SH / SC basic question

[IrishJoe]

Hey guys...
Been in the field for about 7 months now. This in my first solo a/c season as a tech. I was wondering how you guys find your target (NOT ACTUAL) super Heat / SubCooling when there's not a referance chart on the door for DB / WB temps. We come across alot of really old systems (williamson, sears etc) form mid 70's. I'm a little "jiggy" w/ what some of the guys at the shop are telling me. I doesn't jive with what i saw in school.

Thanks
IJ

[hvac-master]

The attached chart will help you determine target superheat. This chart is accurate for R410A and R22 systems and is compiled from American Standard/Trane superheat slide rules.

Target subcooling will be labeled on the unit or with the service data for the unit. When no data is available I suggest setting the subcooling between 10-12 degrees.

[I_bend_metal]

You should always use a chart....every supply house known to man has them and you can usually pick them up for free. I keep one in my tool bag that is laminated for water proofing and another couple in my van for "just in case". Hope you are setting up your airflow properly before worrying about superheat and subcool. Without proper airflow, its all pointless.

By the way....since you are a tech, get your post count up to 15 and apply for pro membership status. There is a wealth of information in the pro sections....we can't really get technical in the open forums due to way too many eyes of the homeowner kind.

Welcome to the site!!

[pecmsg]

By the way....since you are a tech, get your post count up to 15 and apply for pro membership status. There is a wealth of information in the pro sections....we can't really get technical in the open forums due to way too many eyes of the homeowner kind.

Welcome to the site!!

and a new Educational Forum opening soon

[IrishJoe]

great posts, thanks, and FYI....i am trying to get my post count up, but u know how it is as a noo-B tech. I'm better off reading for now than posting :) I have thousands of questions for the privite section, but only soo many "fly" in the general forum

Thanx again

[captube]

You only need 1 more post to apply for pro membership
Here is the link with the info. http://hvac-talk.com/vbb/showthread.php?t=116113

It's best to get that app. in asap so hows the weather :)

[IrishJoe]

mid 70's last week, so a/c service started, still got a heat call saturday's on-call. Time of season for us where it all runs! Then there's the plumbing call Sunday that the toilet plugged on saturdays, but didn't call till sunday, and kept using it. I dumped the shop-vac in thier bushes out front just cause i was mad and discusted :) prolly not very pro!

[bdw293]

Glad I'm not a turd chaser. I would have sold them the shop vac and let them fix it themselves. As far as getting units charged I usually go for a 18-20 superheat on non TXV and 10-12 sub cooling on TXV. If your like most houses in my area no one changes their filter and evap coils are dirty. Homeowner to cheap to clean the. So the 70 / 225 method comes in.

[acbandit_328]

Glad I'm not a turd chaser. I would have sold them the shop vac and let them fix it themselves. As far as getting units charged I usually go for a 18-20 superheat on non TXV and 10-12 sub cooling on TXV. If your like most houses in my area no one changes their filter and evap coils are dirty. Homeowner to cheap to clean the. So the 70 / 225 method comes in.


18-20 degrees may be too high under certain circumstances. Example: 100*F outdoor temp, 80*F indoor DB, 67*F wet bulb= approx. 7*F S.H.

In this scenario, 18-20 would be too high (starving evap). Always use charts, especially if you are lucky enough to find it posted on the unit. The manufacturer has spent a lot of time developing these charts, take advantage of that every time you can!;)

[beenthere]

As far as getting units charged I usually go for a 18-20 superheat on non TXV and 10-12 sub cooling on TXV. I


If your going to take the time to measure what the SH is, you might as well take the time to see what it should be.

[gary_g]

FYI....i am trying to get my post count up, but u know how it is as a noo-B tech. I'm better off reading for now than posting :)

You can post in the "Food and Grill Forum". Those posts count also.

Good luck.

[I_bend_metal]

Hey Joe.....what part of Central Ohio are you working in??

[channelislands]

I obtain super heat readings through indoor air wet bulb, od dry bulb etc use a chart from there to calculate proper superheat as the load changes so does the setting. Subcooling try to go by oe when none around try to set by
10-12 degree range with a 15 degree superheat. As you no fixed metering superheat to charge txv charge by subcooling.

[IrishJoe]

Hey Joe.....what part of Central Ohio are you working in??



I try to not be to specific as i never want to call anyone out, but I'm safe to say around the Lima / Findlay area.

[I_bend_metal]

I try to not be to specific as i never want to call anyone out, but I'm safe to say around the Lima / Findlay area.

I know what you mean and I know where you are....I used to work up there a bit...Lowes in Findlay and their distribution center up there as well. That was one HUGE building! The only roof access was in the middle of the building and it felt like a 2 mile walk to get to any units! But then again that was in my former life of commercial... ;)