generator

[spasm3]

Originally Posted by Astro_Guy
That's a rather high capacity unit as far as portable gas powered generators go. Are you sure you need that much power for emergencies? What's the capacity of the current one?



So i tried running the a/c today as a test. I've never had and outage where i needed a/c , most have been in winter.

So my 8000/10000 surge generator will not start the 4 ton ac unit. So there is no point in getting a newer one as large as this if it won't do that. I can get by very well on a 6000 unit, that would have longer run time.

 

[Astro_Guy]

Originally Posted by spasm3
Originally Posted by Astro_Guy
That's a rather high capacity unit as far as portable gas powered generators go. Are you sure you need that much power for emergencies? What's the capacity of the current one?



So i tried running the a/c today as a test. I've never had and outage where i needed a/c , most have been in winter.

So my 8000/10000 surge generator will not start the 4 ton ac unit. So there is no point in getting a newer one as large as this if it won't do that. I can get by very well on a 6000 unit, that would have longer run time.

Were you seriously expecting it to start it??? Have a look at the nameplate on your outdoor unity and look for the "LRA" or locked rotor amperage spec. This is the starting current of your compressor at 240 VAC. Next, multiply that figure by 240 to obtain starting watts. Divide by 1000 to find starting Kilowatts (Kw.) Ignoring all else, that is what you want, but it gets better.

Voltage will dip when starting an inductive load, such as your AC compressor. Power will drop in proportion to that voltage drop. Multiply your starting Kw calculated above by a factor of 0.7, and you should still have more than adequate starting capacity. From my research on the subject, this is the rule of thumb guideline for commercial applications. Some generator sizing websites even suggest that you can reduce that figure to as little as 0.5 for a home application, although I personally would favor the 0.7 factor for commercial applications. One reputable company has told me in writing that a 10 Kw generator will start my 3-ton unit with 82 amps LRA, which comes to 19.7 Kw. Slightly older single or dual speed units with reciprocating compressors have higher LRAs than the newer variable speed inverter driven Copeland scroll compressors. The unit I speak of is a Carrier Infinity 19, circa 2012.

Have a look at that nameplate and let us know what sort of starting load you are facing. A simple back of envelope calculation, assuming you have a reciprocating compressor, suggests that 17 Kw will easily do the trick. You might even get by with 14 Kw in a pinch.

 

[spasm3]

Originally Posted by Astro_Guy

Have a look at that nameplate and let us know what sort of starting load you are facing.



LRA is 140. My unit is an older r-22 unit from about 2003- 2004. Probably will need replacing in a few years. I see what you mean, my unit is nowhere near starting on a portable gen set.

 

[Astro_Guy]

Originally Posted by spasm3
Originally Posted by Astro_Guy

Have a look at that nameplate and let us know what sort of starting load you are facing.
LRA is 140. My unit is an older r-22 unit from about 2003- 2004

In that case you should consider replacing the A/C if you plan to be in the house more than 2-3 years. R-22 is obsolete and getting very expensive to replace. If you take a long term view, you will actually save money with the increased efficiency of a modern A/C or heat pump unit using R-410a refrigerant. The added bonus here is that a smaller generator will start a newer A/C unit with an inverter driven scroll compressor. While I am not suggesting that you run right out and replace your central A/C, what I do suggest is thinking long and hard before spending another nickel on R-22 refrigerant.

 

[spasm3]

Originally Posted by Astro_Guy
Originally Posted by spasm3
Originally Posted by Astro_Guy

Have a look at that nameplate and let us know what sort of starting load you are facing.
LRA is 140. My unit is an older r-22 unit from about 2003- 2004

In that case you should consider replacing the A/C if you plan to be in the house more than 2-3 years. R-22 is obsolete and getting very expensive to replace. If you take a long term view, you will actually save money with the increased efficiency of a modern A/C or heat pump unit using R-410a refrigerant. The added bonus here is that a smaller generator will start a newer A/C unit with an inverter driven scroll compressor. While I am not suggesting that you run right out and replace your central A/C, what I do suggest is thinking long and hard before spending another nickel on R-22 refrigerant.


