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  1. #1
    Join Date
    Feb 2008
    Posts
    30

    Gas WH thermostat control band

    I have been looking into tankless WHs lately partly because the way my current NG water heater thermostat behaves. The temp at the nearest tap just after a heatup cycle is about 132. But the burner doesn't kick on again until it drops to about 105. This is too cold to get a hot shower after passing through 3 floors of copper pipe. Yes, I can jack the thermo up to the top and the band is something like 140-112. Still marginal for a good hot shower in the winter. Basically, the only time I have hot water is after I have used some. So I have been checking the temp in the AM and when it's low I run enough water to activate the WH. Then all is good.

    I have never had a gas WH before and I wonder if this is typical behavior for the old bimetal style thermostats. If not, what is a proper and typical control band? Are the new self-powered digital electronic gas thermostats, like the Sears/Honeywell any better at this? Are they reliable?

  2. #2
    Join Date
    Jan 2008
    Posts
    89
    Sounds like you've got a defective thermo in that WH. It should be firing a lot sooner than it is.

    I hope the digital thermo units are reliable. I just installed the 12 year Kenmore hydrosense in one of my homes. That one is made by State. I prefer the AO Smith built kenmores, but they were too tall for this application.

    Sounds like a hot-cold recirculating pump might solve your problem. These hook up between the hot and cold water connections in your bath (usually under the sink) and are controlled by timer. It switches on 15-20 minutes before you usually use the shower, and runs water from the HW line back into the CW line, which will kick off the WH and warm up the HW line all the way up to the bath.

  3. #3
    Join Date
    Feb 2008
    Posts
    30
    Thanks for the feedback on the thermostat. I was thinking that it had to be an abnormally wide control range. It has always been that way. The spring feels stiff when I turn the 'stat which makes sense considering the way it behaves. It just takes more force than it should to switch.

    Incidentally, my WH is a State and has been trouble free for 13 years except for the thermostat issue.

    Honeywell makes the Hydrosense controller for the Kenmores so hopefully they will be reliable. I may go with one of those myself although they are slightly shorter than my existing 50 gal State unit. Not that big deal to fit, though.

    Which Kenmores are made by AO Smith? I may consider those, too, if they have the full thickness R16 insulation. I am also looking at the GE 12-year WHs. They don't have the fancy controllers but they are the same height as my current unit and have the thick insulation.

  4. #4
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,396
    Normal. Had a B-W rep tell me the typical gas valve is +/- 18. I have the same issues. Never quite know if I'm getting luke warm water just before the burner kicks in or scalding water since the machine has been running.

  5. #5
    Join Date
    Feb 2008
    Posts
    30
    Yes, I have looked into the recirc pumps. I almost did one 5 years ago but they cost almost as much as a water heater. I suppose the timer operation would flow enough to activate the WH but the pipes wouldn't hold much heat for long after it shuts off, no pipe insulation. A manual switch for the recirc pump would be nice to run it right before shower to heat the pipes and save running a few gallons of water down the drain. But those recirc pumps are just too darned expensive for what they do. Now those full blown reirc systems with insulated pipes sound like just the ticket. Gotta design that in from the start, though. Retrofit would be hideously expensive in a place like mine.

  6. #6
    Join Date
    Feb 2008
    Posts
    30
    +/- 18 degrees would be great! My variation is more like 25-30 degrees. I need to get more feedback on the new digital controllers like the Sears/Honeywell Hydrosense. Their advertising says something like "more consistent temperature" but they don't give numbers.

    Quote Originally Posted by BaldLoonie View Post
    Normal. Had a B-W rep tell me the typical gas valve is +/- 18°. I have the same issues. Never quite know if I'm getting luke warm water just before the burner kicks in or scalding water since the machine has been running.

  7. #7
    Join Date
    Jan 2008
    Posts
    89
    I couldnt find a lot of data on the hydrosense either, but had the same "oh well, at least its a honeywell controller" line of thinking. I know State makes it because the box it came in had a reshipment label from State to Sears and from Sears to the local store. State is part of AO smith these days, so its probably all about the same.

    AO Smith makes the Powermiser 12, which is what I've used the most since its reasonably priced, has a good warranty, is widely available with a trip to the nearest Sears or OSH, and is often on sale.

