Do you have any issues icing up in winter with intake outside?
Air compressor in need of a new one, looking for suggested quality brands
- Thread starter SK13
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I agree with Chris. I have never heard if a 7.5hp being anymore unreliable then a 5hp. The only thing I can say is on any 7.5hp compressor they have the same exact pump as a 5hp but are spinning faster to get more CFM and that wares the pump and valves out a lot faster as a result, the only exception to that would be the 7.5hp with a 10hp pump. The pump on the 10hp compressor is larger by a wide margin and the 7.5hp motor turns slower and will spank the CFM output of a standard 5hp pump even if it has a 7.5hp motor on it.
With regard to the 3ph, I have done my homework on that also and you will not (in my area atleast) be able get the power Co to provide any residence 3ph. It will have to be zoned commercial and on it's own service separate from the house. Along with that the electrical rate $$ is totally different (more expensive) then the residential rate. Along with having an electrition wire and install a 3ph- 220v/110v converter again expensive.
There are ways you can convert single phase to 3ph, I have looked into that too but that can get expensive.
I recently moved and had to temp install my Champion in the basement of the house as I didn’t have room in the garage. Can barely hear it upstairs in the living area. I was going to send the intake outside as well, the wife said don’t bother, it’s not loud.
A 7.5 hp single phase 230V motor isn't any less reliable it is an inefficient expensive electrical option to run over the course of 20 years in comparison to 3 phase. It will have two capacitors on top of it--one for starting and running. It may pull 100amps + on starting. So your sub-panel if you have a decent sized welder connected to it may be an issue. Since you are sharing a pole and transformer with two other users--you may be on the hook for damage to "sensitive electrical devices" being damaged with them experiencing a voltage drop with a 7.5 or 10HP single phase motor. I think in 43 years of doing things--I have seen just a couple of 10hp ones. That's more of an issue the farther down the line from an electrical substation--like being far out into the country. That's one reason why your "compressor guy" recommended two 5 hp units.
Chris_Hamilton
Trying to be the best me, I can be
So a 3 phase compressor wired to a VFD is more efficient? Or only a 3 phase that is directly wired? If the answer to my first question is yes then how does a VFD help with efficiency?
metlmunchr
Member
When we built our shop in 89 we put in a 800 amp 208V 3 phase service. Power company set 3 poles, ran about 500 ft of high voltage lines, hung 3 transformers, and ran underground from there to the meter base on the building. All at no charge. But the days of free commercial power hookups are long gone. Today, that same connection would cost us at least $15,000.
In a body shop where the main use of power other than lighting and hand power tools would be an air compressor and fans for a spray booth, it would be real hard to justify putting in 3 phase power due to installation costs. Personally, if I needed more air than a quality 5hp compressor would produce, I'd rather have two 5hp units rather than a single 7.5 or 10 hp rig for use on single phase power as that gives you a backup as opposed to a single unit that can shut the whole shop down if it goes out.
In a body shop where the main use of power other than lighting and hand power tools would be an air compressor and fans for a spray booth, it would be real hard to justify putting in 3 phase power due to installation costs. Personally, if I needed more air than a quality 5hp compressor would produce, I'd rather have two 5hp units rather than a single 7.5 or 10 hp rig for use on single phase power as that gives you a backup as opposed to a single unit that can shut the whole shop down if it goes out.
Probably not. It may allow some users to avoid the unintended consequences I mentioned sharing a transformer with two other users and having a residential hook-up along with a host of other single phase 230V welders, fans, machine equipment etc. with a separate 200 amp panel for that in garage or home shop. A 7.5 hp 230V 2 pole motor should weigh about 200lb+, have its own picking eye on it, and have two decent sized capacitors on its top. should pull about 40 amps 3450-3600rpm and have a high power correction factor. A real one that is going to work for 20 years isn't cheap--and shouldn't be. If you feed it right, it can work well and is about $1000+. I see a lot of single phase ones that resemble a loaf of sourdough bread in size, don't weight a 125lbs and with wimpy capacitors on top and are made to sell not use for very long in a shop with other electrical hungry equipment and folks who want to wire everything............well.........rather thin.
7.5 HP size is somewhat of a designator for the switch to 3 phase. Single phase may work well for you--but my intent was to inform that for some--unintended consequences can lurk in the shadows.
It really depends on your application. A VFD with a 3 phase can allow speed reduction of the motor and you can tune things in better depending if you desire slower pump speed with some other larger displacement pump. since your compression ratio is fixed on a piston cylinder set-up this can benefit your end desire to have a source of compressed air not a water pump. A better solution is more storage capacity in an additional 120 gallon air tank for a first start rather than concerns with cfm pump output.
