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BadDog wrote: ↑Tue Sep 24, 2019 5:57 pm
It's actually got me pondering that again. But I'll have to go 3PH if I use the Baldor I have, or find a 1PH 7.5 HP motor, and I'm again not sure I care enough to go forward. It's really not inconvenienced me enough to be worth the effort.
Did you ever confirm whether you have the E50 or E57 pump? Or have to wait till you get it in-house?
My pump is an E50. I found an old Curtis brochure. They list the E57 as standard for 5- and 7.5-HP compressors, but not the E50. Maybe it doesn't like to be hot-rodded.
The idea of running compressors in series never occurred to me. I had heard of running them in parallel. I would end up sacrificing a lot of floor area, not to mention electricity. Instead of using 24 amps, I'd be around 50. That's too much, when a 7.5-HP compressor would suck maybe 35.
The idea of putting it in a shed is appealing. The compressor is not loud when running, but when it starts, it sounds like a shotgun going off.
That's unfortunate. From the various references I've been using to refresh my memory, it looks like the E50 is pretty much at it's limit in the incarnation you have, so not much (if any) room to go up. One of the things I remember from my much earlier call to Curtis was the importance of not pushing pumps out of their efficiency ranges. Excessive heat, shortened life, and rapidly diminishing returns were all mentioned.
On dual systems, I think the idea is that by selecting the limits correctly, you run almost all the time off of one, and the other comes into play only rarely when you are really needing serious sustained CFM and it makes up the difference. Done properly with suitable capacities (mainly such that the daily use unit works within its most efficient range), I would think that should be far more efficient than a single heavy hitter almost never used to capacity. In fact, they market "duplex" systems on a common big tank for just that purpose.
Agreed on the noise. Mine is quiet enough running that you can carry on a very reasonable conversation in the bay right next to it. But like you say, when it starts in an otherwise quiet shop while concentrating on something, it can be quite a shock. I've got enough distribution lines all around that it seems impossible to keep it all air tight all the time, so if I forget to close the main ball valve on the tank, it won't start for a day or so (depending on how depleted I left it), but then it is completely unpredictable and unexpected when it comes on.
No one has mentioned heat...
heat is the enemy and the limiter of compressors.
Heat is released as the air is compressed [and absorbed when it expands again at your tool]. the compressor head gets hotter the faster you force it to work, which results in hotter output air.
As it cools, it condenses in the tank or cooler, and loses some of the pressure you just paid for.
So a bigger [more cooling area] pump turning slower will be more efficient, and as you approach it's upper limit efficiency will drop.
But consider this; your 5HP compressor is having trouble keeping up with your DA sander; how much HP do you think your sander has?
Air tools are fantastically wasteful.
I've been using an electric DA sander for 20 years; I killed a blue Bosch one after a zillion hours and bought a festool. These are really expensive tools, and I'm not a guy who shells out cash without a fight. I think the sander is the most expensive handheld tool I own.
It works great and doesn't need a 7HP compressor to make it go. I've done a lot of sanding, whole ship exteriors [loose paint on steel] , and interiors [plywood walls], cabinetry, and car repainting.
I have an electric buffer too; a cheapo, it's big and heavy compared to an air powered one. But I don't use it often.
Back in the late 70's I worked in a garage and one of my jobs was figuring out why the new 5hp compressor kept cutting out.
My late friend and machinist Robert Mann told me; motors only care about current. Measure the current and change the pulley so it's within it's rating.
It turned out the compressor was 220v and the shop had 208 supply. A slightly smaller pulley solved the problem.
You can do the same the other way if you decide to upgrade your 5 hp with a 7 hp motor; do your calculations on pulley size, then check your motor current draw as it's working and approaches top pressure.
Adding a bigger cooling fan will help a lot, and make sure it has enough airflow [not in a small enclosed space].
I have a 1hp compressor with a 1 hour timer. PEX tube runs all over, and there are buttons in each of my workspaces that start the timer. I can unplug the compressor and it's semi-portable. The small tank fills up fast.
It's big enough for painting, impact wrench, nail/staple gun, and blowing dust from things.
The timer is great for an airhead like me, I forget to turn things off.
Hi Steve,
I think that overall you would use less electricity as you would not be using a 7.5 HP motor on one single compressor all the time. You could even get a smaller compressor to have air for your regular jobs and use the bigger one you have now to only boost output when you need larger volumes for a longer duration. It would cycle automatically if you set the starter relay to a lower start pressure than your primary compressor. By all means have the tanks connected so you also have a larger initial reservoir of air.
Happy compressing.
Karel
K. Brouwers wrote: ↑Tue Sep 24, 2019 6:49 pm
Hello Steve and friends
May I make a suggestion? If you have the space add another compressor plumbed in series ...
Cheers
Karel
In parallel, not series. In series means that one pumps air through the other when it runs.
Oops,
You are correct I was thinking of the tanks not the compressor head..
That way the two pressure switches sense the same pressure and you can have one pump start and run before the other is required.
Karel
