Compressor - candidate for rebuild or pass on it?

[JEEPLESS]

Hello all.

I am looking at a CH manufactured late 90s. SCFM specs are 14.3 @ 135 psi and 16.8 @ 90. It's a 230V single phase, 7.5hp setup, 60 gal cast iron tank and 4 piston compressor. It has been sitting for about 2 years since motor "burned up" - make an offer.

What is the best way to determine condition of the tank? Anyone have a good source for compressor parts. CH seems to still carry some items but not everything.

Would be for home use - impact wrenches, die grinders, DA sanders, etc.

 

[impulse922]

7.5hp, 4 cylinder, and 14.3 cfm dont really make sense

 

[Packard V8]

The tank, less than 20 years old, is probably fine.

If CH stands for Campbell Hausfield, the parts should be available from many sources on the net.

Bottom line, that it has been dead in the water for two years without being repaired is an indication of the cost/benefit involved. Only if you can get it for scrap value and then look at what is inside the compressor and how much parts cost. Also, 7.5hp single phase motors are almost never seen in good used condition. They run til they die and then the equipment sits because a $750 motor is more than a hard-used compressor is worth.

jack vines

 

[kythri]

16.8 CFM is not a 7.5HP motor, more like a 4-5HP motor.

That might make a motor replacement more palatable.

 

[JEEPLESS]

Packard - good points. Thank you for the insight.

kythri - I could see where a 5 hp might have replaced an original 7.5 due to cost. I'll have to look at the motor closely and do some research on it.

Here are some pics.

 

[kythri]

kythri - I could see where a 5 hp might have replaced an original 7.5 due to cost. I'll have to look at the motor closely and do some research on it.

Here are some pics.

Based on the ratings on the tank, it never had a true 7.5HP motor.

Now, I don't profess to be an expert, but I've been doing a bunch of reading on stuff lately.

#1, it seems that compressor manufacturers are constantly exaggerating on the motor specs. You'll see "peak HP" and a bunch of other buzzwords that really mean squat. This seems worse on the 120V stuff, but is still prevalent on the 240V side.

#2, a general rule of thumb is that you get about 4CFM for every true HP, though, there is a bit of a loss.

My new-to-me Campbell Hausfeld 80-gallon has a verified 7.5HP motor on it, and it produces 27.2CFM @ 90PSI. Not quite the 30CFM that the 7.5HP x 4CFM would advertise, but darned close.

16.8CFM @ 90PSI equates to perhaps 5HP (5HP x 4CFM = 20CFM).

That's why I'm saying, don't let the cost of a 7.5HP motor keep you from "saving" this compressor, if everything else looks good, as it never had a real 7.5HP motor on it. Look at the cost of a good 5HP motor instead.

Factor that against the cost of a new compressor. Lowe's is selling an 80-gallon 14.0CFM Campbell Hausfeld job for $800. Is it as good/reliable as what you're looking at with a new/working motor? Dunno, but it's something to keep in mind as you're pricing stuff out.

 

[Major Ramifications]

It appears to be a single stage pump, which is why the max PSI is only 135. This reduces the value significantly.
I wouldn't give much for it unless you had or could source a cheap motor for it (4 or 5 HP, as stated earlier).

 

[Packard V8]

X2 on it being an over-rated HP consumer spec motor. A real 7.5hp industrial compressor-duty motor is darn near twice that large. That is why the little guy burned up trying to pull the load.

Again, a real 7.5hp, which is what it needs is going to be difficult to find used and cost a bunch new.

Tell the seller all the reasons why it is junk, buy it cheap, bring it home, play with it and maybe you'll get lucky and find a good affordable motor.

jack vines

 

[impulse922]

honestly.. get a 2 stage.. i have a single stage 3hp(10.2cfm @90) and you are going to want that extra ceiling if you are going to be using a DA or RO sander..

 

[W-Cummins]

If you notice it doesn't say it's a 7.5hp motor ( because it is NOT) it says it has "7.5hp PERFORMANCE" Also a stretch of the truth!....


William...

 

[supertooljunkie]

Electric motors are rated with a "service factor". For example, a 1 HP motor with a 1.5 SF will rate out at 1.5 HP for peak loads. Most motors only have a SF of 1.0, but I have seen as high as 1.7. The SF should be on the motor plate. Most compressor manufacturers really load the SF on the motors they use now. They will claim a 5 HP motor, but reality is a foreign made 3.5 or 4 with a high SF.
Grainger or MSC should have the info needed to determine the motor HP you need for the unit. Then if affordable, buy the correctly sized motor up front, and have a decent compressor

 

[Skin]

X2 on it being an over-rated HP consumer spec motor. A real 7.5hp industrial compressor-duty motor is darn near twice that large. That is why the little guy burned up trying to pull the load.

Again, a real 7.5hp, which is what it needs is going to be difficult to find used and cost a bunch new.

Tell the seller all the reasons why it is junk, buy it cheap, bring it home, play with it and maybe you'll get lucky and find a good affordable motor.

jack vines

no, if its rated for 16CFM at 90PSI with 4 pistons it was never a 7.5HP. True 7.5HP compressors would be at or over 25CFM at that pressure.

Best way to judge a motor is by its running amps rating. Ignore the HP rating. You'd probably end up spending a couple hundred for a new motor. A bit more if you end up with something that has a substantially different RPM requiring a new pulley. Personally i wouldnt touch that thing unless it was damn near free. Looks like one of CH's crappier pumps. Its not stated often here but CH made a lot of trash back in the day though if you go back far enough you can find some good quality again.

 

[JEEPLESS]

If you notice it doesn't say it's a 7.5hp motor ( because it is NOT) it says it has "7.5hp PERFORMANCE" Also a stretch of the truth!....


William...

I did notice that.

I suppose that if one were to stick a few performance related stickers on it, one could theoretically bump the horspower to 10??