Heat pumps on stands for draining.

[Gary Cox]

Hey folks.

Had an inspection today on a dual zone TRANE system. A/C unit and a Heat Pump. Both were resting flat on a plastic base. I mentioned that the heat pump needs to be on 4" stands for draining during the defrost cycle.
I hear tonight they are adding this as a repair in the addendum.

I've searched the net for any reference article, install manuals (they all want money)...anything to add and back up my claim.

Anyone have something out there?

Thanks to the community of fellow inspectors out there.

Gary Cox
VA #3380-000419
ASHI #211556

[Jim Luttrall]

IRC 2003
M1403.2 Foundation and supports.
Supports and foundations for the outdoor unit of a heat pump shall be raised at least 3 inches above the ground to permit free drainage of defrost water, and shall conform to the manufacturer's installation instructions.

How deep does snow get in your area? (you don't have a location in your info)
That would be a concern likely addressed in the installation manual but would also be a common sense item.

[Gary Cox]

Jim your the king!

I'm a virginia boy. We get heavy snow three four times a year.

Thanks a bundle.

Gary Cox

[JB Thompson]

Since the unit was on the plastic pad, does this not meet the code for being off of the ground? (assuming the pad was 3 inches)

We have a Trane plant here in town and several of the guys go to my church. I'll ask them what the instructions say.

[JB Thompson]

Checked with my friends at Trane...

Pad does not count. See page one of attachment (bottom right)


I asked an engineer and his response was that “depending on local weather” means just that. He said that “snow feet” as we call them, are not required in this area.

Of course, we are in TX and the snow is only on the TV :)

I've attached the document.

Hope this helps,
Bruce

[Jim Luttrall]

Bruce, did they expound on what is supposed to be used to elevate the unit above the pad??
I have never seen anything except the unit flat on top of the concrete pad. I have always taken the elevation to mean the pad should be 3 inches above soil grade.

[JB Thompson]

stand by, I'll check

[Jerry Peck]

Notice that in the installation instructions Bruce attached that the minimum clearance is 12", thus two adjacent units would need to be 24" apart, and that no reduction was allowed.

That was similar to the one I ran into on the top of a condo where there were rows of 6-12 units side-by-side-by-side with only 12" between adjacent units.

I contacted the manufacturer and their engineers sent out a letter stating that when two units are installed adjacent to each other, *ONE SIDE ONLY* could be reduced to 18" (I recall it being 18", may have been 12"), the letter DID NOT ALLOW for three or more adjacent units to have any reduction in spacing - 24" between ALL units (except the first two units which were allowed that reduction on *one side only* - the spacing between the second and third unit had to be 24"). That meant the HVAC contractor had to rearrange all of his stands, extend them, and do all kinds of extra work, all because he tried to save 12" between units. I believe there was something like 300 units on the roofs of two like buildings. :eek:

[Scott Patterson]

Bruce, did they expound on what is supposed to be used to elevate the unit above the pad??
I have never seen anything except the unit flat on top of the concrete pad. I have always taken the elevation to mean the pad should be 3 inches above soil grade.

That is what the code requires. Min 3" pad above the ground.

What is in the Trane document relates to that unit. As home inspectors we really have no way of knowing the specific requirements for each and every unit. So I would have to go with the 3" above the ground rule, unless I have the specs for the unit that I'm looking at.

As for local conditions, I think I would just note that in the body of the report of the HVAC section so I would not have to type it every single time.

[Jerry Peck]

I have always taken the elevation to mean the pad should be 3 inches above soil grade.


Correct, the top of the pad where the heat pump sets on is required to be a minimum of 3" above grade ... and ... meet the manufacturer's installation instructions if higher.

From the 2006 IRC. (underlining is mine)

Heat pumps
- M1305.1.4.1 Ground clearance. Appliances supported from the ground shall be level and firmly supported on a concrete slab or other approved material extending above the adjoining ground. Appliances suspended from the floor shall have a clearance of not less than 6 inches (152 mm) from the ground.
- *AND*
- M1308.3 Foundations and supports. Foundations and supports for outdoor mechanical systems shall be raised at least 3 inches (76 mm) above the finished grade, and shall also conform to the manufacturer’s installation instructions.
- *AND*
- M1403.2 Foundations and supports.Supports and foundations for the outdoor unit of a heat pump shall be raised at least 3 inches (76 mm) above the ground to permit free drainage of defrost water, and shall conform to the manufacturer’s installation instructions.