    The powermiser 12 is this model from the AO smith line:
    http://www.hotwater.com/lit/spec/res...RG-SS01506.pdf

    The powermiser 12 has a better warranty than the hydrosense, the hydrosense is 12 years tank and 3 years parts, the powermiser is 12 years tank and parts.

    I guess Sears isnt excited about replacing that honeywell unit in 5-7 years if it fails.

    Both are R-16, have the rotoswirl self cleaning feature that doesnt really work that great, use a pair of magnesium rods and the second rod is a half length that goes in the hot water port...and its really easy to change if you've got a couple of feet of clearance.

    The powermiser is about 65" with the diverter while the hydrosense is about 61.

    Both also have pretty good first hour rates and good efficiency...both qualify for the $30 PG&E energy efficiency rebate. Check your local utility for energy rebates...you might be able to bump up to a better WH for less money. The GE units you're looking at are a little less efficient (I think they're .58?) and dont qualify for PG&E rebates.

  8. #8
    Join Date
    Feb 2008
    Posts
    30
    You're the first data point I could find on the Hydrosense. In general I have found that electronics either fail right away or are good to go for a very long time. So hopefully the Honeywell box will last. After Hurricane Ivan destroyed their WH (among other stuff) my parents got a Whirlpool elec WH with their electronic controller. That failed a couple of times before they got a good one. It was easy to replace and Whirlpool supplied them cheerfully. It's been good for a couple of years this time.... so far.

    The lit says the Hydrosense uses upper and lower temp sensors. I am betting that they are RTDs that feed the temp circuitry and the control band is just a design parameter of the circuit rather than a quirky mechanical device like the bimetal springs. So it could and should be a tighter range. I wonder if it is even tuneable via a potentiometer? But I bet the factory settings will be fine. I am leaning more towards this than taking a chance on the variability of the models with the old style thermostats.

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,790
    Some of your temp variance could be mineral build up on the well.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  10. #10
    Join Date
    Feb 2008
    Posts
    30
    Maybe some. But it has always behaved this way, even when relatively new. At first I even suspected that I had one of those bad dip tubes that would disintegrate and allow cold water coming in to short circuit to the hot outlet. I took the thing apart and the dip tube was fine. :-/

    And I do flush it periodially. Not annually, but usually every couple of years.

  11. #11
    Join Date
    Jan 2008
    Posts
    89
    FWIW, the documentation that comes with the Hydrosense says almost nothing about how the unit works or anything operational on the controller.

    Theres a blinking LED that shows the unit status...one regular blink means everything is working okay, otherwise it blinks out a code that you can look up in the manual that shows a dozen or so fault codes. Thats pretty cool.

    Otherwise, whats on the Sears web site is more info than I could find elsewhere.

    But it does say on the sticker on the side of the unit in the store that it monitors the temp in several different areas of the tank and operates to maintain balanced temps.

  12. #12
    Join Date
    Feb 2008
    Posts
    30
    Well, you got me thinking about recirc pumps again so I just went to the Depot and got one of those Watts units that mounts on the WH hot water outlet. It was more reasonable than the other mostly under sink units I had researched about 5 years ago. Install was easy and it seems to work just fine. It has the timer to set it to run when there is expected demand. In my situation mornings are predictable but nights aren't so I'll probably just set the timer to "on" 24/7 and connect it to an Insteon module. Then I can program it to run in the AM and start it manually from a keypad or remote a few minutes before I need it other times. Timing won't be so critical in the wintertime as any heat loss will just end up in the house anyway. But in summer I'll run it as little as possible.

    With the one included mixing valve it takes care of the long branch of my HW piping that goes to the upstairs bathrooms. I may add another valve to the kitchen sink but that run is shorter so not as critical. I only have to run about 2 or 3 qts out there before I get hot water.

    Maybe I'll get another year or 2 out of my water heater since the recirc should jump start it in the AM and I'll be able to get a hot shower. :-)

  13. #13
    Join Date
    Feb 2008
    Posts
    30

    electronic diagnostics

    My parents' Whirlpool elec has similar diagnostics. But in my experience with theirs whatever flashing pattern it produced basically meant that the controller was broke and you were screwed. :-/ I'm sure the Honeywell will be better. It had better be because that is probably what I will be getting in the not too distant future.

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