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A coil/Condensor sizing

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[#1] Posted: 04/28/2006 - 3:32:46 PM
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Hi all,

I did an inspection just over a year ago. 6 year old condensing unit and 6 year old furnace. Unable to operate AC due to low exterior temps and noted that. Clients used system last year after moving in, thought it was a little weak, but it worked. Turned on first time this year and it froze up. Warranty company HVAC tech and second HVAC tech that came out stated it was mismatched coil and condensor sizes and it should have been caught at inspection since it's an improper installation. It is a 4 ton condensor and 3 1/2 ton A-coil.

Questions: I don't compare the spec plates between the coil and condensor. Do you and should I be? If so, what parameters do you use. Does this fall under the requirements of common home inspection Standards (ASHI, NAHI) as something to be checked? I certainly have no problems owning up to it and making it right if I made a mistake and I'll certainly learn from it. I've never ran into this before. Thanks in advance.



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A coil/Condensor sizing
[#2] Posted: 04/28/2006 - 4:01:52 PM
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Hi,

Well, the standards are one thing but what have you got in your pre-inspection agreement? That's the real standard you're working off of and should be in compliance with whatever standard you use. That said, here's a comparison of what the S.O.P.'s of the 4 major national organizations say about A/C:

A.S.H.I.

Includes the installed central and through-wall cooling equipment.

The inspector shall:

Inspect the installed central and through-wall cooling equipment.

Describe the energy source; and the cooling method by its distinguishing characteristics.

The inspector is not required to:

Inspect the electronic air filters.

Determine the cooling supply adequacy or distribution balance.


N.A.H.I.

Includes the cooling equipment; cooling distribution; operating controls; procedures for Inspection.

The Inspector will:

Describe the type of central air conditioning system and energy sources.

Operate the system using normal control devices.

Open readily accessible access panels or covers provided by the manufacturer or installer, if readily accessible.

Observe the condition of controls and operative components of the complete system, conditions permitting; and the condition of a representative number of the central air cooling outlets in each habitable space of the house.

The Inspector is not required to:

Activate or operate cooling or other systems that have been shut-down.

Inspect gas-fired refrigeration systems, evaporative coolers, or wall or window-mounted air conditioning units.

Check the pressure of the system coolant or determine the presence of leakage.

Evaluate the capacity, efficiency, or adequacy of the system.

Operate equipment or systems if exterior temperature is below 60° Fahrenheit or when other circumstances are not conducive to safe operation or may damage the equipment.

Remove covers or panels that are not readily accessible.

Dismantle any equipment, controls, or gauges.

Check the electrical current drawn by the unit.

Operate digital-type thermostats or controls.


A.I.I.

Includes the central air conditioning including cooling and air handling equipment and normal operating controls; distribution systems including ducts, registers, air filters, fans, pumps and piping, with associated supports, insulation, and fan-coil units if different than heating system; presence of an installed cooling source in each room

The inspector shall:

Observe and report on central air conditioning including cooling and air handling equipment and normal operating controls; distribution systems including ducts, registers, air filters, fans, pumps and piping, with associated supports, insulation, and fan-coil units if different than heating system; the presence of an installed cooling source in each room.

The inspector shall:

Identify energy sources and cooling equipment type.

Reporton condensate drains where visible and accessible.

Operate the systems using normal operating controls.

Open readily accessible and unsecured access panels provided by the manufacturer or installer for routine homeowner maintenance.

The inspector is not required to:

Examine or report on cooling systems when weather conditions or other circumstances may cause equipment damage; non-central air conditioners; gas fired, solar or geothermal cooling system; food, wine or similar storage cooling systems; (Permanently installed wall air conditioning units may be reported on using normal operating controls.)

Report on the uniformity or adequacy of cold air supply to the various rooms.

Examine or report on any humidity control systems or components.


N.A.C.H.I.

Includes the central cooling equipment.

The inspector shall:

Inspect the central cooling equipment using normal operating controls.

The inspector is not required to:

Determine uniformity, temperature, flow, balance, distribution, size, capacity,
BTU, or supply adequacy of the cooling system.

Inspect window units, through-wall units, or electronic air filters.

Operate equipment or systems if exterior temperature is below 60 degrees Fahrenheit or when other circumstances are not conducive to safe operation or may damage the equipment.

Inspect or determine thermostat calibration, heat anticipation or automatic setbacks or clocks.

Examine electrical current, coolant fluids or gasses, or coolant leakage.


