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Discussion Starter · #1 ·
I am trying to use my series connected 63 gallon high recovery unit and 50 gallon "normal" heater. Both natural gas, natural draft. Each seem to work fine seperately. When valved in in series though, the hot water in the morning only seems to be the temp of the first tank, which is 90. I have the second set at 120. Any suggestions. I have them valved so I can run each individually one at a time or either being lead or lag.
 

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smaller is first, you think this would cause the problem?
i stated that wrong, the one with the most BTU should be first (this is typically the largest as well), since it will be doing most of the work heating the cold water as opposed to the second one which is heating preheated water from the first.

as far as temperature, i'm not sure why the temperature wouldn't resemble what is in the second tank since that is the water heater that is actually feeding the line to your faucets.

it may have something to do with your valve setup. a picture is worth a thousand words.
 

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Discussion Starter · #6 ·
a.o. smith has a bulletin out that claims the second water heater wouldn't cycle on until there was an increased demand. Sounds like my problem, as it seemed toward the end of my shower the water was beginning to warm up a little. Still don't understand why it wouldn't cycle on. Two seperate tanks with two seperate burner controls set at different settings. UGHHH!!!!
 

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i bet if you swapped them and put the high recovery unit first where it was drawing in cold water and heating it more it would work just fine. like i said before, you want the high BTU high recovery unit first.

maybe if you lowered the temp of the first unit and raised the temp of second unit it might help a bit, in other words, created a larger temperature difference between the two. that would ease the first unit and draw colder water into the second unit which would probably cause it to cycle on more often.
 

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Discussion Starter · #8 ·
Now that I know they will both work by themselves, I'll try that. They were both right out of the box so I wanted to make sure I didn't have a control issue with the big guy. I won't be able to see results til tomorrow probably.
 

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The water heater temperature control may be inaccurate. Usually enough hot water is used often enough that cold water (50 degrees or less) entering the tank reaches the level of the thermostat (aquastat) to kick the heater on at least once a day. With the 90 degree water from the first heater entering the second heater, that might not be kicking on the second heater for multiple days in a row even though the overall temperature of the water has dropped somewhat. (Once the heater does kick on, it may stay on long engough to get to 120 degrees or so.)
 

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Discussion Starter · #10 ·
Well this morning I checked the hot water and so far its hotter than [email protected]#t.. I swapped the heaters around about 5 last afternoon as Nitro suggested and also lowered the first tank setting just a bit (now 1 click CW past low). I was thinking that you wanted the biggest btu heater to be first simply for workhorse reasons, I wasn't expecting temperature problems. I will leave it this way for a couple days and then play around with settings some more to see if I can introduce a change and narrow it down to temp settings or btu lead lag config.
 
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