Polystyrene "HVAC Quick Reference Cards for Refrigerant Charging & Troubleshooting"! Available at www.acservicetech.com/store Available at www.amazon.com/shop/acservicetech Get a Discount at "acservicetech.com" when you Bundle the Cards with the Paperback & Ebook! Get $5 off- Purchase the Cards and Paperback, use the Discount Bundle Code: "Dec19CP" Get $5 off- Purchase the Paperback and Ebook, use the Discount Bundle Code: "Dec19PE" Get $10 off- Purchase the Cards, Paperback, and Ebook, use the Discount Bundle Code: "Dec19CPE" These three HVAC quick reference polystyrene cards are double sided and designed to be used with Air Conditioners and Heat Pumps to measure the refrigerant level in a unit, charge refrigerant, troubleshoot refrigerant based problems, and measure heat transfer to determine if there is a problem during cooling mode. The Cards are each 5.625" by 8.85" and are made from Flexible Weather and UV Resistant Polystyrene. The print job and cards have been tested from 0°F-130°F. The cards have also been tested with exposure to common refrigerant oils. The Cards Contain: -Finding the Target Subcooling for Systems with a TXV Metering Device -Initial Steps Before Measuring the Refrigerant Charge with Subcooling -Measuring Subcooling to Determine if a System is Undercharged, Correctly Charged, or Overcharged -Example of System Measurement Locations for Measuring Subcooling -Finding the Target Superheat for Systems with a Fixed Orifice Metering Device -Initial Steps Before Measuring the Refrigerant Charge with Total Superheat -Measuring Total Superheat to Determine if a System is Undercharged, Correctly Charged, or Overcharged -Example of System Measurement Locations for Measuring Superheat -Measuring Delta T and Determining if the Temp Drop is Correct -P/T Chart for R-22, R-410A, R-407C, R422B (NU22B), and R438A (MO99) -Instructions for Finding the Sat Temp of R-22 and R-410A -Instructions for Finding the Dew and Bubble Sat Temps of Blend Refrigerants -Refrigerant Weight Per foot Chart -Instructions for Adding the Full Amount of Refrigerant needed -Instructions for Adding Refrigerant into a Running System -Example for Determining the Correct Amount of Refrigerant Needed in an Off, Empty, and Vacuumed Split System -Troubleshooting Guide for Systems with a Fixed Orifice or TXV -Use Measurements such as Superheat, Subcooling, Delta T, Vapor Sat Temp, Liquid Sat temp, Compressor Amps to Determine the Problem. -Use the Guide to Determine Problems such as a Liquid Line Restriction, Low Indoor Airflow, Contaminated Refrigerant, Low Outdoor Unit Airflow, Undercharged, Overcharged, TXV Bulb Charge Lost, Detached or Uninsulated TXV Bulb, Weak Compressor Valves, Reversing Valves Bleeding across the Tubes. -Step by Step Guide for Troubleshooting a Frozen Evap Coil on an Air Conditioner or Heat Pump in Cooling Mode. -Instructions to Determine if the Problem is a Low Refrigerant Charge, Low Airflow, or a Liquid Line Restriction. Check Out The Full Outline of our Book Including Sample Pages at: www.acservicetech.com/the-book Here is the Video Explaining What is Included in the Paperback and E-Book: kzfaq.info/get/bejne/e8hpo5R1urTLlY0.html You can also support our work by purchasing tools and other items after entering amazon through our link at www.amazon.com/shop/acservicech You can support our continued work in making HVACR videos by joining www.patreon.com/acservicetech Thank you for all of the kind and uplifting words in each of your comments! I love to hear your stories and about your journey as you continue to grow in the HVACR field! We are all learning and growing all the time! Thanks to all of our supporting Patrons at www.patreon.com/acservicetech ! I really hope that the book and quick reference cards help each and every one of you in your journey to becoming an invaluable service technician in our industry!

Nothing better than Sunday morning coffee and Hvac videos. Thanks for sharing.

It seems you have a video for something I’m worried about not fully understanding. It’s uncanny and amazing. Thank you sir. I’m going to send you a check when I make some real money in the business , for all the help you’ve given me. 🙏🏾

Thank you AC Service Tech LLC. Your videos are a huge help in learning the trade. You are my go to resource along with a few books and technical manuals. I wish you all well for the services you provide us. Respect from an HVAC/R apprentice in Virginia.

I have your book and I went to ivy tech for a Tech degree. I will say you put it in words that I understand. Thank you.

As a HVAC instructor your book is really great. Keep up the good work.

I bought your book and as a HVAC instructor you explain everything really well my student really like your book

Thanks man for sharing your knowledge! You are the best!

Always clear and concise.

This guy explains the best!!!! Thank you Sir!

Honeywell has an online essay, “Why Delta T is the Magic Number.” My 2010 edition of AHRI’s Fundamentals has a simple graph on page 662 adjusting return dry air for RH, and on page 668 makes the straightforward observation that a low Delta T indicates heat removing capacity has been reduced.

Watching this during my test

Great instruction Craig! Helps me a lot.