We will die in this house, so we will be here long term. No more moving.

Thanks for the info, so far no leaks. Plus i have 3/4 full 30 lb tank of r-22. But i don't expect the compressor to last forever. If much of anything breaks on it, its geting replaced, I've already budgeted for it. The money is sitting aside for replacement.

You are saying a newer 4 ton unit can be started with a big portable genset? I have not really shopped for a/c units yet.

Thanks for you replies.

 

[Astro_Guy]

Originally Posted by spasm3
You are saying a newer 4 ton unit can be started with a big portable genset? I have not really shopped for a/c units yet. Thanks for you replies.

No - but I will go out and have another look at the nameplate on my secondary system, a 2-ton Rheem RP17 heat pump. IIRC - the LRA was less than half that of my Carrier Infinity 19.

I started my whole house backup analysis based upon the need to start that Carrier unit. Later it occurred to me that the kids were growing up and moving out, and that it would not be necessary to start that big unit in an emergency.

Have you had a look at mini-split systems? Odds are that you could replace the big system with two or more smaller systems and then only back up the essential ones.

 

[jhellwig]

I forget what it is that wears out on the compressor but something wears and makes them harder to start as the unit ages. That how a new unit could start easier than an old one. If you had a brand new older unit though it would start easier than a newer unit that is more efficient. A higher efficiency electric motor is harder to start than a lower one due to the design.

 

[Astro_Guy]

Originally Posted by spasm3
You are saying a newer 4 ton unit can be started with a big portable genset? I have not really shopped for a/c units yet.

Yes, I believe it can be done. See https://resource.gemaire.com/is/con..._article_1439195466936_en_ii.pdf?fmt=pdf page 5. This is the installation manaul for a Rheem RP17 3-stage heat pump. Note the locked rotor amperage (LRA) of 35. If we do the math, (35 amps * 240 volts)/1000 watts per Kw = 8.4 Kw. If we apply the 0.7 sizing factor for commercial applications we reduce the initial starting power to less than 6 Kw.

I have a 2-ton RP17 and have been happy with it. The 4-ton unit has a 17 SEER and 8.5 HSPF. That's Seasonal Energy Efficiency Ratio and Heating Seasonal Performance Factor. As of 2015 the federal government has mandated minimum values of 14 SEER and 8.2 HSPF for all central A/C and heat pumps sold in the US. Your exiting equipment probably has a SEER of 10-13. You can use the ratio of the existing unit SEER to the proposed replacement unit SEER to get a reasonable estimate of the operating cost savings. Replacing a 13 SEER unit with a 17 SEER unit yields a 23.5% energy savings. You can get a good estimate of your current system efficiency by visiting https://www.ahridirectory.org/ and using the Search Product Database function. If you want to know for sure, contact an HVAC contractor and ask him to identify both the outdoor unit and coil and then perform the same search.

 

[spasm3]

Thanks, i have gas heat that shares the ductwork. so its just an a/c only unit i would be replacing. Too much work probably to try and make that a split system. I'll check out the links, Running a/c is not a have to. At worst in hot weather we can live in my camper and easily power the ac in that with portable gen.

 

[Astro_Guy]

Originally Posted by spasm3
Thanks, i have gas heat that shares the ductwork. so its just an a/c only unit i would be replacing. Too much work probably to try and make that a split system. I'll check out the links, Running a/c is not a have to. At worst in hot weather we can live in my camper and easily power the ac in that with portable gen.
I was speaking of a specific heat pump model only because it was the last system I had installed. More than a small amount of thought went into it, and I am also pretty far down the road in terms of generator sizing. Just for laughs and grins I pulled up the installation manuals for Rheem RA17 and RA20 central A/C units. Both feature scroll compressors, but one is considered two speed while the other is fully modulating. The LRA specs for 4-ton units were 104 amps vs. 50 amps. Apparently simply having a scroll compressor alone is not the magic elixir needed to achieve a low LRA rating; there has to be some level of modulation that spins up the compressor slowly. I learned something valuable today.

Eventually your R-22 system will need replacement. Yours has already passed the median age for failure. When the time comes, you will have the opportunity to buy something that can be started with a generator.

