# How would you set up two 50 gallon hot water heaters in series?

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• posted on March 14, 2011, 8:10 pm
I bought a home a few months ago and didn't even think to look at the hot water heaters.
A friend suggested today that I set the temperatures differentially; and when I asked why, I realized I had no idea why or to what advantage two hot water heaters would be set up in serial connections. (I'd have used one for the teen's bathroom, and another, in parallel, for the rest of the house.)
Anyway, what's the THEORY and RATIONALE for having two hot water heaters in parallel?
Specifically: - What's the main advantage (is is simply gallonage?) - What is the main benefit? - What is the key drawbacks? And, most importantly: - Would you set the temperatures differently on them or the same?
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• posted on March 14, 2011, 9:16 pm

Two 1.5KW elements in serial will split the voltage in two reducing the power by four so you end up with two 375watt elements.
VD
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• posted on March 14, 2011, 9:24 pm
VirtualDen wrote:

i would bet the pipes are in serial, not the electrical system. doing it your way would mean the water would almost never got above warm.
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• posted on March 14, 2011, 9:27 pm

Ok now that would make more sense.
VD
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• posted on March 14, 2011, 9:25 pm

Oops I missed the part of your questions below. I would say why would you want them in serial.

Two 1.5KW elements in serial will split the voltage in two reducing the power by four so you end up with two 375watt elements.

Two 1500 Kw heater

None
I would reduce both to your convenience. You do not really need this water to be so hot. If it is not to save energy, it is safer for young children or old people if an accident would happen.
VD
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• posted on March 22, 2011, 3:04 am
On Mon, 14 Mar 2011 14:25:48 -0700, VirtualDen wrote:

Just for clarification, they're propane hot water heaters.
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• posted on March 14, 2011, 9:28 pm

More hot water because of the double volume, and faster recovery because you have double (whatever is heating them)
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• posted on March 14, 2011, 10:06 pm

the hot water from #1 heater going into the second heater (in series)doesn't get heated unless it's temp is lower than what the thermostat is set at. and available volume or flow rate doesn't increase,because a tank can only flow so much water,and that flow has to go thru the 2nd tank.
a parallel connection allows both tanks to add to the water supply(double flow) and both tanks do the heating.
I doubt a series connection would pass inspection.
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Jim Yanik
jyanik
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• posted on March 14, 2011, 10:45 pm

I'm certainly not talking about installing them is series, and neither is the OP.
"Anyway, what's the THEORY and RATIONALE for having two hot water

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• posted on March 14, 2011, 10:59 pm

See,it clearly says "serial" connections. that's same as "in series".
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Jim Yanik
jyanik
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• posted on March 14, 2011, 11:42 pm

I don't know what a serial connection is, but here is the op's quote . "Anyway, what's the THEORY and RATIONALE for having two hot water

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• posted on March 15, 2011, 2:12 am

And I explained why. Along with why a serial connection is not used.
If you don't know what a serial connection is,how can you comment on a parallel connection? you don't know the difference,if you don't know what a serial connection is.
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Jim Yanik
jyanik
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• posted on March 22, 2011, 3:03 am
On Mon, 14 Mar 2011 21:12:47 -0500, Jim Yanik wrote:

Well now I'm thoroughly confused.
It sure LOOKS like a serial connection.
The cold water from the well pressure system goes into the first hot water tank and out of the heat pipe of the first tank it goes into the cold inlet of the second tank and out of the heat pipe of the second tank it goes to the house with a recirculating motor somewhere on that final output (I can see the recirculating pump and I can hear it but I don't know exactly how it works.)
So, all that LOOKS serial. The house was built to code I would think, at least originally.
Plus there is that web site that explains serial hookups. So are you SURE that serial hookups would not be to code? Why?
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• posted on March 15, 2011, 12:42 am
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theory as the dual element electric water heater, where the bottom element heats the cold water that comes from the mains or well, and the top element heats the warmed water. It will more than double the amount of hot water available.
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• posted on March 14, 2011, 9:31 pm
On 3/14/2011 4:10 PM, Aaron FIsher wrote:

Which is it? Series or parallel? Or do you want to go from parallel to series?
I worked in a restaurant that had 5 gas heaters in series. The last one in line was hot all the time. When it dropped to a certain temp, it stayed on and turned on the previous heater so it would be suppling warm water to the last heater and so on down the line. The owner was a retired engineer. The purpose was to only heat one tank when that's all that was needed, and as the need for more hot water rose, the other heaters kicked on as needed. You could get over 20 gallons of hot water a minute continuous, never letting the temp fall below... I think it was 150F.
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• posted on March 22, 2011, 2:52 am
On Mon, 14 Mar 2011 17:31:28 -0400, Tony Miklos wrote:

My mistake for not being clear.
They are clearly in series.
The well pumps the cold water which goes to a four-foot high blue steel bladder tank which goes to the first 50 gallon hot water heater which goes to the second 50 gallon hot water heater in series which somehow goes to a hot-water recirculation motor about the size of a small bench grinder motor ... which goes to the bathrooms, laundry room, and kitchen.
My question is why (I'm slowly learning why) and what to set the temperature at (since it's currently set the same for both at about 130 degrees or so).
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• posted on March 22, 2011, 3:17 am
Aaron FIsher wrote:

He had a big unit, working on night-current only(very cheap in our country), and a small unit after it, using day- and night-current. The small unit would quickly heat(big heating element), and would be fed with cooler water later in the day. That combi had a rather constant water temperature for a reasonable price. Thermostats were the same on both machines.
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• posted on March 14, 2011, 9:41 pm

See http://www.chinawinds.co.uk/diy_tips/installation_series_and_parallel.html .
Basically, in series connection, the first one (which gets the cold water) normally does most of the work. The second one, which normally gets pre-heated water, does much less work. During periods of low draw, it may do no work at all, if the inlet water is already at its set point.
So if they're in series, you might consider reducing the setpoint of the first one, to balance the workload of the two units, ie, have them each heat the water by the same number of degrees. That's assuming there is some advantage to doing so. Presumably the lifetime of the heating elements (or burners) is basically so many hours of actually making heat. Offhand I can't see how the lifetime of the tank or the anodes, would vary by workload. Actually I've never heard of a burner failing, and elements and anodes are replaceable, so maybe workload doesn't matter much.
Arguably, keeping one of them at a lower setpoint may reduce standby losses from it, too.
Chip C Toronto.
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• posted on March 14, 2011, 10:04 pm

Lots of hot water when you need it.
I have only been in one house plumbed that way. It was an older couple who only turned on the breaker for the first unit in the series when the family came to visit. They did claim that the tempering factor of bringing the water into the basement pre-warmed it a little in the winter. That seems somewhat reasonable to me. The rest of the time the one was just fine for them.
If I were running both at the same time, all the time, I would set the first in the series a little lower, as low as fit my needs. The second one would be set to deliver water at the temp I wanted. I would do this to save the standby loss on the first unit. Unless you are filling the big tub or have a large family 50 gallons is adequate for most needs.
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Colbyt
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• posted on March 22, 2011, 2:46 am
On Mon, 14 Mar 2011 18:04:33 -0400, Colbyt wrote:

Interesting.
I might even turn OFF the first hot water heater (or set it to something really low, like 50 degrees or something).
The only one who uses a lot of hot water is the teenager (and that kid can freeze because there is no reason to take an hour-long shower anyway).
I wonder if this will affect the hot-water recirculating system adversely though?