Great tutorial Craig.

The delta T you will get in the air conditioning mode depends on the entering air enthalpy (sensible heat + latent heat, or in layman’s terms, return air temperature + return air humidity, plotted on a psychrometric chart). This is the reason you have to take a wet bulb temperature at the return air to determine what the DeltaT should be. Delta T can run from 16-26 degrees on a normally running system, depending on return air enthalpy. The old way of calculating heat pump delta T, without running strip heating in the old days was called the output rule. The rule stated that at 70 degrees outdoor temperature, a heat pump would produce 30 degrees Delta T. For each ten degree drop from 70 degree outdoor temperature you loose 3 degrees on the Delta T, so at an outdoor temperature of 50 the delta T would be 24. This rule applied to the old R22 systems. I do not know if it is applicable to the newer systems, it was a good rule of thumb, that I used may times, when I did not have the manufacturers specifications.

Absolutely priceless information you offer in this video. You are the best

Excellent video partner thank you for sharing!!!!!.

Great stuff, very explained !

Another thing to take note of is that an evaporator delta T is also related to the Sensible Heat Ratio in your area. Having a high SHR (0.85 or above) means most of your heat in the home is just sensible heat, and you would have a larger delta T and less condensate. A lower SHR (0.75 or even lower) is an indication of your home having lots of humidity. The coil will remove more heat from water vapor in the air, so more condensate, but less delta T. These values can be found in the literature provided with your equipment, and are used when doing a Manual D or Manual S.

Nice job and video

Ive been doing this kind of work over 20 years including 2 years of trade school and I have never heard the term delta t until today. I was taught to call it the differential or differential temperature. 🤷‍♂️

👍🏾👍🏾 another great video

Had one last week, leaky ducting, sucking air from wall cavity and attic space. Cut inspection hole under unit, spray foamed and sealed best I could and temp came right back up. Had to recover some juice from it also being over charged, without thinking it through first 2 other techs condemned the 7yr old unit.

I have your book it’s great ! Bu when is a furnace book coming ?

Hey love your stuff bro…can you tell me what is meant by start up process when installing a new unit

Best on youtube....

Craig. Great video. It’s well outlined. For a moron like myself, any way to add graphics with each point presented. Thank you for all you do.

Just did a Delta T check on a old R22 unit with my new ST4 , only a 6 degree drop, lol.

Thanks for this video. I have a 4-head Mitsubishi mini-split system. Delta-T varies at each head: 13, 14, 15, and 20 degrees. Less than a year old. Last year, a week after initial installation there was a leak in one of the lines found (I spotted oil from the leak running down the exterior of the house). The tech fixed it but said there was plenty of refrigerant and so didn't add any after the incident. Should I be concerned?

Buddy you are the best! I did 2year program for hvac and have learned more watching your videos. I am full time licensed sheet metal. I do furnace swaps occasionally some gas lines and a little service for furnaces . But have wanted to get more into the refrigeration side. What would you recommend for simple basic gauges and first tools to buy . For new installations and some servicing on the side. Thank you !

20 degree split is always what I aim for.

Mass air density will be influenced by air temperature. Denser air can absorb (or reject) more heat per unit volume. So correction factors will attempt to measure heat change for a given mass such as BTU gain per pound of air. One might also want to measure the change in humidity to determine how much water was condensed (or vaporized) and include that heat too. Ah sensible heat and latent heat. Drying the air will reduce its volume 2 to 4% or total mass by 1 to 2%. or about 44 BTUs per cubic meter to reduce humidity 50%.

Yep I've had that happen to me where the temp split is 10degrees and everything was installed fine. It was just ridiculously hot. Outside was 118 and inside was 99. The system was able to level off by the time night came around and cooled off to 95 outside where inside settled around 75.

How about a new video like this one on static pressure. Also, what percentage of calls do you find SP within spec. One of the most overlooked measurement drastically killing SEER ratings.

Could you please do a video of combustion analyzer of roof top package unit ? Thanks you

Would you please turn the captions on for this video. It makes it easier to follow for those that want captions. Thank you!

Hi Craig, I was wondering how to measure return temperature on a handler that has no return duct. It's an upflow in a closet (louvered door). Would I measure at the bottom opening of the handler (where filter is located) or should I stick my temp probe through the louvered panel? The supply duct is easily accessible and I can measure that one fairly easily. But unlike in this video, there is no return ducting, the return is the door itself (in a centralized location). Just curious, any tips to help this new tech would be appreciated.

Can you do this same calculation on a furnace or is it only meant for air conditioning?

I just have a question, do you use a wet wetbulb sock while doing a delta T measurement?

If you run a small duct from the supply back to the return lowering the temp of the air going back into the return will that lower the air temp even more coming out the supply? I get 20° but was curious if I was to do this if it would lower the temp by doing this.

Part number for the 3/8" rubber plugs to cover the holes in ductwork?

