Target superheat formula

You said take wet bulb at unit not in the house am i right or did i miss understand the formula

Views: 5411

Replies to This Discussion

You take the Indoor Wet Bulb and the Outdoor Temp

Thank You
Can you explain this superheat formula like way do we times it by 3 and mines 80 and mines cond enterning ambient,.

Thanks Mike O

Target SH = [(3 x indoor wb) - 80 - ambient] / 2 (°F)

Usually, if you are charging an ac , the manufacturer gives you a superheat range they want the equipment to operate at  (usually 6-8 degrees)   The higher the wetbulb the more capacity/cooling will be diverted to removing moisture/humidity.

The super heat will show if the TXV is operating correctly as well.  It is a great tool for diagnosis.  If you are an HVAC dealer, your equipment manufacturer rep will be happy to explain it all to you.

All the various scenarios are to involved to train someone here.

Yikes -- Folks help me out. I am confused. As I recall, the target superheat for a fixed metering device (orifice/non-TXV) is dependent on the return plenum wet bulb (at the plenum, not in the house because what the air conditioner sees is what is in the return plenum, not necessarily the same as the wet bulb in the house) and the condenser air entering temperature.

I checked the formula given against the generic table (originally Carrier) and found the formula proposed is way off (not usable). I gets vastly the wrong answer under many scenarios. For example at 58 return plenum WB and 80 condenser air entering temperature it gives a target superheat of 34F, while the standard table gives a target of less than 5F.

Check out the linked table below from the California Title 24 Standards

On the other hand a TXV is a constant superheat valve -- so it should not change with different return plenum or outdoor conditions. For adjustable TXVs some experienced people (like Rick Chitwood) adjust it to 6 degrees F system superheat (system superheat is based on the temperature of the suction line as it enters the outdoor unit on split systems). For a TXV or EXV it is often not adjustable, but you should suspect a problem if it is high (approx15 F or above) or low (less than 3F).

Attachments:

Discussion Forum

REMRATE Modeling of 2 stage Heat Pumps - Including GSHP

Started by Jeremy Begley. Last reply by David Butler May 16.

Manual S for Water Furnace Equipment

Started by Jeremy Begley. Last reply by Danny Gough Mar 23.

joining ducts

Started by Don Fugler. Last reply by Dara Bowser Nov 28, 2017.

HVAC integration – the past, the present, and the future

Started by Igor Mitbarg. Last reply by Lucifer Prescott Apr 11, 2017.

Efficient furnace with maximum temperature

Started by Thaara Mar 30, 2016.

137 members

152 members

56 members

345 members

16 members

Latest Activity

Rick Barker is now a member of Home Energy Pros Forum
10 hours ago
David Keefe's video was featured

A Climate Report From The Field - Keefe

"A Climate Report from the Field" by David Keefe. Part of a TED-inspired evening session at the HPC Home Performance Conference, Philadelphia PA, April 25, 2018
10 hours ago
Bob Krell's video was featured

Carbon Monoxide Webinar with Bill Spohn - Healthy Indoors Show- Special Live Edition 4-16-18

Guest Bill Spohn, of Tru Tech Tools, joins host Bob Krell, to discuss Carbon Monoxide (CO) in the indoor environment. This show is a recording of a live webinar event on April 16, 2018.
10 hours ago
David Keefe posted a video

A Climate Report From The Field - Keefe

"A Climate Report from the Field" by David Keefe. Part of a TED-inspired evening session at the HPC Home Performance Conference, Philadelphia PA, April 25, 2018
10 hours ago
John White posted a blog post

What to Expect from a New HVAC Unit Installation Cost

The cost of installing an HVAC unit, such as an air conditioner installation in Laguna Hills, will…See More
20 hours ago
Kelly Vaughn posted a blog post

How Cities Can Ensure Better Rentals for Everyone

By Alisa PetersenWhile much of RMI’s research and analysis on home energy performance has focused…See More
yesterday
Brett Little posted an event

Resilient Design in an Age of Climate Change - Free CE Webinar at Webinar Online

May 30, 2018 from 12pm to 1:15pm
A changing climate, sea level rise, drought, and a wide range of stresses in the world are…See More
yesterday
John Oxford posted a blog post

Make 2018 The Year You Fear No Power Outage

Get A Back-Up Generator For Your Home’s “Mission Critical” Power Needs…See More
yesterday
Diane Chojnowski posted a discussion

California's new solar roof mandate

There's an interesting article in GreenTech Media about California's new solar roof…See More
yesterday
Ron Jones joined Diane Chojnowski's group

Job Board

This group is for posting jobs related to all aspects of the home performance industry including…See More
yesterday
Ron Jones joined Diane Chojnowski's group

News & Announcements

Share your news and announcements with the community in this group.To post news or an announcement,…See More
yesterday
Ron Jones joined Sean Lintow Sr's group

Best Practices (Residential)

Best Building, Retrofitting, or even Auditing Practices - what are they, what should change, what…See More
yesterday
Don Fugler added a discussion to the group Kitchen Ventilation

Choosing a range hood

There is so much information - how do you find what you need?With the references listed in Tom…See More
yesterday
Ron Jones joined Bob Krell's group

Healthy Indoors (IAQ)

The Healthy Indoors group is focused on indoor air quality (IAQ), mold, moisture control, radon,…See More
yesterday
"Please send me a contact number to 772-528-2076. I would like to discuss a pup if you still have…"
yesterday
Don Fugler liked Tom Phillips's discussion Kitchen Ventilation Resources
yesterday
"Please send me a contact number to 772-528-2076. I would like to discuss a pup if you still have…"
yesterday
Mike faurot joined allen p tanner's group

Energy Auditing Equipment for Sale, Trade or to Purchase

Discuss the pros and cons of the equipment you are interested in prior to purchase. Post equipment…See More
yesterday
Bob Krell posted videos
yesterday
Ron Jones, universal services and Mike faurot joined Home Energy Pros Forum
yesterday