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Adding an electrical water heater. Only single pole available in box.

2K views 22 replies 10 participants last post by  wirenut1110 
#1 ·
I need to add a 10 gauge line with a 25amp double pole breaker to install an 80 gallon 4500W electric water heater.

It appears that I only have space in the electrical panel for a single pole breaker.

Is there such a thing as a 'slim' double pole that will fit in the single slot?

There is a sub-panel that has room. Can I go off of that?
 
#2 ·
You want a 30 amp 2 pole breaker. If the sub has the capacity you can use that as the supply. There are tandem breakers that allow 2 circuits in a single space but you must determine if your panel allows them. The panel label should tell you. If not post the manufacturer and model of the panel.
 
#3 ·
You can get a tandem breaker...but it does not give you 240VAc....for 240Vac, you have to span 2 spaces...

Do this....assuming your panel is rated for tandem breakers, remove the breaker adjacent to the empty slot.

Then, replace the adjacent breaker to the one you just removed with a tandem....then wire the ckt you pulled off the breaker you removed to the tandem.

You now have two spaces to plug in your double pole breaker for your water heater.

BTW....that water heater is going to use a lot of electricity....I'm assuming you don't have gas?

Have you looked into the heat pump versions? They will use about 1/3rd the electricity.

Also....it would help to put your location in your profile.
 
#4 ·
Y,\

remove the breaker adjacent to the empty slot.

Then, replace the adjacent breaker to the one you just removed with a tandem....then wire the ckt you pulled off the breaker you removed to the tandem.

You now have two spaces to plug in your double pole breaker for your water heater.
This will not give you an empty slot. You need to remove the 2 breakers next to the empty slot and replace with a tandem breaker for the 2 you removed. That will give you the 2 empty slots you need.
 
#5 ·
That is what I said......just not as obvious....

remove the breaker adjacent to the empty slot.

Then, replace the adjacent breaker to the one you just removed with a tandem....then wire the ckt you pulled off the breaker you removed to the tandem.
I should have said...."now remove 'another' breaker next to the one you just took out"....

Or....

Remove the two breakers adjacent to the empty slot....
 
#7 · (Edited)
I'm actually switching from 2 50 gallon propane water heaters to one single 80 gallon electric.

My propane bill to run these 2 water heaters plus have a burner or two on for a total of probably one hour a week is almost $100/month. Gas is $3.10/gallon + taxes here in Jacksonville, FL.

We have 4 full baths with only occasional in-law guests. Baby is on the way. I think we need the 80 mostly because our planned master bath remodel is probably going to have 6 body sprays and probably a rain shower head and a hand shower. So occasionally, we would like the ability to drain that 80 gallon in 10 minutes. :)

If i'm not mistaken, the stand-by losses on electrics are a lot less than the propane units in general.

The "high efficiency" A.O. Smith 80 gallon electric i'm looking at has a published 4721 KWH yearly use. At .13/KWH out the door cost, that breaks down to about $51/month, which means I save $40 or more per month, since i'm thinking we actually use less than that published amount. What we use now is about 2 showers per day and run the dishes every 3 or 4 days. Total cost after 10 years = $6120 + $620 initial cost = $6740

I looked at the heat pump water heaters and although that looks to cost me about $21/month in electricity, the upfront cost difference of about $1580 is huge (these cost about $2200 out the door). It will take 51 months to make up that upfront cost difference when figuring saving $31 more per month using the HPWH. However, long term, I do realize it start to really pay off after 10 years. Total cost after 10 years = $2520 + $2200 initial cost = $4720.

After 10 years, I save $2020 if I go with the HPWH.

I think its more likely that the HPWH will break down within 10 years rather than the conventional electric unit blowing any savings out the window, but that's just my opinion.

Am I missing something here? Input is welcomed.


Now on to the electrical problem at hand.

I have a picture of a 90 amp double pole from the main panel which feeds the sub-panel. In the sub panel is what I assume is 90 amps, since each single pole has two little small 15's on each?

So I think this means that I can't put a double pole 30amp in there?

Is my only option now to double up on another breaker replacing the existing breaker with something bigger?
 

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#11 ·
I'm actually switching from 2 50 gallon propane water heaters to one single 80 gallon electric.


Am I missing something here? Input is welcomed.
You seem to have done the math, but have you considered a continuous hot water heater (propane)? We replace one of our HW tanks with a Rinnai last summer and love it. Only experienced the "cold water sandwich" once.

OTOH, the price of electricity is much more stable than the price of propane.
 
#9 ·
What RJ suggested certainly looks like the best alternative. You already have a bunch of tandem breakers on the bottom of your main box and all the rest of it is already double breakers for 240v. Your only alternative would be to take the tandem breakers in the 2nd slot on the bottom left and move them to the subpanel so you had room in the bottom left 2 slots for the double breaker for your water heater.
 
#10 ·
Before you do anything with that subpanel look at the bussbar conneciton on the subpanel I know SqD did have couple verison and I know you are tempting to use the subpanel for WH connection however as I mention .,

Look at the bussbar to make sure before you run the cable in there.

The reason why due some subpanel do have 6 space verison and some are 8 space verison.

Merci,
Marc
 
#12 ·
Just have to chuckle a bit, sure goes to show where you live make all the difference. In So Cal where I live, natural gas is cheap and relatively stable. I have as many gas appliances as possible. Electricity on the other hand is anything but cheap or stable. SCE just raised our rates 6% or so AGAIN and DWP is planning on double digit increases this year. We have a tierd system, anything over about 400kWh baseline per month and you start paying higher rates. My average cost is 0.27 per kWh. My level pay rate is $385 a month, for 1200ft house. That electric water heater would cost me A LOT here!
 
#13 ·
Just have to chuckle a bit, sure goes to show where you live make all the difference. In So Cal where I live, natural gas is cheap and relatively stable.
I suppose it does. It is used a lot here for heating so the price usually follows the demand. Have a cold winter and the utilities have to buy more a spot rates, they won't get to recover that extra cost until the next year. So prices go up the next year for a regular winter, they recover and the price goes back down.

My average cost is 0.27 per kWh. My level pay rate is $385 a month, for 1200ft house. That electric water heater would cost me A LOT here!
Electricity is fairly stable. We did recently have a large % increase of 15.5% to the new rate of $0.097 per kWh. This was the first increase in about 4 years.
 
#14 · (Edited)
The .13/kwh rate I posted includes all taxes and fees- herdfan, I'd be curious to know where you live. Does that rate you quoted take into account taxes and fees?

How do I know that the sub-panel, which is on a 90amp double pole breaker, won't be overloaded with the 30amp double pole plus all the 15amp single poles shown in the picture?

Can someone explain this to me like I'm a 5 year old? :)
 
#17 ·
Remember the breakers are there just to protect the wiring from getting too hot. A 200 amp main panel might have 300 amps of breakers in it but the loads on each are much less, some not on when others are etc, so the total is usually less than 200 amps, or the main breaker would be tripping all the time.

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#21 ·
A voltmeter is not going to give any useful info on the actual load.

If those breakers are just feeding lights and receptacles, don't worry about the load taxing a 90 amp sub.
 
#22 ·
You can put a clamp on ammeter on the feed into the sub-panel and measure the actual draw when you turn everything on. Measure both legs (black and red) then you can see how close to 90 amps it is. Be careful reaching into the panel because it will have to be hot to do this.

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