Variable speed and/or under driving a compressor.

[Billy Northrup]

Is anyone using a variable speed drive on their compressor? What are your reasons? 1p to 3ph conversion? Power conservation? Less heat and load on parts? Noise? ?Other?

Or maybe a constant current setup where it can haul when the pressure is low and as it builds higher slows the down as eventually utilizing the lowest recommended speed to maintain oil pressure?

Or maybe a pully change as there is no rush..

thoughts?

Thanks!

 

[tbone1004]

most compressors are splash lubricated and need to be run at high RPM in order to maintain adequate lubrication. If you have one that has an oil pump, you could put a variable speed controller or under-drive it, but you have to make sure it is being properly lubricated.
Bauer has a weird hybrid system on their big ones where the last stages are pumped, but the first ones are splashed, so you can't slow those down.
Rix are able to be slowed down which is good if they are the oil-less.
I only know of a handful of obscure compressors that aren't splash lubricated, and none of them were designed for scuba use....

 

[spoolin01]

Rix, splash? The familiar small ones are oil-less. Like to know if there's any reason not to under-drive those.

 

[tbone1004]

Rix, splash? The familiar small ones are oil-less. Like to know if there's any reason not to under-drive those.

sorry, brain fart, shouldn't have been since I have 2 of them in my garage. Correct, no reason not to under-drive those

 

[2airishuman]

Bauer has a weird hybrid system on their big ones where the last stages are pumped, but the first ones are splashed, so you can't slow those down.

I have it on good authority from someone who has worked on these things all his life that they can be slowed down to a considerable degree with only good side effects (less vibration and longer life). I mentioned splash lubrication in particular and he said it simply wasn't a problem. I was contemplating a purchase of a K15 that had been slowed down to about 60% of rated speed when I asked. I ultimately decided to get a much smaller compressor, mainly for reasons of floor space.

The usual reason for slowing down the operating speed of a compressor is to accommodate the available electric supply or whatever motor is inexpensive or at hand. Single phase motors are readily available up to 10 HP but the 10 HP ones are big, heavy, expensive, require a 50 amp circuit, and don't come up on the used market too often. 7.5 HP and 5 HP are much more manageable and are in fairly widespread use for farms, air compressors, and equipment in home wood and metal shops.

 

[KentB]

I have it on good authority from someone who has worked on these things all his life that they can be slowed down to a considerable degree with only good side effects (less vibration and longer life). I mentioned splash lubrication in particular and he said it simply wasn't a problem. I was contemplating a purchase of a K15 that had been slowed down to about 60% of rated speed when I asked. I ultimately decided to get a much smaller compressor, mainly for reasons of floor space.

The usual reason for slowing down the operating speed of a compressor is to accommodate the available electric supply or whatever motor is inexpensive or at hand. Single phase motors are readily available up to 10 HP but the 10 HP ones are big, heavy, expensive, require a 50 amp circuit, and don't come up on the used market too often. 7.5 HP and 5 HP are much more manageable and are in fairly widespread use for farms, air compressors, and equipment in home wood and metal shops.

Is power a big thing in the US to get big services? here in outskirts of Vancouver the spec homes we do have 200A services and most of the custom homes have 400 or 600A services and all have gas for heating, hot water and gas ranges, the big service is mainly for the bazillion pot lights and AC i cant remember the last house i did that had less than 200A and i do 50-60 a year easy.

 

[tbone1004]

Is power a big thing in the US to get big services? here in outskirts of Vancouver the spec homes we do have 200A services and most of the custom homes have 400 or 600A services and all have gas for heating, hot water and gas ranges, the big service is mainly for the bazillion pot lights and AC i cant remember the last house i did that had less than 200A and i do 50-60 a year easy.

two things.
One is getting high voltage power, 240v is usually only found in the laundry room. Have to pay an electrician to get a new circuit with high voltage and high amperage plug in the garage somewhere.
Second one is that electric motors really really don't like single phase AC power, so if you go to a large size motor like is needed for big compressors, you need three phase. Three phase is preferably gotten from the power company but that is several thousand dollars to get that run, or you can use a rotary phase converter which is $50-$100/hp for what you are going to run.

