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Indirect water heaters

Wayco Wayne_2Wayco Wayne_2 Posts: 2,472Member
I have a customer who needs more performance out of her indirect water heater. she can't go larger in storage, but wants more output. Which indirects have the best heat transfer rates and the lowest resistance to flow?


  • kcoppkcopp Posts: 3,325Member
    edited January 2012
    I believe...

    the tank-in-tank design has the lowest flow loss. You most likley have to pipe it in 1 1/4" That would be TTube. Then do the mix valve on it.
  • Jean-David BeyerJean-David Beyer Posts: 2,629Member
    Tank within tank.

    I am a homeowner and have a Weil-McLain Ultra Plus 40 indirect. It is really a Triangle Tube. The domestic tank (inside) holds 36 gallons and the heating tank (outside) holds 6 gallons. They suggest using these pipe sizes between the boiler (varies by boiler size) and the indirect, and a 9 gallon per minute circulator for my size indirect.

    NOTE 1: To ensure adequate flow rate through the

            boiler, use the following pipe size on all

            boiler loop piping (connecting boiler to and

            from the primary/secondary connection):

                  -80   or -105 ­  1" or larger.

                  -155 or -230­  1¼" or larger.

                  -310­              1½" or larger.

               Use at least the minimum piping size

                above and pipe the boiler using only pri-

                mary/secondary piping as shown. Failure

                to follow these guidelines could result in

                system problems.

    Part of this seems to be to ensure adequate flow through the boiler. The amount of hot domestic water available depends, in part, on the temperature of the hot water from the boiler and its flow rate through the indirect. W-m recommend a 190F boiler tempreature to get the rated output. My needs are less, so I run it at 175F. You are allowed to run it up to 210F input, but that would scare me because of the (default) +|- 5F temperature range of the temperature control in the boiler.I fear that putting 215F into the outside tank risks boilnig the domestic water.
  • Mark EathertonMark Eatherton Posts: 5,843Member
    My vote goes to Turbomax...

    99% efficient.

    Keeps mod cons in the con mode when making hot water because it only needs a a boiler water temperature roughly 10 degrees F hotter than the target DHW temperature.

    Copper tube design is self scouring thereby avoiding lime scale accumulation.

    Comes in small foot print sizes, with a BIG heat transfer ability. (T33 = 36 gallons, = 254 GPH of 100deg F rise water with 200K btuH input).

    I am not aware of ANY failures of these tanks I've deployed in the last 10 years.

    Good to see you Wayne. Don't be a stranger :-)

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • HenryHenry Posts: 907Member

    I am sorry to say something bad about a product "made in Quebec" but we have replaced a good number of turbomax units. They fail in high usage such as large apartment blocks and hotels. The best bang for the buck seems to be the HTP S/S indirects or the Viessman units. We have yet to replace any of those!
  • Mark EathertonMark Eatherton Posts: 5,843Member
    edited January 2012
    What kind of failures are you seeing Henry...

    Liming, HXer failure, tank failures?

    What mode?

    Personally, I've had numerous failures of the HTP products, and moved to Turbomax for that very reason, coupled with product efficiency. The HTP heat exchanger is fairly small, has a pretty substantial pressure drop, and takes a mod con out of con mode to do DHW production.

    Viessman does get much closer, having a large surface area, but at a fairly ex$pen$ive price.


    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • SWEISWEI Posts: 7,356Member
    tank in tank

    Really works well with our hard water out west.  The design of the TT inner tank keeps hard water from sticking to the walls and flow resistance is practically nonexistent.
  • HenryHenry Posts: 907Member

    Most if the time, it is tank shell failure. Although we have also had a few with copper heat exchanger failure. It is easy to spot that one when the safety pops!

    I have installed several HTP SSU 60, 80 and even SSU199C. Somehow are installs still let the boiler condense, most of the time. Perhaps it is because we purposely over size a bit.
  • Mark EathertonMark Eatherton Posts: 5,843Member

    Thanks Hank,

    I suppose that any time you are making a gazillion widgets, you can expect to have a certain percentage of failures. Have you requested that the manufacturer give you a post mortem diagnosis on these failed tanks, or did they just end up as land fill?

    I always want to know WHY something failed. It lets me sleep better knowing that it wasn't something that I had done to cause the item t fail early.

    Appreciate your feed back. This is what makes this site priceless to contractors like us. Probably makes the hair stand up on the necks of the manufacturers, but we still have a need to know.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • MpjMpj Posts: 109Member

    I think it would be great if the manufactures did post about there products here, the good and the bad. I find it amazing that when something goes wrong on a product and you call the manufacture and they know about the problem and let you "in" on there little secret ( how to repair or if it needs to be replaced). Just a thought.
  • SpeyFitterSpeyFitter Posts: 421Member
    Indirect vs output

    The Viessmann's Vitocells have a very high output coil for the size of tank as do the new Lochinvar Squires - they both heat up very fast.

