Marshall 357
Member
I am using my friends generator now,I think it is a 4500 watt It will run my power saws but it will not run my Air Compressor and it only a small 110 volt,1 hp motor. What size should I get?
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What is a good size '' watt'' generator
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I'm surprised it won't run your compressor.
This link to Honda may help.
Honda Power Equipment - Honda Generators - How much power do I need?
This link to Honda may help.
Honda Power Equipment - Honda Generators - How much power do I need?
Hi,
You need to figure out how much amperage you will need to complete your tasks first of all. Watts divded by Voltage equals amperage. 4500 watts / 120 volts is 37.5 amps by simple math, that is a lot of current and I can't believe it won't run an air compressor with a 1 HP motor. You should take a look at the tag on the motor, my 1.5 HP motor is 22 amps at 120 volts and I run it with 240 volts for a total of 11 amps. I do most everything in my house, furnace, refrigerator, lights, for emergency purposes with a 2 Kilowatt inverter. [ 2000 watts continuous ] and use my 5000 watt generator to charge the batteries. Keep in mind the advertised wattage on generators is usually peak, not continuous. I hope this helps.
Steve
You need to figure out how much amperage you will need to complete your tasks first of all. Watts divded by Voltage equals amperage. 4500 watts / 120 volts is 37.5 amps by simple math, that is a lot of current and I can't believe it won't run an air compressor with a 1 HP motor. You should take a look at the tag on the motor, my 1.5 HP motor is 22 amps at 120 volts and I run it with 240 volts for a total of 11 amps. I do most everything in my house, furnace, refrigerator, lights, for emergency purposes with a 2 Kilowatt inverter. [ 2000 watts continuous ] and use my 5000 watt generator to charge the batteries. Keep in mind the advertised wattage on generators is usually peak, not continuous. I hope this helps.
Steve
I seems like wattage ratings are as trustworthy as horsepower ratings. Look for something with a higher duty cycle, and if you require it to run all night without attention a suitable sized fuel tank. Idle-down feature is nice too.
OP
Marshall 357
Member
my motor is a 15 amp 120 volt.......can it be wired for 220 volt with out hurting the motor..?
Some motors can be wired to run either 110 or 220, some can't. Do you still have the owners manual? There might be a wiring diagram there or sometimes there will be a diagram on the motor or wiring/junction box showing how to connect to each voltage power.
That is what I have. An industrial dual voltage motor, it is marked as such on the small plate that covers the electrical connnections with the appropiate wiring diagram for each voltage.
To the OP: If it is a purchased air compressor from a retailer it will likely be one voltage only. You must be CERTAIN of it's operating voltage and don't violate it's design intent. Take some time and study what you have.
Steve
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OP
Marshall 357
Member
I read through the manual, It says the compressor needs its own 15 amp line and the motor is for 120 volt only. The compressor is new and the generator is about 10 yr old, it might be a little tired. The Compressor works fine in my work shop on the line we put in for the freezer that also needs its own.Thanks for your help.Guess I will go hunting for Generators now
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OK, I am not a Generator expert, but I have just finished a two month long project of selecting, purchasing, and hooking up a new generator to my house for emergency purposes and can share what I have learned.
After Hurricane Irene hit us this back in September (I believe) we were without power for 6 days, and after the hot water ran out and we threw out over $600 dollars of food, the "fun" was over! I said never again, and went ahead with the task of getting self sufficient.
I purchased a 10,000 watt American made Generac XG series electric start gasoline powered portable generator. One size does NOT fit all with these things. I had to calculate the wattage (amperage actually - then converted it to wattage) to determine what size I would need. I was interested in being able to run most of the household appliance and lighting, as well as being able to run the pool filter in the summer. I know a pool is not an essential thing, but when the weather is very hot if you don't run the filter and chlorination system for a week or two you will wind up with a "swamp".
I was also interested in running at least one of my Central A/C units during oppressively hot weather and wanted enough power that the generator could run all the time without being strained and without running at the maximum output level.
You need to calculate what the draw will be, then step up from there. Most generator companies rate their generators at half wattage usage. In other words they will state a unit might burn at the rate of one gallon per hour at half the rated wattage output. You don't want to run a generator for any extended length of time at much more than 50% capacity.
