Charging via superheat...

[alexb]

This spring, given the cost of electricity, I'm going to ensure I get top performance, by insisting that a technician charge my system via superheat calculation. I know that this is the most accurate method, but also takes a bit of special equipment, and some time.

I fear that if I ask this, I'll get rolling of the eyes from those that don't love their jobs, shall we say. I know that talking about pricing is forbidden, but I've seen other solicit feedback & find companies to do work in these forums. If I'm out of line, let me know; otherwise, if you're in the Baltimore / Howard County, Maryland area, and would like to charge my system via the superheat method (straight A/C, no heat, no heatpump), then send me an instant message on the site here. I have a 2006 2.5 Ton American Standard 13SEER system.

[exquid97]

superheating is the proper way to charge the system with a folwrater or cap tubes, but with your equipment chances are very high that you have a txv valve, if that is the case whoever services your equipment should be doing a subcool.

[tinknocker service tech]

The odds of your system being low refrigerant are slim at best

you should be also looking for someone that will do a good and complete service to your system and not just change the filter and check the refrigerant

you also should want superheat and subcool reading
just one reading tells only half the story

[iraqveteran]

Tink is right.

You need to have the superheat and subcooling checked on your system to really know what is going on.

Get a full service done by a reputable contractor. But don't tell they you want it charged. Its only 3 years old and chances are the charge is good. Tell them you want a routine service completed. When the tech shows up, ask them if they could check superheat and subcooling.

[beenthere]

I hope you mean check your systems charge.
Since it was only put in like 2 years ago.

[HVAC2B]

The odds of your system being low refrigerant are slim at best

you should be also looking for someone that will do a good and complete service to your system and not just change the filter and check the refrigerant

you also should want superheat and subcool reading
just one reading tells only half the story

yeah,like tin says analyze the system properly using s.h. and s.c.
also check the amp draw of the compressor
refrigerant isn't getting any cheaper

[alexb]

OP here: Thanks for the replies. I was always a bit suspect of the charge of that new system. I walked up on the guy who was charging the system, and he had his refirgerant tank upside down & tilted to one side. When I spoke to him, he seemed startled.

Did I mention that they installed *no* line dryer next to the outdoor unit, and they didn't hook up the condensate pump's cutoff wiring to anything; they are just naked wires sticking out of the unit.

For these reasons, I believe they cut all corners...


When I paid for the unit, the guy wanted me to make the check out to him personnally (he owned the company) -He said he was low on money. I looked at him funny, and he said, "Oh, it's my company - I'm not bull-crapping you..."

[Gunnery Sergeant Hartman]

Sounds like a low bid job...

[alexb]

OP: Well, There were only two contractors in this area who would do American Standard. I had someone come out for a Trane system, but he wanted to install what <b>he</b> wanted, and sounded insulted when i tried to suggest anything different.

anyway; the system is in, so that's water under the bridge. What I understand is that given my system definitly has a TXV valve, a technician should check both superheat and subcooling? I thought subcoolling was only for heatpumps(?) and superheat was for A/C-only units with a TXV valve...

[exquid97]

txv valve is a metering device for the refrigerant, it maintains your superheat, so you could have an overcharge on your system and still have a good superheat,thats why it's important to subcool a system with a txv valve, to much refrigerant will give you excessive subcooling.

[I_bend_metal]

I'm not sure what alot of these other guys do when they check a system like you are wanting to have done but the first thing I do is take a hose to it and make sure the outdoor coil is clean from things like leaves or dirt or grass clippings. Let the unit run for a while and then check my superheat / subcooling. Once that is verified I move on to inspecting the contactor, testing the capacitor(s), check amp draw on the compressor and the fan motor, inspect the fan blade for cracks or any damage, check and clean out the disconnect, check line voltage....I am sure there are a few more things I am not thinking of right now.....but if your tech isn't doing these things then he isn't doing you much of a service....just my 2 cents worth.....

[renaissanse man]

Dude, you need a new system.

