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

[Aaron FIsher]

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?

[VirtualDen]

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

[chaniarts]

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.

[VirtualDen]

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

[VirtualDen]

Ok now that would make more sense.

VD

[RBM]

More hot water because of the double volume, and faster recovery because you have double (whatever is heating them)

[Tony Miklos]

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.

[Chip C]

See

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.

[Colbyt]

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.

[Jim Yanik]

"RBM" wrote in news:4d7e883d$0$12977$ [e-mail]:

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.

[RBM]

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

[Jim Yanik]

"RBM" wrote in news:4d7e9a81$0$10366$ [e-mail]:

you better REREAD the post;

See,it clearly says "serial" connections. that's same as "in series".

[RBM]

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

[clare]

It is not that uncommon, so MUST pass inspection. It uses the same 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.

[clare]

Even with series connection you can run kids shower off the first one and dishwasher off the second, etc. The first one heats to a preset safe temperature, and the second heats to a higher temperature, using only as much power as is required to raise the temperature that amount - and can deliver a whole lot of hot water without any significant drop in temperature.

[Jim Yanik]

"RBM" wrote in news:4d7ea7d4$0$13006$ [e-mail]:

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.

[mm]

What temp do you all keep your hot water at.

I like that mine is not hot enough to burn me, but it would probably wash the dishes better if it were hotter, and it would be easier to get the bathtub warm when it cooled off or I made it too cold.

So what temp do you all use?????????

[mm]

I missed it, I think. I think 140 is what the seller of the house told me. I have to find my thermometer.

Thanks.

[jamesgangnc]

There are different options. In series if you set them the same you will have lots of hot water. Downside is that the 2nd one won't actually run a lot and you will have the maximum costs to maintain the water at the set temp. Set the first one a little lower than the second. This gives you really rapid recovery if you use the entire first tank. Also evens out the running time and reduces the maintain temp costs. But this will redcue the amount of hw you can draw in a single go. Parallel doesn't really work well as you can not even the draw. Parallel works better if you dedicate each tank to specific fixtures and appliances. The most common is to have a second tank dedicated to a master bath that has a large tub or spa. Also insures that you (the master) have hw when the kids use all theirs up.

[Steve Barker]

Mine's about 145. Use less hot water the hotter it is. duh.