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Old 06-07-2016, 08:55 AM   #1
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Suburban Hot Water Heater

I can only get warm water while in the electric mode but get plenty of hot water when using propane. What's the most likely cause, heating element or thermostat?


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Old 06-07-2016, 08:58 AM   #2
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#1 make sure the bypass valve is closed..

#2 my heater always is better to recover from propane than electric. I just use it to maintain the temp when at a full hookup. Mine was a 1500 watt unit so I am not sure what the actual comparison to the btu's of propane.

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Old 06-07-2016, 09:08 AM   #3
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Thanks. The bypass valve is in the correct position since I can get hot water using propane. I usually use electric and it's worked fine until this trip. I assumed when a heating element goes bad, that it wouldn't heat at all (continuity or not). I'm leaning towards a faulty thermostat on the electric side but not sure.


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Old 06-07-2016, 09:10 AM   #4
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I do not know enough about how the element would fail. I think they can get caked with crud (mineral buildup) . Mine blew when I ran it without water one time. Easy replacement from home Depot.

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Old 06-07-2016, 12:13 PM   #5
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The great majority of the time the element is either good or it isn't. There's usually no in between. Given that, I'd suspect the thermostat or hi-limit. It's probably the Hi-Limit has weakened and is tripping lower than it should.

It probably wouldn't be a bad idea to pull the element just to be sure.
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Old 06-07-2016, 12:56 PM   #6
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Quote:
Originally Posted by doc73 View Post
#1 make sure the bypass valve is closed..

#2 my heater always is better to recover from propane than electric. I just use it to maintain the temp when at a full hookup. Mine was a 1500 watt unit so I am not sure what the actual comparison to the btu's of propane.

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All Suburbans 6Gal and larger have a gas input of 12,000 Btuh and an electrical element rated 1440W. To convert Watts to btuh simply multiply by 3.41, so the electric element will provide 4910 Btuh.
Thus, the gas provides about 2.4x as much heat as the electric.

By the way, if you want to calculate how many BTU it takes to heat a stream of water, you can use: Q = 500 x GPM x dT (Q is Btuh, GPM is the water flow in gallons per minute, and dT is the temperature difference you want.)

Assume you want to run a 1.5 GPM shower head, your incoming water was at 60 degrees and you want a 95 degree shower. You would need to put
Q = 500 x 1.5 x 35 = 26250 Btuh of heat into the water stream.

If you just want to know how many Btu it takes to heat a certain volume of water by a number of degrees you can use:
Q = Gal x 8.3 x dt. So if you had a 10 Gal storage tank, initially at 60 degrees and you set your thermostat @ 100 degrees. It will take 3320 BTU. A 10 gallon gas/electric suburban would be @ 100 degrees after about 15 minutes with both gas and electric running (I've made a slight adjustment since all the gas input Btus do not get into the water - some goes out as hot exhaust gas). The same scenario with only the electric element would take 40 minutes.
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Old 06-07-2016, 12:59 PM   #7
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Quote:
Originally Posted by DSQR View Post
All Suburbans 6Gal and larger have a gas input of 12,000 Btuh and an electrical element rated 1440W. To convert Watts to btuh simply multiply by 3.41, so the electric element will provide 4910 Btuh.
Thus, the gas provides about 2.4x as much heat as the electric.

By the way, if you want to calculate how many BTU it takes to heat a stream of water, you can use: Q = 500 x GPM x dT (Q is Btuh, GPM is the water flow in gallons per minute, and dT is the temperature difference you want.)

Assume you want to run a 1.5 GPM shower head, your incoming water was at 60 degrees and you want a 95 degree shower. You would need to put
Q = 500 x 1.5 x 35 = 26250 Btuh of heat into the water stream.

If you just want to know how many Btu it takes to heat a certain volume of water by a number of degrees you can use:
Q = Gal x 8.3 x dt. So if you had a 10 Gal storage tank, initially at 60 degrees and you set your thermostat @ 100 degrees. It will take 3320 BTU. A 10 gallon gas/electric suburban would be @ 100 degrees after about 15 minutes with both gas and electric running (I've made a slight adjustment since all the gas input Btus do not get into the water - some goes out as hot exhaust gas). The same scenario with only the electric element would take 40 minutes.
Thanks, I knew someone would know it.

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Old 06-07-2016, 01:50 PM   #8
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Unhappy Install Mistake

Recently replaced hot water element and while unit was open, decided to replace thermostat....just because. Mistake I made was I did not mark or take picture of wires. Realize it is a 110 volt line interrupted by thermostat, but does it make a difference if Power In line is on the top ( reset button end ) or on the bottom. Dumb mistake on my part.
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Old 06-07-2016, 04:13 PM   #9
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While it really doesn't make a difference, the factory wiring is from the power through switch to the hi-limit (reset) through the t-stat and to the element.
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Old 06-07-2016, 05:58 PM   #10
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Heat formula

Quote:
Originally Posted by DSQR View Post
All Suburbans 6Gal and larger have a gas input of 12,000 Btuh and an electrical element rated 1440W. To convert Watts to btuh simply multiply by 3.41, so the electric element will provide 4910 Btuh.
Thus, the gas provides about 2.4x as much heat as the electric.

By the way, if you want to calculate how many BTU it takes to heat a stream of water, you can use: Q = 500 x GPM x dT (Q is Btuh, GPM is the water flow in gallons per minute, and dT is the temperature difference you want.)

Assume you want to run a 1.5 GPM shower head, your incoming water was at 60 degrees and you want a 95 degree shower. You would need to put
Q = 500 x 1.5 x 35 = 26250 Btuh of heat into the water stream.

If you just want to know how many Btu it takes to heat a certain volume of water by a number of degrees you can use:
Q = Gal x 8.3 x dt. So if you had a 10 Gal storage tank, initially at 60 degrees and you set your thermostat @ 100 degrees. It will take 3320 BTU. A 10 gallon gas/electric suburban would be @ 100 degrees after about 15 minutes with both gas and electric running (I've made a slight adjustment since all the gas input Btus do not get into the water - some goes out as hot exhaust gas). The same scenario with only the electric element would take 40 minutes.
It usually takes two beers to heat 6 gal. Of 60 deg water to shower comfort zone for me
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