Then you need to figure out if the appliances or tools will be run on 240 or 120 volts and see which models will accommodate your output needs. You also have to determine what is in your generator budget. The Honda generators are excellent, but for the most part they are mid size units that are ridiculously expensive. I bought the contractor grade (XG series made in America) Generac unit which is a larger unit and is much more reasonably priced. The only downside to the unit that I purchased is that is was not as quiet as the Honda, but then again its output was double, so I would expect that a larger, more powerful motor would make a bit more noise. In my case this generator won't be used much since we do not loose power often, and my home is on an acre of land so the noise factor was not a major concern.
I store the unit in my garage and "exercise" it twice a month. I have already turned off the street power to my home and tested the performance of my generator; I am happy to report it does everything I wanted it to and runs at a very acceptable power level becasue I did do the research before buying to determine the proper size unit. In my neck of the wood we don't loose power often, but when we do it is usually for an extended period of time. I'm now prepared!
Hope that helps a little.
Chief38
After Hurricane Irene hit us this back in September (I believe) we were without power for 6 days, and after the hot water ran out and we threw out over $600 dollars of food, the "fun" was over! I said never again, and went ahead with the task of getting self sufficient.
I purchased a 10,000 watt American made Generac XG series electric start gasoline powered portable generator. One size does NOT fit all with these things. I had to calculate the wattage (amperage actually - then converted it to wattage) to determine what size I would need. I was interested in being able to run most of the household appliance and lighting, as well as being able to run the pool filter in the summer. I know a pool is not an essential thing, but when the weather is very hot if you don't run the filter and chlorination system for a week or two you will wind up with a "swamp".
I was also interested in running at least one of my Central A/C units during oppressively hot weather and wanted enough power that the generator could run all the time without being strained and without running at the maximum output level.
You need to calculate what the draw will be, then step up from there. Most generator companies rate their generators at half wattage usage. In other words they will state a unit might burn at the rate of one gallon per hour at half the rated wattage output. You don't want to run a generator for any extended length of time at much more than 50% capacity.
Then you need to figure out if the appliances or tools will be run on 240 or 120 volts and see which models will accommodate your output needs. You also have to determine what is in your generator budget. The Honda generators are excellent, but for the most part they are mid size units that are ridiculously expensive. I bought the contractor grade (XG series made in America) Generac unit which is a larger unit and is much more reasonably priced. The only downside to the unit that I purchased is that is was not as quiet as the Honda, but then again its output was double, so I would expect that a larger, more powerful motor would make a bit more noise. In my case this generator won't be used much since we do not loose power often, and my home is on an acre of land so the noise factor was not a major concern.
I store the unit in my garage and "exercise" it twice a month. I have already turned off the street power to my home and tested the performance of my generator; I am happy to report it does everything I wanted it to and runs at a very acceptable power level becasue I did do the research before buying to determine the proper size unit. In my neck of the wood we don't loose power often, but when we do it is usually for an extended period of time. I'm now prepared!
Hope that helps a little.
Chief38
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I have an 8,000 watt and it runs everything in my house but the electric stove and the central air.
If I take the travel trailer to a NASCAR track, it will run mine and those of others around me. I have had as many as four trailers running off the one genset and all of us pulling at least one air unit.
Drawback is: Need to run the genset at least once every four months to cycle the unit and keep it operating properly. It takes about a half hour pulling at lest 3/4 of the wattage limit. I hook up a freezer, refrigerator, and several other large current draws.
If I take the travel trailer to a NASCAR track, it will run mine and those of others around me. I have had as many as four trailers running off the one genset and all of us pulling at least one air unit.
Drawback is: Need to run the genset at least once every four months to cycle the unit and keep it operating properly. It takes about a half hour pulling at lest 3/4 of the wattage limit. I hook up a freezer, refrigerator, and several other large current draws.
snowman
Member
Sir,
I'm not an expert either, but I went through the process of buying and setting one up some years ago and had to educate myself in order to know what size to get. You've had some good advice here, but I don't believe anyone mentioned the difference between starting watts and running watts. Electric motors of any size typically require far more electricity to start than they do to keep running. I suspect that this is the reason you couldn't get your compressor going on a 4500 watt unit. The information I consulted(a lot -from a number of sources) indicated that motors may require anywhere from 3-5 times the wattage to start as they do to continue running. Buying a generator of sufficient size will mean taking this phenomenon into consideration. The general rule with generators, I learned, is the same as with air compressors: it's easy to go too small.
Hope this is somewhat helpful.
Andy
ChuckS1
US Veteran
If I was really serious about a backup whole-house generator, the smallest I'd go is 30KW that runs off propane or natural gas.
