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Should it take this long to charge my tank?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by infinitymike, Apr 9, 2013.

  1. infinitymike

    infinitymike Minister of Fire

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    Last year I ran the oil burner with a coil to heat my DHW.
    I finally got an indirect DHW hooked up in the middle of this season.
    It is a Superstor Contender with a 50 gallon tank. I have it set to 125* and there is no differential setting.
    Quite honestly I didn't really pay attention to how long it would take to charge. Until now.
    I haven't needed heat for the past two days so I've been more in tune to the need for DHW.

    I changed the setting on the aquastats, I raised the high limit to 200* with a 30* differential.
    I lowered the low limit which turns on the oil burner to 100*
    I lit a small fire in the morning and when it reached temp I shut it down.
    There was enough demand yesterday and more to come in the evening with showers that I decided to light a small fire at 7pm and brought the boiler up from 140* to 200* and shut it down.

    It was 11:30 pm when I finally took a shower. I was laying in bed and could hear the low hum of the circ pump for the indirect. I woke up at 12:30 and it was still running. I went down and killed the power to the circ.
    This morning the boiler was down to 140* so I light a fire at 5am and turned on the circ pump at the same time. The boiler reached 200* and shut off but the circ kept going for more than an hour.

    Same thing tonight, boiler was down to 130* and after washing a few pots from dinner the zone was running continually for almost an hour.

    Is that normal or is my plumbing wrong.
    I'm still not 100% convinced that my primary/secondary loop (or injection loop as someone said) is plumbed correctly. Maybe that is the cause. Or maybe the 60 feet of 1" pex from the boiler to the loop isn't large enough. I can only imagine how ineffecient my heating is based on how long it takes to bring the tank up to temp and how much extra wood I might have burned:(

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  2. BoilerMan

    BoilerMan Minister of Fire

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    Mike, can you post a diagram of your piping setup? That would be very helpful. When charging my 115gal indirect from 100 to 140, I can bump the high limit (185 and floor injection starts to avoid idle) several times. All said the zone will run for about an hour, but I could pump heat to the indirect's coil much faster if I actually ran the specified 10gpm through it.
    You should run it out of hot water and drain it and refill with cold tap water, then fire the boiler and only let it charge the tank (turn other loads off for the expierement) see how long it takes to charge cold (like 50 or 55 degree) water up to your aquastat's setpoint.

    TS
  3. Woodsrover

    Woodsrover Member

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    I'm finding the same thing running the boiler just for DWH in the am and pm. I think there's two things going on. When you're heating one, two or three other zones in the house there is a lot of warm water circulating around the system. I also think the heat zones are returning water a lot warmer than your indirect is. With just the indirect taking hot water and returning it colder than when everything is running together you're realizing just how much energy it takes to bring water from probably 45 degrees to 125 degrees. With all the hot water running around your heat zones you get more of a flywheel affect. With just the indirect its an uphill climb the whole way.
  4. infinitymike

    infinitymike Minister of Fire

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    Even better a video!

  5. infinitymike

    infinitymike Minister of Fire

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    that makes sense.
    The water in the system lines when heating are well over 125* most of the time.
    and they are never down to 45-50* like the street water.

    But the indirect shouldn't drop all the way down to 50*. It should start getting hot water from the boiler immediately .
    I understand that I am bringing in 50* street water but I can't be using all 50 gallons with one shower.
    It will take longer as the WG water drops in temp during the day and I am trying to heat 50* water with 130-140* water.
    I just thought the recovery time would be quicker.
  6. ewdudley

    ewdudley Minister of Fire

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    I think typically for indirect the hot goes in the top port and return draws from the bottom port, but I don't see how that would make enough difference to cause a problem.

    For the DHW season I think you could disable the big pump on the distribution loop, then close that valve in the loop down on the lower right (I think I'm seeing a valve in the loop down there).

    With the big pump running, the distribution loop is mixed down to a lower temperature. But if the pump was off and the valve was closed then the DHW pump would be drawing the hottest water off the top and returning the cool to the bottom.
  7. arngnick

    arngnick Member

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    I agree but will add that I do not see any insulation on the pipe. If you are running 60ft times 2 I assume you will have quite a loss by the time you get to the indirect and back.
  8. infinitymike

    infinitymike Minister of Fire

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    There is no insulation on the last couple feet because I had to flip flop the supply and return lines as the enter the loop and pulled off the insulation. But the rest is insulated.
  9. heaterman

    heaterman Minister of Fire

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    Mike, a couple things.
    I think you have kind of a hybrid Primary/Secondary system going on there. In a straight up P/S system with the main loop being the primary and each of your zones secondary, you would have each zone supply/return spaced within about 4-5" of each other on the main. This would be just as you have your oil boiler tied in. The feed from the WoodGun is done that way also. The heating loops appear to have the supply and return on different sides of the main loop. This could be causing some ghost flow in the heating loops due to pressure differential between the supply and return.
    Whether that has anything to do with your domestic issue.......I haven't thought that far yet.....