Hello Craig, I tried to find a email to you but could not. Off topic question if you don't mind. Would you have a long form of a manual J you would copy and sell? and What manual J program would you recommend buying for heat gain and heat loss calculations? Is there a good app out there that makes this easier. Thanks in advance. Great book by the way.

at 0:50 , the equation is wrong, i believe the supply should always be colder than return, because the air go through the vapor coil ? shouldn't be return air - supply air = 19 , is it the calculation left/right position wrong ?

So for cooling, is it bad to reduce fan speed to increase the delta temp to be within range?

For some reason this season, I’ve come across numerous package units pulling 30 degree dT’s. With proper charge, fixed speed fan, is there anything else besides airflow to rule out?

I have a heat pump. In heat mode the out door unit shuts down on high pressure safety according to a HVAV technician. He checked air flow across indoor coil and said it was ok. His conclusion was that systems with R410A should not be ran in heat mode when outside air temp is 65 deg or above. Is this true?

Thanks for great video.. I have a question? how do you set only the electric heating strip? do you set the tstat in emergency heat.

Can you confirm the formula shown at 51s. It shows supply minus return.

Hi I am really confused to how you could only get a delta T Of only 23 deg.That would mean that when I first turn on my AC and the room is 88 deg. The evaporator coil is 66 deg. Not 55 deg. And when the room cools down to 75 deg my evaporator is down to 55 Deg. So when is my evaporator in my air handler going to be 45 deg@ 74 psi for R22 on my low side gage? Because that would make the inside air temp. 65 deg. And you could never get a 1.5 ton or 3. ton 36,000 btu AC to cool your home to 65 deg If the out side temp is 86 deg.I am reading a delta T of 30 deg a 55 deg evaporator is giving my home a 75 deg cooled room! Please reply back to me. Thanks ken

Hi your videos are informative! Hi I have a single ductless 12,000 BTU heat pump my set temp is 24° but my room temp is 18 could you explain what may be happening it is -10 outside thanks

so the true delta T is to be measured at the return and supply duct at the unit itself now at the return grill or any supply grill??

Where can I find the Delta T values for mini split units?

Question: Is the temp rise in a gas furnace the same for both stage 1 and stage 2? Hope I am asking this right?

Hey Craig how can I get your book. Right now I'm in UAE

The Delta-T is a relationship to the TXV or Fixed Piston of Air Flow

What do you use to cover the holes that you drilled into the Return and Supply Ducts in order to check the Delta T?

Excellent explanation but what's opinion on my delta T my return temperature is 73 and the supply is 48 so that's a 25 degree delta T but I have my thermostat on 72*, and the outdoor temperature is 84* today

What’s the difference between the E book and the other book that looks like it ?

Can you measure temperature difference comparing ambient temperature vs outdoor condenser temperature?

Now I know what is Delta T , my company everyone keep call TD ^_^

would the delta t be off with a mismatched unit ?

Craig, great info! Really dumb question if you have a moment. Is it possible in AC mode to have a “normal” 20 degree delta T and be significantly low on charge (maybe just above where a coil would ice over)? What I’m struggling with is despite the fact that the refrigerant is there to do it’s job, in theory, because of a lack of refrigerant, the coil should be very cold and still cooling the air going through it. Is this situation possible? Thank you!

Quick question what happens if your sub & superheat are good, pressures are good, but you're only getting a 13 delta T? I ran across this twice both were rheem units.. heat strips weren't on either

I think the Supply temperature and Return temperature is reversed for AC mode.

Hey Craig, my ac thermostat got reset by accident. I gave an question..... my ac thermostat is saying it’s 79 in here, which I KNOW it’s not. I went and brought in an external thermostat and it’s showing 77 which it definitely feels like, that’s way more accurate. So the issue is that my ac keeps showing a higher temp than actual temp, so ac keeps turning on. I feel like it has something to do with the cooling stage 1 on or off? I could be wrong but what should the setting be on, as far as inside/outside cooling stage 1?? Or does that have nothing to do with what’s going on? UGH! 😩😫 pleeeease help

Who's one is right Means any conditions for these 2 cases Plz help ∆T = SAT - RAT or ∆T= RAT-SAT or Both right

are there similar rules for condenser unit Delta T

hi, for fixed orifice system. high heat load would caused high superheat. high super heat would caused high pressure on the high side. wouldn't this high pressure on the high side PUSH MORE refrigerant into the evap to compensate? so the amount of refrigerant going through the orifice varies/changes based on pressure differential between high side and low side. please help me to clarify this concept because you're saying the orifice ALWAYS ALLOWS the SAME amount of refrigerant through and this is where i get confused. your book is just amazing. Thank you.

Do you calibrate everytime you use your dual sensors?

Where can I purchase your books?

causes of LOW delta T?

I thought electric resistant heat Delta t was like 35 f

Can you measure Delta T at the vents? It's 65 degrees outside, and inside my house is 75 degrees. The AC is set to 74 has been running for over an hour and the temp is still 75 degrees. Coming out of the vents is about 66 degrees, which is a Delta T of 9, but I don't know if I can check it at the vents.

Two digital thermometers from harbor freight will save you money than buying that delta t meter