 

[spasm3]

Getting back to generators, forgetting the a/c i can run most of what i want on 6000 watts maybe 5000. Looking at the gensets now, the fuel useage numbers are all over the place. Some list at 25% load some at 50% load.

Might as well get as much run time as possible incase of and extended outage, but its tough to compare.

My current 8000/10000 unit is 18hp v-twin powered ( overpowered) and uses about 5 gallons in about 6 1/2 hours.

 

[bubbatime]

Originally Posted by cpayne5
During outages, I usually use two generators.

One is a 3250 watt Powermate with a Honda GX240 clone. I use it to power lights, the fridges, and a space heater if it's cold out.

The second generator is a 7500 watt Ariens with a real Honda GX390. I use this one to power all of the above and also the well pump or hot water heater as needed.

The Powermate uses considerably less fuel and is quieter, so it is the one that sits there and putters away most of the time during outages.



This. Those 8000/9000 watt units are overkill and are running at 10-15% load most of the time, wasting huge amounts of fuel.

I've lived in Florida for 30 years and have been without power for probably 3-4 months of that due to hurricanes. The most important feature I've learned to love is fuel efficiency. It can be hard to store fuel, and get more fuel, in an outage. Try to get 15-40 gallons of fuel a day; a terrible proposition.

You can power most everything you need in the house on a 2200/2800 watt Honda inverter. These inverter generators will even power a window ac unit in the summer, so you can rather cheaply keep at least one room of the house comfortable, for a lot less money than running the whole house AC.

Were it MY HOUSE, I'd get the 2800 Honda inverter for $999. And then a cheapy Harbor Freight 8750 watt for those time you want to run the water heater or AC/heat pump.

https://www.homedepot.com/p/Honda-2...rizontal2_rr-_-206192156-_-303793554-_-N
https://www.harborfreight.com/engin...i-with-gfci-outlet-protection-63085.html

 

[spasm3]

Thanks bubba time.

My house load is 1 freezer 1 refrigerator. 1/2 hp well pump My furnace is gas so i'm guessing 1200 watts or so. Gas waterheater so no load there. Plus lights and some cooking ability. All my home lights are led so not much load there.

I'd like to only mess with one generator not connect and mess with two, but i get the point in an extended outage. I do want 240v incase i want to cut back other uses and run the washer or dryer if needed, and use the oven/ or cook top. Plus i think my well pump needs 240v.

Some if the 5000 watt sets show about 13 hours on 6.6 gallons or so @ 50% load. A lot of them do appear to be Chondas.

It was nice with the last outage , to be able to move about the house and not worry about what i turned on or off as the 8k could handle it, but i paid for it in fuel. I've heard that our winter here may be worse this year but who knows.

 

[Astro_Guy]

Originally Posted by spasm3
Getting back to generators, forgetting the a/c i can run most of what i want on 6000 watts maybe 5000. Looking at the gensets now, the fuel useage numbers are all over the place. Some list at 25% load some at 50% load.

Might as well get as much run time as possible in case of and extended outage, but its tough to compare.
For what it is worth, I run two refrigerators, one 15 cubic foot freezer, the blowers and ignitors for the gas hot water heater, furnace and kitchen stove, the dishwasher, an outlet in the powder room so the misses can use her hair drier, and the 1/2 HP garage door opener on a 3500 watt Champion. For extended outages we run a cord over to the neighbors for their refrigerator. Naturally not all of this is starting or running simultaneously. My generator consumes 4 gallons every 12 hours at 50% load. I think bubbatime is on the right track. Save your 8000/10,000 unit for the day when you have a new A/C that it can handle.

 

[hatt]

If you don't want to worry about things you need to get a standby with a big propane tank.

 

[spasm3]

Originally Posted by Astro_Guy
Originally Posted by spasm3
Getting back to generators, forgetting the a/c i can run most of what i want on 6000 watts maybe 5000. Looking at the gensets now, the fuel useage numbers are all over the place. Some list at 25% load some at 50% load.

