Single Pole Contactors & Crankcase Heaters
HVAC School - For Techs, By Techs
Bryan Orr
4.9 • 1K Ratings
🗓️ 17 September 2020
⏱️ 61 minutes
🧾️ Download transcript
Summary
Kaleb, Joe, and Eric join us again to discuss some myths about single-pole contactors. We also cover some weird crankcase heater wiring configurations.
When you have a single-pole contactor on a unit with no other resistance crankcase heater attached, the contactor energizes the compressor but is NOT a source of crankcase heat. That myth about single-pole contactors likely stems from a misunderstanding of Ohm's law and resistance heat.
We care about crankcase heat because we want to prevent refrigerant from migrating into the compressor during the off cycle. A crankcase heater keeps the compressor shell warm and prevents vapor refrigerant from condensing in the compressor. Overall, crankcase heat helps prevent flooded starts and oil loss. Some crankcase heaters can be wrapped around the outside of the crankcase, and others can be inserted into the compressor.
The crankcase heater and compressor winding can connect across an open contact to form a series circuit. (If you hook across L1 and T1 so that the other side has constant potential when the contact is open, a path can go to the crankcase heater.) The resistance in the compressor winding can contribute to the crankcase heat strategy, but Joe and Eric argue that the resistance is insignificant.
Overall, we need to remember that resistive heat is resistive heat; in a resistive circuit, your wattage is your wattage, and you can convert that directly to BTUs.
Kaleb, Joe, Eric, and Bryan also discuss:
- Two-pole and three-pole contactors
- Resistive heat
- Operating A/C and heat pumps in low-ambient conditions
- Ohming compressors
- Jumpering in place of a single-pole contactor
- Wire sizing
- Loud thumping when the unit shuts off
- Trickle current during the compressor off cycle
- Power factor, reactive power, and actual power
- Low-resistance circuits
- Capacitor purposes, wiring, and sizing
- Small charge and flood back prevention
- 3/8" lines
Learn more about Refrigeration Technologies HERE.
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Transcript
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| 0:00.0 | This episode of the HVAC School Podcast is made possible by our sponsors. |
| 0:09.2 | And the first sponsor that I want to mention is Refrigeration Technologies. Refrigeration Technologies has been a sponsor |
| 0:14.6 | of the HVAC School Podcast for a long time. |
| 0:16.9 | And a supporter for even longer than that, |
| 0:18.6 | I've used their products for many years. |
| 0:21.3 | If you haven't tried their pan and drain treatment spray, it's a very unique product. |
| 0:26.0 | It's an enzyme-based product that you can spray in the drain pan. |
| 0:30.0 | We use it in a lot of different applications, restaurant, grocery store applications, |
| 0:33.6 | as well as air conditioners and ductless systems in order to treat the drain pan to help prevent that |
| 0:38.3 | nasty sludge, but also to reduce odors. |
| 0:41.6 | We like it for many different reasons, and on the ductless side especially,. We like it for many different reasons and on the |
| 0:43.1 | duckelus side especially we really like it for reducing odors. It is a safe to use |
| 0:47.3 | product. It is rated for use in food prep areas that is the pan and drain spray from refrigeration technologies |
| 0:55.1 | also I want to thank Navac and Navac Global.com Navac makes all kinds of |
| 0:59.2 | really excellent tools for recovery evacuation working, working with refrigeration tubing, and one of their |
| 1:06.3 | really nice products is the NRDD recovery machine. |
| 1:10.0 | The NRDD recovery machine is a good workhorse Recovery Machine. |
| 1:14.2 | It has a digital display, it has a variable speed compressor in it, and it does a really good job of |
| 1:21.1 | not only doing liquid recovery quickly quickly but also really good job at |
| 1:24.7 | handling vapor. |
| 1:25.8 | The speed and vapor is really great. |
| 1:27.6 | So find out more about the NRDD and everything that Navac makes by going to |
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