# Power distribution using an interlock solution



## Rene (Feb 5, 2021)

Hi All, 


I am new to this forum. I am thinking of having an interlock solution installed to be able to use my house electrical system to distribute the available power from my generator. 

Generator: Firman T07571 7500/9400 watts 
Plan: use an interlock on my main panel to switch from utility power to generator power using a 50 AMP plug wired into the panel by an electrician. 
Objective: 

Run one of my two 2.5 ton ACs at a time. (for the purposes of my questions it is assumed that the gen will be able to run one of the ACs at a time). 
Run as many additional appliances as generator power will allow. 
 
Each ac unit has a 30 amp breaker in the panel. 
Here is where my knowledge gets weak. 
Panel configuration (general) for the items I want to power but not necessarily at the same time. 

Left (odd numbered breakers) handles all the ceiling lights of the house along with the 2 AC units. 
Right side handles all of the wall plugs in the house 
I am guessing that the Generator feed is divided into 2 ~ 30 AMP poles which would be connected to the two sides (one 30 amp connection to each) of my breaker panel. 
Questions: 

Assuming above is correct, can I draw more than 30 AMPs from one side/pole? For example, run one AC (assume it is pulling 30 amps) and 3 rooms of ceiling lights? All off the left side of my panel which would exceed 30 AMPS for the left pole. I am trying to understand whether I need to manage power consumption at the pole level (3750) rather than at the gen set level (7500) regardless of how much a single pole is drawing? 

My gen set is rated for 9400 surge watts, is that divided between poles meaning surge of 4700 per pole or would the gen be able to handle 9400 from just one of the poles (left side)? 
 
I apologies in advance if my questions don’t make sense due to my ignorance on generators/wiring. 


Thanks


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## Old man here (Nov 5, 2020)

Rene said:


> Hi All,
> 
> 
> I am new to this forum. I am thinking of having an interlock solution installed to be able to use my house electrical system to distribute the available power from my generator.
> ...


See answers to your questions by expanding your post above.


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## Old man here (Nov 5, 2020)

Here is an actual example of my Heat pump Start and operation power draw. I have a whole house power monitoring system to monitor my electrical usage.


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## Old man here (Nov 5, 2020)

Here is an example of a typical wash cycle on the cloths washer, it is impossible to perfectly load balance both side of your breaker panel under normal household electrical usage.


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## Rene (Feb 5, 2021)

Old man here said:


> See answers to your questions by expanding your post above.


Thanks for the quick answers and information. 
My electrician did say that we would need to install a "Hard starter" on the ACs to get them started, but he didn't mention a soft starter so thanks for that.

Yes my ACs are heat pumps, single stage . The emergency heat is electric and I would keep that off as I live in the south and my concern is hurricanes during the warmer months. Here are the specs.










Plan B for AC is to run 2 room ACs for sleeping and fans during the day.

I suspected that I would have to manage power by pole. I have a spreadsheet with each breaker by pole listed. Then I have each appliance listed that would be drawing power and what breaker it is on. That way I can monitor power consumption at the breaker and pole level.

You mentioned that the 30 AMP AC breaker is drawing from both poles so then if for some reason I get the central AC working I should divide its load (RLA 14.1) between the 2 poles on my spread sheet. Is that correct?

On balancing the load between poles, I figure a balanced plan is better than not having a plan, even if the reality is different than the plan.

Finally, I have not pulled the trigger yet on any of the installation so I can go down to a 30 AMP plug but my gen does have a 50 AMP output plug. The only reason i would go with a 50 Amp plug and equivalent wiring is in case I decide to upgrade the gen in the future. Here are the gen's connection stats.










Thanks


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## Old man here (Nov 5, 2020)

Rene said:


> Thanks for the quick answers and information.
> My electrician did say that we would need to install a "Hard starter" on the ACs to get them started, but he didn't mention a soft starter so thanks for that.
> 
> Yes my ACs are heat pumps, single stage . The emergency heat is electric and I would keep that off as I live in the south and my concern is hurricanes during the warmer months. Here are the specs.
> ...


Sorry, I didn't notice the generator had a 50 amp outlet on it. Best to go with the 50 amp inlet then, like you say "if you wanted to get a more powerful generator later."
Install 6 Gauge wiring from your inlet to the breaker panel. 6 Gauge is required for 50 amps.
Also, go ahead and install a 50 amp breaker when you install the lockout switch and wiring. The 30 amp breaker on your generator will be your overload protection.

A Hard Start will not reduce your LRA on startup of your compressor. it only shortens the startup duration. The Hard Start also creates more stress on the compressor due to generating more torque due to the faster start.

A Soft Start actually increases the life of the compressor by slowly ramping up the current to start the motor.
It can lower the required start current by 50 to 60% or more.
I will be installing one on my Heat Pump this spring.
Look up the Hyper Engineering Sure Start site for more information. They cost more than a Hard Start but there is a reason.

It looks like you have all the other details worked out in your detailed plan.
Keep us up to date.