100a service is "Standard" down here, and 150-200a service is not uncommon for the larger homes.

 

[2airishuman]

Is power a big thing in the US to get big services? here in outskirts of Vancouver the spec homes we do have 200A services and most of the custom homes have 400 or 600A services and all have gas for heating, hot water and gas ranges, the big service is mainly for the bazillion pot lights and AC i cant remember the last house i did that had less than 200A and i do 50-60 a year easy.

As @tbone1004 says, U.S. single family homes are typically wired for 100A, 150A, or 200A single-phase service with unusually large houses (over 3000 square feet) sometimes being wired for more than that. Polyphase service isn't ordinarily available at all in residential locations, and if it is, the construction costs are usually prohibitively high.

But the real problem with running a 7.5 HP or 10 HP compressor isn't the power coming into the house, it's a problem of power being available where the compressor is located -- garage, basement, outbuilding, etc. It varies depending on the property. I've got a 50A 120/240V outlet in my garage and could run anything off that. But in some places there is a lot of distance and finished walls and it's much cheaper to run a smaller motor on an existing circuit.

 

[KentB]

two things.
One is getting high voltage power, 240v is usually only found in the laundry room. Have to pay an electrician to get a new circuit with high voltage and high amperage plug in the garage somewhere.
Second one is that electric motors really really don't like single phase AC power, so if you go to a large size motor like is needed for big compressors, you need three phase. Three phase is preferably gotten from the power company but that is several thousand dollars to get that run, or you can use a rotary phase converter which is $50-$100/hp for what you are going to run.

100a service is "Standard" down here, and 150-200a service is not uncommon for the larger homes.

hmm interesting Im a class A gas fitter so Im licensed to work on absolutely any gas appliance here including boilers that are 7-8 stories tall and Im also responsible for all the electrical on it, not matter the voltage, phase or amperage.
my electrical knowledge is far from black to black white to white ground to ground.
that said I live just outside Vancouver BC where the average spec home is 4500+ sq ft and I do atleast a couple homes a month over 7500 sq ft+ i live about 5 min away from the ruskin dam which is a pretty high producing dam but the rest of BC has huge hydro dams so power is cheap and plentiful.
its code in vancouver for 220 power in garages to charge electric cars most homes have 220 behind dryers, ranges, lots of homes have pools and hot tubs which have 220 power.

also panels typically have room left (atleast here) no need to hire a sparky to add a circuit for anything if your the least bit mech. inclined. turn the service off first if your new to wiring into panels ( id recommend for most people) and sizing wire properly is easy enough to find online.

available power where compressor is located i understand but even then realistically its hard to size it right too.
I just picked up a coltri MCH6 and it needs 220V 20A which unless you have a mini split you wont find in a house. and thats a small compressor. any bigger and you dont want to have to pick between cooking and filling tanks or hot tubs and filling or AC or filling
dryers are 30 amp ranges are 40A. hot tubs are typically 40 big badass ones get to 50-60 AC ranges from 30-50 depending on tonnage so really your looking at electrical work regardless by code every "appliance" needs its own circuit . but a 5-10-15k compressors whats 500-1000 for a breaker and some tec cable buried outside?
but Im only familar here where the housing market is completely stupid. an hour out of vancouver a lot of 7000 sq ft without a house is 600 grand+ $200 sq ft for a house Im gonna be in a townhouse my whole life

 

[BRT]

10hp single phase 230 volt motor will draw 43 amps or so. By code this will require a 54 amp circuit which by default is a 60 amp circuit. It will momentarily pull 4-5 times that 43 amps on startup. The only likely 60 amp circuits in your house are going to your large electric furnace. It doesn't have a receptacle. The motor is going to cost around $900 plus the ride. The starter will have to be a size larger than for 3 phase or a 7.5hp. The #4 tec cable will probably cost $7-8 a foot.