I recently completed a job running new dedicated appliance circuits for a coffeehouse. One machine was an Espresso machine with electrical requirements for 240/120volts 30amp breaker. I installed a NEMA 1430R dedicated receptacle to power the appliance. Power is supplied via 10/3 cable. Because the device is located beside a water source I installed a 30AMP GFI breaker in the panel, a GE panel using THQL breakers.
Since the customer opened shop 2wks ago they’ve complained of persistent tripping of the breaker, mostly during the busy times in the mornings and afternoons. There is no pattern or common factor occuring when it trips, it just trips and needs reset. The breaker doesn’t trip, the GFI part of it does creating the need to press the reset button. It is wired for 240/120 correctly. It really needed only 20amps, but the vendor recommended I just put it on a 30amp since the rating was close to 20amps and he feared tripping. He’s the vendor so I followed his instructions.
Any ideas why it keeps tripping and how to stop the false trips? The customer is wanting me to swap it for a non-GFI breaker which my inspector recommends against.
Replies
Not an electricain, but I would start by trying another of the same type of breaker, the odds are you just have a bad breaker.
If that doesn't fix it, then I'd guess you'll have to check each connection in the circuit.
Is it possible there is hot vapor getting into the junction box or receptacle from the expresso machine?
That might be the culprit.
"It is as hard for the good to suspect evil, as it is for the bad to suspect good."
-- Marcus Tullius Cicero, statesman, orator, writer (106-43 BCE)
Hot vapor?? Hmm, I guess that is possible, I don't know much how the machines work really. I was thinking of a bad breaker, but they're awfully expensive, about $70 a pop, I suppose I could swap it and if it is bad get my money back to make for an even exchange. Or if the new one trips, then I'm outta $70 since I couldn't return it since it's not defective.
Except for a few specialized applications such as pools, spas, and ice melting ONLY 120 volt circuits need to be GFCI protected.
Also, according to the 99 NEC for non-residential applications you only need GFCI in bathrooms and rooftops. NONE is need in the kitchen or wet bar area.
And it really adds a very limited amount of safety for an application like this. It is a ground appliance, it is not likely to be droped into water while pluged in, and it is not freaquently plug and unpluged and operated off of extention cords of unknown quality. All things that the GFCI used to protect against.
Just as a refigerator or DW that is a few feet away from the sink is does not need GFCI protection.
That said the first thing is to look a the breaker it'self. And Bob has a good point about steam in the box.
But there is also a good chance that the problem is in the Expresso machine. Have you ask the company if these are commonly connected to GFCI's? Have tried measuring any leakage currents?
Bill, I agree with you, thanks for the thoughts. The inspector said he would not REQUIRE the GFI but he strongly recommended it because it is beside a sink and if some idiot employee tries to do something in the sink and espresso at the same time, he was just thinking of the "what if" scenario. Indeed it is grounded and not likely to be dropped into a bar sink (the thing is huge and weighs a ton).
Good point about the Fridge or DW not needing a GFI, plus they are well grounded. I have a plain 30amp DP breaker I originally bought for it. Sounds like I can reasonably switch it out for that one based on your advice.
Bill: would it make sense for him to change out the GFI breaker for a standard breaker, and then a 15 or 20 Amp GFI receptacle at the machine for testing purposes?
"It is as hard for the good to suspect evil, as it is for the bad to suspect good."
-- Marcus Tullius Cicero, statesman, orator, writer (106-43 BCE)
240 volt GFCI's receptacles are not "common". Not sure if they are any made at all. I have never seen any.
>>240 volt GFCI's receptacles are not "common". Not sure if they are any made at all. I have never seen any.
Some how I got the impression the expresso machine was 110. Must have been a senior moment!
"It is as hard for the good to suspect evil, as it is for the bad to suspect good."
-- Marcus Tullius Cicero, statesman, orator, writer (106-43 BCE)
The Espresso requires both 240 and 120 according to the manufacturer and vendor. I"ve never seen a 30amp GFI wall receptacle, nor one capable of 240/120 except for an actual breaker device in the panel.
My guess is there is a loose wire or a short in the machine. Maybe when it is so busy and they are cleaning up, some water gets into the body and creates the short, even for a split second. Keep the GFCI unit. It's tripping for their safety.
I don't think you'll get a straight answer on this but just for kicks and giggles, ask if it happens at any particular time; like when they are cleaning up, pouring, steaming, changing the grounds, bumping into it, etc.
