Hi forum-
I'm in the process of getting an HPWC installed, and I would like to feed it with 100A (as I have a 72A charger in my X). I also have a 20kW Generac whole-house generator with an automatic transfer switch. My electrician is looking at some options for how to do the install. I've seen the few messages at the end of the FAQ / Q&A thread which seem to ask some of these same questions, but didn't have any solutions. I'm curious if anyone has figured out a good solution here, but I'll also share my thoughts (and experience) here in case anyone else runs into this.
The main issue is the generator can't handle the full charging load, so we need a way to kill the HPWC load when we lose power and the generator kicks in. Generac sells load shed modules for this type of application, but they only go up to 50A capacity. (basically these big fat car charging circuits are pretty new, and they haven't had to deal with big loads like this in residential settings in the past). That's obviously not ideal since it limits me to 40A charging (I believe the 50A limit would force me into the 50A circuit / 40A charging selection on the HPWC).
A few ideas we had were:
1) The electrician said he could install a 100A relay, and feed that relay off a separate circuit that comes off the panel, and put the load shed in the path of the relay control. When the generator kicks in, it sheds the load controlling the relay which then kills the 100A feed to the HPWC unit. The downside is this is not a typical everyday thing that's done in residential settings, and he thought it might cost in the neighborhood of $500 extra.
2) If the HPWC had some ability to provide a low-power cutoff circuit, that could be wired into the generator transfer switch load shed unit. The generator's transfer switch provides dry contacts for this purpose that will be normally closed, and then will open up when the house load is transferred to the generator. This is how my AC condensor is wired - essentially the dry contact is put in the path of the low voltage (24VAC I believe) path to the condensor so that it never turns on when the generator is engaged. (Actually it's programmable since the load isn't absolutely too much, but may be a little taxing, but that's a different story). I called Tesla, and they don't seem to support this in the HPWC (but they were double checking - fingers crossed!). This one is too bad, it would be *much* easier (and cheaper) to eliminate the need for the high current load shed unit entirely, and just have the control circuit in the HPWC shut charging off when the disconnect relay opens. Ah well...
3) A separate panel before the transfer switch (as suggested in the FAQ / Q&A thread) doesn't seem to make sense (i.e. it would probably cost more than #1)
4) Any other clever ideas? I can't believe that no one has done this before. Or maybe no one has bothered to do a >50A installation with a (Generac) generator before?
Thanks in advance.....
I'm in the process of getting an HPWC installed, and I would like to feed it with 100A (as I have a 72A charger in my X). I also have a 20kW Generac whole-house generator with an automatic transfer switch. My electrician is looking at some options for how to do the install. I've seen the few messages at the end of the FAQ / Q&A thread which seem to ask some of these same questions, but didn't have any solutions. I'm curious if anyone has figured out a good solution here, but I'll also share my thoughts (and experience) here in case anyone else runs into this.
The main issue is the generator can't handle the full charging load, so we need a way to kill the HPWC load when we lose power and the generator kicks in. Generac sells load shed modules for this type of application, but they only go up to 50A capacity. (basically these big fat car charging circuits are pretty new, and they haven't had to deal with big loads like this in residential settings in the past). That's obviously not ideal since it limits me to 40A charging (I believe the 50A limit would force me into the 50A circuit / 40A charging selection on the HPWC).
A few ideas we had were:
1) The electrician said he could install a 100A relay, and feed that relay off a separate circuit that comes off the panel, and put the load shed in the path of the relay control. When the generator kicks in, it sheds the load controlling the relay which then kills the 100A feed to the HPWC unit. The downside is this is not a typical everyday thing that's done in residential settings, and he thought it might cost in the neighborhood of $500 extra.
2) If the HPWC had some ability to provide a low-power cutoff circuit, that could be wired into the generator transfer switch load shed unit. The generator's transfer switch provides dry contacts for this purpose that will be normally closed, and then will open up when the house load is transferred to the generator. This is how my AC condensor is wired - essentially the dry contact is put in the path of the low voltage (24VAC I believe) path to the condensor so that it never turns on when the generator is engaged. (Actually it's programmable since the load isn't absolutely too much, but may be a little taxing, but that's a different story). I called Tesla, and they don't seem to support this in the HPWC (but they were double checking - fingers crossed!). This one is too bad, it would be *much* easier (and cheaper) to eliminate the need for the high current load shed unit entirely, and just have the control circuit in the HPWC shut charging off when the disconnect relay opens. Ah well...
3) A separate panel before the transfer switch (as suggested in the FAQ / Q&A thread) doesn't seem to make sense (i.e. it would probably cost more than #1)
4) Any other clever ideas? I can't believe that no one has done this before. Or maybe no one has bothered to do a >50A installation with a (Generac) generator before?
Thanks in advance.....