125A Panel Questions

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  #1  
Old 10-25-12, 09:46 AM
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125A Panel Questions

My condo was built sometime in the 70s and I am wanting to make a few small changes in the home.

The panel houses Murray EP breakers and is rated at 125A.

I am looking to install a 64A Electric Tankless Water Heater. Is it possible to install a 80A breaker in this panel on top of all the other things such as the dryer without overloading the panel? My main concern I suppose is running the appliances at the same time and do not want to overload my panel.

I have one open space but I plan on consolidating some breakers with tandem breakers to free up the space I need in the panel (there are some tandem ones there already).

Any and all advice would be appreciated, I am planning this out a few months ahead of time so I can get all the supplies and eliminate any roadblocks.

TIA

Matt
 
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Old 10-25-12, 09:48 AM
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Welcome to the forums.

What is your reasoning for choosing a tankless heater? Generally speaking, they are the right choice only occasionally - the concept is better than the actual application.
 
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Old 10-25-12, 09:58 AM
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No real reasoning only that our water heater is very old and we are wanting to save energy costs overall in the long term. Could it be that our water heater is so old is uses more energy and has to heat more since the sediments harden on the bottom over time?
 
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Old 10-25-12, 10:05 AM
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Yes, a new water heater could save you money but the tankless heaters have a lot of installation and equipment cost which usually makes a heater with a tank cheaper even in the long term. In your case, I think it likely you would have to have an electrical service upgrade to install this unit.
 
  #5  
Old 10-25-12, 10:11 AM
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Two things you need to check out:

Tankless heaters are typically more efficient, though from my personal research when I needed to replace my tank heater, the savings over 10 years just about offsets the additional cost of the heater. Plus, my research was natural gas... I'd imagine electric would be less of a savings. But, do your own math, don't trust us Also be sure to look at recovery times and how many fixtures can run with hot water at once.

Often, an electric tankless heater requires at least a 200A service. You'll have to do a demand load calculation (see Google for a calculator) to see what size service you need. You mentioned an electric dryer. Do you have electric heat? Electric stove?

Good luck!
 
  #6  
Old 10-25-12, 10:17 AM
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Its an all electric condo nothing else. The tankless water heater I am looking at requires 64A so I figured I would go with a 70A breaker.
 
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Old 10-25-12, 10:24 AM
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You would probably need to upgrade the electric service to your unit and possibly the whole building. Given that your feeder cable run through other units I would not think it would be feasible to continue with the electric tankless.

You really need to find out your current service size and perform a demand load calculation.
 
  #8  
Old 10-25-12, 10:25 AM
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Does "All-Electric" mean electric heat in addition to electric cooking and laundry appliances?
 
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Old 10-25-12, 10:28 AM
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You would be fine with that and 125 amp service if you could control when it turned on well enough but have someone run hot water while the stove and the dryer are on and I can see you tripping your main. I don't think you have enough juice for the unit in addition to the idea the marginal energy usage savings on these units don't really offset their increased upfront cost.

I would stick with a tank heater and flush it a couple times a year to avoid sediment buildup.
 
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Old 10-25-12, 10:29 AM
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Yes all electric everything...period.
 
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Old 10-25-12, 10:32 AM
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Oh, geez, I didn't even think about heat and AC draw....
 
  #12  
Old 10-25-12, 06:28 PM
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Its an all electric condo nothing else. The tankless water heater I am looking at requires 64A so I figured I would go with a 70A breaker.
That would take an 80 amp breaker, nothing smaller. Without a load calc I can tell you a 125 amp service is not enough, but you should still do the load calculation so you can notify your power company of the load being added when you upgrade the service to 200 amps. If the added load damages their transformer and they didn't know you added a major load to their system, you could be responsible for the damages.
 
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