Higher amp breaker replacement, can the panel support it?

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Old 11-15-16, 01:40 PM
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Higher amp breaker replacement, can the panel support it?

Hello everyone, I want to replace my water heater with a tankless model. I need to run a 70 amp breaker in place of the 30 amp that's already there. I know I need to run new 6 awg wire but my question is if the box can handle it. I believe it's a 150 amp box judging by the 2/0 AL feeder wires. There are no labels on the box to tell me anything. I will try to add pictures
 
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Old 11-15-16, 01:59 PM
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Old 11-15-16, 02:14 PM
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Doesn't look to me like you have enough capacity - that tends to be the first problem people encounter with tankless heaters.

Why are you giving up the tank?
 
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Old 11-15-16, 03:25 PM
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Mainly because of space. Are these typically rated at 240 volts?
 
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Old 11-15-16, 03:33 PM
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Tankless heaters normally take 2-3 240 volt circuits.

To answer the original question you would need to do a demand load calculation.
 
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Old 11-15-16, 03:47 PM
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Old 11-15-16, 03:55 PM
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With 2/0 aluminum I suspect the service is 125 amperes. What is the rating on the main circuit breaker?

I notice there is an awful lot of rust on the exposed steel of the circuit breaker ties and other parts. Might be getting towards time for a service replacement.
 
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Old 11-15-16, 03:56 PM
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Name:  Capture+_2016-11-15-17-54-55.jpg
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This says I'm good to go. Did I miss anything?
 
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Old 11-15-16, 04:05 PM
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Can't read that report. You need to put it in photobucket and link it here.

You'll need to add up all your large usage appliances.

I see.....
2P30A - for current water heater
2P30A - probably for electric dryer
2P50A - probably for electric range
2P70A - probably for heat pump electric reheats
2P40A - probably for A/C compressor

Lot of current load to add an additional 70A.... even with the removal of the 2P30.
 
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Old 11-15-16, 04:06 PM
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Did you read the specifications on that heater? They weren't available on the Home Depot site you linked to so here is a better site. iHeat Magnum S16 Whole House Tankless Water Heater 16KW – Tank The Tank

Note that the specifications state it is for warmer climates. You have not filled in your profile so we cannot know where you live.
Made for southern climates and warm to moderate incoming water temperatures, the Magnum S-16 tankless water heater will supply a water temperature rise of 95 degrees F at 1 GPM and 48 Degrees at 2 GPM.
Most shower heads are rated at 2.5 gpm or higher. That means that your incoming water temperature had better be 60 degrees or warmer year round unless you prefer cold showers.
 
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Old 11-15-16, 04:07 PM
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The main breaker has no markings indicating what amprage it's rated. The rust is only on the ties as you said, all the buds bars look good.
 
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Old 11-15-16, 04:11 PM
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https://www.amazon.com/iHeat-Electri.../dp/B018A3CR6S

It's rated at 3.5 gpm, I live in Houston TX, I think it will work fine.
 
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Old 11-15-16, 04:16 PM
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Old 11-15-16, 05:23 PM
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In your load calculation I do not see anything listed for the 70 amp breaker in your panel now. PJ mentioned it might be electric heat strips for the furnace/heat pump.

Also, you can only use #6 copper if you run conduit and use THHN wires to feed the tankless. If you use a cable, such as romex, you will need to run #4 copper.
 
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