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## Old man here (Nov 5, 2020)

Rene said:


> Yes my ACs are heat pumps, single stage . The emergency heat is electric and I would keep that off as I live in the south and my concern is hurricanes during the warmer months. Here are the specs.


On another note here, my backup heat is also electric. 15Kw total.
I have two separate breakers going to my Air Handler/Furnace unit and one breaker for the heat pump (all three breakers are double pole for 240V).
One of the two breakers going to the Air Handler/Furnace supplies power to the transformer for the thermostat, control circuit, sequencers, signal to start and shut off the Heat Pump, and power and control for the blower. Lets call this "Breaker #1")

The second breaker supplies power for the separate 5Kw heat strip only. (Lets call this "Breaker #2")
If I turn off Breaker #1 nothing operates!
I can turn off Breaker #2 and everything works as usual. The only thing is that the additional 5Kw heat strip does not come on. 
Disabling the backup heat can be done but, I would only have your authorized AC technician do it. There are ways, but I will not go into it here.
Wow, that was long winded!


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## Old man here (Nov 5, 2020)

Rene said:


> The emergency heat is electric and I would keep that off as I live in the south and my concern is hurricanes during the warmer months.


Just another thought about this.
Depending on the outside temperature and dew point, your Heat Pump can go into defrost mode while heating your house. When this happens a reversing valve in the unit reverses and basically turns the Heat pump into cooling mode.
The backup heat will be needed to counteract the cold air the Heat Pump is suppling.
This can happen at any outside temp while your Heat pump is heating your home.
I'm sure you are aware of this though.


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## Browse Deweb (Jan 16, 2021)

Rene said:


> Thanks for the quick answers and information.
> My electrician did say that we would need to install a "Hard starter" on the ACs to get them started, but he didn't mention a soft starter so thanks for that.
> 
> Yes my ACs are heat pumps, single stage . The emergency heat is electric and I would keep that off as I live in the south and my concern is hurricanes during the warmer months. Here are the specs.
> ...


Take a look at the Microair EasyStart soft starter for your ACs:








EasyStart™ 364 Soft Starter


EasyStart™ single phase soft starter lets you start your A/C without buying a second or bigger generator or inverter & run 2 air conditioners on a 30-Amp cord.




www.microair.net





I looked at the Hyper-Engineering soft starter, but I decided that the Microair 368 is the one I would get if I could run my 4-ton off of my Honda. Unfortunately, it would probably start, but I don't want to worry about running the generator so close to (or over) it's rating. I have a mini-split in the basement that can keep us cool if the weather is crazy hot.

Yes, any 240V AC or other device will be drawing from both legs of your panel.


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## somedumbguy (Sep 17, 2020)

Sorry to chime in late Rene, but can you say some more about this? 

"Left (odd numbered breakers) handles all the ceiling lights of the house along with the 2 AC units.
Right side handles all of the wall plugs in the house"
Seems like that arrangement may dedicate more circuits to overhead lights than you need. How many circuits and amps can the panel handle? In my case, the challenge in balancing for the generator was splitting up the kitchen outlets evenly, They are the high power users (toaster oven, dishwasher, toaster, microwave, coffee maker, refrigerator, hot water dispenser, etc). If you have started to convert the lighting to LED bulbs, you don't need much power there. 

I had to move some stuff around in order to balance for my generator hookup to the panel. Remember that just four 13 amp appliances in your kitchen running at the same time will eat up most of your generator power. My circuits weren't very well balanced originally; one pole had significantly more stuff on it. But its a 200 amp panel and I doubt if I would have ever noticed a problem with utility power.


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## Rene (Feb 5, 2021)

I generalized and in reality the lights and plugs are on both poles. I also have a 200 amp panel/supply. I have a spreadsheet with all of the appliances I plan to use on the genset along with which pole the corresponding circuit that the appliance will be on. I have simulated my projected day and night loads and I am not exceeding the poles limits (30 AMPs). I am having more trouble with exceeding the surge limit of my genset in my projected scenarios. So full disclosure, I plan on running the genset off of natural gas which will drop the power specs to 5500/6900 watts. I have abandoned the idea of running one of my central ACs as it was projected to exceed the gensets surge capability of 9400 (running watts were 4301 and surge was 5037 (30% of LRA with soft start), total 9338). Add the fridge (a must) and I am over. 

Knowing my family's power usage, it is more realistic for us to run more of our typical daily appliances and then reduce power consumption at night to run 2 room ACs for sleeping. I keep reminding myself that our power outages, 1 in 5.5 years, only last ~48 hours and before that in our previous house we had 2 in 8 years each under 48 hours. Another concern I have with adding a soft start is voiding the warranty of my ACs which I still have around 4 years left. I may revisit this if we find that our room ACs for sleeping are not enough.

Thanks to all for your input.


