Hydrovane 502 "wavering" at startup [video link]

[miks]

Hi all. I've got an older Hydrovane 502 compressor. This compressor worked flawlessly with my Haas Super Mini Mill for several years after I got it used. Then for various reason I had to put it in storage for a couple years. I recently dusted it off and wanted to get it back in service. I did a full filter and oil change on it. For some reason though it's having intermittent startup issues. I made a video of the issue: link here: https://tinyurl.com/nhfamdyt.

Sometimes the compressor will fire up fine. Other times it will hesitate and then hit full speed (this is shown in first startup in the video). And other times it will just "waver" and never hit full speed (shown in second and third startups in video). Note that I wait a little while between startups because I'd read somewhere it was bad for the caps to power-up in rapid succession. Again, the startup is erratic - doesn't seems to matter if there is already air in the air end or not.

A local tech thought it might be a faulty check valve from the air end into the receiver. I replaced that and it's still erratic starting. (And it will do it if I disconnect the air end from the receiver and just blow directly out from the airend, so no check valve involved.)
I also just replaced the start capacitor. Again, erratic - sometimes will fire up fine. Other times will waver.

Any other ideas? Could this possibly be a bad Run capacitor? Thanks for any input. Cheers!

https://tinyurl.com/nhfamdyt

 

[m_c]

That is weird.

If the motor was being overloaded and wasn't getting up to speed, I'd expect it to trip the overcurrent protection fairly quickly.
First thing I'd do, as it's probably the simplest check, is measure the voltage at the motor when it's 'wavering', just to make sure that the motor is getting full voltage.

 

[knighty]

Is it better when its warmed up? Your new oil could be a bit thick

Take cover off electrical box and post a photo?

 

[miks]

That is weird.

If the motor was being overloaded and wasn't getting up to speed, I'd expect it to trip the overcurrent protection fairly quickly.
First thing I'd do, as it's probably the simplest check, is measure the voltage at the motor when it's 'wavering', just to make sure that the motor is getting full voltage.

Hi m_c. Thanks for the input. I checked the voltage this AM. First, I'm getting about 211~212V at the outlet. Also I noted I'm getting 60Hz at the outlet (I'm here in the USA). FWIW, this outlet was run directly from the shop panel by a certified electrician just for this machine so I was assuming the power was fine. We are in a light industrial workspace with tons of power (3Ph available).

The motor plate indicates a voltage of 220-240 and 50Hz - pic below.

I tried to power the compressor up and immediately got the wavering. I checked across the power leads during the wavering and was seeing 201~202.4V (pic). I then tried to get a video of the voltage during wavering and when I did that the compressor fired up fine (very slight hesitation at start up but then ok). I powered down and restarted two more times, both ok. See video below. The voltage at the motor each time it was running fine was ~208V. I wasn't able to get a video of the voltage at wavering, but again when I first checked that was ~202V. As I mentioned, I have already replaced the start capacitor. Is it possible this is a run capacitor issue? And does that 202.4V voltage look like a red flag when it's wavering? Anything else to check? LMK what you think. Cheers!

Voltage during proper operation video
[sorry for all the fumbling in the video - I'm doing this solo, holding leads in one hand, and camera in other]

 

[miks]

Is it better when its warmed up? Your new oil could be a bit thick

Take cover off electrical box and post a photo?

Hi knightly. I'm using the recommended oil for this machine - Hydrovane brand CS300. I did a full regular service when I started having this issue - replaced the oil, air filter, oil filter, and a couple orings in the service kit. The wavering seems to happen at any time - doesn't seem to be related to being warm or not. Pics of box below.

 

[m_c]

Those voltages seem fine. Maybe a bit low, but some drop under load is to be expected.

Did you manage to measure directly on the motor when it's wavering?
If the voltage at the motor is over 200, it means the control circuitry should be fine, as I'm wondering if there's something stopping the motor from getting full voltage.

 

[miks]

Those voltages seem fine. Maybe a bit low, but some drop under load is to be expected.

Did you manage to measure directly on the motor when it's wavering?
If the voltage at the motor is over 200, it means the control circuitry should be fine, as I'm wondering if there's something stopping the motor from getting full voltage.

m_c: Yes, maybe that wasn't clear above: "I tried to power the compressor up and immediately got the wavering. I checked across the power leads during the wavering and was seeing 201~202.4V (pic). " So, the 202.4V shown in the pic above is *during* waver. Does that seem like low enough voltage that could cause that? Just seems so weird that it would run sometimes and waver sometimes.

I've ordered a new run capacitor but have no idea if this issue is being caused by that. Again, I've already replaced with Start capacitor with a new one and still have the issue.

 

[miks]

m_c: Sorry, probably should have said "across the motor leads" not "across the power leads". Pic below shows where I'm checking at the motor.
To recap, voltage across the motor leads:
During waver: 201~202.4 (pic above, post #4)
When running ok: ~208 (video above, post #4)

 

[miks]

I post this issue also to Practical Machinist. Just got a post from someone there saying:

"There's your problem. It's definitely a 50Hz 3000rpm nominal, 2870rpm actual, motor (made in England, so to be expected). The 220-240V matches European and UK single phase voltage. At 60Hz, it'll be happier with 260V-270V*.

