Air Compressor power question

[boslab]

Please excuse me I haven’t read all the replies my iPad seems to be acting up.
It sounds like the unloader valve isn’t doing the job and the motor has to fight the partially full cylinder of air, you can hear that, you want that compressor up to speed before it gets to do any squeezing air, I’d check it
I fitted a bigger unloader pressure switch to my cheap air pumper, it really made a difference, the one on it was a tiny tube.
I’ve done a manual unload with a 1/2” ball valve inserted in a tee between the head and non return valve ( cheap ones usually leak air between the receiver and the cylinder)
Mark

 

[Jaxian]

When I first started my shop I had a single phase 7.5hp IR reciprocating compressor. Every time it started my lights would dim and my CNC's would error.

This was with 200 amp service and #2 wire. I was stumped.

One of the big issues and people here have alluded to it was that I had a 10kva transformer on the pole out front connected to my shop with #2 wires.

Power company replaced that with a 50kva transformer and 4/0 wires and I never had power drop issues again. Might need to look upstream of your place.

 

[BT Fabrication]

We have a 1200A 208V 3 phase service at our shop. What they don't say is that if you draw 1200A the voltage will drop to 183 volts.

In some areas they'll refuse to upgrade your service capacity, not because of the capacity of the wires, but because the resistance is so high you won't have enough voltage left.

yep, even a 400A service is only rated at 340A continuous i believe

 

[Almost Retired]

Lotsa people tend to mess that up. He probably means 10/3.

you cant buy 10-2 and no ground romex nowadays
when electricians say 10-2 they actually mean 10-2G so 2 insulated conductors + bare ground
10-3 would be 3 insulated conductors + G so four conductors all together
not necessary for single phase whether 120 or 240 unless you also require a neutral on a 240V cct

 

[Almost Retired]

We have a 1200A 208V 3 phase service at our shop. What they don't say is that if you draw 1200A the voltage will drop to 183 volts.

In some areas they'll refuse to upgrade your service capacity, not because of the capacity of the wires, but because the resistance is so high you won't have enough voltage left.

im not sure what you are trying to say but
if you are talking about utilities ability to supply more than you are already using
then yes. if the supply to that area is already maxed out, then they would have to run a second line from a second substation, possibly from a second transmission line that would all need to be built

bigger wire means LESS resistance, LESS voltage drop, more amps available for use
their refusal to increase the size of your service drop is because
A) it will cost them time and money
B) nothing electrical is rated for 100% load, 100% of the time
the limit is 80% continuous load and a few percent below that is recommended

even if they supply the shop with a bigger service drop (and they actually have the available capacity to do it)
your service and things downstream will begin to burn out

if there had been a proper load study done for that shop before it was built
it very likely would have a much larger service and you would not have issues

on the other hand if there have been several large loads added to the shop since it was built, it is the owner's fault for not paying for a service upgrade at that time

 

[Almost Retired]

The line from mains panel (@house) to shop sub panel was just installed 4 years ago (I hired electrician), and is buried in conduit, with no splices. There has been no digging or disturbance of that area.

Will check/tighten connections at sub panel.
Will check house lights for dimming at compressor startup - however no indication of that up to this point.

the question is what size wire did he use to your shop and how far is it from the main panel?
an easy check is go to the main panel and see if the breaker for the shop is at least 100A
if the shop breaker is smaller than 100A then so is the wire, not good

next is the distance to the shop, more than a hundred feet? calls for a bigger wire than normal for the breaker size

 

[Bill D]

Would a load reactor, just for the ac load, help.
AKA line reactor.
Bill D