Generator inlet sizing help

[Mike1903]

yikes.. Yea. You'll likely need 240V for that (there are 120V options). I'm in the south - there are various conditions below freezing where a heat pump will not get it done. Make sure you (OP) get one designed for the type of cold conditions where you are.... I spent most of snow-apocalypse in Texas alternating heat pumps because they were darn near useless... We had to suppliment with propane in the shop to keep it above 50 degrees.

To clarify, i am well covered for winter. In case of power outage, I could turn off heat pump and switch to furnace that is running off a 15A circuit (basically the fan for air handler). It is the summer time when heat pump is acting as an A/C on a 30A circuit and the air handler on 15A that I need to size up.

Great information on this thread....
It is crazy how much the prices of the wires have gone up (like everything else).
100ft of 10/3 Romex at Big Orange is $246 versus $400+ for 6/3.

 

[theoldwizard1]

It is crazy how much the prices of the wires have gone up (like everything else).
100ft of 10/3 Romex at Big Orange is $246 versus $400+ for 6/3.

100' of 2-2-2-4 MHF is $243 +shipping.

 

[theoldwizard1]

To clarify, i am well covered for winter. In case of power outage, I could turn off heat pump and switch to furnace that is running off a 15A circuit (basically the fan for air handler). It is the summer time when heat pump is acting as an A/C on a 30A circuit and the air handler on 15A that I need to size up.

And what is the LRA ?

 

[Mike1903]

100' of 2-2-2-4 MHF is $243 +shipping.

that’s pretty good. Where did you see it?
I wasn’t considering AL wires but will take a look.

 

[Mike1903]

And what is the LRA ?

I need to find it. The label of the Bryant heat pump is rubbed off, so need to check its specs. Will post an update

 

[theoldwizard1]

I need to find it. The label of the Bryant heat pump is rubbed off, so need to check its specs. Will post an update

Not sure what model you have but LRA ranges from over 50A to over 150A.

 

[Mike1903]

100' of 2-2-2-4 MHF is $243 +shipping.

I see the place that has it. One issue I can see the big conductor sizes is additional pieces to connect them to to the inlet box and breakers as they are too thick.
On the cables, I saw 2-2-2-4 AL SER cable at Lowes for $1.40/ft or Quadruplex AL URD for about the same. Same concern as conductor thickness but looks like a cheap way to oversize the cable run from the panel to the inlet.
Thoughts?

 

[sparky 1971]

#2 probably will not fit the inlet and the inlet enclosure isn't big enough to allow for reducers.
Don't make this too complicated. Every generator interlock I have installed, mine included, has been set up for 30 amp generator. You might want to step to #8 wire for voltage drop. You have to consider not only the length from generator to panel, but panel to point of use. When the time comes to actually put the generator to use, you will quickly learn what you can and can't do. My previous house had all gas appliances and I could do everything except run the AC on a 5500 watt unit. I've bee n in the current house now for almost six years and haven't had to use the gen yet. I do know I will be limited, but not sure how much. Electric dryer and heat pump water heater.

 

[theoldwizard1]

I see the place that has it. One issue I can see the big conductor sizes is additional pieces to connect them to to the inlet box and breakers as they are too thick.

You can splice AL cable to smaller gauge copper using the properly rated splices.

On the cables, I saw 2-2-2-4 AL SER cable at Lowes for $1.40/ft or Quadruplex AL URD for about the same. Same concern as conductor thickness but looks like a cheap way to oversize the cable run from the panel to the inlet.

SER and Quadruplex have restrictions on where they can be used.

MHF requires conduit within a building.

 

[AP514]

Bottom line is the OP has the generator already purchased and it only will do 31A max on that 50A line so why not save his money and just go with the lower 30A connect/cord ?

As far as starting the heat pump. Just Spitballing here.....
Without a Hyper Soft-Start kit or the like..It will never happen. If the A/C unit is 2.5ton or even less....Maybe a 2.0ton it will draw 85-65 Amps on start. The addition of the Hyper SoftStart might bring it down to half that much ?
This puts him on the edge for in rush.... but once running the heat pump probably only draws 14 Amps ?
Unless we get the LRA off the data plate it is all just speculation.

 

[Terry D]

Even if you would upgrade to a 10kw generator, it will still give you only 40 amps. A 15 kw will give you 60 amps. Does your area have frequent power outages for a long period of time? I recommended a #8 earlier for voltage drop. If you wanted to plan for the future, put a 6/3 copper romex in. You could just change the receptacle and breaker later if needed. I believe the largest portable generator is around 17.5 kw, that will give you 70 amps, but they are a beast and very expensive. Anything bigger would be a pad mount

 

[Mike1903]

Finally, had a chance to look at the plate on the heat pump. RLA is 16.5 and LRA is 77.0, minimum circuit size is 21.3A and max fuse is 30A HACR type recommended by the manufacturer.

I assume even with a soft start type device, the LRA won't come down to the 20s. In that case, either I step up to a larger capacity whole house standby gen or give up the idea of running AC off gen.