ONE TEAM - ONE FIGHT!!!

Mike

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A coil/Condensor sizing
[#3] Posted: 04/28/2006 - 5:01:54 PM
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Quote:Originally posted by fyrmnk

It is a 4 ton condensor and 3 1/2 ton A-coil.



That's a bunch of crap anyway... a 12.5% mismatch on sizing either way makes no difference. The system will flow at the rate the expansion valve allows.

Chad Fabry
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[#4] Posted: 04/28/2006 - 5:51:48 PM
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Kevin

The HVAC guys are full of crap!


Captain

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A coil/Condensor sizing
[#5] Posted: 04/28/2006 - 5:58:01 PM
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It use to be standard practice to oversize the evap coil by 1/2ton for better dehumidification (larger coil surface).

I don't see how undersizing the coil would make it freeze. When a coil freezes it due to lack of air flow (dirty fan, dirty air filter), a refrigerant leak, operating the system in low ambient condition without low ambient controls.

However, I wouldn't under size the coil/oversize the condensing unit. Too small of an evap coil will provide inadequate cooling while providing to high of a superheat back to the compressor. If you derate a system by installing a smaller evap or expansion valve then you have to do some type of liquid injection for proper super heat back at the compressor (proper cooling of the compressor). While it is true that the expansion valve controls flow it depends on the type of expansion device. If it is a capillary tube it flows at a fixed rate which depends on pressures and temperatures. On the other hand if it is a TXV you can adjust the valve for proper superheat/flow. Not to mention electronic X valves.

At any rate, I seldom, if ever, try to figure out if the evap coils is matched to the condensing unit. When I run a system I check for proper delta T across the evap, check the outside unit to make sure there are no marbles in the can, give the disconnect a once over, make sure there are no signs of oil around the lines or fittings and make sure the armaflex it still in good condition, especially when it runs through a hot attic.

Terry



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[#6] Posted: 04/28/2006 - 7:51:55 PM
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I agree with Chad, Captian and Terrance.

I've specifically asked HVAC guys why I sometimes see mismatched coils on coolings systems and they've explained that it was deliberate and calculated. However, they have explained that it should always be (I believe) it was the evap coil that should be larger. (Don't quote me on that part because I honestly don't remember and hope someone will chime int and nail that part down.)

For a small period of time I used to actually report mismatched coils until I realized this is beyond our expertise and more than likely the HVAC guy knew what he was doing. (Even though they can't seem to assemble systems airtight worth a hoot.)

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[#7] Posted: 04/28/2006 - 11:53:27 PM
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If "Unable to operate AC due to low exterior temps and noted that". How could you be held responsible? Your only indication of a major mismatch (which this is not) would be how the unit operates. Which case if it fails, you call it out to an HVAC guy. But, you did call it out to an HVAC guy just by stating "Unable to operate". If you were an HVAC expert and designed systems and advertized that to your clients, then it might be a problem. You are not responsible to compare spec plates. I do not compare spec plates and it's not required in Tx. (The most Air Cond. State in the world).
The true danger is when liberty is nibbled away, for expedients, and by parts ... the only thing necessary for evil to triumph is for good men to do nothing. Edmund Burke
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[#8] Posted: 04/29/2006 - 12:17:09 AM
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Yep, what they all said. Not our job, well beyond the scope, and probably not even the problem to start with. No way I'd cover that, and I don't believe for a minute they could make me either.

The service guys and contractors (all kinds) seem to be getting more and more into the mode of claiming anything they find or fix should have been caught at inspection. I don't know if it's revenge or they're just trying to look good for having *out-done* us. All I can say is that if most of them were doing thier job as thoroughly as I do mine, we'd all be out of work. I'm not worried.

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[#9] Posted: 04/29/2006 - 03:58:41 AM
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Well said, Brian!

Speaking of miss-matches, the equipment gets better and the installations get worse cancelling all the manufacturer's good efforts and the poor consumer's alleged benefits.

HVAC contractors have a huge gap to close, themselves!

They're not high on my list these days simply because their shortcomings spell flat out laziness and carelessness. And, you know that the installations on their own homes are perfection.

In example: Yesterday's new construction home inspection revealed the HVAC system had:

- Holes at the corners of the metal ductwork junctions as round as a dimes!

- Gaps around the suction line where it entered the evap coil big enough to plunge your pinky finger into.

- Gaps where the blower and evap coil cabinets joined big enough you could see right into the unit and the same where the ducts joined the unit.