If you want to get really anal, you can set up a video camera during the busy times when it usually trips. I think you will notice a pattern.
Is it hard wired or a plug-in? If plug-in, is the plug secure/ tightly fitted? (Edit: Oh yeah, you covered that in the orig. post. Ooops!)
F.
Edited 6/30/2004 12:06 pm ET by Frankie
Pyrotechie,
FYI, the 2002 NEC requires GFCI protection for 120V receptacle outlets in commercial kitchens (Section 210.8(B)(3)).
As far as your espresso machine situation--
1. To comply with the NEC and derivative local code, you have to install the equipment per it's U.L. listing. So I say go with the circuit ampacity listed on the appliance nameplate or spec sheet.
I'd be a little suspicious of the equipment supplier suggesting that you use a 30 amp circuit. A lot of people have the attitude that if some is good, more is better. That isn't the case with overcurrent protection.
2. Because this is a 240/120 appliance/circuit, even if the 2002 Code is in effect in your area, the installation wouldn't be subject to the GFCI requirement.
3. GFCIs can trip due to moisture, combined with the dust on a receptacle faceplate and plug blades. It happens all the time to GFCIs in bathrooms, and it's called nuisance tripping. When the fog clears, and the moisture on the faceplate evaporates, the GFCI will generally re-set and hold.
4. How long is the cable run from panel to outlet, and how is it secured? A long run of NM (romex) that's fastened with tightly-driven metal staples can have enough capacitive coupling to irregularly trip a GFCI breaker. Another possibility is a fault in the cable, like a weak spot in the insulation, creating a high resistance fault. This could cause enough leakage to trip the GFI only under high load conditions.
5. The GFCI breaker could be bad (too sensitive). Swap out and try new one.
6. The GFCI might be tripping because of actual current leakage in the machine. Heating elements can develop high resistance faults, leaking enough current to trip a GFI, but not enough to trip a breaker. I'd test this by installing a standard breaker and measuring the current on the equipment grounding conductor (EGC), using an ammeter.
You'll have to put the ammeter in series with the EGC, and you can do this either at the panel, or you could make a test adaptor to do it at the receptacle. A regular amp-clamp (clamp-on ammeter) probably won't be near sensitive enough. I've got a clamp-on microammeter that's designed for just this sort of thing, and boy, is it a timesaver.
Anyway, if it's a fault in the appliance, and everything is working as intended, you'll see current on the EGC. Because the problem is erratic, you may have to watch the meter for a while (or use a recording meter, or one that captures min/max values). A current of 5 mA or so (for 0.2 second, if I recall right) will trip (or should trip) the GFCI.
I think that using a DMM to measure the resistance of the appliance case to the hots and the neutral is worth a try, but a high resistance fault might not show up under the 9 volts that DMMs use to measure resistance. So a negative restult doesn't mean anything.
Another option is a megger. Put 500 or 100 volts across the leads of the machine and see what the resistance is. That'll usually turn up any insulation or other fault.
So, anyway, what if you do find 6 or 7 mA (or even more) leakage to ground? Many appliances, especially older ones, do leak a little current. That'a a problem only if the grounding path is lost or compromised.
The inspector's suggestion to use a GFCI breaker has no basis. I'd use a standard two-pole breaker (of the right ampacity), a locking plug and receptacle, and I'd check the impedance of the EGC to make sure it's solid.
Good luck,
Cliff
Cliff,
Regarding #4..the cable run is about 40 feet from the panel. It has a junction splice because I reused an existing 10/3 cable already there that was only half as long as the run I needed to make.
I used plastic staples and I don't nail them home, just enough to hold the cable.
If there is leakage due to a weak spot in the insul is that cause enough for concern that I should replace the cable? Or is it fine but merely a nuisance as far as a GFI is concerned and of no concern if I swap for a regular?
The best (most efficient) way to determine the cause of the tripping is to do some testing--install a standard breaker, and start by measuring leakage current on the EGC at the panel, because it's the easiest. If there is enough current on the EGC to trip the breaker, then test to determine where the leakage is occuring.
I wouldn't replace the cable unless I meggered it and found a problem. Not that it's the cause of the problem, but I wouldn't cobble together two short lengths of cable for a dedicated branch circuit. Not against Code, (except for maybe the good workmanship requirement), but bad practice. Those unnecessary splices are just trouble waiting to happen.
