# Generator sizing advice for a newbie



## HouTX (Oct 7, 2021)

Please bear with me as this question has been answered many times before I am sure. I have had 3 reputable companies come by for a Standby generator quote. I have a 125 amp main panel, 5 ton AC, 2400 SQFT house, all LED lighting, double electric oven (soon to be replaced with a gas range). All remaining major appliances are gas (furnace, cooktop, dryer, water heater). I have one installer quote me a Generac 18kW unit w/managed ATS, or a 22kW for “peace of mind” both with 200-amp ATS. 
Another is quoting a Cummins 20kW with 100-amp ATS “only one with written guarantee to run 5-ton AC”, 
and a 3rd is quoting a 22 kW Generac with 200 amps ATS. 

The quotes are $1000’s apart hence I am seeking your advice. We don’t expect to light up the house like a Christmas tree during an outage, but being in Houston, we would want the AC to run, along with our refrigerator, some lights, computers, & TV. We have had multi-day outages twice this year and expect that to continue. What size should I go with? I am attaching a picture of my AC tag. Thanks in advance.


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## iowagold (Jan 22, 2020)

i would update the service panel to a 200 amp.
most new codes require this on new construction.

and it is nice to have a 40 space box. 
i prefer square D qo series.
that is the commercial version.

from there....

do a BIG inventory of your power.
pm me if you need inf for a custom meter setup so you can see your live power consumption.
you need the base line min power, and then the max power used in the summer time.

you need 25 to 50% larger gen that your load max....
that leaves you with plenty of room to start motors etc.
and that gets in to a fuel consumption thing as well..
larger gen takes more per hour in fuel....
i prefer a multi fuel gen set up so you can choose your fuel for what is available.

cat makes a nice gen set.
they are a bit more but worth the extra bucks on the mid sized larger gens.

just a bit of food for thought


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## Browse Deweb (Jan 16, 2021)

I recommend the liquid cooled Cummins RS25 along with an EasyStart 368 soft starter for your HCAV unit. You don't want an air cooled screamer running at 3600 RPM powering your house for long periods of time. The RS25 is much quieter and more efficient.


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## macdenewf (Sep 3, 2021)

HouTX said:


> Please bear with me as this question has been answered many times before I am sure. I have had 3 reputable companies come by for a Standby generator quote. I have a 125 amp main panel, 5 ton AC, 2400 SQFT house, all LED lighting, double electric oven (soon to be replaced with a gas range). All remaining major appliances are gas (furnace, cooktop, dryer, water heater). I have one installer quote me a Generac 18kW unit w/managed ATS, or a 22kW for “peace of mind” both with 200-amp ATS.
> Another is quoting a Cummins 20kW with 100-amp ATS “only one with written guarantee to run 5-ton AC”,
> and a 3rd is quoting a 22 kW Generac with 200 amps ATS.
> 
> ...


Morning HouTx.
The size of your generator really depends on what youre looking to power continuously. I have a portable 13KW nat gas generator, have a 4300 sq foot house with a pool and i can honestly say...the one i have can pretty much start up and run all of the large devices in my house...and not be overloaded ( i also installed a power meter to watch the loads ) 

The last time i got a quote for a whole home generator the company wanted close to 12 grand for a " minimum" sized generator ...ithink they were quoting a general 14KW ....and 15 grand for something larger ..seem to recall it was a 20KW generac 
i chose the portable route as i'm good with emergency power capability ( pulling the generator out - plugging it in) vs convenience power ( having it automatically come on)

After that last winter storm we had in texas, and a ton of my friends knowing i had a portable and had power the whole time , ive helped well over a half a dozen friends install portable generators, and 3 of them we converted to Nat gas and connected to their meter.
The best deal ive seen on a portable of a decent size is the Pulsar 12KW. thats 12KW starting, 10KW running. On Nat gas, they derate about 20% from gasoline but haven't seen one yet that couldn't run an AC, fridge, freezer and as you say - with all LED lights - the lighting load isn't even noticeable.

