Electric Water Heater Element replacement

[RetiredInFl]

Hello all ... just came across this forum (thanks Google).

Just had a 15 year old AO Smith Electric WH replaced in a home we recently moved into. The original WH was a 4500 Watt 40 Gal unit and was replaced with a 50 Gal 3800 Watt AO Smith model by a local plumber. Would have done the job myself except lifting a 120 LB tank 3 feet up onto a platform ain't good for my 75yr old back! It was my bad not specifying 4500 Watt (they make both) but it never crossed my mind. In any case, I see replacement elements are cheap enough and I consider myself a long time DIY'er and have previously rewired much of my previous home so dealing with electrical is not an issue.

I am wondering if I can simply replace the 2x3800 w elements with 2x4500 w elements. From reading it seems both TANK versions are IDENTICAL except for the element itself. The breaker is 30AMP and wiring from fuse panel to tank is 10guage which was fine and proper spec on the original 4500 watt tank. My only concern is if the INTERNAL WIRING INSIDE THE TANK (which is only a couple feet of wire) is the same between the 3800 & 4500 watt units. Just wondering if anyone knows. I would guess it's the same but just want to be sure.

Thanks!

 

[Twowaxhack]

You can just swap elements the internal wire is 12ga.

 

[RetiredInFl]

You can just swap elements the internal wire is 12ga.

Thanks, that is what I assumed. Can I push it to 5500 watts? Are they the same length?

 

[sarg]

Be sure you have at least a 25 amp breaker on the line for the heater for 4500 elements and a 30 amp breaker for the 5500. Assuming 240 volt line and a 125% margin for safety. I would not push 12-2 wire for 5500 watts. ( almost 23 amps )

 

[RetiredInFl]

Be sure you have at least a 25 amp breaker on the line for the heater for 4500 elements and a 30 amp breaker for the 5500. Assuming 240 volt line and a 125% margin for safety. I would not push 12-2 wire for 5500 watts. ( almost 23 amps )

Thanks. Breaker is 30amp and wiring from panel is 10 gauge. If the small amount of the INTERNAL wiring in the tank to the elements and tstat is 12 gauge as the other poster suggested is that doable for 5500 or shouldn’t I push my luck beyond 4500?

 

[sarg]

Just opinion but I do not need hot water recovery any faster than my 4500 elements provide and I have a much smaller tank than you now have.

 

[Twowaxhack]

Thanks. Breaker is 30amp and wiring from panel is 10 gauge. If the small amount of the INTERNAL wiring in the tank to the elements and tstat is 12 gauge as the other poster suggested is that doable for 5500 or shouldn’t I push my luck beyond 4500?

I believe the Rheem water heaters that are sold with 5500w elements have 12ga wire between the thermostats and elements.

 

[sarg]

Makes you wonder if Rheem uses heavier insulation on the 12ga wire used in their 5500 units because the standard 12ga wire is rated for 20 amps and the 5500w elements could draw 23 amps ( with the mandated safety factor the requirement would be just under 29 amps. )
RetiredinFl = I would not "push my luck" ..... never been a fan of electrical fires.

 

[Twowaxhack]

Makes you wonder if Rheem uses heavier insulation on the 12ga wire used in their 5500 units because the standard 12ga wire is rated for 20 amps and the 5500w elements could draw 23 amps ( with the mandated safety factor the requirement would be just under 29 amps. )
RetiredinFl = I would not "push my luck" ..... never been a fan of electrical fires

I’ll put this to bed, I’ll call Rheem today.

But for kicks, I have this one in my 40 gal Rheem electric and it’s been running fine for 2-3 yrs now.

I bought two but only installed one in the top of the tank.

 

[RetiredInFl]

Makes you wonder if Rheem uses heavier insulation on the 12ga wire used in their 5500 units because the standard 12ga wire is rated for 20 amps and the 5500w elements could draw 23 amps ( with the mandated safety factor the requirement would be just under 29 amps. )
RetiredinFl = I would not "push my luck" ..... never been a fan of electrical fires.