If a surgeon sewed his patient up like that they'd bleed to death. A boat built like that would sink to the bottom in seconds.

It's just downright shameful and inexcusable! I mean WHY BOTHER to show up for work? In fact, please do EVERYONE a favor and DON'T show up for work!

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[#10] Posted: 04/29/2006 - 04:21:50 AM
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While we're on the subject, Terrance, you seem to know your stuff.

I do get a little nervous when I see that the refrigerant lines weren't changed out and don't equal the diameters of the new coils lines. (Typically they'll be smaller.) I always write that up as needing a look-see by a specialist.

What do you think about that?


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[#11] Posted: 04/29/2006 - 06:29:36 AM
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There's really little variation in standard line sets. I have the Carrier design manuals as well as the Trane design manual however, these get more into commercial/industrial applications.

Attached is a link for a pretty good PDF on sizing. http://www.thermopride.com/Man..._I&O.pdf

As you can see the sizing doesn't vary a whole lot and assuming (bad word, I know) that the installation was correct to begin with not changing out the line set doesn't cause any red flags to pop up however, I do point out if the condensing unit is newer and the liquid line dryer is still old, if the armaflex is shot or if the disconnect is rusted and in need of replacement. You should always install a new liquid line dryer whenever you have to open up the system as well as pulling a good vacuum to purge moisture and non-condensible.

In commercial applications where there is a remote condenser, not condensing unit, it is advisable to change out the hot gas line. The hot gas line really takes a pounding from the constant high temperatures and the expansion and contraction during cycles. This is an area that is prone to leaks over time.

Terry



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[#12] Posted: 04/29/2006 - 07:34:29 AM
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What do the manufacturers say about installing an evaporator coil that is smaller than the condenser unit. Everything I have read says that they need to be matched, even though many have a larger evaporator coil (like mine).

Logic tells me that you do not want a smaller evaporator coil.

I do compare the size of the units to each other and to the size of the house. I was an EW on a case a few years back that the HI did not call out a 5 ton unit on a 1600sf house. We could not defend the home inspector. The house had many moisture problems all attributed to the over sized A/C system.

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[#13] Posted: 04/29/2006 - 07:56:58 AM
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Quote:Originally posted by Scottpat

I was an EW on a case a few years back that the HI did not call out a 5 ton unit on a 1600sf house. We could not defend the home inspector. The house had many moisture problems all attributed to the over sized A/C system.


What was the outcome Scott, ever hear?

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[#14] Posted: 04/29/2006 - 08:14:16 AM
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Well, just to be clear on my question, sometimes I'll see that the old line set diameters are significantly smaller that the lines on the new equipment and they've just crimped and soldered them. Is that OK?
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[#15] Posted: 04/29/2006 - 08:30:29 AM
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Unless you look up the manufactures specs you really don't know the size. So lets just say that the compressor and coil are off 3000 btus from the plate then they match. Or they can be off by a ton.

The point being that this unit has been in service for six years and now there is a problem with "mis match" bull crap.

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[#16] Posted: 04/29/2006 - 10:32:00 AM
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Not to mention it's kinda comical that a "specialist" is trying to blame a "generalist" for what his fellow "specialist" did. They're the ones that earned the title "technician". It's silly.
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[#17] Posted: 04/29/2006 - 10:36:07 AM
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<div style="stylequote" id="quoteN">Quote:Originally posted by mgbinspect

Well, just to be clear on my question, sometimes I'll see that the old line set diameters are significantly smaller that the lines on the new equipment and they've just crimped and soldered them. Is that OK?
</div id="quoteN">

The PDF file I mentioned would be wise to consult as a quick rule of thumb. These will get you in the ballpark as to sound an alarm or not. I would guess that if the hair on the back of your neck starts standing up, default to an expert. Sometimes I view conditions that I'm not comfortable with. If I could charge by the hour I could research these items for the client however, I punt. It is time to move on and get busy with the next inspection. In any case I would always ask for the phone number of the "expert". I always like to talk to the people to get their view on the problem. Sometimes it's fun to do with the client present. Only do this if you have sea legs.

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[#18] Posted: 04/29/2006 - 11:02:09 AM
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Quote:What was the outcome Scott, ever hear?

Terry



The home inspector lost, as did the real estate agents, the HVAC company who installed the system and the previous homeowner. I think the HI part of the damages was around $10,000. The total award if I recall was near $85,000.