You will need someone to connect tup the mechanical interlock, install the generator inlet box and connect to you gas meter ( if you choose to convert from how it is sold) but it is a quarter of the price of a whole home generator...so if its emergency power you want...this might be a decent option....but if you have the money..the whole home generators are great.

DM me if you want me to send any pictures of the install and what it looks like when up and running. Heck,im in Spring Tx...so youre even welcome to come by and look at the setup yourself.

Cheers
Mac


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## Browse Deweb (Jan 16, 2021)

You could also get two portable inverter generators like the Honda EU7000is and convert them to also run on natural gas or propane. This is what one of our forum members did.









Got a second EU7000, more work to be done.


Hey, so I pulled the trigger on a second EU7000. Both units fit nicely in the enclosure I built last year. I have 6 gauge cable running from my inlet box. But need to update other parts of the system. I want to feel out some options and get some opinions. 1. Inlet box.… Got to install a 50amp...




www.powerequipmentforum.com





You'd likely still need a soft starter for your 5-ton HVAC unit though.


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## pipe (Jun 27, 2021)

Simple: Do NOT have as your goal to run the old technology 5 ton AC. Leave it alone in a power outage.

Install one or two small inverter heatpumps (Mitsubishi, Fujitsu, Daiken) for the 2 most used rooms, ie. master bedroom, living room or kitchen.
Cost for 12,000 BTU Mitsubishi Hyperheat (yes it both cools and heats automatically) is today around 1650.00

Any 220v inverter generator with a 30amp interlock will easily run at less than 2000 watts your house


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## macdenewf (Sep 3, 2021)

Browse Deweb said:


> You could also get two portable inverter generators like the Honda EU7000is and convert them to also run on natural gas or propane. This is what one of our forum members did.
> 
> 
> 
> ...


Would love the dual inverter option...but darn those are expensive. by the time you get 2 Honda UE7000s and the parallel kit...im pretty certain you'd be over 9 thousand dollars. 

The kit for the AC is good idea though...my neighbor had kits installed on both his ACs and im certain they were a couple hundred each installed by an AC technician.


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## LaSwamp (Mar 16, 2021)

macdenewf said:


> Would love the dual inverter option...but darn those are expensive. by the time you get 2 Honda UE7000s and the parallel kit...im pretty certain you'd be over 9 thousand dollars.
> 
> The kit for the AC is good idea though...my neighbor had kits installed on both his ACs and im certain they were a couple hundred each installed by an AC technician.


The Honda solution is the best solution, but as you noted, it's the most expensive. There are less expensive options. Champion and Wen make larger inverters, although for some reason they are not parallel capable. Standard generators get pretty powerful. My brother in law just bought a Duromax 13 kw generator for his camp at Grand Isle. Looks like he paid about $1,500 for it. I haven't scoped it yet, but it's rated at 12% THD which isn't bad for a non-inverter.


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## macdenewf (Sep 3, 2021)

pipe said:


> Simple: Do NOT have as your goal to run the old technology 5 ton AC. Leave it alone in a power outage.
> 
> Install one or two small inverter heatpumps (Mitsubishi, Fujitsu, Daiken) for the 2 most used rooms, ie. master bedroom, living room or kitchen.
> Cost for 12,000 BTU Mitsubishi Hyperheat (yes it both cools and heats automatically) is today around 1650.00
> ...


I have a 4 ton downstairs and 3 1/2 ton upstairs AC. That 13KW northstar nat gas generator i have can take them both no troubles...too bad they discontinued that one....and it can run the pool pump at the same time 

The pulsar 12KW can start and run both ACs when running on gasoline but i struggle to start up the 2nd one when on nat gas....simply lose too much power when running on nat gas. 

But as for someone who has run my Acs on portable power...and have helped multiple friends install their portable generators...the AC is the 1st thing we check to see if it will take the load well...and can honestly say - hasn't been a problem. 

I don't think i'd shy away from running an AC. the 5 Ton is a little larger than either of my single Acs but lower combined and based on the AC label that was provided will only be pulling 25 amps when running ...leaving lots of headroom for a fridge, freezer...etc.

