A customr calls me they just install a new 40 gal hot water heater electric. I ask the customer who connected the unit to the electric, he wouldn't give me a straight answer. Anyway I take a ride over there check the connections at the water heater everything is ok. I do some troubleshooting and find out The connections inside the panel are burnt. I then realize they a two pole 25 amp breaker feeding the hot water heater, but only number 12 wire to the water heater. So I install a 2 pole 20 amp breaker cut off the burnt part of the wire and connect it the breaker and trun it back on, presto, problem fix. They have hot water everybody is happy, but on by way back to the office I realize that maybe that breaker and wire are not size right, for that hot water heater. I remember the name plate say 4500 watts so i divide by 240 and I get 18.75 amps. I think i am missing something is this going to be ok or do you think I will be getting a call about this. I forgot my camera sorry no pics but if i go back I will take some pics.
Hot water heater
- Thread starter jm1470
- Start date
- Status
- Location
- Windsor, CO NEC: 2023
- Occupation
- Hospital Master Electrician
See 422.13.
charlie
Senior Member
- Location
- Indianapolis
I don't think it will hold in the long term. It should have been 10 AWG Cu with a 30 ampere, two pole circuit breaker. 
Thanks probably why somebody put a 25 amp breaker on the original one.
- Location
- Windsor, CO NEC: 2023
- Occupation
- Hospital Master Electrician
You're giving somebody more credit than they probably deserve. If they were aware of that section, they'd probably be all over 240.4(D).
Jim W in Tampa
Senior Member
- Location
- Tampa Florida
The 25 amp breaker was not the problem.Promlem be same if it was a 20 ,25,30,50 breaker. The undersized wire simply got hot. Now go back out there and change the wire to #10 and 30 amp breaker. Be sure and give them full credit for the first trip.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Maybe but how often do you think a water heater will run continuously for 3 hours. I know we must figure it based on a continuous load but I bet the problem was a bad breaker or bad connection not the overheating. #12 wire should have no problem with 18.75 amps.
ptonsparky
Tom
- Occupation
- EC - retired
With family home for the holidays and a death in the family the following week ours probably ony had two days of not runnining 3 hours at a time.
I have seen a lot of water heaters with #12 and no damage. Seen enough with damaged #10. Usually PP connections.
I have seen a lot of water heaters with #12 and no damage. Seen enough with damaged #10. Usually PP connections.
- Location
- Illinois
- Occupation
- retired electrician
I don't agree that the wire got hot because it was too small...it got hot because it was not terminated correctly. #12 is 25 amp wire in the 60?C column and will not exceed that temperature with a 25 amp load. Yes I know that 240.4(D) says we can't use #12, in most cases, with a 25 amp breaker. I am not sure why, but it is not because the wire will get too hot.
ishium 80439
Senior Member
I've always wondered that as well. If 14 AWG is rated for 20A and 12 AWG is rated for 25A why is there a restriction on actually using them to their capacity? (This has probably been covered here before but I figured since this is pertinent to the OP this wouldn't be an awful place to bring it up).
The "small conductor rule" goes back to the 1956 NEC when type RHH ( a 90?C conductor) insulation was limited to the same ampacity of type RH (a 75?C condcutor).
Jim W in Tampa
Senior Member
- Location
- Tampa Florida
The connection got hot. That might been because of bad connection. #12 would have been getting warm with given load. The install needs breakered at 125% because like it or not its cont. load. We can not put a 20 amp breaker on this load and meet the 125% and can not use a 25 amp breaker on #12 for this type of load. What we have now and before was illegal install.
ishium 80439
Senior Member
So haven't the past 53 years brought us advances in insulation that would essentially make this ruling null? Is it just that the CMP's are busy saving us from ourselves w/ TR and AFCI that this has gone this long unchanged because there is no money to be made from it? (Me cynical? Nah!)
- Location
- Illinois
- Occupation
- retired electrician
Warm, yes, but it would not exceed 60?C unless the current exceeds 25 amps, there was a problem with the termination, or there were other factors such as high ambient or more than 3 conductors in the raceway or cable.
GrayHeadedMule
Member
Boy oh boy!! A forum full of electricians!!!
Well first of all it is NOT a "hot" water heater:!
Why would you need to heat hot water?:-?
It's a water heater!
Well first of all it is NOT a "hot" water heater:!
Why would you need to heat hot water?:-?
It's a water heater!
Boy oh boy!! A forum full of electricians!!!
Well first of all it is NOT a "hot" water heater:!
Why would you need to heat hot water?:-?
It's a water heater!
"Well first of all it is NOT a "hot" water heater".
I just felt of my water heater and it's hot, so it is a Hot water Heater.
"Why would you need to heat hot water"?
So that I can take a Hot Bath.
"It's a water heater"
Yep, that's what it is...and a Hot one at that.
steve
ptrip
Senior Member
"Well first of all it is NOT a "hot" water heater".
I just felt of my water heater and it's hot, so it is a Hot water Heater.
"Why would you need to heat hot water"?
So that I can take a Hot Bath.
"It's a water heater"
Yep, that's what it is...and a Hot one at that.
steve
Thank you both for the giggle!
My opinion, no matter how little it counts :wink:, is that it's a "water heater", not a hot water heater ... just as it's a "lamp", not a bulb!
Jim W in Tampa
Senior Member
- Location
- Tampa Florida
Are you saying we cant heat hot water ? Bet i can.
iaov
Senior Member
- Location
- Rhinelander WI
I gotta agree with Dennis and Don on this one. The breaker does not open because the wire gets hot. I believe the 12awg/20 amp rule and 14awg/15 amp rule are to save the public from themselves.
Jim W in Tampa
Senior Member
- Location
- Tampa Florida
A 20 is not legal in this install. The wires got hot for 2 reasons. First because of bad connection 2 nd because a 19 amp load is helping it get hot.The breaker size had nothing to do with the wires burning.
- Status