No more gas - going electric - compressor conversion

[Steevo]

Update:
I powered-up my project compressor today, and the motor has no problem at all spinning the pump. It breathes well, has good suction and pressure flow.

It did, however have a faulty check valve, so when pressure started to build in the tank, it breathed back out the unloader breather, which can be seen just above the gauge in the picture below.

So, I decided to remove the old valve assembly and build a new configuration, designed to be used for an electric setup.

I removed everything above the 4-way pipe fitting seen in this picture:

And I designed a new plumbing configuration that will provide a check valve, and an unloader tube for a pressure switch.
I'll post some pics of the modifications tomorrow, and I should have a new check valve for my new configuration on Tuesday, so I hope to finish it then.

 

[Steevo]

Ok, I have replaced this:

With this:

The right side of that 1" tee will have a 3/4" check valve in it, that the pressure line from the pump connects to, and will have a 1/4" unloader line to the pressure switch to bleed off head pressure for startup.

Parts should be here Tuesday, so I can finish putting it together.

 

[trbomax]

I'm glad that motor/ratio setup worked for ya! I would have never figured it that way,but???. Overall nice job.

 

[Steevo]

I finished re-plumbing my compressor today after UPS delivered my check valve from Grainger.

Runs great. Starts and stops as it should, and the new unloader works to exhaust head pressure at shutoff.

So I tightened up the belt, buttoned it up and re-installed the shrouds.

The only issue I have is that the brand new high-pressure relief valve I installed, is leaking very slowly, producing a barely audible hiss when all is quiet.
I tried pulling the relief valve a few times to clear any debris on the valve seat, but it still seeps slowly. I only had it pumped up to 150#, and that is a 200# relief valve, too.

I may stop in and pick up a new one at Grainger tomorrow, since I’ll be in the neighborhood.

Basically, she’s finished, and I just need to hook up the big ¾” line I had made to go between the compressor and my hard-piping system in the shop.

A completed conversion from gas to electric compressor.

I want to thank all of the helpful members here for their feedback, advice, and pictures, and even drawings! It helped a lot.
Thanks specifically to Kamracer1, zeke, trbomax, lomonte and nikonika.

 

[kams1973]

Excellent job on the check valve! Definately replace the relief valve, it should not leak.

 

[930dreamer]

Great job using the clamp in reverse to tension the belt.

 

[Rosco 62]

Thanks Steevo for posting the pictures. It sure helped me with my conversion. Rosco

 

[antjaw25]

I know this thread is long dead, but I am about to start the same conversion. Just wondering if this unit is still holding up. Did you ever go to the dual belt or did the single work out.

Thanks!

 

[theoldwizard1]

The best thread sealant I have ever used is Loctite 567. It does have to set overnight and it dries HARD. If you use it on brass/copper fitting, you WILL have to heat them to get them to come apart !

 

[volaredon]

would be more inclined to do the opposite... why the switch to electric?

 

[antjaw25]

Because I will be using the compressor in my garage as a permanent mount. The one I got was an old gas model with a blown motor (already removed).

 

[Tomjohn]

Done the same conversion this summer. It's holding up well , I have it connected to a 60 gallon tank for a total of 90 gallon capacity .

 

[antjaw25]

TomJohn,
What motor and pulley setup did you use?

 

[Tomjohn]

I used a 5 horsepower marathon 1750 RPM motor and a two grove 8 inch pulley . I drilled and taped the original gas engine mounting plate . I was able to place the motor to allow me to use the original v belt .

 

[antjaw25]

TomJohn.
Can you give some details on the plumbing between the compressor output and the tank. Specifically the electric pressure switch, check valve, pressure relief valves, and the connection from the check valve to the unloader. Also any part numbers and pipe fitting sizes would be very helpful.

I noticed in the original configuration of the unit I have (Gas Model), there are 2 pressure relief valves; one 325 PSI before the check valve (I'm assuming to protect the pump), and one 200 PSI after the check valve (I'm assuming to protect the tank). In Steevo's conversion, he only plumbed in one pressure relief valve valve (200PSI) after the check valve. I'm wondering if that should be a concern.
Thanks!!

 

[Steevo]

antjaw25,
Mine is still going strong. I did switch to a two-row pulley and dual belts before mounting it up on the pallet rack in my shop:

 

[antjaw25]

Steevo, I am having a tough time selecting the correct check valve. Do you know the part number on the one you purchased?