My primary objectives were to provide emergency power at the most reasonable price. Emergency power in Houston pretty much has to include AC....and as i didn't want to spend the money on a whole home...i found the largest reasonably priced generator i could. That pulsar is a great deal for the money but if a person wanted just a little more power...there are a couple of other options with 15KW. Westinghouse has a 15KW/12KW running thats already dual fuel...so converting to to nat gas is simple...but it doubles the price for those few thousand extra watts.

Im my mind it comes down to a couple of simple tradeoffs.

Are you looking for Emergency backup power...or convenience backup power. if convenience....get the whole home
if emergency power....How much money are you willing to spend? If you don't mind spending 3k on the generator...get the 15KW and convert to nat gas. If your budget is less...get the 12KW

anyway....just my 2 cents worth.
Cheers


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## macdenewf (Sep 3, 2021)

LaSwamp said:


> The Honda solution is the best solution, but as you noted, it's the most expensive. There are less expensive options. Champion and Wen make larger inverters, although for some reason they are not parallel capable. Standard generators get pretty powerful. My brother in law just bought a Duromax 13 kw generator for his camp at Grand Isle. Looks like he paid about $1,500 for it. I haven't scoped it yet, but it's rated at 12% THD which isn't bad for a non-inverter.


Northstar also carries a 7500 watt inverter that is parallel ready....but still 3500 a piece. i would love to try one out though.....55 db vs the wayyy louder standard 75 to 80 dB gen sets



https://www.northerntool.com/shop/tools/category_generators+inverter-generators+4294961771



Im actually a fan of Northstar generators. they have a whole range of course but their higher end products are well built.


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## pipe (Jun 27, 2021)

macdenewf said:


> I have a 4 ton downstairs and 3 1/2 ton upstairs AC.


One of our 4 bedroom houses has 48,000 BTU's of heatpumps (cooling and heating). inverter systems. Our 3 refrigerators are 220v inverters. Our poolpump is a 220v inverter and all SWCG and Hydrochloric Acid injection systems are 220v. Our 4,500watt water heater can be toggled from 220v to 120v via a 3-way switch, effectively using only 1,125watts power. A single Honda eu7000isnan runs all of this and more using less than 3,000watts on a 95+F day and the house inside temperature is 70 F.


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## macdenewf (Sep 3, 2021)

pipe said:


> One of our 4 bedroom houses has 48,000 BTU's of heatpumps (cooling and heating). inverter systems. Our 3 refrigerators are 220v inverters. Our poolpump is a 220v inverter and all SWCG and Hydrochloric Acid injection systems are 220v. Our 4,500watt water heater can be toggled from 220v to 120v via a 3-way switch, effectively using only 1,125watts power. A single Honda eu7000isnan runs all of this and more using less than 3,000watts on a 95+F day and the house inside temperature is 70 F.


I think if i had my time back when i built the home - i would have used heat pumps vs nat gas heating and AC cooling...but sadly not in a position to add heat pumps without seriously re working drywall to install the cassettes. but if my pool heater dies....it will be a heat pump...as id love to get cooling capability too.
Out of curiosity....ive never seen a 220 fridge in the US. Did you install them for efficiency purposes? Easy to find?
Cheers


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## HouTX (Oct 7, 2021)

Thank you all for your input and suggestions. One of the 3 companies called me yesterday and reduced their quote on the Generac 22 kW by $2k so I signed up. I guess they are realizing that even with two major multi-day outages this year, and the condition of the Texas grid exposed, the market will only bear so much. In Houston most will pick an AC even if the rest of the house is in the dark! This way I will not have to pick one or the other, thanks again.....


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## pipe (Jun 27, 2021)

macdenewf said:


> ...ive never seen a 220 fridge in the US.