I agree to "not pushing my luck." That being said, I have read over the years that the LENGTH of a piece wire also has an effect on how much current it can safely carry. There can't be more than a few feet of wire inside the tank and a few INCHES between the tstat and element.. Compare it to "running": The further a person runs the more tired s/he can get no matter what they weigh.

 

[RetiredInFl]

I agree to "not pushing my luck." That being said, I have read over the years that the LENGTH of a piece wire also has an effect on how much current it can safely carry. There can't be more than a few feet of wire inside the tank. Compare it to "running": The further a person runs the more tired s/he can get no matter what they weigh.

I just found this:

For a fixed (same) supply voltage and same load, the CURRENT in wire with short length would be more than the wire with longer length, The difference may not be noticeable or sufficient. The difference in current would be due to resistance of wire, which would be less for short length of wire.

Normally length of wire is not a criteria for carrying current through it. The wire Diameter is the deciding factor for current carrying capacity of a wire. However, if the distance between supply point and end user is too large say a few or hundreds of Km, it is also becomes a factor for assessing the current capacity of wire.

Another thing to note is that a wire rated for say 10 amps current can also carry 20 Amps current. The current ratings are based on safe temperature rise of the wire. It depends on many things like duty cycle of load, ambient temperature of environment, length of wire, and medium in which wire is being used. For very long lengths (say in Kms) the wires are rated as per the voltage drop in it for rated current.

 

[sarg]

Below is a copy-paste from the Home Depot site on Rheem heaters and a guy asking the specific question and Rheems' answer. ( Page 15 of Q&A)
Not really an answer --- just a CYA.
And just an observation --- Many of the Rheem reps answers were downright silly.


Q:Why does this unit have 12 ga internal wiring rated for 20 amps when the 5500 watt elements draw...
byRobert|Apr 2, 2021
1 Answer


Answer This Question
A: Hi Robert and thank you for your question. You would want to follow the use and care manual that comes with the unit as those are based of national codes at the time the unit was manufactured.
byRheem|Jun 19, 2021

 

[Ludington]

Why do you want the higher wattage ? Just for faster recovery ?

 

[Twowaxhack]

Why do you want the higher wattage ? Just for faster recovery ?

Of course.

 

[Twowaxhack]

The only info I’ve found showing 10 ga internal wiring is for simultaneous operation of 4500w elements.

So if you can run 9,000w on 10 ga, 5500w should work on 12ga internal wiring.

You must have 240v. 208v would derate the element.

If you’re getting your info from Gene Haynes website, he just copies and pasted info and I’ve corrected him before.

 

[sarg]

Threads like this make me ponder adding another rule to my list.

"Doing stupid **** can get you killed."

 

[Twowaxhack]

Below is a copy-paste from the Home Depot site on Rheem heaters and a guy asking the specific question and Rheems' answer. ( Page 15 of Q&A)
Not really an answer --- just a CYA.
And just an observation --- Many of the Rheem reps answers were downright silly.


Q:Why does this unit have 12 ga internal wiring rated for 20 amps when the 5500 watt elements draw...
byRobert|Apr 2, 2021
1 Answer


Answer This Question
A: Hi Robert and thank you for your question. You would want to follow the use and care manual that comes with the unit as those are based of national codes at the time the unit was manufactured.
byRheem|Jun 19, 2021

That’s actually a great answer the rep gave.

The wiring diagrams are on the last page of the care and use manual and it shows 10ga internal wiring for some configurations of the model it comes with.

10ga is only shown being used with simultaneous operation or 3phase.

12ga isn’t specified but examples of 10ga are.

Look for yourself.

 

[sarg]

Remember the original conversation was using 5500W elements in a manufactured 3800W unit.

 

[Twowaxhack]

Remember the original conversation was using 5500W elements in a manufactured 3800W unit.

If it has 12ga INTERNAL wire then it’s fine.

240v and 10ga 30 amp breaker Aka branch circuit

 

[MicEd69]

Don't confuse the ampacity of 12-gauge Romex wire, 20 amps, with 12-gauge copper wire that has higher rated insulation, 25 and 30 amps. Appliance manufacturers do not use Romex for internal wiring.