As far as whether possible leakage in the cable can be ignored, well, if there's enough leakage somewhere to trip a GFCI, it may be nothing (like 6 or 7 mA leakage occassionally due to moisture at the face of the receptacle). Or it may be a low-level ground fault in the heating element of the machine, in the building wiring (maybe in the receptacle?), in the cord of the machine, or in the internal wiring of the machine or the heating elements. And if it's ####ground fault, it may eventually get serious enough to cause the breaker to open, or not.
If you want to find the cause of the tripping, start with the simplest, cheapest stuff first and use the process of elimination.
Without the right test grear, I'd replace the GFI breaker with another GFI to rule out the breaker as the problem. Expensive? Yes, but cheaper (for this one job) than buying some test gear.
If the replacement breaker trips, then I'd swap out the receptacle. If it still trips, then I'd run a temporary cable and use it to power the machine to see if it's the cable. If there's still a problem, it's in the machine, or its cord or attachment plug. And that's not your problem.
That still doesn't answer the question of whether leakage--where ever it occurs--is serious or not. So you're back to measuring the fault current through the EGC. Which would be the place I'd start.
Good luck. Intermittent problems are the worst (or the best, if you're billing T&M), and require the most spohisticated test gear.
Cliff
My electrical engineer spec'ed all GFCI outlets in a commercial kitchen on my last project. The electrician said that he would be back in 3 months to replace all of the outlets with GFCI breakers. In his experience the outlets always trip due to moisture in the kitchen. Have you seen this problem?
I haven't seen this, because my area uses a Code (the 2001 California Electrical Code) that is essentially the same as the 1999 NEC. So new restaurant kicthens around here don't have to install GFIs.
Cliff
I'm no expert, but I believe a GFCI won't work in a three-wire circuit. The device compares the current coming in through the hot with the current going out through the neutral. If the two amounts don't match precisely, the GFCI trips. I suspect the pot uses 120 volts to keep warm, but when you make a fresh pot of coffee, it uses a full 240 volts through the heating elements, like some electric cooktops. On 240 volt mode, current comes in one hot and goes out the other. If a light comes on that is wired 120 volts, then more current comes in one hot than goes out through the neutral, and you get a trip.
If NEC doesn't require it, I would suggest skipping the GFCI.
A GFCI compares the current in ALL of the wires that go through the sense coil.
But that is something to watch for. I believe that there both pure 240 GFCI breakers and 240/120 breakers where the 2 hots and neutral all go through the sense coil.
And if the wrong one is used or if the neutral is not feed through the GFCI breaker then you will get false trips.
But I suspect that they would be much more repeative unless the 120 is ONLY used some some rarely used features.
More likely the 120 is used for the controls.
"I'm no expert, but I believe a GFCI won't work in a three-wire circuit. "
the only thing against what you said is the fact that they make DP GFI breakers with a neutral connection on the breaker also. So, it would seem GFIs are capable to handle 240/120, at least those designed that way.
I'd bet that steam causes the tripping.
Unless the inspector insists, it seems to me that the best solution is to use a regular breaker.
Yeah Dan, the inspector is NOT insisting on it. He said he would've passed my inspection without it. He only emphasized he strongly recommended I use a GFI. Initially I wondered if the appliance would cause false trips, he said it shouldn't. Now I respect my inspector, he knows a lot, but from what I"m gathering from the replies, maybe he's not bright in all areas, I dunno.
I'll try the other stuff mentioned but I"m sure I'll just swap it out for a plain jane breaker.
Possible causes include: a maladjusted GFCI circuit breaker, defective cabling or the cable got pinched during installation, an intermittent situation with the receptacle likely involving a neutral/ground contact or problems with the espresso machine involving a ground fault. Pretty basic.
That said IMO there is one check to be made and then onto solving the problem. remove the cover plate on the receptacle receptacle and check for any problems with a strong light. Perhaps a slightly skinned neutral contacting, or nearly contacting, enough to leak just a bit of current to the ground, possibly with the help of a little stream. I have seen this before.
Even if you don't find any thing pull the receptacle out and restuff it neatly just to make sure. If there is any presence, or suspected presence, of steam or moisture put on a weatherproof plate. Just to make sure. This would be a good time to give the cord cap and cord a very close look before moving on to the machine itself.