220 Volt Refrigerators | 240 Volt Refrigerators


Shop our huge inventory of 220 volt refrigerators and save on the top brand names like Whirlpool, GE, Frigidaire, Amana and more. Only at 220 Electronics, your trusted source since 1979.




www.220-electronics.com


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## Ground Fault (Jun 9, 2020)

HouTX,
I'm up here NE of you a few miles, in the Big Thicket. I have researched the same stand-by generator purchase questions you pose for almost two years. I still have not pulled the trigger yet, because as Don Henley laments, _"The more I know, the less I understand._" "Deer in the headlights" as my research has left me, what I have gathered from monitoring the threads on this fine forum is this:

1. Paul is right: get a 200amp service if possible. Mine was forty-five years old. I just replaced mine, from the service drop down, masthead and all. Expensive, but if you are like me you'll sleep better afterwards.
2. Deweb's advice will extend the life of your generator: Limit your search to only stand-by generators that run 1800rpm, NOT 3600rpm. Dual fuel if possible.
3. Water-cooled per Deweb as well. You KNOW how hot and humid it gets here in August/September. Air cooled may be sufficient in more northern climes, but that dog ain't gonna' hunt here. Not for long anyway...
4. Of greatest importance, and an almost universally-held opinion on this forum, regardless of the sincere assurances offered by the sales reps that beat a path to your door, DO NOT PURCHASE A GENERAC. I own one. A 3600rpm air-cooled Generac. It and my tools have become intimate. As Roger Daltrey declared, _*We won't get fooled again!*_"

I offer a alternate idea. IF when you become tired and jaded of the permanent stand-by option search as I did, please give serious consideration to stepping back a bit and reconsidering what you are trying to accomplish. We both know that our first priority is preservation of our frozen food, then our thoughts IMMEDATELY turn to getting momma cool and _off our back_. There is more than one way to skin that cat. I too was being quoted $12-15K turnkey, but with subtle sales caveats included that protected the distributor/installer/SERVICER. I gathered enough lucidity to pause with the purchase. Blessed with time to consider, and the help of this forum, I read through those caveats well enough to see that there were potential, almost certain dark clouds on my horizon post-purchase that the sales rep had knowledge of and for which they did not want to be held liable. They had been sure to "told me so" before the purchase to protect them from liability. Does that bring to mind any of the things they told you? For me...Full Stop. So the light went off: Why not buy portable power of lesser but still sufficient capacity and use window A/C's instead of trying to provision with enough amps to overpower my central air's LRA's? Less than HALF the price. Even for the best generator brand out there.

You already have the NG knocked out. I'm thinking something in the 8-10,000 running watts range that will deliver 6500-7000watts on NG. More than enough to run what you have _without the central air_, especially considering all that you have that runs on NG. Buy a couple of 10-12,000Btu window units and put them in strategic windows, install momma under one, then get in the $50 Walmart blow-up pool in the back yard and ride it out. [Buy TWO pools (ask me how I know), SE Texas post-hurricane necessities.] Been there, done that. Country boy can survive. The money you save is yours to keep.

And if you decide to go through with it, most on here recommend still getting a back-up generator.


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## LaSwamp (Mar 16, 2021)

pipe said:


> 220 Volt Refrigerators | 240 Volt Refrigerators
> 
> 
> Shop our huge inventory of 220 volt refrigerators and save on the top brand names like Whirlpool, GE, Frigidaire, Amana and more. Only at 220 Electronics, your trusted source since 1979.
> ...


Look at the Hz for those models. They are designed for use for a 50 Hz system. That tells me they are for European markets.


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## iowagold (Jan 22, 2020)

yea on the 50 hz
they make lp fridge and freezers too!
and those LP refer truck chillers work well too!
the amish down in my area use those for stores as well as whole house ac.


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## HouTX (Oct 7, 2021)

iowagold said:


> i would update the service panel to a 200 amp.
> most new codes require this on new construction.


I was told I have 200 amp service at the meter but my panel is 125 amps. So should I be upgrading the breaker panel to 200 amps?


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## iowagold (Jan 22, 2020)

yup!
change out the panel and the wiring from the meter to the panel needs to be new heavy as well.
most service feeder triplex wire from the pole is good for the 200 amps these days.
but the wires from the meter socket to the service panel may be too small and needs to be 4/0 if aluminum for HD
and i do like metal conduit to the breaker panel from the meter socket or the disconnect at the meter.

oh yea new nec and fire code requires a disconnect at the meter now.
pm if you need links for those.