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[#19] Posted: 04/29/2006 - 11:11:23 AM
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[quote]Originally posted by Scottpat

I was an EW on a case a few years back that the HI did not call out a 5 ton unit on a 1600sf house. We could not defend the home inspector.

Was that before the state adopted the ASHI standards? It had to be. The standards are crystal clear on that issue.

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[#20] Posted: 04/29/2006 - 1:40:15 PM
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Quote:Originally posted by Scottpat

Quote:What was the outcome Scott, ever hear?

Terry



The home inspector lost, as did the real estate agents, the HVAC company who installed the system and the previous homeowner. I think the HI part of the damages was around $10,000. The total award if I recall was near $85,000.


$85,000??? For what, pain and suffering? I know, mold caused by the lack of proper dehumidification.

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[#21] Posted: 04/29/2006 - 2:07:57 PM
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Quote:Originally posted by Brian G.

[quote]Originally posted by Scottpat

Was that before the state adopted the ASHI standards? It had to be. The standards are crystal clear on that issue.

Brian G.
Momentarily Confused



You're assuming that the judge respects things like contracts, state licensing standards of practice, or anything else. Judges can be just as (or more) capricious as anyone else.

My single lawsuit was an object lesson in how worthless contracts are, how obtuse & obscure the law is, how narrow & goofy judges can be, and how important good report writing must be, to keep one's ass out of the sling.

Kurt in Chicago

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[#22] Posted: 04/29/2006 - 2:23:50 PM
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Sheesh! That's down right scary.
"This above all: to thine own self be true." - William Shakespeare
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[#23] Posted: 04/29/2006 - 3:54:39 PM
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Kevin,
Keep in mind that a lot of evaporator coils can be used for two different size air conditioning units. It all depends on how you read the name plate. Example: A Goodman CAPF4860C6A is rated for 4 to 5 ton use. 48 = 4 ton and 60 = 5 ton. Both numbers go together. This is a 4-5 ton unit. Look at some of the coils at http://www.alpinehomeair.com/v...oducts=0 and you will see what I'm talking about. Your 3 1/2 ton coil may also be rated for 4 ton depending on the manufacture.

Jeff Euriech
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[#24] Posted: 04/29/2006 - 3:56:36 PM
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I guess I'm having difficulty trying to decide what should be called out as mismatched units or components on an air conditioning unit. As an example:

The condenser and evaporator being two different sizes/ratings. For the most part, trying to figure out the size of the unit becomes a guessing game. Especially if you are trying to read the model number or serial number. I've been told that you take the first set of numbers that you can divide by 12 and that will tell you the tonnage. However I see numbers like 604842. Is that a 5 ton unit or a 4 ton unit?

I'm under the impression that if you have a Carrier condenser and a York evaporator (different name brands) you now have a mismatched unit. It may not work efficiently. Do you call these out?

Yesterday's inspection had a 8 year old condenser unit and a 21 year old evaporator. Is this a matched unit? As seer ratings change it's my understanding that coil size changes also. So this unit may not work very efficient.

I have heard that you can go 1/2 size larger on an evaporator if it is an air conditioning unit. However, if it is a heat pump it must be the right size.

Currently I would think that if you are going to call out mismatched units or components, you need to do everything and not only size.

Jeff Euriech
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[#25] Posted: 04/29/2006 - 7:32:59 PM
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Thanks for all the replies. Jeff, thanks for that link.

It was an International Comfort Products (isn't that Goodman as well?) AC and a Goodman furnace. I'll go check the plates and help the client with researching the issue. Looks like some good discussions and a lot of different views on this issue. Thanks again.


Kevin Wattenbarger
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[#26] Posted: 04/29/2006 - 8:50:08 PM
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Below is a reply from an HVAC tech web forum on the subject at hand:



"That's not a real mismatch. In the Houston, TX area they successfully undersize coils to remove more of the humidity.

First, you need to be sure the blower is set properly for the necessary cooling air flow. A 4 ton condenser unit should have ~1600 cfm of air flow. Next be sure the filters are clean and all supply registers and returns are open. Lastly, you need to visibly inspect the evaporator coil to be sure it's clean. Until you know you have the proper load (air flow) on the evaporator coil, there's no point in doing anything else.

Once you know the air flow and coil load are correct, then check the charge. If the previous owner didn't have a freeze problem, you shouldn't now. Last way to stop the freezing if all else fails is remove the piston/orifice metering device at the coil and use a thermostatic expansion valve."


Kevin Wattenbarger
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