Once you have covered those bases move on to the likely problem, the espresso machine. Most of these units start out fine but they are basically boilers with a lot of manhandling, temperature fluctuations and rough use. They tend to get more interactive with age. Most are not easy to work on with parts and seals that need increasingly frequent tweaking and replacement located deep behind heavy steel shields that seem to require the complete disassembly of the machine to get to.
The shields are vital if the boiler explodes to contain the blast. Very exciting when one blows. Potentially deadly if the shields are not properly in place. Even the safety valve blowing off will just about wake the dead.
On to the real problem. I suspect that one or more seals has developed a leak. These leaks are spraying steam at or above the electrical controls or interlock system. This moisture, probably with a bit of crud's help, is causing an intermittent ground fault that is tripping the GFI.
Solutions: correct the leaks, check for any cover plates missing or misattached that would deflect the steam or condensation from the steam away from any electrical components, some of these are likely under or behind the boiler so they might be hard to see or get to.
Hint:If you get good at repairing espresso machines this can, given the general lack of repair talent available, become a career in itself. I know one guy in Florida that commonly drives across Florida to service espresso machines and makes a nice living at it. Waiting time for his services is around two weeks. Every coffee shop has a machine and most need work.
Failing to stop the leak, entirely possible given the difficult in getting parts and installing them, replacing any barriers, possibly manufacturing one, would be an option. If that isn't in the cards moisture proofing the connections may be your best option.
Some care in material selection will be required as temperatures tend to be high and damaging the components, wiring insulation or connections would multiply the problems. You could try cleaning the control wiring terminations to remove any dust or crud that would trap moisture. Spraying the connections down with silicon spray once clean might help but be careful which spray you use. Avoid oils as they can eat the insulation. I have had some luck preventing shorts and corrosion by applying silicon plumbers grease or stick type wire pulling lube. This stuff repels water quite well.
You might consider 'Liquid Tape' or 'Scotch Coat' but be sure any connections that may need to be detachable don't get glued in place. 'Scotch Coat' particularly can be difficult to shift once hardened. Great stuff for sealing connections but tenacious.
Installing a drip cap or barrier to keep any condensation or steam jets at bay might work. Purely a case by case basis. I once made one out of an aluminum can. If you use plastic be aware of the heat from the boiler. Any conductive parts will need to be kept away from the electrical connection and arranged so it doesn't damage the wiring. Neat trick but it can work.
No specific recommendations but based on experience you can have fun, and drink lots of free coffee, working out a solution.
"That said IMO there is one check to be made and then onto solving the problem. remove the cover plate on the receptacle receptacle and check for any problems with a strong light. Perhaps a slightly skinned neutral contacting, or nearly contacting, enough to leak just a bit of current to the ground, possibly with the help of a little stream. I have seen this before."
Good Idea. I had a system that I desgined on a newspaper printing press. I did mostly the software for a local company that builts the electroncis for another company that make the dampening systems (water spray used on ofset printing) and installs them.
The system consists of a central control pannel and local control pannel and nozzle controlleers on each press bay. They are all communicate with twisted pair half-duplex line.
Anyway at this one newspaper they kept complaining that they had electrical noise. The system worked fine when the presses where off, but lost communications when they where running, but the local controls still worked.
Check all of the grounding, went over all of the power wiring, etc, but kept having problems.
I went to the plant with an scope and monitored the communications line. It wen bonkers when the press was running, but it did not appear to be "common" electrical noise. It is all daisy chained, left and right from the central pannel. Started disconnecting and isolated to the left leg. Then started removing the pannels from the local controls and it stopped again.
Close inspection showed that there was a couple of strands of wires that where not under the connector terminal and when the press was running it would viberate and hit the grounded case.
"Spraying the connections down with silicon spray once clean might help but be careful which spray you use. Avoid oils as they can eat the insulation. I have had some luck preventing shorts and corrosion by applying silicon plumbers grease or stick type wire pulling lube. This stuff repels water quite well."
There are also conformal coating designed for appliations like this, such as tech-spray fine-l-kote. It is available from many electronic suppliers such as Mouser and ContactEast
Well 4LORN, that is very detailed and worth a million bucks. Geesh, thanks for all those angles. I am very sure somewhere in all that you said I will indeed find the problem and map it right back at something you said.
