3 ton unit - 2200sq ft home

[Scott Schultz]

saw a 3 ton heat pump serving a 2-story 2200 sq.ft home. This was the only unit. In the couple of hours that I was there, the unit seemed to do a decent job at cooling the home down. 3 tons seemed a bit small for this size home and I am wondering how it will perform in the long run. short-term (2.5 hour) seemed fine. any thoughts?

[rwand1]

Its better to undersize the A/C. Much also depends on the insulative values of the house, siting, and air tightness. Also if return ducts are mounted at the ceiling this will assist greatly in the cooling. Since hot air rises all the warm air pools at the ceiling.

[Bruce A. King]

It depends on how well the house is insulated and the number of windows etc.

On that house, it should have 2 thermostats with zoning valves for the best results.

[Bruce M. Graham, III]

I have 3.5 ton, water source hp, on 2950 ft., works great. I will probaly add zoneing to it next year along with a masterbath upgrade. There are a lot of factors that get consideration when sizing a unit. I looked at a retail space once that needed 5 ton of AC just for the lights.

[Scott Schultz]

R-30 cellulose in attic. I just don't want to get a call down the road from the homeowner telling me that his a/c unit is constantly running to maintain the temperature. It would have been nice for the builder to zone the a/c but it's one thermostat (upstairs location) for the entire home. Like i said, it seemed to do fine in the short term. General rule of thumb is 1 ton to 500-600 sq.ft. Would you recommend an hvac guy to evaluate or leave it be? This is the first time I've come across a 1 ton per 750 sq.ft of home so I just wanna be sure before I give the report. I mean, it's not the end of the world to recommend the builder get an hvac guy to look at it and let him make the call.

[Blaine Wiley]

Originally Posted by Scott Schultz

General rule of thumb is 1 ton to 500-600 sq.ft. Would you recommend an hvac guy to evaluate or leave it be? This is the first time I've come across a 1 ton per 750 sq.ft of home so I just wanna be sure before I give the report. I mean, it's not the end of the world to recommend the builder get an hvac guy to look at it and let him make the call.

If the unit was working properly at the time of the inspection, that is what I would report.

The inspector is not required to:

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

Many things determine whether the system is sized properly for the home. My house has a 3 ton unit for 1800 sq. ft. In VA, my house had a 3 ton unit for 2800 sq. ft. Both are/were adequate.

[cbottger]

I mean, it's not the end of the world to recommend the builder get an hvac guy to look at it and let him make the call.

If you are dealing with a Builder who do you suppose he would have come look at the unit. The guy that installed it. Surprise Surprise
[quote]

Would you recommend an hvac guy to evaluate or leave it be?

Leave it be don't go there you as an inspector with no HVAC training as Blaine stated are only required to operate the unit from its stat to many variables. If you can calculate the heat load go for it if not leave it be.

As an HVAC/HI I don't go there unless I am 100% postive that the unit can not cool the home and I will call for a heat load to be performed. I would say this has happened only twice in my tenure as a HI. And there were special circumstances

[Bruce A. King]

On vacant homes, don't forget the extra air volume present due to lack of personal items. The A/C system will work much better with the house full of stuff and with window coverings installed.

[David A. Andersen]

As you do not know what your doing (or you wouldn't be asking), I would recommend that you keep away from attempting to report anything on what you suspect concerning equipment sizing.

This evaluation is not within the scope.
Guessing will get you in trouble.
If you call in an HVAC guy and it's ok, your wrong.
If you say it's ok, you might be wrong.

Document your findings at the time and date of inspection. Indoor and outdoor conditions.

If you write anything beyond your scope, you had better know what your talking about. There are heat/cooling load calculations (which are a hell of a lot more complicated than ton/sf) that can be done. Even the HVAC guy won't likely get it right. The more you say, the more you may get in trouble.

First off, unless the system has a zoning system, you can not effectively heat and cool a two story house with one unit. This has to do with the psycrometric properties of air, not equipment design.

When the weather changes, the client may get uncomfortable. If you said it was properly sized, they may be knocking on your door, asking for you to explain. Sizing is not the only thing that effects HVAC control.

[rwand1]

First off, unless the system has a zoning system, you can not effectively heat and cool a two story house with one unit. This has to do with the psycrometric properties of air, not equipment design.

I think it depends more on number and placement of return air ducts. My home is 2 story and the A/C works fine and there is no zoning. Cold air is heavy and takes more to push it to second floors. Ideally the return air ducts should be at ceiling level to pull the hot air off ceiling imho.

cheers,

[David A. Andersen]

That is true, but you can't change the register locations between heat and cooling mode in seasonal changes. Do you have forced air heat as well as cooling? Look at where you live also. ON and AZ are not the same.

If there is not a properly located and balanced return register on the second floor, there is no way to get the hot air down to the unit (if it is located on the ground floor or below).

It takes a very good system designer to get the friction loss right to operate two floors on one system, not that it can't be done...

[Greg Bell]

I would at least recommend that the client get a copy of the energy survey that was used to determine if that size unit is adequate.

[Scott Schultz]

thanks for the replies. I simply reported that the ac was working properly at the time of inspection without getting into the size of the unit. I realize that this is beyond the SOP but so are a hundred other things that we do. I just don't want a phone call later on if that unit craps out and they find it was too small for that size house. But, I do understand where everyone is coming from and decided to take that route. Thank you.

[Blaine Wiley]

Originally Posted by Scott Schultz

I just don't want a phone call later on if that unit craps out and they find it was too small for that size house.

If you set the expectations with your client through your pre inspection agreement, and explain to them at the inspection that you cannot tell them through a visual inspection whether the unit is properly sized, you won't get that phone call. If you do get the call, you can remind them what you explained to them at the inspection.

[Scott Schultz]

clients aren't always present at inspection, as was the case here.