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HVAC School - For Techs, By Techs

Apr 25, 2017

In this episode, Bryan speaks with James Bowman from Rectorseal about hard start kits, PTCR devices, run capacitors, compressor overheating, and the Kick Start product. We also go pretty in-depth on potential relays and how they operate.

Hard start kits are mechanical potential relays connected to a capacitor, and they aid in starting the compressor. They come in two-wire and three-wire types. However, they have some pitfalls. For example, they are easy to abuse. You may also come across a "hard start kit" that does not have a mechanical potential relay (such as a PTCR), which is not a true hard start. Many of those false kits are low-quality and borderline dangerous.

The start cycle starts in approximately 0.4 seconds. A proper hard start kit will help the compressor start in less than 0.4 seconds. Two-wire electronic start kits don't react quickly enough and cannot remove themselves from the circuit in time. Two-wire mechanical potential relay kits, on the other hand, measure voltage between run and start, unlike a three-wire device that measures the voltage between common and start. Three-wire devices are typically okay, but they are not a universal component that can fit every unit.

Rectorseal's Kick Start kit is an aftermarket kit designed to work on most units as a replacement for the OEM kit. When dealing with aftermarket hard start kits, the best practice is to know your equipment and the hard start kit's compatibility with the unit. Hard start kits work especially well with reciprocating compressors with long line sets and HVAC systems with hard shutoff TXVs.

Bryan and James also discuss:

  • Potential relays
  • Back EMF
  • Start capacitors
  • Testing run capacitors under load and with meters
  • Looking at systems holistically
  • Copper plating inside compressors

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