOT to put out a book! You've got some talent! Do you mind if I steal it for a good laugh at one of the NCT seminars?

[Jae Williams]

Originally Posted by dandersen

Even though I disagree with the "Split", I also take them!

BUT, you can not use the information to determine the PERFORMANCE of the equipment. Your using the wrong tool for the job.

There is a workshop in CO.

The problem with some of this HVAC information is that so many are trying to do too much with too little.

Air duct design is another whole area in the HVAC world. It also has a direct effect of "Comfort" in the house. There are many reasons for low air flow, long straight runs from one side of the house to the other is not necessarily one of them! Did you know, you get more air pressure at the end of a 60 foot straight duct run than at the first takeoff at the unit? Why? Air (like water) does not like to change directions. Remember "things in motion want to stay in motion"? Before air will turn at the first takeoff, the air must hit the end of the 60 foot duct and build up "static" pressure, which forces the air sideways.

Turning the air flow results in a Dynamic Loss which results in this low air flow at the first takeoff. The air flow through the straight run of the main trunk line has less resistance, therefor the air passes towards the path of least resistance and does not readily change direction.

Have any of you seen the ranch house with an attached garage on one side of the house that was converted to a family room? Often a supply register is installed off of the end of the main trunk line. The result is a massive amount of air flow into that room and a resulting drop in the rest of the house.

Return duct as well as supply ducts must be balanced! Not a 10 x 10" !

Ever so true. There are various reason for "taking splits", but none of those reasons have much to do with a home inspection. I take 'em, too, but I have other reasons than most do.

Air conditioning is a very involved science, and one should not attempt to derive very much information from one or two particular sets of readings. A home inspection should only indicate the unit was working at the time of the inspection. If one wishes to run the unit for a length of time to cool the house during the inspection, fine--but do not make any more of that than is necessary.

If one were to read how an air conditioner actually operates, I think the average HI would not believe it. It does not operate as one might think. "Hot" is used to cool, and "cool" is used to heat...which leads to that really neat invention--the evaporative coil. It's where the evaporation takes place that is so astonishing.

So if one is not truly versed in the field, it is best to mess with it as little as possible.

[Russel Ray]

Originally Posted by trausch

Re. the kitchen faucet leak escalade - that has got to be the funniest thing I have read all day - Russel, you have GOT to put out a book! You've got some talent! Do you mind if I steal it for a good laugh at one of the NCT seminars?

Steal it.

Keith Swift came up with the original version. I think he heard it at a report writing seminar.

I actually left out the next to last version:

Kitchen faucet leaked at time of inspection and needs to be repaired by a licensed plumber before close of escrow.

[Russel Ray]

Originally Posted by jwilliams4

So if one is not truly versed in the field, it is best to mess with it as little as possible.

Wise words for life, not just home inspections.

[Brian E. Kelly]

Originally Posted by jwilliams4

Ever so true. There are various reason for "taking splits", but none of those reasons have much to do with a home inspection. I take 'em, too, but I have other reasons than most do.

Air conditioning is a very involved science, and one should not attempt to derive very much information from one or two particular sets of readings. A home inspection should only indicate the unit was working at the time of the inspection. If one wishes to run the unit for a length of time to cool the house during the inspection, fine--but do not make any more of that than is necessary.

If one were to read how an air conditioner actually operates, I think the average HI would not believe it. It does not operate as one might think. "Hot" is used to cool, and "cool" is used to heat...which leads to that really neat invention--the evaporative coil. It's where the evaporation takes place that is so astonishing.

So if one is not truly versed in the field, it is best to mess with it as little as possible.

Jae, try not to make more out of it than there really is. Compress a gas or liquid and it gets hot, evaporate a liquid or expand a gas and it gets cold. When you think about it, it is quite simple. If it was as complicated as many here make it out to be, it would cost a lot more to buy, operate, and maintain. You can't swing a stick here in AZ with out hitting an HVAC guy.

[Russel Ray]

Originally Posted by bkelly2

Compress a gas or liquid and it gets hot, evaporate a liquid or expand a gas and it gets cold. When you think about it, it is quite simple. If it was as complicated as many here make it out to be, it would cost a lot more to buy, operate, and maintain.

Which is why heat pumps work so nicely here.