Is a DOB relay at the condenser recommended for a residential split system?

[gagecalman]

Is a DOB relay like the ICM206 at the condenser recommended for a residential split system?

I was also wondering if there's a produce that will help if the furnace is 120-volts because if the leg not supplying it is lost the 120-volt transformer will keep the DOB energized as well as the contactor but the compressor will stop. If the leg is energized quickly the compressor will start right back up which is not good and it could also rotate backwards.

 

[fitter30]

Most if not all electronic termostats have in their program a setting for 5 minute timer compressor off. Most scroll style compressors start unloaded. 5 minute dob relay if the thermostat doesn't have a timer is a good idea.

 

[manwithtools]

Don't most modern compressor units have it built into the control board? In addition new thermostats have compressor delays built into their functionality.

 

[gagecalman]

I understand if the transformer is on an air handler and is 240VAC. If only one leg drops the 24VAC is lost and the DOB start the delay.


But if the transformer is on a 120VAC furnace and the leg not supplying it is lost the 120VAC transformer will keep the thermostat and DOB energized as well as the contactor but the compressor will stop. If the leg is energized quickly the compressor will start right back up.


Is there a product that will fix this?

 

[PoorUB]

I understand if the transformer is on an air handler and is 240VAC. If only one leg drops the 24VAC is lost and the DOB start the delay.


But if the transformer is on a 120VAC furnace and the leg not supplying it is lost the 120VAC transformer will keep the thermostat and DOB energized as well as the contactor but the compressor will stop. If the leg is energized quickly the compressor will start right back up.


Is there a product that will fix this?

https://www.icmcontrols.com/product/icm492/

 

[98ssuck]

Hypothetically those things could happen with losing phases and what phase energizes the control transformer. But what problem are you trying to solve?

 

[gagecalman]

https://www.icmcontrols.com/product/icm492/

Thank you. Exactly what I was looking for!

 

[pcmeiners]

. If the leg is energized quickly the compressor will start right back up which is not good and it could also rotate backwards.

How is the compressor going to rotate backwards, utility AC comes into the unit and converted to DC, then back again in modern VFD mini splits. The control board is controlling rotation, not the utility power legs.

 

[gagecalman]

How is the compressor going to rotate backwards, utility AC comes into the unit and converted to DC, then back again in modern VFD mini splits. The control board is controlling rotation, not the utility power legs.

Residential split system. I never mentioned mini split.

 

[bob smith1]

DOB is delay-on-break, you want DOM, delay-on-make, or otherwise usually called time delay. You don't need 5min, and I like adjustable. what you need to watch for is overlapped circuits where the stat serves a delay, then a relay. but you need to ensure that in any scenario, the compressor won't attempt a hot restart. What is common is power glitches. You want that compressor to take a break.