Question for Electricians

[rladner]

I'm installing a manual transfer switch for a portable generator. I'm installing a Reliance subpanel. Its all pretty straight forward except for one part. I would like to be able to run one of my A/C units (I know I need a large generator for this, that's not the question). My question is... Can I do this with the subpanel I have? Here are 3 pictures. 1 of my breaker box with the AC unit breaker, 2 of the Reliance subpanel. The AC breaker is a 40 amp. The subpanel says Max 30, but I would be using both A & B, per design of the Reliance Subpanel. Basically I just want to know if this is possible? Safe? or should I just forget trying to run an A/C unit and pick some other rooms to send power to?

Thanks in advance

[Greenheadless]

There is no need for the manual transfer switch with that sub panel. You won’t be able to run your generator with the sub panel though.

[rladner]

There is no need for the manual transfer switch with that sub panel. You won’t be able to run your generator with the sub panel though.

what do you mean I won't be able to run my generator with the subpanel? Do you mean I won't be able to run the A/C or won't be able to run the generator at all?

[TexasBob]

I'm not an electrician by any means. Couple thoughts, worth what you paid for them.

Get a soft start kit for the A/C to keep you under the 30 amps. It is safe to try it from a straight line perspective- your wiring is rated for 40 amps and if you pull more than 30 the sub panel breaker will trip (assume your connection between the two is 40 amp rated). That said, you will likely trip the 30 without a soft start.

[RonRon]

The 40 amp breaker serving your a/c unit does not mean that the a/c is pulling 40 amps while it is running. It is more than likely pulling a lot less, A/C breakers are oversized to allow for the start up load, not the running load.

Go to the a/c unit and read the rating plate, which is riveted to the side of the unit. Look for the RLA [running load amps].............this is what the unit will use while it is running.

Now, look at the LRA ..[lock rotor amps],...this is the amp load that it uses for the split second that the unit is starting up. This determines what size breaker or fuse that you use for the a/c.

Now, look for the maximum fuse size [or breaker size].........this is the size of breaker that you should use, so that it will not trip out on start-up. This is the size of breaker that you need to put in the subpanel.

It is a good idea to put a start kit on the a/c............this reduces the start-up time [remember, we are talking a split second], but, it lessens the chance of tripping the breaker

There is a 99% chance that your unit pulls less than 30 amps while running...............so, to answer your question, you should be fine putting the a/c load in the subpanel.

[rladner]

Looking into a soft start kit. Everything is starting to add up. But I bet I won't be complaining the next time to power goes out for an extended period of time.

[db@100]

Don't forget, you must also put the breaker for the blower in the sub panel.

[rladner]

The 40 amp breaker serving your a/c unit does not mean that the a/c is pulling 40 amps while it is running. It is more than likely pulling a lot less, A/C breakers are oversized to allow for the start up load, not the running load.

Go to the a/c unit and read the rating plate, which is riveted to the side of the unit. Look for the RLA [running load amps].............this is what the unit will use while it is running.

Now, look at the LRA ..[lock rotor amps],...this is the amp load that it uses for the split second that the unit is starting up. This determines what size breaker or fuse that you use for the a/c.

Now, look for the maximum fuse size [or breaker size].........this is the size of breaker that you should use, so that it will not trip out on start-up. This is the size of breaker that you need to put in the subpanel.

It is a good idea to put a start kit on the a/c............this reduces the start-up time [remember, we are talking a split second], but, it lessens the chance of tripping the breaker

There is a 99% chance that your unit pulls less than 30 amps while running...............so, to answer your question, you should be fine putting the a/c load in the subpanel.

So if I'm reading this right, it says 30 amp is all that is needed correct?

[bowhntrmatt]

yep, your AC is currently on the wrong size breaker. Should be on a 30.

I would definitely recommend the soft start kit (easystart micro air or something like that). Without it there is a chance the AC won't start at all depending on the genny size. Either way, it'll dampen the blow on startup.

[bowhntrmatt]

Also don't forget to put your furnace circuit on the transfer switch as well or that AC won't do you any good!

[60 Deluxe]

It is situations such as yours that convinced me that I wanted the flexibility to run anything in my breaker panel using the generator. The most straight forward way to do that is to switch between power company and generator before the power ever hits the main 150 or 200 amp breaker at the top of your panel. Once you do that, you no longer have to be concerned with questions such as this. They are sort of hard to find but there are manual transfer switches available that are built for whole house transfer. If you do go this route, please realize that the transfer switch is the new primary and it needs to be protected by a circuit breaker in between the meter and switchgear. I only say this because there are models available that do not come equipped with a circuit breaker.

[RonRon]

Yep........the 40 amp breaker is too big, per the manufacturer's spec's. All you need is the 30 amp. Also, note that you are only pulling 13.6 amps while it is running. And as has been mentioned, put the furnace blower breaker in the subpanel too.

[White Falcon]

I would hire a electrition to do the work. You don't want to burn your house down.

[powderburner]

I had a panel like that. and I changed it up because of some of the issues people on here have brought up.
Get this

https://www.amazon.com/Generator-Interlock-Compatible-Homeline-Breaker-Professional/dp/B0BV31CJMM/ref=sr_1_6?dib=eyJ2IjoiMSJ9.Lh4qaBmjDKezJ2TXAuFj5dDSoXF6RQyzWNJk2kcHuejZ_r6KzFKzWtQEcB22TRz9-MPt6fLreI27d6vuFWMgMQEvsWxxwNTrpufWjQut_QuQwSTbunEvsRn0H65JmS1oo9tW_N4_qwwLeuAfBq5iFZfsZiVV3Ke9fc4V2APlxwTPpWdyLUVWVaJFrFrJ-Jk2HjuaMFThVCP2JXeHoA0uVyC5a5pF836kfcQOqTuib79vGEBChWz6k-V4ZjwSDMUbw0vD-wxjmbf759yaCfVogU8EqATrfF0HwzEyKOECP_Y.VJUn13eySXry7XVjIYbBfHeSOpKjZi1iJBInzv1DeG0&dib_tag=se&hvadid=616987059065&hvdev=c&hvlocphy=9027821&hvnetw=g&hvqmt=e&hvrand=431848131531757389&hvtargid=kwd-8395406677&hydadcr=8459_13573152&keywords=square+d+interlock+kit&qid=1723571883&sr=8-6

Then get another breaker and wire it our to a generator plug.

That way you turn off your main and "lock it out" then you back feed your panel from the 40A generator breaker.
Then you can turn off and on what ever room or stuff you want to run from your panel.
I was able to run everything in my house but the AC after the hurricane.

I added 2 window units to me hurricane stuff and was totally fine for 4 days.

[dbaio1]

I would hire a electrition to do the work. You don't want to burn your house down.

Yep I know someone that did not and it did burn down and to the ground. Insurance is not paying so far.