Electric newb - venturing into a 30a HERMS

[Dustin_J]

Hi everyone,

Initial tuning/testing went fairly well, but there were a few challenges. 1 has to do with the MyPin TA4 autotune being wonky, but that should be sorted out thanks to some other posts here which suggest manually setting the P & I values and turning off D.

The slightly more annoying problem is that the GFCI tripped at one point. Just to summarize, the controller is set up for 50amps, with a 50amp GFCI breaker in the main panel, and 5500 and 4500 watt elements in the HTL and boil kettle, respectively. In terms of the process, the HLT element and 1 pump were on for about 30 minutes during some initial testing, temp probe calibration etc, and everything was fine. I then decided to fire up the boil kettle element while also running an autotune cycle on the HLT PID. After about 25 minutes of this (with both elements firing at full power multiple times from what I could tell), the GFCI tripped. There were noticeable signs of shorts anywhere. The breaker itself felt warm, but certainly not hot, to the touch. I reset the breaker and tried to see if things would cause any problems If only the boil element and the 1 pump were running. Doing this for 45 minutes didn't cause any issues. I then shut off the boil element and ran another autotune cycle with only the HLT element active - no problems there.

All of the connections in the controller itself were secure with no signs of scorching. I'm planning on double-checking everything in the elements/enclosures (Hot Pods), the stove cord/plug, the wall receptacle the controller plugs into, and the GFCI breaker in the panel. Any other thoughts on where to look and what to look for? It seems odd that something would short and trip the GFCI only when both the HLT and Boil Kettle elements are firing simultaneously but not when they are operating separately.

 

[doug293cz]

I think it's more likely that the overcurrent breaker tripped rather than the ground fault protection. A return current fault should not be load dependent, but it sounds like your trip was load dependent. Sounds like something is drawing more current than it should, or your breaker wants to trip at less than 50 amps.

I would suggest measuring the resistance of your heating elements. The 5500W element should have a resistance of about 10.5 ohms, and the 4500 should be about 12.8 ohms. If either is significantly less than that, then it is drawing more current than it should. Also, did you turn your pump on while both elements were powered up? A motor can draw much more than it's stated current consumption on start up.

Brew on

 

[Dustin_J]

I think it's more likely that the overcurrent breaker tripped rather than the ground fault protection. A return current fault should not be load dependent, but it sounds like your trip was load dependent. Sounds like something is drawing more current than it should, or your breaker wants to trip at less than 50 amps.

I would suggest measuring the resistance of your heating elements. The 5500W element should have a resistance of about 10.5 ohms, and the 4500 should be about 12.8 ohms. If either is significantly less than that, then it is drawing more current than it should. Also, did you turn your pump on while both elements were powered up? A motor can draw much more than it's stated current consumption on start up.

Brew on

Thanks Doug! The pump was continuously running during all of this, so no sudden starts. I tested resistance as suggested with my (cheap) meter that reads ~.9 ohms when I touch the test leads together. The boil element (4500w) reads 13.7 ohms, and the HLT element (5500w) reads 11.4 ohms. So, with subtracting .9 from each reading, it looks like they're dead on. FWIW, all of the wiring for the breaker, the wall plug, and box looks to be in order. I guess it's the GFCI breaker, which isn't a huge surprise given that a lot of the reviews I saw for the GE 50A gfci breakers (or the spa panels they are included with) discussed low/nuisance tripping. But, my panel doesn't list alternatives, so I'll try another GE breaker.

 

[ancientmariner52]

For what it might be worth, Harbor Freight sells a mini sized meter that includes a clip on ammeter. Small enough to reach into a small panel and check current on individual legs. I think I paid less than $15 US.

Caution. You have to put your hand in a box with live 240 power. At your own risk. I did not say this. I was never here.

 

[lschiavo]

I'm an electrician for twenty some years now. Breakers can do weird things. When I get a call for a tripping breaker, I usually have the customer cycle the breaker on and off a few times. New breakers come in the tripped state. I never just turn them on from that state... Usually off/on/off/on a few times to make sure the internal mechanism is working and properly set. This takes a FIRM snap back and forth (no limp wristing here). I have saved a few customers a service call with this advice.

Like Doug said, I don't think you were tripping on GFCI. The breaker is weak or just not properly reset...

 

[NerdBrewer22]

From what i'm calculating you have a potential of 10kw @ 240v which could suck in 41,6Amps. So I guess that your pumps don't use the rest of the unused load (in addition to the control system load) so i could be tripping from some temporary overload. But I can't be sure of it. Also can you show us how you wired the GFCI breaker ? Because it could trip from ground fault if the neutral is not connected properly.

As for myself, I helped my brother to assemble a similar system. Except that we decided that we did not needed both Boil / HLT elements to be running at the same time. So we used a 30A breaker in the home panel and a 50 amp GFCI breaker (Spa panel - used only for the GFCI purpose).

 

[Dustin_J]

Thanks for the suggestions guys. I flipped the breaker (firmly) back and forth a half dozen times, even though it has been switched on/off a handful of times already. Figured it was worth a shot.

Regarding the wiring for the GFCI breaker, I can't get a picture right now b/c the wife and BIL are marathoning movies and wouldn't take kindly to a power outage. It's wired so that the white (neutral) pigtail from the breaker goes to the neutral bus bar. Red, black, and white/neutral all go straight into the breaker (in their respective positions) from the 6/2-8/2 50A range cord that is connected to the brewing control panel. Ground from the cord goes to the ground bus bar on the other side of the panel I've triple-checked this and things seem to be in order. FWIW, both the test button on the breaker and the "e-stop" on the panel, which is wired to send current from one of the hot lines to ground, tripped the GFCI breaker during testing.

I did a "water" brew today and everything went great, but it was more of a process test for what I'll normally do for single, 5-10 gal batches, so I didn't actually need both elements on for a long period of time. Everything worked beautifully. I'll keep poking at it, but I think it's just a finicky breaker.