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## HouTX (Oct 7, 2021)

I have lived in this house for 21 years without an issue with the panel. I had an old Federal Pacific panel replaced as soon as I moved in. What is the benefit of a 200 amp upgrade?


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## iowagold (Jan 22, 2020)

HouTX said:


> I have lived in this house for 21 years without an issue with the panel. I had an old Federal Pacific panel replaced as soon as I moved in. What is the benefit of a 200 amp upgrade?


up to the latest code.
also helps with resale.
and the outside disconnect is a cool thing as well
and it helps with more spaces to separate branches in the house.
and more parts for the later model panels.

if you are looking at ats units.
most new ats units are for 200 amp service.


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## Ground Fault (Jun 9, 2020)

Paul is right: merchantability (and resale value) of your home one day. Also, *cost of continued ownership* until then. Specifically, insurance costs. Among many other questions, all insurance companies ask if the structure has at least 200 amp service in their pre-qualifying guidelines. If no then most decline to quote. Those that will, well, they are not your front-line insurers for the most part, _and their rates are significantly higher than the other companies._ They pay fire claims that result from overloaded 125 amp services, so they perceive additional risk, and they rate accordingly. I see these rate disparities on a daily basis. I rep for 27 of them, and my son-in-law is the State Farm agent in Dayton. I can assure you Hou that in your 21 years there you have bought that 200 amp service several times over in paying higher insurance rates. I recommend getting the 200 amp service, then shop your home insurance around for better rates. It couldn't hurt. Break even point is not that many years from now. If not, then at least add Increased Cost of Construction endorsement to your home insurance policy. I sell a ton of insurance in Harris County. My customers have had dealings with the Houston FD Fire Marshal there. If you burn he's infamous for making people bring the undamaged portion of their structures up to current code. He can do the same thing for hurricane damage _if he wants to_. No occupancy permit until you do. Without that endorsement then that current code-retrofitting expense comes out of your pocket. Just had a church in North Shore have a steeple fire due to lightning. About $375,000 in damage. He stepped in. Turns out it's another $800,000 to bring the sanctuary up to code. Buy the 200 amp now. It's just good...insurance.


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## HouTX (Oct 7, 2021)

That is very interesting. I have multiple homes in Harris County and I have never had an insurance company ask me about electrical service. I shop for insurance every couple of years with the major players, some will not insure aluminum wiring or galvanized plumbing. In fact when I recently replaced galvanized with PEX the carrier does not offer a discount, they said it is insure Yes/No, but no discount for PEX.


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## iowagold (Jan 22, 2020)

HouTX said:


> That is very interesting. I have multiple homes in Harris County and I have never had an insurance company ask me about electrical service. I shop for insurance every couple of years with the major players, some will not insure aluminum wiring or galvanized plumbing. In fact when I recently replaced galvanized with PEX the carrier does not offer a discount, they said it is insure Yes/No, but no discount for PEX.


ha!
yea some are just going to give you a cookie cutter policy....
and hope you will never do a claim!

i have a great agent up here...
we sit down and check on coverage at least once a year and tweak on policies.

and yes now that electric power is a real thing in some areas with fires and real bad storms.
they are checking in with the questions on last time it was updated...
and sometimes they are sending out the under writers to take a look!!
a basic inspection of the property!
and do a written evaluation of the issues.
I had that after the dechero here... we switched under writers after that.

kinda surprised on the pex change out. and no discount..
they must to have already had you on the low cost plan??