24" OD, 200 psi 80 gallon receiver tanks 175-200psi are in one word--CHEAP and the most material/labor efficient to make. Small tank manufacturers make the best profit making these and push these to the compressor makers. Light to build, economies of scale, good for most end users. 80 gallons is about 11CF. Pump off at 160-175 psi means you have 10-11 atmospheres in the tank or 800 or so CF relative to the outside.
metlmunchr
Member
The efficiency of a VFD averages about 95%. 3 Phase motors in the 5-10hp range average 91% eff. When you run the 3 phase motor on a VFD, you would multiply motor eff and VFD eff to get overall eff around 86-87%. A 1750 rpm farm duty single phase motor has an efficiency of about the same 87%.
All that said, motor efficiency is nothing to be concerned with in a normal shop. A 10hp 3 phase motor operating on 3 phase power will only be about 7 cents/hour cheaper to operate than a 10 hp single phase farm duty motor (assuming a somewhat normal power rate of 15 cents/kw-hr}. If that makes a difference to a shop, its got problems motor efficiency ain't gonna cure.
A farm duty rated motor is a quality single phase motor made to be somewhat abused. It is not some over rated cheaply made POS like you often find on homeowner rated type compressors. Most any 7.5 or 10 hp 1750 rpm single phase motor will carry a farm duty rating unless its a motor built for some special purpose, and none of them are cheap.
I bought my 7.5 IR around 2005 and it has the big motor with two big capacitors on top and a large pump, but I think IR started building them else where some time after 2005, because they are not the same today--at the same place I bought mine. It cost around $1600 back then, I should have bought 3 of them
Treeslayer
Mike
isn't the hp rating really more about running amps? seems like i used to know this........25 or so amps is 5 hp? i forget the actual number.
i guess im asking, what is the true running amps single phase vs three phase.
i guess im asking, what is the true running amps single phase vs three phase.
1A Rock
Promoted Users
I don't agree with this statement, CFM of the actual compressor is what you have to work with. It dose not matter how big your storage is ,what the compressor puts out is what you have to work with. More storage is just more storage and can't compensate for a slow or small compressor.
crashtech
Combo Man & Mod
Well, it kind of can if your workload is intermittent. Like going around a big paint job but then having a long flash time. I have extra air storage to help smooth out times of high demand. Most air usage is not constant, though there are exceptions.
This thread is interesting as I have learned a lot about compressors is not something I've studied much.
I have the 7.5 80-gallon igerso rand at home 24 years old and replaced belts 3 times but I use the green belts.
We bought two more for the plant 15 to 18 years ago and one needed a regulator about 5 years ago.
We replaced the one with a screw type because it was close to the door and would bother the order line people when running.
Sold the one the screw replaced to a local guy.
Yes, the IRs do make noise but they have treated me well.
I have the 7.5 80-gallon igerso rand at home 24 years old and replaced belts 3 times but I use the green belts.
We bought two more for the plant 15 to 18 years ago and one needed a regulator about 5 years ago.
We replaced the one with a screw type because it was close to the door and would bother the order line people when running.
Sold the one the screw replaced to a local guy.
Yes, the IRs do make noise but they have treated me well.
About 15-20 years ago I worked at a shop that ran on 3 phase power. Light bill then was around 500 a month. We didn't use much it seemed , mostly lights. (And they also had a screw compressor ) kept track of meter readings for couple of months and they showed it should not be that much. One day a man retired from the local electric utility was there to look at his son's car we were painting and we asked him why it was so high compared to what we were using. He said we were being charged for the 3 phase transformer on the pole. Then it made sense.
I bought a 15hp rotory screw for really cheap but it’s 3 phase a roto converter for it cost the same as a new compressor. And 3 phase power and monthly rate is insane. So I went with an e max 10hp piston compressor. Good for 70000 hours pressure lubed pump 1750rpm makes 38 cfm at 100 psi and 34 cfm at 175 psi. Really durable and they have a cooler built in to them. Was looking at other screw compressors a cheaper brand but really was concerned with reliability and long term longevity. I’m going to plum my 120 gallon tank on my screw into the system and should work fine. They are on sale this week at air compressors direct with free shipping.
Here is what happened to my 40amp breaker that powered my compressor when I bought it 18-20yrs ago. It's not so much the running amps as much as the surge amps which can hit 60-70amps on start up. I had to run new service cable and rewire a new sub panel I now have a 100amp panel with enough reserve power to accept what I do in my workshop.
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Treeslayer
Mike
oh wow........if memory serves i have a 50 amp on mine. i checked, its 25.5 amps running. no signs of any thing like that in the panel box as of yet here.
glad you caught that could have went bad real quick
Whitesnake
Newbie
Damn, that could’ve went bad. I’ve seen my fair share of melted breakers. Correct start up is where the major amp draw is. Esp when cold as you stated. And a disconnect at the compressor is always smart. Obviously there’s other things that also play a role such as how far compressor is from panel, gauge wire to compensate for distance, etc but you seem pretty knowledgeable so you know that. You def have a real 5hp not a box store “5hp” to melt 40amp breakers lol. You show sub panel? Is this at another location in your shop off the main shop service? Or a sub panel from a house service to a home shop?