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ChuckS1:
A 30 KW generator will provide 250 amps at 120 volts.......that's enough to run a few homes! Most of us with relatively new homes only have a 200 amp main breaker, and of those 200 amps probably less than half ever gets used at one time.
I did look into the Natural gas 17KW and 20KW generators and even though they were pricey, the reason I wound up getting a portable unit was not all about the purchase price, but about the fact that my Town taxes us on these type of units at about $200 bucks a year! They view them as permanent just as they do a central A/C unit. Since I will probably use this thing about once every 10 years or so, I did not feel it was worth the original purchase price PLUS the yearly taxes. If I lived in an area that lost power more frequently, the Natural Gas would have been the way to go.
Chief38
A 30 KW generator will provide 250 amps at 120 volts.......that's enough to run a few homes! Most of us with relatively new homes only have a 200 amp main breaker, and of those 200 amps probably less than half ever gets used at one time.
I did look into the Natural gas 17KW and 20KW generators and even though they were pricey, the reason I wound up getting a portable unit was not all about the purchase price, but about the fact that my Town taxes us on these type of units at about $200 bucks a year! They view them as permanent just as they do a central A/C unit. Since I will probably use this thing about once every 10 years or so, I did not feel it was worth the original purchase price PLUS the yearly taxes. If I lived in an area that lost power more frequently, the Natural Gas would have been the way to go.
Chief38
I second ChuckS1, the propane and natural gas are the way to go for a whole house. I believe the prices have come down and would go with a propane emergency generator.
OP
Marshall 357
Member
wow thats alot of info thanks everyone
Peter M. Eick
SWCA Member
More advice.
Get a good quality one if you are going to run electronics on it. Some are very "forgiving" on the voltage and frequency and can fry hardware. We found that out during Hurricane ike.
2nd, get a big enough one. Our Honda 2000watt handled the fridge, lights, tv and battery charging but not much else. I now added a single room AC to the mix and will buy a 2nd 2000 watt mate-able honda so I can run everything at once with power to spare.
Trust me, 10 days on a generator is a long run and it was hard on the family to scrimp on power all day. More would have been better but fortunately it was not hot. If it were hot, it would have been miserable and we would have bailed on the homestead.
Get a good quality one if you are going to run electronics on it. Some are very "forgiving" on the voltage and frequency and can fry hardware. We found that out during Hurricane ike.
2nd, get a big enough one. Our Honda 2000watt handled the fridge, lights, tv and battery charging but not much else. I now added a single room AC to the mix and will buy a 2nd 2000 watt mate-able honda so I can run everything at once with power to spare.
Trust me, 10 days on a generator is a long run and it was hard on the family to scrimp on power all day. More would have been better but fortunately it was not hot. If it were hot, it would have been miserable and we would have bailed on the homestead.
cussedemgun
Member
standby power source
Re: generator sizing
A few points have not been touched yet.
1) for a whole house setup, be REALLLY, REALLLY sure you have it wired thru a proper disconect switch so there is NO possibility of energizing the incoming line. If your generator feeds back thru the utility wires & energizes a transformer, it can produce high voltage on the utility company's transmition lines & cause serious safety & liability problems.
For this reason alone, instalation is best done by a licensed & bonded electrical contractor.
2) Your air compressor is a motor running a compressor, connected by a belt & pulley system. By changing the pully sizes, it is possible to reduce the torque required to start thus making due with a smaller power supply.
3) Rental companies are your friend. When you are ready to buy, rent the same size unit for a test drive.
4) Wire size & length of run will affect power delivered & is a serious consideration, especially when figuring peak power will be needed.
Sorry if I am just compounding an already LARGE question.
Good luck, Jim
Re: generator sizing
A few points have not been touched yet.
1) for a whole house setup, be REALLLY, REALLLY sure you have it wired thru a proper disconect switch so there is NO possibility of energizing the incoming line. If your generator feeds back thru the utility wires & energizes a transformer, it can produce high voltage on the utility company's transmition lines & cause serious safety & liability problems.
For this reason alone, instalation is best done by a licensed & bonded electrical contractor.
2) Your air compressor is a motor running a compressor, connected by a belt & pulley system. By changing the pully sizes, it is possible to reduce the torque required to start thus making due with a smaller power supply.
3) Rental companies are your friend. When you are ready to buy, rent the same size unit for a test drive.
4) Wire size & length of run will affect power delivered & is a serious consideration, especially when figuring peak power will be needed.
Sorry if I am just compounding an already LARGE question.
Good luck, Jim
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