Combining two compressors for more capacity

[Toolhorder]

How does this work?
I have an IR 2 phase 80 gallon 5HP compressor that runs everything in my shop now but it runs constantly with my tire machine going or heavy die grinder use. I got a used 60 gallon compressor in trade from a friend and it’s older US made compressor. I’d like to run them so I can get more capacity if that’s possible.

 

[Tynee]

I’d suggest a check valve on the outlet of each, upstream of your volume bottle.

 

[bob15]

You could disconnect the 60 gallon compressor and use just the tank with the 80 tank and compressor. Or dedicate one compressor to one piece of equipment.

Not sure how much air a tire machine really uses, unless you are using it for 50 minutes out of every hour.....We had one on the farm and it didn't use that much air.

My old IR compressor will kick on, fill the tank and then shut off with me using the die grind the whole time. What model model compressor (besides T-30 which means nothing for cfm output)?

 

[phoenix5x]

Basically just tie the 2 tanks together. Outlet of one tank to the inlet of the other tank. The compressor Will run longer, but your capacity will increase So it should be fewer cycles. Question though, Did you add to the shop so the single tank wont keep up any more? Or might there be a problem with the compressor losing some throughput? Maybe valves need looked at or a leak somewhere? Because if you add the extra tank you may be faced with the same situation where the single compressor cant fill 140 gal while using it.


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[Hankoh]

I have used two compressors piped together for exactly what you need (more CFM for sandblasting in my case). I just used a "tee" to connect the output hoses from each of the two compressors, and the third side of the tee to the blaster. Just turn on both compressors and that is it. My two compressors were set similarly (on/off points on the switches controlling the compressors). It worked fine for me. The compressors would turn on and off at slightly different times (the pressure switches are not at exactly the same point - mine are not finely accurate) but that doesn't matter.

 

[Mr_B]

Just use motor & pump off donated unit and plump it to 80gal tank and wire it with time delay so kicks in after first one up to speed or fiddle pressure switch so staggered.
Can work really well .
As others suggest check current compressor health before committing to anything ...

 

[OccupantRJ]

I have used 3 compressors before to blast with. The usual compressor, then 2 others that had a valve along with a male end on the outputs to plug into the nearest quick disconnects of the air piping. The piping does not care where the air is coming from, and different pressure settings staggers the electrical loads of starting. I have an outdoor port to attach my 110 cfm portable compressor to if I need some real air in the shop to run both blast cabinets at once, or everything I have, for that matter.

 

[dscheidt]

You can just pipe them together, and adjust the low limit of one so it's higher than the other. than the first compressor will come on, and if pressure keeps falling, the second will start. That assumes they're both the same pressure rating. if they're not, its more complicated.

Shop I used to run had three compressors. They were a 7.5 HP, 5 HP, and 5 HP. We had a car wash with a bunch of air motors, it would take the whole output of the 7.5 HP machine to run. They were all ganged into the same piping that served the shop, with valves to disconnect any or all for service, and drip leg for water to not drain back to a tank. the system was set up with one of the 5HP machines set up so it came on when the system pressure fell to ~170 psi. The 7.5 machine came on when the pressure fell a bit further, and the last machine at 150 PSI. They all shut off at about the same time, at 175 psi. At some point, one of the machines broke, and the compressor shop installed a controller that alternated which of the 5hp machines was lead, which was lag.

 

[sberry]

The breaker is off to the blue 5, my main is a 3. Tanks all connected but I wire wheeled for 20 minutes the other day, 4 alum wheel beads before the pressure sagged and was done by then. I flip the big one on for blasting and can connect another one from my truck if I needed to.

 

[Citation]

Maybe I missed it but a few important questions.

1. What pressures are the two compressors rated to run at? Are they basically the same or much different?

2. Several posters gave answer that confused me, OP, are you interested in increasing tank capacity (reserves), pump flow or both?

So #1 would worry me since 60 gallon compressors typically are single stage and thus likely to cut out at 140-150 psi. I think the OP said his current compressor was a 2 stage and thus likely to run 150-175 psi. The higher end of that range probably exceeds the limit of the 60 gallon blow off valve. This isn't an insurmountable problem as you can adjust the 80 gallon pressure switch to cut in/out at a lower pressure. However, you will lose some effective tank capacity when you do that.