[catmanacman]

while they are there have them blow the drain line

[mattm]

Did I mention that they installed *no* line dryer next to the outdoor unit,

It probably has one already factory installed in the condensing unit.

[alexb]

renaissanse man thinks I need a new system? A 2006 American Standard? I can't mention price here, but this system has to last 18 years like the old 1988 Carrier did.

Anyway, except for the refer. check and the capacitor check, I can do my own PM as far as cleaning & checking for damage etc etc..

I paid for someone to come out back when i was on the Carrier, and he just checked the charge; no other PM; can't remember what I paid though; that was 2003 or so. I paid alot to have the system evacuated & recharged the year before the Carrier went belly-up. I thought this would give it a few more years, if there was particulates in there etc etc.. They didn't replace the filter/drier at that time though.

Checking superheat & subcooling requires [more] time, and involves using special thermometers etc etc.. (I know I'm preaching to the choir...) -Measuring the temp at the evap - does that require removal of the AH cover, or can the measurement be made right where the refer lines enter/exit the unit? Do you have to be on one side or the other, of the TXV valve?

[Shophound]

What has yet to arise from this discussion is exactly why you suspect something is wrong with the refrigerant charge.

Are you not staying comfortable during warm weather? Refrigerant charge is not always the prime culprit there. High energy bills? Same answer.

A system can be properly charged (or at least have the amount of refrigerant it is supposed to have via the nameplate and adjustments for lineset length) and still not perform up to par due to ductwork design, leaky ducts, restrictive supply air registers, undersized returns, placement of supply registers within a room, etc. The house itself can also affect comfort and energy use...a house with leaky, single pane windows and sliding glass doors will be harder to keep comfortable than a house with thermal pane windows and doors.

Going after the refrigerant charge as the very first thing can often be like placing the cart before the horse. If your system is not leaking, it does not need a charge unless it was under or overcharged in the beginning.

[alexb]

I suspect improper charge from the beginning. --Remember how I stated that the tech had the canister upside-down & tilted to one side & seemed startled when I came up behind him & asked him something..?

My system is keeping me cool enough, but with ever-increasing energy prices, I'd like to have someone tell me to my face, "Sir, according to super-heat, and sub-cooling guidelines, your charge is a-OK..." I usually have the charge checked in the spring, as a matter of normal PM.

Given the extra effort it takes to do a subC and superH calculations, would you do this if asked by the customer? Is this type of check part of a "PM" call, or are you required to charge extra for this type of examination?

[hvacrmedic]

I suspect improper charge from the beginning. --Remember how I stated that the tech had the canister upside-down & tilted to one side & seemed startled when I came up behind him & asked him something..?

My system is keeping me cool enough, but with ever-increasing energy prices, I'd like to have someone tell me to my face, "Sir, according to super-heat, and sub-cooling guidelines, your charge is a-OK..." I usually have the charge checked in the spring, as a matter of normal PM.

Given the extra effort it takes to do a subC and superH calculations, would you do this if asked by the customer? Is this type of check part of a "PM" call, or are you required to charge extra for this type of examination?

Checking superheat and subcooling is a part of every PM I do, unless its a PM on a gas furnace. As far as I'm concerned, if these aren't checked, then a PM wasn't done. However, I don't really see how what you saw translates to "the guy was a hack". There is nothing wrong with inverting the refrigerant cylinder, in fact you're supposed to do that with 410A unless it has a dip tube in it. However, it isn't a problem even if it was R-22 if the guy knew how to throttle it correctly. That he was surprised by you walking up is also no surprise to me. When I'm concentrating on something that I'm doing I'm easily startled too.

In any case, it's a good idea to have it checked out before the season starts. But I'll tell you this, just because a tech measures superheat and subcooling, this doesn't mean that the system is going to be 100% because of it. There are a great number of things that can be out of whack that affect system performance.

[beenthere]

I'd do it that way even if you don't ask.

[bzzline]

For best performace fill it up in cool spring weather so you can let it out in summer when its hot.