Thread: Temp dif split

Hey you old pro's out there.
What's going on when I get only a 10 degree split from the Electric AC?
Low on Freon?
Two in a row today?

And while your reading;
Lets here who reports Glass Blocks in the shower enclosers.

Inspector Kevin

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"Lets here who reports Glass Blocks in the shower enclosers."

Not sure what you're getting at. Glass blocks are considered structural. Are you saying they should be safety or tempered?

Kevin, ten degree temp differential in and of itself means nothing.
You can't draw a conclusion without more information. Was the day cool, warm, house cool or warm, abnormal airflow, was it a high eff. unit, etc.
About all you can tell from that is that the unit is working, but not that is is working correctly.
Jim

Kevin,

The facts are that most believe that only taking the temperature differential (between the return and supply air) is a means of determining if the unit is functioning or cooling as needed. Having a TD of 15-22 degrees is only an indicator of the system. Not how it is actually performing. Although, you will always hear the real estate agent state that the unit is good because of the TD being in that range.

Keep in mind, that a blocked coil is one thing that you (or most) do not determine during the normal visual inspecton and without removal of components of the unit. It is possible to have a blocked coil and still have a temperature diff between 15-22 degrees--- MEANS NOTHING!

The presence of a blocked coil will provide the TD with skewed numbers to go by. The range (of temperature differential) becomes greater as not enough air moves thru the coil, providing everyone relying soley on the TD with bad information.

The air flow restriction is obviously an issue that is very decieving. Conversely, the opposite is true with too much air flow-- the numbers become too low/ narrow, which may not allow enough humidity to be removed from the air.

If you take the TD in a home when you first get there, that would cause issues with your numbers as well. The unit needs to be running (in my mind) about an hour to determine if it's cooling or not (notice I did not say functioning).

Richard

Kevin, one other thing is to allow the air conditioner to run for a few minutes (10 min or so), to ensure you are allowing it to get to steady temperature.

The above reasons are some of the reasons I stopped even bothering to take TD measurements many years ago.

Give the unit a good 'looking over', you can see a dirty (blocked) coil, and you can also see if someone just 'scraped or brushed over' the surface of the coil, leaving the coil still 'dirty and blocked'.

Look for leaking air (that skews TD readings too), look for blocked, crimped, collapsed, damaged, leaking duct work (yes, that also skews TD readings), look for a filter, a dirty filter, feel the 'U' shaped fittings on the coil which connect the lateral refrigerant lines running through the coil and make sure they are all cold (I think the upper ones being warm are an indication of low refrigerant - one of the a/c guys here will correct/re-state that as needed), look ... look ... look ...

By the time you are through 'looking', unless (or even if) the system is brand spanking new (new construction) your list will be large enough to recommend having the system cleaned and serviced by an a/c contractor, then after cleaning and servicing, have the a/c contractor advise the condition of the system.

If it's brand new, it's brand new ... and under warranty, but that does not mean it is 'right'.

If it is not brand new, it's old and dirty ... and under warranty or not, you want to look for signs that it is operating as it should be, however, you will be writing down the signs showing that it is not operating as it should be.

I found very few which did not need cleaning and servicing BEFORE anyone could assess if the system was operating properly. Being as HIs do not clean and service a/c systems (at least *I* did not), that means that most a/c systems will need cleaning and servicing *before* they can be pronounced 'A OK'.

Dave:
I always run the the AC hard for at least an hour.
I love freaking out the seller when there home.
I run all the facuets, crank the Ac down, turn the bath fans on, all of it.

Jerry:
I saw no other issues. It was a 3 year old system, clean A-coil and filter.
10 dg split. I wrote it up. My 10 year old system still puts out a 15 dg split.


Glass blocks (in the shower enclosers or anywhere) are not labled as tempered. Somewhere I thought I was taught they should not be used in trempered glass situations. They will chip and/or shatter. I see them all the time.

Inspector Kevin

Kevin,

Regarding the glass block.

From the IRC.
- R308.4 Hazardous locations. The following shall be considered specific hazardous locations for the purposes of glazing:

- - Exception:

The following products, materials and uses are exempt from the above hazardous locations:
- - - 10. Glass block panels complying with Section R610.

- SECTION R610
- - GLASS UNIT MASONRY

- - - R610.1 General.

Panels of glass unit masonry located in load-bearing and nonload-bearing exterior and interior walls shall be constructed in accordance with this section.

"My 10 year old system still puts out a 15 dg split"

I've seen 30 year old system putting out a TD of 30 - filter so dirty it looked like a block of wood, coil almost the same - little air flow, high TD, NOT WORKING though.

A 3 year old system? I've seen those with dirty coils - from the time of construction (construction dust) and lack of changing the filters. You were there and I was not, so I have to go with what you say.

Just to clarifiy how we report the cooling system in Tx.-- which makes the TD (an indicator only) more important than if it were to include the ducting and vents as some might otherwise think;

Our reporting system is broken down into three categories, not just heating or cooling, but separates the ducting and vents as a stand-alone item of reporting.

Having separated out the Ducts and Vents from the Heating and Cooling section does make the temperature differential a little less subjective than if the ducting and vents were in that equation. However, it does nothing to validate the cooling system if the coil cannot be fully observed-- which you won't be able to.

I do wonder how many folks out there actually report the temperature differential when the split is too high... The lack of reporting of this condition can and may cause degridation to the ducting and insulation from the sweating. Our Texas summers are partcularlly damaging to units installed in the attic when the split is too high.

Richard

When taking temperature differentials the only thing being accounted for is sensible heat, depending on your location this can be high or low & not an indicator of the systems true performance.

What would be of true benefit is to take wet bulb temperature readings in addition to dry bulb readings.

With both of these readings & the known airflow moving over the evaporator you can determine the total, sensible & latent capacity of the equipment.

What really is an eye opener is to take these measurements at the equipment & then take them across the duct system to allow for losses.

David, welcome to the board, I take it from you posts that you are a HVAC tech. Could you give us a little of you background on yourself so we can put your comments in better perspective? You can go into the profile section and give as much or as little information as you like. For instance, since there are regional differences due to climate, etc. it helps to know what part of the country you are from.
Thanks for participating, I think most here on the board are ready to learn and readily admit we don't have all the knowledge.
Jim

Thanks for the welcome Jim, I am involved in the HVAC field for a living.

I am very fortunate that I am able to be in the field doing the work as well as write & teach on certain subjects in the industry.

I am located in central KY which has a pretty varied climate, I get to see lots of variations of weather.

I don't claim to know it all if I quit learning it would get really boring, I just try to help where I can with what I do know.
Looking forward to learning as much as I can from the site.

Originally Posted by Richard Rushing

.
I do wonder how many folks out there actually report the temperature differential when the split is too high... The lack of reporting of this condition can and may cause degridation to the ducting and insulation from the sweating. Our Texas summers are partcularlly damaging to units installed in the attic when the split is too high.

Richard

Very good Richard! and your right this is more critical than any split being to low any day.

need more info ac or heat mode? is it a heat pump, straight ac with strip heat?

So the Glass Blocks "are" the Exception and Ok to use?

Kevin

Originally Posted by Kevin Fuqua

So the Glass Blocks "are" the Exception and Ok to use?

Kevin

Yes.

But "are" "one of the exceptions", notice that was exception #10.