Non-bleed TXVs and Hard Starts - Short #257
HVAC School - For Techs, By Techs
Bryan Orr
4.9 • 1K Ratings
🗓️ 16 September 2025
⏱️ 10 minutes
🧾️ Download transcript
Summary
In this short podcast episode, Bryan talks about non-bleed TXVs and whether they need hard starts.
A non-bleed (hard shutoff) TXV is a metering device that shuts off during the off cycle; it closes shut when there is no superheat. This strategy prevents refrigerant migration, especially in cases where we have long line sets. Liquid refrigerant stays in the condenser and is kept out of the evaporator, suction line, and compressor crankcase.
When we have a non-bleed TXV, the compressor may have a hard time starting under the conditions created by the hard shutoff TXV (high head pressure, low suction pressure). Reciprocating compressors are more likely to have this problem than a scroll or rotary compressor. If you have a short line set, 230+ voltage, and a scroll compressor, you probably won't need a hard start kit. You may need a hard start kit if you have a reciprocating compressor, a longer line set, or 208V power.
The OEM will recommend a hard start kit that is suitable for the equipment. Aftermarket hard start kits are okay if a compressor is old and struggling, but they're not the preferred option and should be as close to the OEM's recommendation as possible. Hard start kits typically consist of a start capacitor and a potential relay. Positive-temperature coefficient resistors (PTCRs) also exist, and these have a resistor that heats up and eventually takes them out of the circuit. Hard start kits should not be added to inverter-driven equipment and are not meant to compensate for voltage drop issues; they can cause more harm than good if they're used when they're not necessary or not used correctly.
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Transcript
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| 0:00.0 | Hey there, friends and family. |
| 0:06.1 | This is the HVAC school podcast. |
| 0:08.3 | The podcast where I think nowadays I'm mostly just talking to family. |
| 0:11.9 | And that's not a bad thing because I have like a million zillion family members. |
| 0:15.6 | Just kidding. |
| 0:16.2 | I'm not talking to family because family does not listen to my podcast. |
| 0:19.3 | Let's be honest. |
| 0:22.6 | And this is the podcast that helps you remember some things you might have forgotten along the way as well as helps |
| 0:26.0 | you remember some things you forgot to know in the first place. And we're talking about non-bleed |
| 0:30.2 | TXEs and hard starts today. But before we do that, we want to thank our great sponsors. |
| 0:36.9 | Refrigeration Technologies at refrigetech.com and specifically the new Viper Wetrag Heat Shield, |
| 0:43.8 | the revolutionary flame-resistant welding pad designed to be used either wet or dry. |
| 0:50.6 | Find a Viper wet rag heat shield at a distributor near you or go to TrueTechTools.com and use offer code, get schooled for a great discount at checkout. |
| 1:00.0 | Navak at navak global.com. Carrier and carrier.com? |
| 1:05.5 | Fieldpiece.com. |
| 1:06.2 | Fieldpiece.com. |
| 1:09.8 | All right, so first off, what is a non-bleed hard shut-off TXV? |
| 1:13.9 | And it doesn't have to be a TXV, frankly. |
| 1:15.8 | It could be electronic expansion valve, anything that shuts off during the off cycle. |
| 1:21.4 | And why does a non-bleed TXV, otherwise known as a hard shut-off TXV or HSO. |
| 1:28.5 | Why does it shut off during the off cycle? |
| 1:31.4 | Well, it doesn't have a brain, it doesn't have a computer in it, |
... |
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