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## Old man here (Nov 5, 2020)

Rene said:


> I generalized and in reality the lights and plugs are on both poles. I also have a 200 amp panel/supply. I have a spreadsheet with all of the appliances I plan to use on the genset along with which pole the corresponding circuit that the appliance will be on. I have simulated my projected day and night loads and I am not exceeding the poles limits (30 AMPs). I am having more trouble with exceeding the surge limit of my genset in my projected scenarios. So full disclosure, I plan on running the genset off of natural gas which will drop the power specs to 5500/6900 watts. I have abandoned the idea of running one of my central ACs as it was projected to exceed the gensets surge capability of 9400 (running watts were 4301 and surge was 5037 (30% of LRA with soft start), total 9338). Add the fridge (a must) and I am over.
> 
> Knowing my family's power usage, it is more realistic for us to run more of our typical daily appliances and then reduce power consumption at night to run 2 room ACs for sleeping. I keep reminding myself that our power outages, 1 in 5.5 years, only last ~48 hours and before that in our previous house we had 2 in 8 years each under 48 hours. Another concern I have with adding a soft start is voiding the warranty of my ACs which I still have around 4 years left. I may revisit this if we find that our room ACs for sleeping are not enough.
> 
> Thanks to all for your input.


I applaud you for your well thought out plan.
The fact that your power outages are infrequent and short, I think you are going the right direction without spending too much money.


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## somedumbguy (Sep 17, 2020)

Rene said:


> Knowing my family's power usage, it is more realistic for us to run more of our typical daily appliances and then reduce power consumption at night to run 2 room ACs for sleeping. I keep reminding myself that our power outages, 1 in 5.5 years, only last ~48 hours and before that in our previous house we had 2 in 8 years each under 48 hours. Another concern I have with adding a soft start is voiding the warranty of my ACs which I still have around 4 years left. I may revisit this if we find that our room ACs for sleeping are not enough.
> 
> Thanks to all for your input.


I wonder if there is a simple way to use two generators; separating the AC compressors from the rest of the house. I have a "leftover" generator after retiring my old one. I would have liked to use this two generator solution but couldn't figure it out without lots of complication/expense. Anyone else look into this? The advantage is that you can repurpose your "retired" generator for a non-critical use (AC) and avoid buying/running a really big/loud generator for every outage even when you don't need all that capacity.


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## Browse Deweb (Jan 16, 2021)

somedumbguy said:


> I wonder if there is a simple way to use two generators; separating the AC compressors from the rest of the house. I have a "leftover" generator after retiring my old one. I would have liked to use this two generator solution but couldn't figure it out without lots of complication/expense. Anyone else look into this? The advantage is that you can repurpose your "retired" generator for a non-critical use (AC) and avoid buying/running a really big/loud generator for every outage even when you don't need all that capacity.


You would have to have a generator plug between the condensing unit and the existing disconnect, wired in parallel. You could then remove the disconnects prior to connecting the generator. This would probably not be legal since there would be a way of connecting the generator while main power was still connected (assuming the disconnects were not deactivated).


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## Rene (Feb 5, 2021)

somedumbguy said:


> Sorry to chime in late Rene, but can you say some more about this?
> 
> "Left (odd numbered breakers) handles all the ceiling lights of the house along with the 2 AC units.
> Right side handles all of the wall plugs in the house"
> ...


Hey Somedumbguy (no offense), I wanted to update you and everyone. I had the interlock installed and discussed with my electrician balancing the load across the poles. Apparently I made a bad assumption that the poles ran vertically and that all breakers on one side (excluding 240 volt) were on one pole while all the breakers on the other side were on the other pole. He straighten me out and explained that the poles run horizontally and alternate by row. He went on to say that my panel was about as balanced as you can get, at least from the utility power perspective.

We tested the setup and everything ran well. I can't belive it but I am actually looking forward to a power outage. lol Thanks again to all for the great input.


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## somedumbguy (Sep 17, 2020)

Rene said:


> Hey Somedumbguy (no offense), I wanted to update you and everyone. I had the interlock installed and discussed with my electrician balancing the load across the poles. Apparently I made a bad assumption that the poles ran vertically and that all breakers on one side (excluding 240 volt) were on one pole while all the breakers on the other side were on the other pole. He straighten me out and explained that the poles run horizontally and alternate by row. He went on to say that my panel was about as balanced as you can get, at least from the utility power perspective.
> 
> We tested the setup and everything ran well. I can't belive it but I am actually looking forward to a power outage. lol Thanks again to all for the great input.


Thanks, Rene, I was wondering about that! My panel's poles feed down to the breakers through a set of interleaving metal fingers that catch the metal plug-on tang of the breakers. I thought all panels looked like that, but I only have experience with one brand. It looked like a rube goldberg mess the first time I saw it without breakers installed, but later I realized that is necessary to get a breaker for a 240V circuit to physically connect to both poles without making breakers long and skinny rather than simply use two 120 breakers sandwiched together like mine are. When I first saw your post, I thought "wow, this guy has a panel that gets rid of the weird interleaving metal bars! I wonder how it works? What brand is it? What do the breakers look like?" I was going to ask you to take all the breakers out of the panel and send us a picture of it but I didn't have the nerve.


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