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coil recovery - no good

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Steve Eayrs
Steve Eayrs Member Posts: 424
in THE MAIN WALL
assuming the coil is plugged. In other words I would only pull the coil after checking the pump and impeller, and makin sure you have circulation, and then only if, (when the dhw tnak is cold) the delta T on the boiler dhw S&R is under 20-40 deg. or so.... depend on the demand.
Steve

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  • jim f
    jim f Member Posts: 182
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    coil recovery

    i have a customer that is running out of hot water. history. 10 year old 3 section weil mclain with coil and 10 year old superstore storage tank. when i arrived found piping to be all wrong. re-piped storage tank- still no recovery. went further as to check the dip tube. found dip tube faulty - replaced dip tube and thought i was in the clear. got a call today still no recovery. wow. my next ( i guess) would be replacing coil. should i be looking for any other problems?? thanks in advance
    jim f.
    tri-city heating and cooling.com
  • keith
    keith Member Posts: 224
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    firing rate

    The 1st thing that comes to mind is when do they run out H.W.? Is it when they are filling the tub, multiple showers, ect. Did they ever have sufficient H.W.? If so has the consumption changed? Maybe they are just trying to achieve the impossible.
    I am assuming we are talking about an oil fired boiler. If so, is the unit at the max firing rate?
    Can you acid wash the coil to improve the heat transfer?
    What is the delta T that is required?
    Good Luck
  • John@Reliable_2
    John@Reliable_2 Member Posts: 104
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    is the pump working?

    John@Reliable
  • Jed_2
    Jed_2 Member Posts: 781
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    What is the water source?

    If this is a 10 year old Super Stor, I don't think the coil can be changed(welded). Is there sediment build up covering the coil, located at the very bottom of the tank??

    Just a thought.

    Jed
  • jim f
    jim f Member Posts: 182
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    heres some more infothe unit is firing at max firing rate (.85 gph @100 psi). the water source is city water with decent pressure. the 006 is working with thermostat on storage tank set @ 120*. the boiler aquastat is set at 180 high 160 low with a differential of 15*. the more i thoght about it the more i was leaning towards the coil. i am not a big fan of acid washing coils. (potential problems for leaks). i did quote on replacing coil and customer accepted. doing the job on saturday. thanks for the input everyone.
    jim f.
    tri-city heating and cooling . com
  • jim bannister
    jim bannister Member Posts: 20
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    hot water coil

    If this is a booster tank piped off of the tankless, check for the check valve being defective and mixing cold water with the hot on the recirculating line. Also, check for both the circulator operating and that the impellor is still intact. These are cheaper than replacing the coil without being positive about the fault.
  • eleft_4
    eleft_4 Member Posts: 509
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    pump??

    If it's a storage tank why does it have a circulator pump?

    al
  • Unknown
    Unknown
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    Al , its a bronze pump

    to circulate the water through the coil . Jim , with the pump running , did the outlet of the coil stay hot ? We have that happen often when a salesman sells a new aquabooster on an old boiler with a shot coil . You turn the pump on and get a blast of hot water on the coil out , then it goes lukewarm . How did you pipe the tank and the coil ?
  • jim f
    jim f Member Posts: 182
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    i piped the coilby this diagram on page 6


    http://www.bardhvac.com/digcat/techdoc_cd/pdf-file/2100-339.pdf
  • Tom M.
    Tom M. Member Posts: 237
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    hot water or steam?

    Is this boiler for forced hot water or steam. If it is for steam, the outside of the coil could be as gunked up as the inside. Also if it is an oil-fired steam the tankless coil should be in the left rear of the boiler and not in the front opening. I know it sounds crazy but I've seen it before. If this is the case, the coil will not be under water.
  • eleft_4
    eleft_4 Member Posts: 509
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    pge 6 shows hook up to an electric water heater

    Jim,
    The cold inlet needs to go thru the tankless, the flow needs to match the tankless rated output. If you feed the cold to the tank, it will cool the water in the tank. The pump will circulate thru the tankless and bring the water temp up when there is no water being drawn out. When the hot water is being used the cold water is injected into the tank but does not get heated until the pump circulates it thru the tankless, this demand is probably greater than the rating on the tankless. The oldies worked well mounted higher than the coil with out the pump but did not work well with a pump.

    jm$.02

    al
  • MikeB34
    MikeB34 Member Posts: 155
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    No recovery

    Did you check for a mixing valve problem in the house plumbing? if the tank was all pipied wrong, maybe you should look at that. Amazing the # of times I found a bad valve or tap injecting cold water into the hot water system. Just kill the hot water out and turn on a couple of hot taps. if H2o appears, voila! problem found.
  • kk_2
    kk_2 Member Posts: 57
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    Tankless or indirect???

    You mention a SuperStore, which implies indirect. You also mention the coil in the boiler, which implies tankless.

    Is this thing piped so that the hot water from the tankless coil in the boiler is being circulated through the heat exchanger in the SuperStore? If so, I would think it would work horribly. You'd be going through 2 heat exchangers, and would end up with very little hot water coming out of the SuperStore.

    Just a thought.
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