If not a heat pump but a straight a/c condenser unit, the IRC addresses it differently:
- M1305.1.4.1 Ground clearance. Appliances supported from the ground shall be level and firmly supported on a concrete slab or other approved material extending above the adjoining ground. Appliances suspended from the floor shall have a clearance of not less than 6 inches (152 mm) from the ground.
- *AND*
- M1308.3 Foundations and supports. Foundations and supports for outdoor mechanical systems shall be raised at least 3 inches (76 mm) above the finished grade, and shall also conform to the manufacturer’s installation instructions.
- *AND*
- M1401.4 Exterior installations. Equipment installed outdoors shall be listed and labeled for outdoor installation. Supports and foundations shall prevent excessive vibration, settlement or movement of the equipment. Supports and foundations shall be level and conform to the manufacturer’s installation instructions.





Either way, though, it is still a minimum of 3" above adjacent grade (soil, sod, mulch, etc.).

[JB Thompson]

Snow foot kit (or was it Bigfoot kit?) Order it from a dealer. I wonder if this diagram will show....?

file:///C:/DOCUME%7E1/Bruce.TPI/LOCALS%7E1/Temp/msohtml1/01/clip_image001.jpg

[JB Thompson]

I can't seem to save and resend this image. Looks like a short tubular device that sits in a flat square. Round peg, square hole and all that. :)

[Jerry Peck]

You mean something like this?

Heronhill - BIG FOOT SUPPORT SYSTEM (2 UNITS) (http://www.heronhill.co.uk/productdetails.cfm?prodID=BIGFOOT2)

[JB Thompson]

just the feet, not the frame

and the square pads were smaller. For some reason, the image I rec'd will not allow me to save it or I'd send it on.

Anyway, you probably don't get much snow in Florida either.

The Trane engineer said that they're only used based local weather.

[Jim Luttrall]

According to the document posted, it says "3 to 12 inches above the pad or roof top depending on weather"
Either nobody pays attention to the instruction manual or I don't know the difference between a pad and a pad.
It does not say 3" above the ground but rather the pad or rooftop.

[JB Thompson]

Right, that's what my buddy said (above post). The pad doesn't count.

And yet, here in TX, I've never seen them...ever.

Though the document does state that it is for better drainage in snow and ice. Hence why we've never seen them.

[Jerry Peck]

According to the document posted, it says "3 to 12 inches above the pad or roof top depending on weather"
Either nobody pays attention to the instruction manual or I don't know the difference between a pad and a pad.
It does not say 3" above the ground but rather the pad or rooftop.


Jim,

That's because *the pad* is required to be a minimum of 3" "above adjacent grade, and that stand is ' mounted on *the pad* ' ;) at whatever clearances are required.

I suspect the reason is at least twofold: 1) those bases are not designed to be mounted on/in the ground; 2) if not on a flat roof and on the ground, there would be no weight to those bases to properly secure and anchor the unit down.

[Stephen Rasmusson]

Jim,

That's because *the pad* is required to be a minimum of 3" "above adjacent grade, and that stand is ' mounted on *the pad* '
;) at whatever clearances are required.

I suspect the reason is at least twofold: 1) those bases are not designed to be mounted on/in the ground; 2) if not on a flat roof and on the ground, there would be no weight to those bases to properly secure and anchor the unit down.


Here in Minnesota I was told by a respected local Lennox contractor that the unit would need to be supported above the pad a minimum of 12 inches to ensure that ice/frost buildup does not damage the lower portion of the coil on the condenser unit. Ice will form like in an old refrigerator on the coils, and when the defrost cycle melts the frost on the upper portion and the unit is flat on the pad, the drain holes will fill with ice, flow of the melted frost will stop and ice will build up. Higher elevation of the pad will not necessarily allow for drainage.
This is really a problem when the temps reach a steady 10 Degrees or below. It would be a shame for the owner to have to replace the unit due to improper elevation.

[Rick Hill]

Code asks for 3" above grade for drainage of defrost water. The pad would seem to meet that standard. The legs under the heat pump would seem to be optional, but a good idea for areas of deep snow.