Thanks

 

[antjaw25]

Steevo, I am having a tough time selecting the correct check valve. Do you know the part number on the one you purchased?

Thanks

Ok,
Nevermind. I got her all plumbed up now. Motor mounted. All I have to do now is run to Grainger and pick up a belt and some oil.

Sorry for so many questions; I'm just trying to do this right without spending extra money where it's not needed. Since this unit was given to me and had been sitting unused in storage for 5+ years, I'm still not even certain that the internals of the pump are good and that it will pump air.

I assume I would be able to determine how good the pump is (firstly if it still compresses air) by the amount of time it takes to fill from 0-175psi.

With that being said......

Does anyone know how long it should take to fill a 30 gallon tank from 0 to 175psi using a 2475 pump (spinning 1020 RPM's) driven by a Baldor 5hp electric motor (spinning at 1725 RPM's)?

 

[maxpower_hd]

I cannot see the photos on this computer but I think I have the same compressor. I actually got mine free. I have it on good authority that the head is good but it is missing the gas motor and most of the plumbing. Where were you able to find the specs? I am trying to find out what it looked like when it was new.

I was thinking of making it electric but I don't really need another electric one. So I think I am going to go back to gas and put an off brand Honda on it. But I need to figure out what all else I need to get to get it running again including the pulley size.

I guess my Google skills **** because I couldn't find much except the specs like I was buying one. Not the parts for it. I will try to get pics this weekend.

Thanks.

 

[maxpower_hd]

I am able to see the pics now and I checked the numbers on mine and it is the same compressor. Where were you able to find the manual? Do you have a link?

I inherited mine from a previous vendor that I took over for and would like to put this back in service as a mobile unit for a service trailer eventually.

Thanks for the thread.

 

[antjaw25]

Here ya go.
http://www.ruralking.com/media/blfa...Compressor_7.5hp_80_Gal_2_State_2475N7.5V.PDF

 

[Tomjohn]

The compressor was shipped from the factory with a check valve . I removed the vent for the high idle valve , I then installed a 1/8 compression fitting and connected it to the unloader with a 1/4 copper tube . I will get some better pics tonight .

 

[maxpower_hd]

Here ya go.
http://www.ruralking.com/media/blfa...Compressor_7.5hp_80_Gal_2_State_2475N7.5V.PDF

AWESOME! That should help. Thank you very much.

 

[antjaw25]

Tomjohn,
I would love to see those pics. I have another unit that I am going to convert. I just assumed that I wouldn't be able to use the original valve assembly that is set up for the gas motor models. I would much prefer NOT having to completely re-plumb this one if I can get away with just a pressure switch with unloader, copper tubing and some fittings.

 

[volaredon]

Steevo;

If I had a horizontal tank compressor, I think I'd have it turned around, seems youd have problem getting to the things that you'd most likely have to get at for maintenance with the belt being away from the wall... yes I can see it being easier access to the belts like you have it, but in my experience, being able to get at the popoff valves, pressure switch and oil drain/fill will be more frequent necessities...

 

[oilslick]

Why does everyone run magnetic starters, looks like stevo is getting by without one unless I missed that part. What do they do , or why do I need one. I spent 200 on one for my last 5hp quincy and am building another but wondering if I really need it.

 

[Steevo]

Steevo;

If I had a horizontal tank compressor, I think I'd have it turned around, seems youd have problem getting to the things that you'd most likely have to get at for maintenance with the belt being away from the wall... yes I can see it being easier access to the belts like you have it, but in my experience, being able to get at the popoff valves, pressure switch and oil drain/fill will be more frequent necessities...

volaredon,
I originally installed it that way to get the air outlet on the end by the right wall, where my plumbed air system is configured with the regulator and filter, etc. Looking back, I could have just used a longer flex hose to turn it around the other way. I have been up there to drain and refill the oil and check the contacts on the pressure switch. It isn't bad when you can stand up next to it on the pallet rack decking. Oh, and I have removed the whole belt guard system because it vibrated/buzzed and bothered me.