But before you start buying buck/boost transformers, check the resistance of the centrifugal switch in the motor, just in case.

*Torque is proportional to current and with an inductive/low power factor load, the current tends to be inversely related to the frequency. So 60Hz needs more voltage to generate the same current and torque than 50Hz"

m_c, knightly, etc - does this sound like it could be the issue? The compressor has never operated properly in this building so maybe that's what's going on. Do either of you know how I can check that centrifugal switch the other poster mentions?

 

[dave h 2]

At 60hz it will want to spin faster and the low volts makes it worse. You need 230v ideally.
The switch is made when the motor is stationary.
It's possible the wavering is the switch bringing in the start coil, then dropping out as the revs go back up. Rinse and repeat.
Maybe someone else has a big load on your feed.

 

[angellonewolf]

im assuming thats a standard socket in the us

would it not be easyer to just take it to a mates house idealy thats been tested to be a higher volts than you got ?

 

[knighty]

watching the video again on PC (was on phone before)

I'm surprised it's not blowing/tripping a fuse running like that

If I were you I'd hang on doing anything else until the start capacitor is replaced, you don't want to change too many things all at once

if it is a low voltage / high frequency issue... you could always swap the motor for a local one

 

[m_c]

The combination of low voltage/UK spec motor might be the problem.
I'm kind off surprised that something sold in the US didn't have a US spec motor fitted.

If you're not sure about motor specs, the key bit you need from the motor specs is the 90L frame size, 2 pole motor, and around 3HP.
You'll then need to figure out which face mount is needed, along with shaft diameter, and then you might have to do a bit hunting, as aren't the US still mostly on NEMA motor sizing, not IEC?

 

[miks]

watching the video again on PC (was on phone before)

I'm surprised it's not blowing/tripping a fuse running like that

If I were you I'd hang on doing anything else until the start capacitor is replaced, you don't want to change too many things all at once

if it is a low voltage / high frequency issue... you could always swap the motor for a local one

Yes, I've already replaced the Start capacitor and it didn't improve. I just received a new Run capacitor today and will install that tomorrow to see if that helps at all.

I could do a motor swap but that would be some work to fit the coupler, mounting, rewiring, etc. Anyway if I have to do that I guess I can.

 

[miks]

The combination of low voltage/UK spec motor might be the problem.
I'm kind off surprised that something sold in the US didn't have a US spec motor fitted.

If you're not sure about motor specs, the key bit you need from the motor specs is the 90L frame size, 2 pole motor, and around 3HP.
You'll then need to figure out which face mount is needed, along with shaft diameter, and then you might have to do a bit hunting, as aren't the US still mostly on NEMA motor sizing, not IEC?

I don't know the history of the machine so not sure how it got here. I got it from a car shop that had been using it, and then I used it for several years without issue (in a different state and building).
Noted on the motor specs. I'm hoping to not have to swap the motor entirely. Again, it was running fine in my old building. It seems more and more like the low voltage could be the issue. I may speak to the electrician about a boost/buck transformer or if there's any way to get 230V at the outlet rather than ~210V.

 

[knighty]

What does the pressure guage on the end of the compressor do while its wavering ?

Can't really remember the internals in detail from when I rebuilt mine... I'm half wondering if pressure is building inside the rotor housing?

 

[miks]

What does the pressure guage on the end of the compressor do while its wavering ?

Can't really remember the internals in detail from when I rebuilt mine... I'm half wondering if pressure is building inside the rotor housing?

I installed a new run capacitor tonight. It fired up fine. Then tried again a minute later and it wavered and lagged. I just went to make a quick video of the air end gauge to see what it was doing under waver and now it fired up fine like 7 times in a row. Heck if I know what's going on. I did check the voltage at the motor when it was running fine and I'm seeing about 211V. And I did check the voltage at the motor when it was wavering at that was like 201~202V. So, dunno. I'm going to speak to the electrician about a buck/boost transformer to get the voltage up to 230V or more. The consensus seems to be that voltage might be low for this Euro motor (it's got 220-240V, 50Hz on the motor plate, and I've got ~208-214V and 60Hz at the outlet).

 

[knighty]

have you had it running much? maybe give it a good run

there's a pressure control valve in the head of the compressor - right where the air comes out of the compressor / next to the pressure valve on the compressor itself, so you could leave a tap open on the air tank itself and leave the compressor running for half an hour and you won;t do any harm

(compressor itself needs air pressure for the oil return to work, which is why it has that valve / it's own pressure gauge)

 

[miks]

have you had it running much? maybe give it a good run

there's a pressure control valve in the head of the compressor - right where the air comes out of the compressor / next to the pressure valve on the compressor itself, so you could leave a tap open on the air tank itself and leave the compressor running for half an hour and you won;t do any harm

(compressor itself needs air pressure for the oil return to work, which is why it has that valve / it's own pressure gauge)

Just ran the compressor for 30 minutes without issue, just venting straight out of the airend. It did get quite warm but I gather these are designed to run long and hard. It fired up fine, too, no hesitation or wavering. I tend to think more and more it's a source voltage issue. I'm going to meet with the building electrician to see if I can get a boost transformer installed to get the line voltage to at least 230V, which is more in the design spec of this motor.