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Indirect HW vs conventional gas HWH

CouderayCouderay Member Posts: 314
I'd opt for the indirect


  • jerseygirljerseygirl Member Posts: 3
    Indirect HW vs conventional gas HWH

    Hi,we are renovating a house and installing new gas hot water baseboard heat in a 2700 sf colonial with 2 1/2 baths. We are a family of 4, inc 2 young children, we live in NJ.

    GC has proposed 2 types of systems - one a gas boiler with a 75 gallon gas HWH and the other a gas boiler with indirect HW. He called it a boiler-mate - a tank attached to the boiler for HW. Obviously, boiler would run year round with indirect vs conventional gas HWH.

    The reason for suggesting the indirect is he wanted to move the boiler to a mechanical room on the opposite side of the house from the playroom. ( Old furnace was smack in the middle of the basement, chimney was removed during renovation.) To locate the furnace there, he can only run one vent out the side of the house, hence the indirect HW system. Alternative is to locate the boiler and HWH on the opposite side of the house (playroom side) where there is more room for required 2 vents and equipment would be located along outside wall and he will make a closet around it.

    We have hard water.

    So, my question is, which is a better, more efficient set up bearing in mind that either costs me the same? He will install either system I choose.

  • Uni RUni R Member Posts: 589

    An indirect has far lower standby losses (hot water in the tank cooling down when it is not being used) and you will only have one burner to service. It also keeps the boiler conditioned over the summer... definitely not a difficult choice.
  • I opted for

    I'm for any brand but boliermate by Amtrol
  • jalcoplumbjalcoplumb Member Posts: 172

    The indirect might cost more but it will out perform the standard water heater. Most indirect units have a lifetime warranty. I agree with the post about not using the Amtrol Boiler Mate. I have seen the coils gunk up with sediment and need to be cleaned, not to mention a lot of leakers.

    A standard 75gal gas water heater will make about 80 gallons of water per hour vs. a 30gal SuperStor Ultra at 154 gallons of water per hour. A 30gal Weil McLain Gold Plus will make around 140 gallons per hour. This is based on a boiler size of around 110,000 btu with a properly sized circulator properly sized feed and return pipe.

    I prefer to use them with a modern condensing and modulating boiler like a Munchkin, Ultra, Trinity or Knight boiler. These boilers have a 90%+ AFUE and hold only a couple of liters of water vs. the standard cast iron boiler, which has an average AFUE around the mid 80% range. This makes a difference when you are using the boiler all summer long to make hot water.

    Good luck on your endeavor,

    Joseph A Landree
    J.A.L. Co. Plumbing & Heating
    East Windsor, NJ
  • FloydFloyd Member Posts: 429
    No brainer....

    the indirect is the only way to go.... esp. if you have hard water, but if it is a tank in tank design. The indirect that use a coil to heat the dom. water will give trouble.
    Also I hope that the GC isn't doing the work himself, and has a sub to do the heating work. I have had to follow many GC's around that think they know heating also, and fix their's high eff. heating systems require much more knowledge to do them properly then the heating systems of the past.
    Just my experience, but my son and I compared gas bills from last month, basically used gas for hot water and cooking only for the month, he has a standard gas heater and I an Ultra boiler with a WM indirect. My gas bill was 20 dollars less than his, there are six in his house four in mine....

  • Bill ClintonBill Clinton Member Posts: 38
    hard water

    Some hard water conditions are bad enough to cause problems with certain indirects. The heat transfer coil is often finned to increase surface area and can "lime up" when heating hard water. Avoid finned coils.

    Alternates to finned coils are available. Buderus makes an indirect with large diameter smooth coil. Triangle tube makes a tank-in-tank design that has a large, smooth heat exchange surface. There are others.

  • Wayco WayneWayco Wayne Member Posts: 2,467
    Triangle tube

    Smart 50 indirect is my fav. It is distributed from Jersy too. Down near Cherry Hill. WW

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • jerseygirljerseygirl Member Posts: 3

    Thanks for all the responses. GC is not doing the work himself. Subcontractor suggested the indirect to GC, but GC did tell me a "boilermate" and called it a tank for the hot water and I would never run out of HW. I will ask for more specifics, but now I am confused about whether I should get a coil or a tank and what is a Boilermate by Amtrol - coil or tank? Our hard water gunks up everything plumbing wise, so that could be an issue. Also, why does no one like the separate gas HWH that would only have to run in the summer instead of running the boiler?

  • Mike EMike E Member Posts: 81

    I don't know if you've had a chance to read this yet, but here is the reply I gave to your post on the other forum.

    * Posted by aemeeich_ on
    Sat, Sep 2, 06 at 1:33

    I would also reccomend an indirect installed with your boiler as opposed to a tankless coil, or a stand alone water heater.

    Most standard gas water heaters have an energy factor of about .6 This roughly means about 60% efficiency. The reason they have such low efficiencies is because of the flue running through the middle of the tank of hot water. You are loosing heat up the flue at all times throughout the day.
    Electric water heaters have EF's in the upper 90s, however since electric is so much more expensive than gas in many areas, inefficient gas heaters are still cheaper to run than electric.

    Boilers with a tankless coil are basiclly the same as a gas water heater. The boiler has to stay hot all day long, just to be ready IF you use any hot water throughout the day. They are also constantly loosing heat up the chimney. (Some gas boilers have flue dampers that automatically close during the off cycle - and those systems don't loose as much heat.) Since the boiler is constantly loosing heat, the burner has to fire to maintain heat throughout the day - even though you aren't using any hot water. If you look at most european boilers, you'll notice that none of them have tankless coils. Europe is ahead of us in hydronic technology since fuel costs are so much higher there. They do things as efficiently as possible. Also, if you look at most new high efficiency american boilers, you'll also see that they no longer offer tankless coils.

