Question...Help Please

[mhawley]

Today’s inspection was a single story home built in 1999. It was 3300 sq-ft and had two 5-ton units. One unit was original from 99 and the other was a 2002. Each unit supplied separate sides of the home and each had their own thermostat, one for the East side and one for the West side. Also the garage has two active ceiling registers to condition the two car garage space. The total sq-ft under air with the garage is still under 4000. The home has a tile roof, a radiant barrier and most of the windows are tinted.

When I was doing my post inspection wrap-up with my customer I explained to her that the home’s AC system may be potentially oversized and “Might” not adequately remove the moisture from the home during the hot summer months and she should obtain the original heat gain/heat loss study to determine if the units is properly sized.

The homeowner said when the house was built it had 2 units however she upgraded one of the units in 2002 to make the home cooler and did not remember how many tons the original unit was. She started getting a slight attitude with me and said in a snooty wayt the best AC Company in the county installed the system and she has never heard of an AC system being to big.

I have 2 questions:

1 - As far as the garage having ceiling registers that are in use, is that allowed? The ductwork was a combination of sheet metal and foil covered flex. Even though the home is a single story my thought are in the event of a garage fire flames would easily spread into the attic space. Is there a code referencing AC ceiling register on single story homes? I know the seller is going to look into my every finding. I just want to make sure I am correct.

2 - Is there a chance that the system is “Not” oversized and I am making an issue over nothing?

Thanks in advance and Jerry your MB is GREAT!! I look forward to seing it grow and grow. Thanks for always helping.

[Jerry Peck - Codeman]

Hi Matt,

Before getting to your questions, the first thing I noticed, and am sure you noted on your report, was that there were two a/c systems, one for each side of the house (that is okay) but then you added " Also the garage has two active ceiling registers to condition the two car garage space.", and THAT is not acceptable, not *IF* those were supplied off one of those systems.

My guess is that they were supplied off one of those systems, probably the 2002 system, which was most likely replaced to provide the conditioned air for the garage.

Here are a few things I thought of:
-> I am going to presume that the master suite is on the same side of the house as the garage as that is the typical layout used. Based on that assumption, the rest of the house was most likely on the original 1999 5 ton system, and the master suite was most likely on a 1-1/2 ton to 2 ton system. The master bedroom system was then replaced with the 2002 5 ton system.
-> The duct work for the 2 ton system is likely very undersized for the 5 ton system *IF* the same duct work is used for the entire system. It is possible that the HVAC contractor installed a new supply plenum and distribution boxes from which the original duct work only serves the master suite and new duct work goes straight to the garage. That is a large presumption and would need to be verified by an HVAC contractor who would need to determine what cfm of air is needed where, and is the duct work correctly sized for that.
-> Here is the problem with the above - the garage is not allowed on the same system which is serving the interior living space. Which means that no matter 'how correctly sized the duct work may be as it is now connected, it is not allowed to be connected that way'.

The end result of the above is that the system which supplies the garage must be disconnected from the living space system, which means the (if my presumption is correct) master suite system will need to be replaced with a properly sized system and the duct work re-routed for that system and that area.

Which leaves us with the newer 5 ton system for the garage. That is a lot of capacity for only a two car garage which is insulated, and, if not insulated, should not be conditioned. That would mean the walls, the garage door(s), and the attic ceiling would need to meet minimum insulation requirements.

From the 2001 Florida Building Code, which would have been in effect when the a/c system was replaced: (underlining and bold are mine)
- SECTION M918
- - FORCED-AIR WARM-AIR FURNACES
- - - M918.6 Prohibited sources. Outside or return air for a forced-air heating system shall not be taken from the following locations:
- - - - 6. A closet, bathroom, toilet room, kitchen, garage, mechanical room, boiler room or furnace room.

The argument will likely be given that there is no return air in the garage (presuming there is none) and thus there is no code violation.
The following addresses that as when a space has supply air to it, there must be return from it to avoid pressurization of that space. Thus, return is required (not having a return air is in itself a code violation), and, once installed, the return air becomes a code violation. One "door" referenced in the code section below will be the door from the garage to the living space.

- M601.4 Balanced Return Air. Restricted return air occurs in buildings when returns are located in central zones and closed interior doors impede air flow to the return grill or when ceiling spaces are used as return plenums and fire walls restrict air movement from one portion of the return plenum to another. Provisions shall be made in both residential and commercial buildings to avoid unbalanced air flows and pressure differentials caused by restricted return air. Pressure differentials across closed doors where returns are centrally located shall be limited to 0.001 inch WC (2.5 pascals) or less. Pressure differentials across fire walls in ceiling space plenums shall be limited to 0.001 inch WC (2.5 pascals) by providing air duct pathways or air transfer pathways from the high pressure zone to the low zone.

I could post more code references, such as from Chapter 13, the Energy Efficiency code section which requires heated and cooled spaces to meet minimum insulation requirements (such as I mentioned early on in this answer), but, there is so much wrong with that installation that providing more code sections is not needed.

I typed the above before reading your questions, however, many of my guesses were borne out in your posted information and questions.

Now to your questions:
-> 1) That has already been answered above.
-> 2) The main house system may not be oversized, however, the garage system is so incorrectly installed in so many ways (see above information) that the garage system needs to be removed from the living space system (likely the master suite system) and that alone makes everything else moot.

Codeman

[mhawley]

Thanks Jerry,

One 5-ton system supplied half the home (Master bedroom, living room two bathroom and formal dining area). The other system supplied the family room 2 guest bedrooms, a 1/2 bath, bathroom and garage. The garage and master bedroom are at oppiste ends of the home.

So bottom line is since the garage is supplied with conditioned air - It should not also supply any part of the main home...Is that correct? Also the registers will allow flames to enter the attic space and should not be there...Is that correct?

It sounded like they decided they wanted to cool the garage and replaced the smaller unit with another 5-ton. They seamed to think bigger is better as far as AC's go. Both return were in the house. One in the master bedroom ceiling at one end of the home and the other at the split hall ceiling opposite on the opposite end of the home

Here is what I have under the cooling section so far -

The home's cooling system consist of two 5-ton units capable of cooling approximately 6000 Sqft. The total tons of both units is higher than required. This condition has been known to cause systems to cycle on and off to quickly and not adequately remove moisture from the air. The original heat gain/heat loss study can be obtained from the building department to determine if the units and ducts are properly sized.

The garage has two ceiling monted registers (See Photo #1). In the event of a fire in the garage flames are susceptible to entering the attic space.

Is that correct? I know this lady is going to challenge everything I write. I just want to be sure I am correct and fair.

Thanks again Jerry, any and all suggestion are very much appreciated.

[Jerry Peck - Codeman]

[mhawley]

Jerry,

Thank you very much for your time and help. I just have one more question.

I know having a return in the garage wouId be a problem because of of contaminated air from stored items in the garage. Since there are not returns in the garage and only supply registers what problems does that cause other than not being code compliant? My thought was flames entering the attic space in the event of a fire. I do not know if there were dampers. I just want to have the answers to any questions the sellers throw at me. I know that will be one of them and i'm curious myself.

Thanks again Jerry, I am grateful, hope all is well.

[Jerry Peck - Codeman]