I confess to not knowing squat about espressos. Heck I don't even drink coffee (but maybe I should take it up now that I may have good reason to). I put a 1430R receptacle in a single gang box. I meanto to put it in a 2 gang box wiht a single gang plate, but....long story on that one, but it did make cramming the wires in there a rather interesting puzzle in itself. Kinda like one of those horseshoe or chain link puzzles....so let me allow for the possibility that somethings going on in the single gang box.
On the other hand, suggestions of steam and water vapor seem to be commonly stated here by yourself and others. I wouldn't necessarily have ever considered that except for the fact a number her have mentioned it and you seem pretty sure it is a likely culprit here. It would make sense, as the GFI only trips during moments of heavy use. That is the only pattern here if there is one at all. so putting 2 and 2 together....heavy use resulting in increased steam...I'll bet that will turn out to be the root of this mess.
Incidentally this is a brand spanking new machine. Of course that doesn't mean anything, but just stating it for the record.
Question, if I just swap the GFI for a regular breaker, and this steam thing truly is going on and the cause of it, is it serious enough that I'd WANT it to stay on the GFI? I mean can it result in a lethal shock of some sort if steam is the culprit? Or wuld it be so miniscule not to worry about it but that the GFI is sensitive enough to detect it?
I would just make doubly sure that the thing is well-grounded, perhaps installing a separate ground wire from the unit to a nearby ground (water pipe, steel girder, etc) that you know is good or can check.
Or, if the thing is hard-plumbed to metalic pipe, just install bonding straps across any spots in the pipe (unions, plastic fittings, etc) that would threaten it's continuity.
Edited 7/1/2004 9:35 am ET by DanH
Isn't the 14-30 a 4 wire receptacle? The cord is a 10-3 as in two phase conductors and a ground? If you have any current on the equipment ground it will trip. I think it would work if it had a 4-wire supply cord to the machine. This way you can have two phase conductors, a neutral and a ground.
We have festivals every year and the "240 supply vendors" use L14-30 4-wire receptacles on GFI breakers and the only time I have a problem is when the vendor use an adapter tying the neutral and ground together.
I think if that were the problem it would trip all the time.
Jeff,
Yeah, 1430 is a 4 wire if you count the ground. But you use 10/3 w/ground.
I'm sorry , I thought the designation 10-3 on SJ type cord included the ground.
Well if I'm wrong I know everyone and their dog will tell me, but here's my thought process. I hear homeowners complaining a lot about GFI's tripping. Silly me, I'm thinking geez, doesn't quality matter anymore? Hmm. Trend. They were plugging things in to them that tripped them (not being sarcastic), and no I don't know the word for the specific element, but refrigerators, irons, dehumidifiers - something in the appliance kicks the thing on or off - and I was told by one electrician that this is what does it. The GFI is made to sense an abnormal current, and reads that kicking on as such. I don't know if that steers you anywhere. It's kind of like directions via landmarks to an out of stater. I'm wishing I'd committed to memory his terminology.
"If you pick up a starving dog and make him prosperous, he will not bite you. This is the principal difference between a dog and a man." - Mark Twain
"Well if I'm wrong I know everyone and their dog will tell me, but here's my thought process."
Arf, arf, arfarf, arf!
Arf, arf.
Arf, arf, arf, arf, arf, arf?
Arf, arf, arf.
Arf!
Sorry about that.
The dog really knows the code and how to use the computer, but he only knows how to spell one word. So he ask me to translate.
"The GFI is made to sense an abnormal current, and reads that kicking on as such."
But those are normal currents.
The way that it works is that it has a sense coil with all of the load carrying currents flow through it. If there are the same the output is zero. If they differ by 6 ma or more then it trips. That means that some of the current has been diverted, ie ground fault.
Now compressor driven equipment is no always leakage free, for several reasons,one being the moisture that is produced durin gthe defrost cycle. But that should really not be a problem as they are grounded.
But they are also highly inductive loads and when they start there is big phase shift in the current. That can confuse the GFCI.
You should never see this problem with something like an iron.
But as was mentioned earlier there might be moisture problems in the unit.
Bill, thanks for the translation.
I'm wondering, though, if there were some nuances which didn't come through? {G,D&R}
"It is as hard for the good to suspect evil, as it is for the bad to suspect good."
-- Marcus Tullius Cicero, statesman, orator, writer (106-43 BCE)
He is more eloquent than I am, now if I could only teach him to spell.
And if you don't believe that you need to listen to his vocabulary of yeps, yaps, and whines.