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40 Gal Non-Simultaneous VS Simultaneous  Rate Topic 
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 Posted: Mon Sep 11th, 2017 10:23 pm
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turtle
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Greetings I have a 40 Gallon electric (Currently a 4500W element) in a small space that will not fit a larger tank ( yes I tried ) and there is no other space to add another water heater.

I am curious what the improvement in recovery time would be by converting it to a Simultaneous with a second 30A 240V circuit ( that is available ).
I actually have a spare 'upper' thermostat with the safety button that I can install on the lower position.

I guessed the volume of gallons above the 'upper' element to be around 10 and subtract that from what I guess to be the volume above the lower (30) then assume the longer running lower will be the recovery value.
From my calcs it seems the recovery time of a 40 gal Simultaneous would be 40 Min and the Non is about an Hour, so a 20 Min savings which is not bad.
If i run the numbers with a 5500W element I get down to 1/2 hour recovery time for a Simultaneous.
I have also thought of turning the temp way up and adding a mixing valve, but I kinda like the idea of the 5500w elements better.
Does anyone have any thoughts / opinions / experience with this?
Thanks in advance.

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 Posted: Thu Sep 14th, 2017 03:58 am
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eleent
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Hello,  As long as you can deal with running two circuits... likely #10 copper wire, for powering two 5500 watt elements, you should be fine.  This will take modifying the heater, which the manufacturers strongly dislike and will likely void the warranty also. As to time savings, it really depends on what temperature you need.  Usually 110 F will serve a shower, with little cold mixed in, and with two elements running you'll have it quickly.  Still, you shouldn't need a cold start very often. One plus of your scheme is that you'll likely get a much longer shower, or multiple showers, particularly if you use a low flow (like 1.5 gpm) showerhead. To your question of mixing valve vs higher wattage elements, I'd go with the latter.  There simply is less to go wrong.  ;)

Yours,  Larry

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 Posted: Thu Sep 14th, 2017 04:36 am
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geno03245
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4500 watt non-simultaneous 21-31 GPH
5500 watt + 5500 watt = 11000 watt simultaneous 53-75 GPH
Depending on thermostat setting and seasonal incoming water temperature
Calculate-water-heater-recovery.html

Opinion:
Wiring extra breaker and running another 10 gauge wire for simultaneous operation is safer than increasing water temperature.
How to wire simultaneous water heater

Very hot water poses extreme risk of scalding, and/or rupture of rusted tank..
Prevent tank from rusting by replacing anode rod.
Anode rods at waterheaterrescue

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 Posted: Thu Sep 14th, 2017 09:42 pm
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turtle
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eleent wrote: Hello,  As long as you can deal with running two circuits... likely #10 copper wire, for powering two 5500 watt elements, you should be fine.  This will take modifying the heater, which the manufacturers strongly dislike and will likely void the warranty also. As to time savings, it really depends on what temperature you need.  Usually 110 F will serve a shower, with little cold mixed in, and with two elements running you'll have it quickly.  Still, you shouldn't need a cold start very often. One plus of your scheme is that you'll likely get a much longer shower, or multiple showers, particularly if you use a low flow (like 1.5 gpm) showerhead. To your question of mixing valve vs higher wattage elements, I'd go with the latter.  There simply is less to go wrong.  ;)

Yours,  Larry
Thanks for the opinion. Yeah warranty is out the window :) No mixing valve and simultaneous wiring it is. Wiring is easy for me anyway as I am an electrician by trade.
  Next ill just try out running the two existing elements as simultaneous. Then later rewire the internals of the waterheater with some quality temp rated 105C #10 copper stranded type MTW and do the 5500W upgrade.

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