Load shedding relay question

mark32

Senior Member
Location
Currently in NJ
Hello,

I installed a Cummins generator last year along with their service rated ATS. At the time I failed to install any load shedding capabilities. A few nights ago the owners power went out and when the gen tried to start the home's two a/c's it went offline, not sure if the gen's breaker tripped or not, only spoke to their handyman about it. Anyway, I spoke with the gen's salesman and he said they don't sell a proprietary relay, I just need to get the same one everyone else has been using. I'm waiting for him to email the manual but what is everyone using out there? The home owner also has a pool pump, might want to put that on some type of module as well, any ideas?
 

eHunter

Senior Member
Hello,

I installed a Cummins generator last year along with their service rated ATS. At the time I failed to install any load shedding capabilities. A few nights ago the owners power went out and when the gen tried to start the home's two a/c's it went offline, not sure if the gen's breaker tripped or not, only spoke to their handyman about it. Anyway, I spoke with the gen's salesman and he said they don't sell a proprietary relay, I just need to get the same one everyone else has been using. I'm waiting for him to email the manual but what is everyone using out there? The home owner also has a pool pump, might want to put that on some type of module as well, any ideas?
What size and model # genset?
 

templdl

Senior Member
Location
Wisconsin
Understanding that their are 2 a/c units is there one that you don't want to run during an emergency mode?
If so simply target the circuit that controls that a/c unit. A simple IceCube relay that opens its contacts when energized to disconnect the control circuit would work. It could be as simple as when the generator starts to generate 120v the 120v pulls in the 120v coil of the relay. Buy looping the control circuit to the n/c contacts of this relay which may be located at the ATS or at the generator itself, when the generator starts it pulls in the delay and opens the control circuit of the a/c unit which prevent that unit from operating.
 

mkgrady

Senior Member
Location
Massachusetts
You can buy a DLM modules made by Generac. It is a simple two pole 50 amp relay with a 120 volt coil.

If your ATS has automatic AC shedding you don't need the relay. The ATS might have a couple of dry contacts that you run the condensor control circuit(s) through. When the gen can't handle the AC load it opens the contact or contacts if you have more than one AC.

For something like a pump or an electric dryer or stove you run the branch circuit through the relay. Generac ATS's have 120 volt outputs to control the heavy loads using the above mentioned relays. I don't know if the ATS you installed have any of the controls I described
 

mark32

Senior Member
Location
Currently in NJ
Thanks for the replies. I actually discussed this with qcroanoke last year and I had previously forgotten his recommendations so here's what I'm planning on using: http://www.grainger.com/Grainger/DAYTON-Relay-5X827

Thanks again qcroanoke and the others for the help. By the way, this Cummins ATS does not come with any relays from the factory, but for the price they should.
 

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qcroanoke

Sometimes I don't know if I'm the boxer or the bag
Location
Roanoke, VA.
Occupation
Engineering
Thanks for the replies. I actually discussed this with qcroanoke last year and I had previously forgotten his recommendations so here's what I'm planning on using: http://www.grainger.com/Grainger/DAYTON-Relay-5X827

Thanks again qcroanoke and the others for the help. By the way, this Cummins ATS does not come with any relays from the factory, but for the price they should.
Can't really tell by the picture but on the right hand side of the transfer mechanism is that rocker switches?
you may could use them if they change states when the switch transfers.
If not you know what to do. ;0)
 

templdl

Senior Member
Location
Wisconsin
Thanks for the replies. I actually discussed this with qcroanoke last year and I had previously forgotten his recommendations so here's what I'm planning on using: http://www.grainger.com/Grainger/DAYTON-Relay-5X827

Thanks again qcroanoke and the others for the help. By the way, this Cummins ATS does not come with any relays from the factory, but for the price they should.
That was my suggestion. Pull in the 120v coil when the generator starts which would open n/c contacts disconnecting the thermostat circuit of the a/c. Piece of cake.
 

mark32

Senior Member
Location
Currently in NJ
Thanks y'all. Onto plan B, I visited the site yesterday and talked with the owner. He wants me to install time delays for the a/c's because, during the episode I previously mentioned, he turned the a/c's on one by one and they ran fine. So for now we'll give the time delays a shot. He wants to lock out the pool pumps so I looked into that. He has a pool panel, 50' from the house, that's being protected by a dp 20. There are two (Wired @ 240v's) pumps, one is 1.5hp, the other is .75hp, not sure if they run simultaneously, but I'd like to install something that could handle them both at the same time. I found this Dayton:

http://www.grainger.com/Grainger/DAYTON-Power-Relay-3X748?BV_UseBVCookie=No&ItemKey=3X748&seoUrl=DAYTON-Power-Relay-3X748

Specs say it's good for 1.5hp motor or a 30a induction load. Question is if this relay could handle both motors at once? There are two 120v circuits in this panel as well but the customer never mentioned the 20a breaker tripping so the load likely isn't all that great. In addition, I need whatever relay I use to have a 12vdc coil, at least if I use the ATS's load control cable(s). Thanks again to Mike for his help behind the scenes.
 
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