    Concerning the indirect, you would normally want to see a good size delta T between the boiler temp and the indirect setting. Most are designed to work with 35-40* to hit the rated recovery. Once you get down below 15-20* delta T the recovery rate really drops off so I would think that a long recovery time is going to be normal if you're working with a 140* boiler water temp.

    One question while I'm thinking about it.......Is the domestic tank pump set up as a priority load on your zone panels? Some of those Argo controls had that option so heating demand could be turned off while the indirect recovers.

    I think an easy way to tell what is going on would be to check the water/pipe temperature on all for guzinta/guzoutta locations where your Wood Gun ties into the system. If the flow is right you should have nearly the same temp at the inlet of the WoodGun supply as you do at the outlet of that tee going into the main loop. If there is a temp difference of much over 5* at those two locations, you will know that the primary loop is flowing more gpm than the Wood Gun is dumping into the system. So while you may have 140-150 at the wood gun inlet, it's getting diluted with the water running around the primary loop before it gets to the tee for the indirect. This will also slow your recovery rate way down.

    Check those and see what you find. You want to know temperatures at..........

    A. Supply from the Wood Gun
    B. Supply to the main loop
    C. Return to the Wood Gun
    D. Return from the main loop

    Nice Video BTW. :)
  10. ewdudley

    ewdudley Minister of Fire

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    He's got a 00R on high speed pumping from the boiler and mixing valve to the 'primary loop' through 120 ft nominal 1" PEX round trip, vs a 007 on the 'primary loop', so it's fair to assume there's mixing on the order of one to one.

    There's a valve that closes off the supply side of the loop from the return side. I'm saying just close that valve and disable the 'primary loop' pump and call it good for the summer.
    heaterman likes this.
  11. nate379

    nate379 Guest

    My heating system it similar to yours, but I'm running a natural gas boiler.

    If I drained my 50 gallon water tank and filled it back up with cold water (about 45* water here) it would take it about 45 mins to be heated to 125*. My boiler is set to 140 on, 160 off.
    Only time I've run low on hot water is when running my pressure washer off the water tank. After 30-40 mins of washing something the water will start getting luke warm at best.

    Maybe an issue with the small piping? All "main" runs are 1.25". Reduced at the zone valves to 3/4"
  12. heaterman

    heaterman Minister of Fire

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    Didn't notice the valve but what you say would indeed work.
  13. infinitymike

    infinitymike Minister of Fire

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    His answer about all this was "your getting heat! Right?!"
    I feel like I am driving my truck with 1 flat tire and 3 tires with low pressure. Sure I am moving but how effeceint am I and how long before something else goes wrong.

    In your experience, do you think there would be any consiberably gain in moving the lines around to a true P/S system and/or increasing the supply lines from 1" pex to 1.25" or 1.5" My guy originally wanted to use 1.25" but then said the fittings were to hard to find locally and said ahh don't worry 1" will work.
    To late now, but he hasn't gotten any work from since the botched up job. And quite honestly I haven't found a plumber locally that knows how to do a P/S system. You guys have taught me more, so I'm on my own with you guys to help me.
    Anybody need any advice on how to frame a house? we can barter!;)
  14. R Mannino

    R Mannino Member

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    I think the 1" is fine for the primary and moving plenty of heat, the coil in the indirect is small and that is what is taking so long for the tank to satisfy.
  15. infinitymike

    infinitymike Minister of Fire

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    That's plausible.

    I will say this. Since the indirect was hooked up, I have taken the hottest showers in the 8 years I've been in this house.
    That old oil bomb with a coil couldn't keep up and in less then 5 minutes I had like warm water.
    I have yet to run out of piping hot water even when the circs are running for 45 minutes.

    I just think that it's a waste of electric and a lot of wear on the pumps.
  16. infinitymike

    infinitymike Minister of Fire

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    Hey I just noticed you are from LI.
    I'm in Northport and you?
  17. R Mannino

    R Mannino Member

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    A little further east, Ridge.
  18. R Mannino

    R Mannino Member

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    Indirects are the best, you have a lot of hot water there ready to use. Standby loss is your biggest enemy with heating and DHW, that's why tankless coils suck, high standby losses.

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