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## Chip (Sep 4, 2021)

Browse Deweb said:


> I recommend the liquid cooled Cummins RS25 along with an EasyStart 368 soft starter for your HCAV unit. You don't want an air cooled screamer running at 3600 RPM powering your house for long periods of time. The RS25 is much quieter and more efficient.


hi. I have a 12.5k/9500 Westinghouse dual fuel and as far as AC… 1, 3 ton with a Amrad Hard Start Kit and a 4-ton with a 5-2-1 Hard Start and I can run either but just not both simultaneously. Reason is I need to run a 1HP well pump that takes 2000 running watts And 3000 to start. 
so, can you advise if these “ Easy Start-368” can be installed by a civilian or would I need a HVAC guy? I installed my hard start kits myself.
Also any idea how much these reduce the LRA vs the hard start kits….
I think my 3 ton went from 77 to 49 starting amps with the Amrad Hard Start…

also, once you convert a dual fuel (gasoline & Propane) to natural gas. Can you ever use gas or propane again??


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## drmerdp (Apr 10, 2018)

Chip said:


> hi. I have a 12.5k/9500 Westinghouse dual fuel and as far as AC… 1, 3 ton with a Amrad Hard Start Kit and a 4-ton with a 5-2-1 Hard Start and I can run either but just not both simultaneously. Reason is I need to run a 1HP well pump that takes 2000 running watts And 3000 to start.
> so, can you advise if these “ Easy Start-368” can be installed by a civilian or would I need a HVAC guy? I installed my hard start kits myself.
> Also any idea how much these reduce the LRA vs the hard start kits….
> I think my 3 ton went from 77 to 49 starting amps with the Amrad Hard Start…
> ...


Soft start kits are only a little more complicated to install. if you installed the hard start kits then your likely capable. Watch some videos and read the instruction thoroughly.

Soft starts usually cut inrush by 50%. The added benefit is the unit puts the compressor on a delay. That means the inside air handler fan motor and condensers fan motor both start first followed by the compressor. Preventing the surge of all 3 motors starting at once.


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## Chip (Sep 4, 2021)

thanks so much!



drmerdp said:


> Soft start kits are only a little more complicated to install. if you installed the hard start kits then your likely capable. Watch some videos and read the instruction thoroughly.
> 
> Soft starts usually cut inrush by 50%. The added benefit is the unit puts the compressor on a delay. That means the inside air handler fan motor and condensers fan motor both start first followed by the compressor. Preventing the surge of all 3 motors starting at once.


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## Browse Deweb (Jan 16, 2021)

I installed the EasyStart 368 in about 5 minutes. It's just 4 wires, one more than a typical 5-2-1 hard start kit, which I used to have. The soft start is better for your compressor as well as reducing the inrush. The hard start doesn't really reduce inrush spike, but it does start the compressor faster reducing the length of the spike in current. A current meter with min/max recording doesn't really catch the faster current spike, so it appears as though the hard start is reducing startup current. It's not...at least not significantly.

Here is a guy installing the EasyStart:


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## macdenewf (Sep 3, 2021)

Chip said:


> hi. I have a 12.5k/9500 Westinghouse dual fuel and as far as AC… 1, 3 ton with a Amrad Hard Start Kit and a 4-ton with a 5-2-1 Hard Start and I can run either but just not both simultaneously. Reason is I need to run a 1HP well pump that takes 2000 running watts And 3000 to start.
> so, can you advise if these “ Easy Start-368” can be installed by a civilian or would I need a HVAC guy? I installed my hard start kits myself.
> Also any idea how much these reduce the LRA vs the hard start kits….
> I think my 3 ton went from 77 to 49 starting amps with the Amrad Hard Start…
> ...


I’ve bought kits from Nash fuels for a dual propane / nat gas. When converted, if you want to run on propane you install a load block thst let’s you choke back the propane. Worked like a charm on the pulsar 12kw I converted about a month ago. 
cheers. 
mac


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## iowagold (Jan 22, 2020)

nash has some of the better load blocks right now.
that is what we use here on all of the kits.


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## Ground Fault (Jun 9, 2020)

> That is very interesting. I have multiple homes in Harris County and I have never had an insurance company ask me about electrical service.


OOOPS. My bad: It's ineligible for 100-amp or less service, some requiring underwriter review of any that are > 100-amp, sub 200-amp. Also, ineligible with a service that contain fuses rather than breakers, and/or homes or outbuildings wired with aluminum wiring. And, of course, asbestos anywhere.


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