Might as well get as much run time as possible in case of and extended outage, but its tough to compare.
For what it is worth, I run two refrigerators, one 15 cubic foot freezer, the blowers and ignitors for the gas hot water heater, furnace and kitchen stove, the dishwasher, an outlet in the powder room so the misses can use her hair drier, and the 1/2 HP garage door opener on a 3500 watt Champion. For extended outages we run a cord over to the neighbors for their refrigerator. Naturally not all of this is starting or running simultaneously. My generator consumes 4 gallons every 12 hours at 50% load. I think bubbatime is on the right track. Save your 8000/10,000 unit for the day when you have a new A/C that it can handle.


Thanks, thats pretty good, I will need a 240v and most of those seem to be a 5000 watt unit. I can't run my well pump on 110v. And thats what i really need during an outage.

My 8000/10000 unit is going away as it uses too much fuel and is 20+ years old, I want a newer unit to rely on. By the time i get a new a/c in a year or too it will be almost 25 years old.


I hate to say it but the lowest fuel consumption generator that is 240v that i can find is an HF 3500 watt unit. It claims 16h run time on 4 gallons.

 

[spasm3]

Originally Posted by hatt
If you don't want to worry about things you need to get a standby with a big propane tank.


I have natural gas, so that would be a plus. I am replacing all my windows this spring with low E 366 glass, and i have cash aside for the a/c if it goes out. I just don't want to spend 10k right now for a stand by unit. ( i don't do debt

).

I am easily capable of moving and connecting the portable unit. In 20 years when i retire, i will have a stand by unit. If i buy one now, it will probably need replacing when i retire, so i'll hold off on that.

 

[Astro_Guy]

Originally Posted by spasm3
I hate to say it but the lowest fuel consumption generator that is 240v that i can find is an HF 3500 watt unit. It claims 16h run time on 4 gallons.
Looks like a winner for your application. Big enough to run the well pump, refrigerator and a few extras, yet easy on gas. Let us know what oil you go with after the break-in run.

 

[JimPghPA]

Just a note for those who have a generator and electric hot water heater:

If you run a 240 Volts AC electric water heater on 120 Volts AC it will consume 1/4 the amount of wattage that it consumes on 240 Volts AC. This is because at 1/2 Voltage it will draw 1/2 the normal amount of current. 1/2 Amps times 1/2 Voltage equals 1/4 Wattage.

Of course at 1/4 wattage it will take four times as long for the water heater to heat up cold water after hot water is drawn from it.

 

[tig1]

Originally Posted by spasm3
Originally Posted by Astro_Guy
Originally Posted by spasm3
Getting back to generators, forgetting the a/c i can run most of what i want on 6000 watts maybe 5000. Looking at the gensets now, the fuel useage numbers are all over the place. Some list at 25% load some at 50% load.

Might as well get as much run time as possible in case of and extended outage, but its tough to compare.
For what it is worth, I run two refrigerators, one 15 cubic foot freezer, the blowers and ignitors for the gas hot water heater, furnace and kitchen stove, the dishwasher, an outlet in the powder room so the misses can use her hair drier, and the 1/2 HP garage door opener on a 3500 watt Champion. For extended outages we run a cord over to the neighbors for their refrigerator. Naturally not all of this is starting or running simultaneously. My generator consumes 4 gallons every 12 hours at 50% load. I think bubbatime is on the right track. Save your 8000/10,000 unit for the day when you have a new A/C that it can handle.


Thanks, thats pretty good, I will need a 240v and most of those seem to be a 5000 watt unit. I can't run my well pump on 110v. And thats what i really need during an outage.

My 8000/10000 unit is going away as it uses too much fuel and is 20+ years old, I want a newer unit to rely on. By the time i get a new a/c in a year or too it will be almost 25 years old.


I hate to say it but the lowest fuel consumption generator that is 240v that i can find is an HF 3500 watt unit. It claims 16h run time on 4 gallons.



Why would you hate that. However if you need a Generator to power a well and AC the 5KW unit most likely won't be large enough. I have a 5KW, 6250 start Coleman and it does power my 24,000 window AC, but I don't run the frig at the same time.