I'm assuming the OP wants to combine the tanks and outputs of both compressors. Assuming the pressure ranges overlap nicely that's as easy as adding a T fitting to the air line and feeding both tanks into the system (or one tank into the other tank). I'm going to guess the 60 gallon compressor doesn't have as good a pump as the IR. So in that case I would set the pressure switches so the IR cuts in first (for example, IR cuts in at 130 psi, 60 gallon at 125 psi). I would also want the IR to be the last one to cut out (say 150 while the other cuts out at 145). Since I don't know the pressure ranges of these compressors I'm just throwing these out as examples.

The logic here is I want the IR pump to do most of the work since it's likely rated for heavier duty. Under light load the system gets drained to 130 psi and the IR kicks in and refills both tanks (and takes about twice as long as it does right now). Of course since you have two tanks it takes about twice as long between refreshes. However, if the load is heavy and the IR pump can't keep up then pressure will continue to drop. So once it's at 125 psi the second pump kicks in. Now pressure builds until 145 when the 60 gallon pump turns off. The IR runs until pressure gets to 150.

I used 5 psi as an example. All that's important is that the IR is always the first on and last off because I'm assuming the 60 gallon pump would wear out too quickly if it were the one to always run when loads weren't so heavy. While the nicer pumps typically on 80 gallon compressors are rated for 100% duty cycle, many of the pumps on 60 gallon compressors are lighter duty and only rated for 50-75 duty.

So yes, I think it can be done but it may require dropping your system pressure and playing with the cut in/out pressures of both compressors.

 

[md21722]

Citation raised some good questions. 60 gallon tank compressors are often single stage and the tanks are NOT rated for 200 PSI which is what dual stage compressors tanks are typically rated for. Be safe! Check the tank data plate! Use a check flow valve to ensure the 60 gallon tank is not over pressured.. OR change the pressure switch on the dual stage to cut out around 150! Otherwise there is no issue with simply T'ing the compressors together. I have a dual compressor setup in my shop. You can really control the moisture/water if you have a 3rd tank that the running compressors T into. The 3rd tank acts as a big expansion tank that drops a ton of water.

 

[redmondjp]

Good discussion but please be aware of the duty cycle of the compressors being used - the 60-gallon one is probably consumer-grade and has a fairly low duty cycle. It's not going to be a happy camper if it is in continuous operation for more than 10-15 minutes. You can up the duty cycle somewhat by adding forced-air cooling to the motor and pump (I like a $15 Walmart box fan but there are lots of options).

Also, most compressors are only rated for so many start/stop cycles per hour. This is because the very high current draw inside the motor during startup really heats up the windings, and it takes several minutes of the motor running to dissipate this heat out of the motor. Too many starts tilts this equation the wrong way and the motor will overheat (leading to insulation damage and premature motor failure).

Both of the above issues are often overlooked, but are very important when considering what to buy and how many hours something will last.

 

[Mr_B]

no point in using extra tank.
80 gallon more than enough, just use other motor/pump as a helper for the existing tank.

 

[LXCam]

I'd tee them together with check valves but I would highly suggest you get a alternating relay and wire it in to the starters. This will allow each compressor to get a little rest every other cycle. You can also wire them to combine if needed, but I wouldn't suggest it.

Here's one that would allow you several options if needed.

http://www.eaton.com/Eaton/Products...laysTimers/AlternatingRelays/index.htm#tabs-1

 

[bob15]

Citation raised some good questions. 60 gallon tank compressors are often single stage and the tanks are NOT rated for 200 PSI which is what dual stage compressors tanks are typically rated for. Be safe! Check the tank data plate! Use a check flow valve to ensure the 60 gallon tank is not over pressured.. OR change the pressure switch on the dual stage to cut out around 150! Otherwise there is no issue with simply T'ing the compressors together. I have a dual compressor setup in my shop. You can really control the moisture/water if you have a 3rd tank that the running compressors T into. The 3rd tank acts as a big expansion tank that drops a ton of water.

I've never seen a 60 gallon tank that wasn't safe at 200 psi (because some places/companies will put the larger 2 stage compressors on those smaller tanks); meaning you can use them with a compressor that has a 175 psi cut-off switch.

I do agree that the OP should check the nameplate

 

[jgromada]

Does this really need to be another compressor? I have an old 8 Gallon compressor and was thinking of adding this 11 Gallon tank to give more capacity for some small painting jobs. https://www.harborfreight.com/11-gallon-portable-air-tank-65595.html

The motor was upgraded to a 2 hp since it was originally owned by a contractor who ran multiple framing nailers off of it.

 

[Mr_B]

^
second motor and pump far more benefit than tank size when already dealing with a decent tank size .