Powewall peak kw demand question - Zero Net Energy Home

[Younis]

Sorry if this is duplicative (please let me know where this is discussed) but I wanted to confirm I am doing my logic correctly while electrifying my house. I am planning to get a Heat Pump Space Heater moving away from natural gas. I then plan to get Solar and a PowerWall to move the house to a net zero energy home.

My concern is that Ill be told that one of these units cant be on the Powerwall 2 circuit. In the event of a long-term outage, I could just turn off the AC or Heater as needed.

Heat Pump outdoor condenser: Bryant Model: 286BNA036000 FLA:18.5 for Compr, .6 for Fan, Total:19.1 Volts:208-230
Heat Pump Indoor Air Handler: Bryant Model: FE4ANF003L00 FLA: 4.3 Volts:208-230

So my total FLA would be 23.4 at 230 volts max would be 5.382 kW, which is under the 7kW peak of PowerWall 2. Is this reasonable? I also plan to get a Heat Pump Water Heater but the load would be very low, more like a traditional plug load device. I'm sure im' missing something, let me know

 

[Shygar]

Are you planning to get one or more than one powerwalls? The peak goes up after each one. I don't see why you couldn't backup your whole house on 2 powerwalls but I'll leave it to the electrical experts to say for sure.

 

[mongo]

@Younis
I think the rule of thumb for the backed up panel is: no breaker over 30A if there is only 1 Powerwall, 60A if two Powerwalls, and so on.
With two or more PW, you should have no trouble. Are you going to backup water heater, kitchen, dryer and are those electric also? City water or well?

 

[Younis]

Was planning a HP Water Heater which is very low power, but dont have the specs. We are on city water and have an electric Dryer. So if the device is on a breaker over 30amp, they won't put it on the Powerwall? Im trying to avoid a second PowerWall if I can, its only 1000 sqft house.

 

[mongo]

Was planning a HP Water Heater which is very low power, but dont have the specs. We are on city water and have an electric Dryer. So if the device is on a breaker over 30amp, they won't put it on the Powerwall? Im trying to avoid a second PowerWall if I can, its only 1000 sqft house.

Right, the peak output of the PW is ~7kW, which is a 30Amp breaker at 240V. So if the load needs a higher breaker than 30, it may pull more than the PW can put out.

Can you keep the current furnace and add the heat pump in parallel by putting its coil in place of the current AC evaporator? That would give you a heat source that won't drain your batteries nearly as fast during outages.

 

[Younis]

@mongo, currently Natural Gas and Im hoping to maximize a local rebate that covers up to $13k in rebates by switching to electric heat pump. With this 30amp rule I think I would be under at 23 FLA?

 

[cr0ntab]

According to this spec sheet:

https://dms.hvacpartners.com/docs/1009/Public/00/PDS286B-02.pdf

Page 7, far right column

Your 3 ton condenser calls for a 35A breaker max.

In theory you could install a 30A and be within the constraints of the single power wall.

 

[Shygar]

Are you specifically talking about what happens during an outage? Because in normal day-to-day operations you can use a single powerwall for things that take more than 30 amps of power. I have a single powerwall and everything in my 2000 sqft house is backed up except my 30 amp AC and my 60 amp Tesla wall connector. But since those loads are monitored by the built in Neurio, the powerwall still supplies power to them up to its limit, and the grid or solar takes the rest.

What everyone is talking about here is specifically if you are trying to keep these high load things running during an outage. Again, not an electrician so correct me if I am wrong somewhere. I do know with AC units some of them can spike in the immediate starting up of the AC then go back to a normal operation. So that initial spike might be higher than 30 amps very briefly before settling into a normal operation.

 

[mongo]

@mongo, currently Natural Gas and Im hoping to maximize a local rebate that covers up to $13k in rebates by switching to electric heat pump. With this 30amp rule I think I would be under at 23 FLA?

Magic 8 ball says it's not looking good. If it really pulls 23 amps when running, that (5.5kW) is more than a single Powerwall can supply continuously (5kW). And that is ignoring the rest of the house.
However, going from the doc @cr0ntab provided, the operating load seems lower, especially if you can force it to stay in the lower of the two stages. Caveat being, you'll still only get 6 hours of run time with one PW.

 

[miimura]

According to this spec sheet:

https://dms.hvacpartners.com/docs/1009/Public/00/PDS286B-02.pdf

Page 7, far right column

Your 3 ton condenser calls for a 35A breaker max.

In theory you could install a 30A and be within the constraints of the single power wall.

None of those units in the PDF are going to start when the grid is down. The LRAs are 52-118 amps.

 

[mongo]

An alternative may be the Chiltrix systems, they are low inrush and can be paralleled. I haven't used them, but they look interesting.

 

[miimura]

York Affinity YZV series has high efficiency and an ECM motor. However, it would still require 2 Powerwalls to run when the grid is down.

http://www.upgnet.com/PdfFileRedirect/5523960-YTG-A-0618.PDF

 

[cr0ntab]

An alternative may be the Chiltrix systems, they are low inrush and can be paralleled. I haven't used them, but they look interesting.

I really really really wanted to go down this route, but it's so freaking expensive.

I couldn't bring myself to do it, I'll likely end up going with straight mini splits :|