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Anyone interested in knowing tank-in-tank jacket losses?

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Uni R_2
Uni R_2 Member Posts: 589
in THE MAIN WALL
Yes... the copper is all wrapped - it has recirc so wrapping was absolutely necessary - but the recirc is off now.

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  • Uni R_2
    Uni R_2 Member Posts: 589
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    Anyone interested in knowing tank-in-tank jacket losses?

    If anyone is interested in knowing the jacket losses for a Phase III tank-in-tank indirect I might just have the perfect lab.

    I have a Smart 50 that isn't busy right now because my house is listed and I'm living elsewhere so no hot water is being used right now. I have a PC that I can plug into the GasCom port on my Prestige 110 and monitor it extremely well for multi-day periods to get an idea of the daily loss.

    I'm hoping my "lab" sells soon, but dang I'm gonna miss my system. ;-)

    Any interest? If so, what temp(s) for the indirect? Anything else critical for testing, hysterisis for example?
  • Steamhead (in transit)
    Steamhead (in transit) Member Posts: 6,688
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    Sure!

    maybe 125-130 tank temp or so, like many we find in the field....

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Unknown
    Unknown
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    I would like to see your results

    I install the same systems but never really checked the loss.
  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
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    supposed to

    be 1/2 degree an hour ad nauseum..

    I suppose to split hairs you could increase tank temp and see what happens to standby loss..organizing my sock drawer would be next on the list...;)
  • Ross_7
    Ross_7 Member Posts: 577
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    I'd be..

    interested for sure!
  • sootmonkey
    sootmonkey Member Posts: 158
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    none

    Yeah, It might be interesting to see what the losses are when the tank is at 120 or 130 degrees and then compare them when the tank is at 150 or 160 degrees.
  • Uni R_2
    Uni R_2 Member Posts: 589
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    First test started...

    Switched on the hot water at 4:09 pm. The tank was at room temp in a 65° basement.

    By 4:45 the water was at 152°, the boiler had shut off and the standby test started. Modulation down from 5300 RPM max fan speed starting at 4:26 for those interested.

    The min/max temp of the boiler closet itself will be loosely tracked as well since it was up to 72.5° from 64.9° by 4:45. Both the boiler and the DHW tank are in a 30" x 7' enclosed closet area.

    I'll start a new post in a couple of days with some findings. The GasCom monitor will run continuously plus I'm logging the gas meter as well.
  • Unknown
    Unknown
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    Just curious UniR,

    is the copper piping to & from the tank protected with a thermal trap/insulated?
    Wouldn`t this also effect the S/B losses?

    Dave
  • Uni R_2
    Uni R_2 Member Posts: 589
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    Copper Dave?

    Copper Dave? It's all twisted, just like me. LOL

    The black iron is absolutely minimized in length. In fact, the Smart tank is turned 90° so that its back is towards the boiler to keep the piping at its shortest possible length. The pipes are wrapped, although far from perfectly.
  • Unknown
    Unknown
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    Actually old friend,

    I was referring to the potable side. ;-)

    BTW- See my smileys?, I have learned a few more things thanks to you!

    Dave
  • Unknown
    Unknown
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    How are You Doing,,

    joj;l;lj Shithead!

    Dave
  • Unknown
    Unknown
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    Good Man,

    I`ll be watching you`re findings with baited breath.

    Hope we get a chance to have a beer before you fly the coup!

    Dave
  • Uni R_2
    Uni R_2 Member Posts: 589
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    So far...

    The boiler appears to be firing for roughly 7 minutes every 7 hours.
  • Uni R_2
    Uni R_2 Member Posts: 589
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    The lab sprung a leak...

    Long story short, I guess the 7 mins of rapid heatup every 7 hours resulted in the bottom of the pump flange leaking - it hadn't leaked before so this was strange.

    Luckily it was noticed before the open house tomorrow. The flange is tight, the floor is once again dry and the test is back on.

    I first looked at the PC GasCom monitor and saw a "Insufficient Gas Pressure" warning. I was wondering if I hadn't paid my gas bill, because as I scrolled back through time, I could see the odd blip where the fan spun up to ignition speed but never started so spun right back down. The low water pressure sensor must just shut the gas off directly. Once I looked at the water pressure gauge and saw that it was zero, I knew something had happened and sure enough when I went around the other side and looked at the boiler I saw the puddle.
  • kpc_74
    kpc_74 Member Posts: 14
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    any update?

  • Uni R
    Uni R Member Posts: 663
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    I will early next week...

    On the initial run the tank was set at 152° and the boiler was using about a cubic meter of gas per day (40,000 BTUs) to cover the standby losses. The boiler, a Prestige 110 was running for about 6 to 7 minutes every 6 to 7 hours to maintain tank temp. A cubic meter here costs around 50 cent so that's $180 a year although in the winter the jacket losses add heat to the house. The losses are high, but 152° is pretty hot.

    I am now running a test at 128° and I suspect the standby losses will be a lot lower. The problem with the tank in tank is that the outer boiler water is even hotter than the domestic water inside the inner stainless tank, at least initially, so the jacket has to be that much better to insulate the higher temps.

    I typically kept my tank at just under 120 so the boiler would condense making hot hotter and then once a week cranked it to 60C/140F, but that's something that really should be done in an automated way.

    In a perfect world, maybe someone could develop a small battery powered controller to replace the rotary dials on the Phase II tanks so that it could be cranked up to a sterile temp once a week like a Vito, maybe on a wash day or weekend if there is a heavy hot water load, and then let it idle over night and bring it up to lower temps on weekday mornings.

    The "lab" is sold so I will have to wrap up testing during July. Then there will be about a 99% change of getting stuck with forced air home. Not many boilers in NorCal, or solar for some strange reason. :-/
  • Uni R_2
    Uni R_2 Member Posts: 589
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    128* Results

    With the tank peaking around 128* on the domestic side the results were as follows:

    Test started June 19th at 1:30 pm.

    The boiler fired 11 times since then. Maximum interval was almost 11 hours until the first refire and then almost down to 8. 5 hours for the next 2 and then they stabilized more or less. The average interval was 9 hours and 8 minutes. The average firing time gas on to gas off was 4 minutes and 10 seconds.

    The boiler would fire at an average rate of about 97 MBH over the first minute as it picked up from 3600 RPM and spun up to 5300 RPM (avg about 4750). At this lower tank temperature, the boiler would not begin modulating back down before the gas was cut so the subsequent 3+ minutes were fired at approx 108 MBH according to the meter.

    Over the 101 hour period from finishing its 1st firing to starting its 11th firing, 10 firings consumed approx 73,166 BTUs (approx 2 M3 or $1 of NG) - or roughly 724 BTUs per hour.

    I'm gonna redo the higher temp test the next time I am away.

    *****

    One thing I never knew about the MCBA on the Prestige is that every 24 hours it exercises the system pump for 10 seconds. It would see the blip each day at 7:21 pm.
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