BACK

#RTU

Tech Tips:

Measuring RTU Curbs with Adapters in Place

Each commercial rooftop unit (RTU) needs to be mounted to a curb. A curb supports the RTU and provides openings for the supply and return ductwork (which can be massive compared to what we see in residential and light commercial HVAC). Occasionally, we’ll need to do an RTU changeout and put in a bigger or […]

Crane Considerations for RTU Installation

Sandhill cranes are protected by the Migratory Bird Treaty Act (MBTA) of 1918. Non-migratory subspecies, like the ones we see in Florida, also have special protections, and hurting a crane can land you in jail or put you thousands of dollars in debt. (Plus, it’s just plain awful.) For that reason, we need to do […]

5 Things to Consider When Maintaining a Commercial Package Unit

If you are primarily a residential technician working on equipment under 5 tons, there are many similarities between the systems you are used to and 5-20 ton rooftop units common to the light commercial market. There are MANY additional things to consider on larger equipment, and here are just a few. Wash Fresh Air Filters […]

Q&A – RTU Tips – Short #196

In this short Q&A podcast episode, Bryan answers Jeremy's question about checking the charge on rooftop units, and he gives some RTU tips. Rooftop units often come in sets, so you can use a thermal camera to look at all of the RTUs and compare them. A thermal imaging camera may even show you where […]

IaVsrDxldXkHhBuq
#commercial hvac #Rooftop #RTU

Check out our most recent video

How to Evacuate an AC system, Full Vacuum Procedure

Our latest Podcast

HVAC School – For Techs, By Techs

Real training for HVAC ( Heating, Ventilation, Air Conditioning and Refrigeration) Technicians. Including recorded tech training, interviews, diagnostics and general conversations about the trade.

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.

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

Purchase your tickets or learn more about the 7th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

Subscribe to our podcast on your iPhone or Android.

Subscribe to our YouTube channel.

Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android

Search Episodes

Non-bleed TXVs and Hard Starts – Short #257

09/16/2025

Bryan Orr

Scroll Compressors & New Refrigerants w/ Copeland

09/11/2025

Bryan Orr