Generac load management on split AC condenser

[Jps1006]

We put in a 20kw generac with the load managing transfer switch. The HVAC is a four zone multi stage with a split system condenser. It has a Y1 and Y2 (Ylow and Y on the circuit board). Instinct tells me it will be fine if I run Y1 through ac1 in the Tswitch and y2 through ac2 in Tswitch. What I don't know is if there is something else possibly going on that could harm the system to control the stages this way. My supplier didn't know and said to contact an AC contractor. I will put it past the startup guy next week, but hoping someone here has had experience with these more advanced systems and a generator.

 

[mkgrady]

Normally you run the condensor control circuit through normally closed dry contact of the ats. Why not just do that?

 

[Jps1006]

Normally you run the condensor control circuit through normally closed dry contact of the ats. Why not just do that?

The condenser has a "high" and a "low". What I was afraid of doing was interrupting the condenser without regard or knowledge of the other logic involved. For example, if when the unit decides to go from low to high the DC variable speed motor will ramp up. If I open the condenser control circuit, what are the possible ramifications for other parts of the system not included in the logic?

The factory start-up guy says Generac always recommends running the red (power source to the T-stat) through the ATS contacts. I thought Generac recommended like mkgrady says, the condenser control circuit (typically Y).

For this setup I ended up running the red through, that way the whole system goes down when the Generator sees an overload and the HVAC system can cycle through its own logic when it comes back up. I would have preferred to shed between "high" and "low" in the event that "high" overloads the generator with other loads, but "low" was sustainable, but I don't want to put an expensive system at risk when I only have 95% certainty no harm will come, just in case there is something unaccounted for in that 5%.

 

[kwired]

If you interrupt the "R" terminal you also disable heating, if this is a heat pump or has electric heat that probably is not a problem, but if gas, oil, or other heat source this may not be desired.

My heat pump interrupting the "Y1" will disable the compressor. Interrupting the "Y2" only interrupts a solenoid valve in the refrigerant system. If Y2 is called for but not Y1 the system does nothing but energize that valve

Take a look at the schematic for the unit to see what Y1 and Y2 actually go to, I would bet it is similar to what I just described.