Having issues I have a three phase 208 service each leg is 120 V to ground no high leg, and I have two hot water heaters ran in tandem one hot water heater, feeds water into the Herzing winery, the issue I’m having is one water heater keeps blowing the fuse on the B phase all voltage is within reason 125 V per leg on 230 V rated fuses and I have proper continuity where it needs to be across those heating elements. I have no continuity between phasing ground everything checks out fine and as soon as I hook up the bee phase. It immediately burns the fuse within 1 ms.
Single phase water heater fuse issues
- Thread starter Roscoe
- Start date
- Status
- Occupation
- Licensed Electrician
That's because your meter does not put enough of a load on the circuit to blow a fuse.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
I agree more details needed, 3 phase or single phase, wattage, single element dual element or simultaneous dual element, how are they connected to the branch circuit, size of OCPD.
ptonsparky
Tom
- Occupation
- EC - retired
New install or existing?
New - you screwed up.
Existing - check for a shorted or ground faulted element.
New - you screwed up.
Existing - check for a shorted or ground faulted element.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Which might not show fault continuity with a low voltage applied.
If you do not have a megger, wire an incandescent lamp (220V) in series with the B leg and look for current on EGC and neutral.
ptonsparky
Tom
- Occupation
- EC - retired
At 1ms clearing time, the fault should be pretty obvious.
This is a single phase water heater, dual elements they do run simultaneously, and they are running at 208 volt derived from a and B phase of three phase Service keep in mind this three phase Service has no high leg. It’s 120 V per leg to ground or neutral.
This is a standard 4500 W water heater, which is on 25 amp bus fuses. The only thing I can think of is at some point at the switching station down the road some of their gear that regulates voltage downstream to our platform transformer was stuck due to the cold weather a few months ago and we were running at a very high voltage on one of the phases. My thoughts are maybe that corrupted one of the elements but who knows?
- Occupation
- Licensed Electrician
That's quite a stretch.
ptonsparky
Tom
- Occupation
- EC - retired
Plumbers change water heating elements. It's not that difficult.
- Occupation
- Licensed Electrician
ptonsparky
Tom
- Occupation
- EC - retired
The water heater does not care what the voltage is to ground. All it wants is line to line. 208 elements on 240 will heat faster. 240 on 208 heat slower.
You would think it’s just a bad element. I went and got my other meter did an ohms test on it and it had a very poor reading so we called the plumbers and the plumbers are coming to install new elements.
ptonsparky
Tom
- Occupation
- EC - retired
I don't have a 240 volt time current chart handy, but a 30 amp FLSR blows at .01 second and 700 amps. I suspect similar for an FLNR.
Agreed , we only installed the service for both water heaters some time ago , the only reason we were alerted was do to the plumbers replacing some cast iron above them. Do to the fact that one is plumbed into the other they would never have lost hot water . Every thing tested fine on our end of the service call. The plumber had noticed the second water heater was cold to the touch.
- Occupation
- Licensed Electrician
Well, if there was a problem with the power company I don't think the only problem that would show would be a water heater that nobody even cares about.
Well I remember when it happened because we were installing high bay lighting and it fried three of our battery chargers
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
The heater is across two phases, A&B. Each phase is fused at 25A. Only the fuse for phase B opens. That could only mean a fault to ground on that side of the heating element connected to B phase. Just for giggles, I would disconnect the wiring from the heating elements fed from the B phase and power it up. See if there is any current draw on the A phase and ground.
-Hal
-Hal
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
especially with 240 volt rated elements on a 208 system. If POCO regulation were stuck on highest tap this think would maybe see about 235 volts max instead of a normal around 212-216.
Megger and knowing how to use it will probably find OP's problem pretty quickly.
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