Cedarberg 50A RPC troubleshooting

[M.B. Naegle]

So full story, we bought a new Cedarberg model 50A 5HP RPC for a job 8-10 years ago. It didn't work and I can't remember if we got any help from the OEM or if we were in enough of a rush that we just put it aside to fix later and we bought another 5HP RPC to get the job going. We've worked with a lot of Phase-a-matics and have had very few problems. This was our only Cederberg and I think we got it because Phase-a-matic was out of stock at the time, or it was on sale, I don't remember,
But
I'm now in the position of having a new-old Cedarburg that isn't working and am trying to close up that loose end. The problem it's having is that when put to power, it briefly turns very slowly and grumbly before tripping a 30amp breaker. Kinda like a 3 phase motor single-phasing. We've triple checked our incoming connections, voltage, etc. and still no go. I've sent Cedarburg and email and left a message on the phone and haven't heard back from them. So for one I'm curious if others have had good experiences with them in the service/support department? Anyone have any advise on how to fix it? I don't even care if it's under warranty, and I'm leaning towards the possibility that our employee that initially wired it did something wrong, but in any case I'd like to try to fix this thing before we just eat the cost of the converter.... 10 years later....

 

[dalmatiangirl61]

My 20hp - 50A phase a matic is on a 120A breaker, it used to be on a 70A breaker. I'm wondering if 30A is enough for that unit, no experience with Cederburg, or why their 5hp unit is rated for 50A.

 

[JST]

First question is whether the start circuit is working at all. Odds are that it is not.

For starting, a capacitor is connected between the generated leg and one of the incoming lines. It is disconnected (usually) when up to speed.

So, there is a contactor for that capacitor, and if it does not close during turn-on, the converter will try to start on the balance capacitors (if any), which generally will not work well. I'd start by checking for that.

It needs to open again once started, so make sure that happens as well.

If that is working but still no joy, then the start capacitor may be bad or not connected right.

Oh, yeah... one other thing.... If there is a question about connections, make sure the input is what is connected to power (and not the output).

Also make sure that there is a contactor which disconnects the output during start-up. Most will not start if loaded during start-up.

 

[M.B. Naegle]

My 20hp - 50A phase a matic is on a 120A breaker, it used to be on a 70A breaker. I'm wondering if 30A is enough for that unit, no experience with Cederburg, or why their 5hp unit is rated for 50A.

Sorry, the '50A' is the model, not the amperage. It's a 5hp unit, so hopefully more amps isn't what it needs, cause that alone would disqualify it from most applications we'd use it for. We sell RPC's with some of the machines we carry if the customer is working out of a garage or out in the sticks, and 90% of the time it's used with that single machine so we wire it with a motor starting switch and twist plugs so all they have to do is connect the 220 1 phase side of a power cord and go to work. Most of them don't need any more than 30 amps total for the machine and the converter. We've had issues with voltage variances causing problems in the machines before, but even then the RPC's do their job.

I've never had to dig into the innards of these things until recently so I'm learning. Cedarbergs control box is rivetted together (except for the part that you make connections at of course) so I was hoping to hear from Cedarberg before "breaking the seal" on the box, but I'm going to open it up and see if anything stands out.

 

[dalmatiangirl61]

Sorry, the '50A' is the model, not the amperage. It's a 5hp unit, so hopefully more amps isn't what it needs

That makes much more sense, my brain saw 50A and went straight to amps

 

[JST]

That makes much more sense, my brain saw 50A and went straight to amps

Me too, but I didn't believe it.

 

[jim rozen]

From the symptoms, also suggest problems with

Start capacitor(s) - open, missing defective, incorrect connection
Starting contactor - not closing or coil open
Missing connection to manufactured leg for start circuit.

 

[rons]

Start capacitor(s) or connection circuit. Same thing has happened to me when trouble-shooting.

 

[M.B. Naegle]

Cedarburg got back to me and were very helpful. The guy I spoke with said they discontinued this model, but that the start capactitor should be the issue. They had one on the shelf, so now we wait...

 

[SomeoneSomewhere]

I'd measure the start cap before throwing parts at it. Any other start cap of comparable uF and voltage should also do the trick.

 

[M.B. Naegle]

Just to follow up: I bought a new start capacitor from Cedarburg, but it didn't solve the problem. This unit doesn't have a contactor, but uses a solid state relay that I'll try to source a replacement for.

I'm wondering if it's just miss-wired internally, but there's no schematic to verify that. Unless the solid state relay is the issue, I'm thinking this RPC would be better used as an Idle motor for a DIY RPC project.