Why does everyone run magnetic starters, looks like stevo is getting by without one unless I missed that part. What do they do , or why do I need one. I spent 200 on one for my last 5hp quincy and am building another but wondering if I really need it.

oilslick,
I planned to add the mag starter as soon as I was moved in and started to do work in the shop, but that project has been back-burnered many times in favor of other more important or more fun projects. I have inspected the pressure switch contacts (25A rated), and they look better than the points in my old Chevy used to. I may get around to it in 2016, as I really want a on/off switch on the rack near the compressor, so I can stop using the breaker to turn it on and off.

 

[maxpower_hd]

I finally started working on my free compressor. I thought I would post a couple of pics since I was back in here to get the link for the parts again from Antjaw.

This is how I got it and the engine I bought to power it:

 

[maxpower_hd]

One thing now that I am going through the drawings and parts list. It doesn't show the pulley side of the unit or the pulley on the engine side. Does anyone happen to know the engine side pulley diameter for the gasoline version?

Thanks

 

[antjaw25]

Pump side pulley is 13.5. I bought an 8.75 inch pulley for the electric side.
http://www.amazon.com/gp/product/B007YLTNTM/?tag=atomicindus08-20
http://www.amazon.com/gp/product/B007YLTOYG/?tag=atomicindus08-20
I went with the dual groove because that is what the pump side pulley is.
As long as your gas engine is running 1700ish RPM's and has a 1-1/8” shaft this is what you need.

 

[maxpower_hd]

I think the shaft is actually 1" diameter and the maximum rpm is listed at 3600. So maybe just a different bushing. I don't think the engine would ever run at full rpm. Thanks again antjaw for the help.

 

[maxpower_hd]

Well antjaw. you got me thinking and I ended up finding a formula online to determine the pulley size. I guess I need to make sure I know the size of my compressor pulley first. I will have to measure it since it looks like they can be anywhere from 13" up to 18" depending on how it was equipped originally. Mine had a Honda 13HP on it new. I thought it was a 13" pulley but now after looking at so many numbers I need to actually measure it to be sure.

Then I guess I will use the engines max RPM for my RPM number since I really don't know what RPM it will run at nominally. I can guess at about 2000 but it's just a flat out guess assuming it won't ever run at max RPM of 3600.

 

[rwagner59]

Why does everyone run magnetic starters, looks like stevo is getting by without one unless I missed that part. What do they do , or why do I need one. I spent 200 on one for my last 5hp quincy and am building another but wondering if I really need it.

The magnetic starter is there to start motor under load or higher current than a regular pressure switch may be rated. The start current for a 5 HP motor will be in the 125-150 amp range and the pressure switch is likely not rated for more than 30 amps.
It also provides motor protection against overload or under voltage conditions. It does help protect your investment.

 

[Todd.Brock]

If the motor is thermally protected, you could technically get away without a magnetic starter. If thermally protected motor typically will have a reset button on it. I found a 5 hp/25 or 30 amp capable pressure switch with an unloader valve and an on/off/automatic switch for about 25 or 30 bucks on eBay. I think it was sunny brand, or something like that Surplus center also sells the same pressure switch with140 cut in 175 cutout

 

[maxpower_hd]

Well I worked through the pulley debacle and I think I am OK with what I need there thanks to Ant again. I do have a 1" shaft so I will need a different sheave. Let me work through this and see if it all makes sense to you guys or if I am missing something before I go ordering a cart full of stuff.

I found the formula to determine the pulley sizes needed here http://www.eq-repair.com/compressed.htm. The formula I am using to determine the engine side pulley is compressor pulley DIA x compressor RPM/motor RPM. So in my case my max RPM for the compressor is 1600 and my max RPM for the motor is 3600 and the DIA of the compressor pulley is 14". So 14" x 1600 RPM/3600 RPM = 6.222". So a 6 1/4" pulley should do the trick the way I am mathing. I am not a mathemagician so I would appreciate any feedback from those who aren't as mathematically challenged as I.

One last question for you Antjaw if you don't mind. When you converted yours to electric, was there a check valve in the tank where the unloader valve was mounted to prevent air from backing up into the head? Mine doesn't have one, or any of the stuff that is supposed to be there, so I don't know if it needs one or not. I thought maybe the unloader valve set up somehow eliminates the need for one. My thought was just buy one and put it in anyway to be on the safe side.

Thanks guys. This is the most help I have needed so far so I do appreciate this thread and the feedback you have given me thus far. I stumbled on this thread at the right time.