    I'm also partial to the Bradford White RTV series at the moment because I have installed a fair number of them and I've also yet to see or hear of a failure of one. They are 444 stainless steel which handles chlorides better than some 300 series stainless tanks. They produce a Dual Coil Indirect the RTV-75D. Not sure if 75 gallons is too big but this dual coil tank has good output.

    I think, could be wrong, but I think AIC's new REX indirect is sort of like a turbomax concept (reverse indirect) but made out of stainless, but I'm still trying to get some product specs on it - just saw some basic pictures and info on their website on it.
    Class 'A' Gas Fitter - Certified Hydronic Systems Designer - Journeyman Plumber
  • bob eckbob eck Posts: 863Member

    Take a look at using Triangle Tube Smart Stainless Steel Indirect water heater. Their heat exchange surface is one of the largest. Store the water at 180*F and use a temp valve to send to faucet at 120*F. Why do you not have the home owner install low flow shower heads like the Alsons/Delta 655C 1.6 GPM heads. If there is room look at installing a fiberglass storage tank before the IDWH. 80 or 120 gallon temper the cold incoming water temp. If water temp is from a city supply the incoming water temp could be as low as 45*F get that temp up with storage. Does the home owner have Nat gas or LP gas? what about a tankless gas water heater?
  • HenryHenry Posts: 907Member
    HTP & instant

    I understand that HTP manufactures for others. As for instant heaters, STAY away if you are in cold climates. We stopped installing them some time ago as they cannot give us 145, yes 145 rise in January and February! Our water temperatures go down to 34F during this period. I have the city charts. Also, most homes don't have 1.5 to 2 GPM faucets!

    There is no need and it really does not work here, a seperate storage tank before the indirect. Let the mod/con do its job with the indirect.
  • hot_rodhot_rod Posts: 11,629Member
    How much boiler?

    Do you have to drive it? If you want fast recovery you need horsepower to drive it. A dual coil tank with both coils connected gives you a lot of hx surface. Look for a brand with large diameter coils. Caleffi comes to mind. One concern with reverse indirects is plugging of the copper cool mainly with hard water and high boiler side temperatures. They can plug at the header where all the tubes connect.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Jean-David BeyerJean-David Beyer Posts: 2,629Member
    a seperate storage tank before the indirect

    "There is no need and it really does not work here, a seperate storage tank before the indirect. Let the mod/con do its job with the indirect."

    When I first heard about putting a separate uninsulated storage tank before a hot water heater, it seemed like a pretty good idea. Free heat to take the chill off the water before the hot water heater got it.

    But really, where does that "free heat" come from. In my case, if I had such a tank, it would be in my unheated garage, so there would be precious heat available when I needed it most. Had my mod-con been installed in the house somewhere (kitchen, perhaps?) the heat would come from the air in the house -- air that would have to be heated by the boiler. So why waste the space for that extra tank? The heat has to come from the boiler in any case.
  • SWEISWEI Posts: 7,356Member

    If you put that tank behind a south facing window, paint it black, and surround the back and sides with a bit of foil-faced foam insulation, you get a solar batch pre-heater.  In the summer, it should take care of itself without the boiler.
  • icesailoricesailor Posts: 7,265Member
    Indirect Power:

    AMEN !!!

    Like bringing a pocket knife to a gun fight.
  • icesailoricesailor Posts: 7,265Member
    Sunny Thoughts:

    How well does that work once the sun goes down and before it comes up?

    Like designing heat loss in a room facing the south and allowing for Solas Gain, when it is coldest in the middle of the night and the moon is up. No wind and radiational cooling.

    I'll need the scraper on the windows of the truck tomorrow.
  • SWEISWEI Posts: 7,356Member

    On the location of course, but you can add a layer of coated glass in front of the tank which will cut the re-radiation significantly.  Then there are motorized drapes.  Or go to a full solar thermal system with drainback or glycol if that makes sense.  There are very few locations in the US where solar thermal DHW makes no sense at all.
  • Jean-David BeyerJean-David Beyer Posts: 2,629Member
    But but

    If I had that window, I could put up a piece of thin cardboard, paint it flat black to absorb the heat, and use that heat to heat the room. So the opportunity lost by doing the flat black pre-heater tank comes out even. The energy that goes to heating the water is the same energy that could otherwise be used to heat the house.

    There is no free lunch.
  • hot_rodhot_rod Posts: 11,629Member
    a few dual coil options

    here is how I have connected the dual coils to maximize the performance. It could also be done with a 3 way zone valve. The upper coil is heated first for quick recovery, then switch to the bottom coil. Assuming there is not a recirc pump connected to the system.

    I like the large diameter smooth coils in hard water conditions.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
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