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AC Repair

What Is Delta T In HVAC? HVAC Delta T Explained

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In HVAC, delta T measurement is used to confirm adequate heat transfer at the indoor evaporator coil. We are going to look in-depth at what is delta T in HVAC, how we measure it, and what low delta T and high delta T mean. Namely, delta T in heating and cooling is the temperature difference … Read more

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Condensation On AC Vent: 1 Cause, 5 Culprits + How To Fix Vent Sweating?

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condensation around ac vents

“Condensation is dripping from the ceiling vent; is this AC vent sweating normal? How to stop condensation on air vents?” This is quite a common AC vent problem. We see water droplets on air vents (usually on the ceiling vents). The ducts are sweating profusely and dripping on our walls, floor, carpets, furniture, and so … Read more

Categories AC Repair Leave a comment

Low Superheat Normal Subcooling: 3 Causes + How To Fix AC?

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low superheat normal subcooling causes and fixes

Low superheat normal subcooling is a less frequent AC problem. It happens when some culprit is decreasing superheat, but, very importantly, it doesn’t affect subcooling. Let’s look at what is causing low superheat and normal subcooling issue, and fix it (to avoid compressor flooding). Namely, we can look at culprits that cause low superheat here, … Read more

Categories AC Repair, Air Conditioners, Refrigerants Leave a comment

High Superheat Normal Subcooling: High CFMs Or Excessive Heat Load

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measure superheat is high while subcooling is normal

“Subcooling is normal, but I get high superheat. What is causing this? How can I fix high superheat normal subcooling?” This is quite a common air conditioner issue. Namely, we can find cases of high superheat normal subcooling by: Looking at every culprit that causes high superheat here. Removing the culprits that cause high or … Read more

Categories AC Repair, Air Conditioners, Refrigerants Leave a comment

Low Superheat High Subcooling: It’s Overcharged AC, Here’s Why

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low superheat high subcooling measured with a manifold hvac gauge

Low superheat high subcooling is a common issue with AC units. There are 5-6 low superheat causes and 3 high subcooling causes. By comparing these causes, we can see which ones are the reason we have low superheat and high subcooling. Here is a chart of low superheat causes (on the left) and high subcooling … Read more

Categories AC Repair, Air Conditioners, Refrigerants Leave a comment

Low Superheat Low Subcooling: Only 1 Cause + How To Fix It

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Low superheat low subcooling is quite a paradoxical AC problem. How can you have low superheat and low subcooling at the same time? We will explain what causes low superheat low subcooling issue in air conditioners, and how to fix it. Here is what low superheat and low subcooling means: We get low superheat when … Read more

Categories AC Repair, Air Conditioners, Refrigerants Leave a comment

High Superheat High Subcooling: Only 2 Possible Causes + Fixes

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It’s not rare to see high superheat high subcooling problem in AC diagnostics. When both superheat and subcooling are elevated, there are only 2 possible culprits. We will look into these culprits and lay out how to fix high superheat high subcooling AC problem. For this situation, we need to have: Actual measured superheat is … Read more

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High Superheat Low Subcooling: Only 1 Major Cause + How To Fix It?

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high superheat low subcooling

High superheat low subcooling is the most common combination we find when diagnosing AC units. In order to normalize both high superheat and low subcool, we have to understand why these 2 key parameters are abnormal. Namely, we have written about: High Superheat Causes here. We have high superheat when the actual measured superheat is … Read more

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What Causes High Or Low Subcooling? 4 Culprits + Fixes

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low subcooling and high subcooling causes

We use subcooling for a range of AC diagnostics. Both high subcooling and low subcooling will give us a key insight into what might be wrong with our air conditioner. To fully take advantage of our subcooling measurements, we are going to check these two insights: Low Subcooling Causes. As we will see in the … Read more

Categories AC Repair, Air Conditioners, Refrigerants Leave a comment

6 Low Superheat Causes: Low CFMs, Overcharged Or Oversized AC

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low superheat causes

Low superheat can flood your compressor. That will ruin the compressor, and you will likely have to spend $1000s for a new air conditioner. That’s why it’s very useful to understand what causes low superheat and how to fix it. We are going to cover all 6 low superheat causes, going one-by-one, detailing why low … Read more

Categories AC Repair, Air Conditioners, Refrigerants Leave a comment
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HVAC metrics:

SEER = (1 × EER100% + 42 × EER75% + 45 × EER50% + 12 × EER25%)/100

EER = BTUcooling/W

HSPF = BTUheating/W

COP = Q (useful heat)/W (input work)

ACH = CFM x 60/Area x Heightceiling

Total Heat (BTU/hr.) = 4.5 x CFM x Δh (std. air)

Sensible Heat (BTU/hr) = 1.1 x CFM x Δt (std. air)

Latent Heat (BTU/hr) = 0.69 x CFM x Δgr. (std. air)

1 HP = 746 Watts

1 kW = 3413 BTU

 

Recent Posts

  • What Is Delta T In HVAC? HVAC Delta T Explained
  • Condensation On AC Vent: 1 Cause, 5 Culprits + How To Fix Vent Sweating?
  • Low Superheat Normal Subcooling: 3 Causes + How To Fix AC?
  • High Superheat Normal Subcooling: High CFMs Or Excessive Heat Load
  • Low Superheat High Subcooling: It’s Overcharged AC, Here’s Why
  • Low Superheat Low Subcooling: Only 1 Cause + How To Fix It
  • High Superheat High Subcooling: Only 2 Possible Causes + Fixes
  • High Superheat Low Subcooling: Only 1 Major Cause + How To Fix It?
  • What Causes High Or Low Subcooling? 4 Culprits + Fixes
  • 6 Low Superheat Causes: Low CFMs, Overcharged Or Oversized AC
  • 6 High Superheat Causes + How To Fix High Superheat
  • Target Subcooling Chart? There Is No Chart, Here’s Why
  • Target Superheat Chart + Calculator, Formula, R22, 410A Examples
  • All 16 Refrigerant Types + Lists Of Refrigerants (HFC, HC, HO, etc.)
  • How To Calculate Subcooling? Formula, Subcooling Calculator (R22, 410A, etc.)
  • How To Calculate Superheat? Formula, Superheat Calculator (410A, R22, etc.)
  • How To Measure Subcooling? Easy 9 Step-By-Step Guide
  • How To Measure Superheat? Easy 10 Step-By-Step Guide
  • Understanding Superheat And Subcooling In HVAC: 101 Explanation
  • List of Low GWP Refrigerants: 69 Refrigerants Below 500 GWP
  • Water Dripping From Split AC Indoor Unit On Wall, Floor: Normal?
  • Understanding EAEER: Energy Adjusted Annual Energy Efficiency Ratio
  • Attic Floor Insulation R-Value: Floor R-Value Chart (R13-R38)
  • 4 Smallest Portable AC Units (Below 1.60 Sq Ft Footprint)
  • 5 Smallest Window AC Units For Small Windows (Compact)
  • Refrigerant GWP Chart For 61 Freons (R410A, R134A, R22, etc.)
  • What Is GWP In HVAC? Global Warming Potential Explained (R22 Example)
  • Blown-In Insulation R Values: Loose-Fill Chart (Cellulose, Fiberglass, Wool)
  • Batt Insulation R-Value Per Inch + R11-R49 Thickness Chart
  • How Many Soffit Vents Do I Need? Soffit Vent Calculator + Chart

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