What is an acceptable differental tmp

[gporter]

is between 10 and 15 good?

[Larry D. Kage]

I like to see 14 to 22 or so but many things can affect that including humidity and outside temperature.

[Roy D. Cooke, Sr]

Originally Posted by gporter

is between 10 and 15 good?

Yep ,
I am happy 10 to twenty .
Others think we are doing it wrong.
........... Cookie

[gporter]

Thanks

[David A. Andersen]

Do you have a dart board?
Any number will do. It changes hourly and daily anyway.
A dry bulb temperature differential may work pretty accurately in Arizona because the relative humidity is low and changes are slight, but I would be far from comfortable with guessing about it in Florida.

[W. Michael Chris]

This is how I break it down:

Less than 12ºF - inadequate differential. Recommend servicing.
12-14ºF - considered marginal operation. Recommend servicing.
14-16ºF - considered acceptable.
16-18ºF - good operation.
18-20ºF - very adequate operation.
20-22ºF - slightly excessive differential.
22-24ºF - excessive differential - air path may be restricted.

Hope this helps.

[Roy D. Cooke, Sr]

Originally Posted by wchris1

This is how I break it down:

Less than 12ºF - inadequate differential. Recommend servicing.
12-14ºF - considered marginal operation. Recommend servicing.
14-16ºF - considered acceptable.
16-18ºF - good operation.
18-20ºF - very adequate operation.
20-22ºF - slightly excessive differential.
22-24ºF - excessive differential - air path may be restricted.

Hope this helps.

Can that not vary example Home temp is 65% or the home temp is 90%.

......... Cookie

[Jeffrey R. Pope]

I agree with Mike's breakdown.

Regardless of inside or outside temps (assuming summer conditions, not winter), the system should cool the air passing the coils to a difference of 16 to 20 degrees.

I have recently discovered that the IR camera gives very accurate information on these temps. You can actually see the air (through thermal imaging) moving into, and out of the system.

[Charley L. Bottger]

Please Lord is this thread subject going to start again I am going to set back and watch this one

[wsiegel]

I would say that about 90% of the time I dont even report the temperature drop. If you have dirty sir handler coils, a dirty filter, damaged ducts, or dirty coil fins on a conenser unit, the machine is now no longer functioning as intended and needs to be cleaned / serviced. I get a look of surprise on a lot of the realtor faces when I tell them I will not report the drop. I tell tem that first they need to clean the system and then test the drop. These machines are made to run with clean filters, coils and non damaged ducts.

[David A. Andersen]

It appears you are both in an arid environment.

You can actually see the air (through thermal imaging) moving into, and out of the system.

I am sorry for being such an *****, but you can not determine BTU capacity through dry bulb temp measurements and you can not see air with the BCAM.

Flir makes a CAM that can see gas, but it does not operate in the same range as the BCAM.

You may be able to see moisture temps in the air, but if you have that much moisture in the air, dry bulb temps are more than worthless as an HVCA evaluation.

I sure wish someone with a masters degree in thermodynamics would get in here and shed some new light on this subject because my posts are about as obtuse as the damn latent heat your trying to measure with a dry bulb sensing device.

Regardless of inside or outside temps (assuming summer conditions, not winter), the system should cool the air passing the coils to a difference of 16 to 20 degrees.

How can you say this? I expected more from you Jeff. You really dive into things. NACHI is now global. You can't be telling someone from the South East (and places like that) that they can be doing these things! The only way you can tell what the unit is doing is by tapping into the refrigerant system! Yes, it is outside of HI SOP. It is also a violation of the Clean Air Act and you could be fined or go to jail! Why do so many SOP's and State Laws say HVAC evaluation is outside of what we do? Because it is illegal to do it without certification!

Does anyone know what a high efficiency HVAC unit is?
Basically, it is a 2.5 ton compressor in a 3 ton condensing unit.
Larger coils lower head pressure, thus lower amp draw.
Units run longer with less of an amp draw.
Small units work on latent heat long before that can effect the sensible temperature.
You just can't say that you need a 20 degree delta T. The unit is running at capacity, but because of OUTDOOR conditions, it has a lot of work to do before it can effect the dry bulb air temp inside the house.

A gas or electric heater is a sensible heat device.
You get a predetermined BTU output from natural, propane, oil and electric. Refrigerant systems don't work anything like this! It is very VERY dependant on outdoor air temps (not referring to geothermal).

[Marcel R. Cyr]

Funny Charley. ha. ha. I'll join ya.
Any cold one's.

Marcel

[Charley L. Bottger]

Originally Posted by mcyr

Funny Charley. ha. ha. I'll join ya.
Any cold one's.

Marcel

Going to need more than one this could get long and nasty again.

[Michael Larson]

Originally Posted by mcyr

Funny Charley. ha. ha. I'll join ya.
Any cold one's.

Marcel

Great idea Marcel. Might be a good show again.

[Brian E. Kelly]

Originally Posted by mcyr

Funny Charley. ha. ha. I'll join ya.
Any cold one's.

Marcel

An excellent idea Marcel, don't mind if I do.