    Now an indirect coupled with a cold-start boiler wastes very little heat. The indirect tanks are very well insulated and loose very little heat throughout the day - some as low at 1/4* per hour! When you use hot water in the mornings, the boiler will fire to heat up the new cold water, then when it is satisfied, the boiler will shut off - usually for the rest of the day (or the next time you use alot of hot water). The boiler will then cool down, and will no longer be loosing heat up the chimney. This works best with a low-mass boiler that will heat up and cool down very quickly.

    You should seriously consider taking the next step up and base your system around a modulating/condensing boiler. These boilers can see up to 99% efficiency if the system is designed correctly. Example -
    This is just one brand, there are many different models from most manufacturers.

    Have your contractor size the baseboard to run with 140* water at design conditions - or even lower (preferably 120*) This way you will be in condensing territory at all times, and be running at peak efficiency.

  • MarkMark Member Posts: 312

    Im in New Jersey too...not that has any bearing on your question :o).

    An indirect (or boilermate) is technically superior to a conventional water heater, hands down. It has less heat loss (insulation) , much quicker recovery rates (returning to set water temp), more capacity (in terms of how many gallons of hot water it can deliver in one hour) and are more efficient.

    I was faced with a similar decision and actually removed a 1.5 year old conventional heater (code issues from a boiler replacement) and opted for an indirect.

    Down side of the indirect...its more costly to purchase and install. But that cost is easily amortized. They are more efficient and last longer. Youll use less fuel over a longer time. Conventional heaters last only about 8-10 years and are only about 60% efficient, yuck!

    As another poster mentioned, your installer must insure the boiler, circulator and piping (pressure drops) for the indirect are sized properly or you will not achieve the 'advertised' ratings of a given indirect heater.
  • rucomfyrucomfy Member Posts: 10
    Question. please

    In reviewing the Smart 50 Triangle Tube website I noticed that the Smart 50 can be piped with ZV or circ. I have three (3) zone system with ZV and one 007 pumping away.
    How do you pipe the Indirect with ZV, do you use another 007 in place of the Zv shown on the schematic. It would seem to me that if a used a Zv I would lose a lot of capacity unless HW makes a 1.25 Zv or do they? Thanks
  • frankfrank Member Posts: 202

    Taco makes a 11/4" ZV, but I believe the wireing requires that all other ZV's be Taco also. [Not a bad product]. You should install a propriatory relay for all the ZV's, do not install another Circ. bwdik?ijap
  • Bob ForandBob Forand Member Posts: 305
    Crown Megastor


    Crown Megastor ( maybe others ) have a cleanout port on the top of the indirect. This would be good in your situation as the coil can be cleaned if necessary. The Crown Megastor also has a lifetime warranty. It is a stainless steel indirect tank. Check out Crown boiler website for more info..
  • jerseygirljerseygirl Member Posts: 3

    many thnaks for all the responses
  • Ray LandryRay Landry Member Posts: 114

    in response to the large diameter zone valve question, I have always preferred installing a dedicated circ for the hot water loop on a boiler for a few reasons 1) if a circ fails, you get no hot water, if a zone valve fails open, you get scalded, 2) zone valves which are slow to close can result in over heating of the tank 3) more often than not the pump connected to the boiler is undersized for that of an inderect 4) it's easy to do! I generally use a taco ZVC relay when I run into a system that has zone valves as the method of heat zoning. wire you t stats and zone valves as normal on the relay, but on the last zone (priority zone) install your aquastat for the domestic on the thermostat terminals, and jumper your end switch terminals. Wire your hot side of the pump to the N/O and common terminal on the priority end switch relay, and the neutral shares a common neutral with the incoming line voltage. Your heating pump goes to the extra end switch terminal wired witht eh same method as mentioned above
  • DaveDave Member Posts: 1,405
    Indirect water heaters

    I just installed (with help) a Weil Mclain Ultra 155 with an Amtrol Boilermate.

    In Ontario, we require a double wall design, so this reduced our options to a few such as the Weil Mclain, or Amtrol.
    My installer recommended the Amtrol, and saved a couple hundred dollars.

    In hindsight, I wish I stuck with my original idea of the Weil Mclain. I found out after the fact that the Amtrol has standby losses of 1 deg per hour. The Weil Mclian is less then half of that.

    So I am going to buy some reflectix, and wrap another inch around the tank, and hopefully bring it down.

    Other then that, the indirect is amazing with a high efficiency, high output boiler. With the built in support for priority hot water, and separate temp setpoint, it works like a charm.

    I tweeked the boilermate to operate from 108 down to 103.
    The pump used to run on for 30 seconds, which would bring the tank up to 116.
    I then upped the run/on to 90 seconds, as the boiler still had 146 deg in it. After 90 sec, the boiler is 132, and the tank is 122.

    It is truly endless hot water. If the tank is at the bottom of the cycle (103) when my son starts his shower, the boiler kicks in, and within a couple of minutes, the boiler shuts down at the top (108) while he is showering.
  • DaveDave Member Posts: 1,405

    ANyone got any experience on superstor vs amtrol water heaters? (i need an inderect model) today :-)
  • Paul FredricksPaul Fredricks Member Posts: 1,542

    I don't know about the other brands, but Honeywell makes larger bore zone valves that look like their standard valves. It's been a while since I've used one, but if I remember right they have a "CV" rating on them that might have been like .35 or 3.5 or something like that. I have used them in the past on indirects with no problem, though I prefer to use a circulator for maximum recovery.
  • TroyTroy Member Posts: 479
    Superstor, superstor,superstor

    I would use the superstor over amtrol even if it was twice the price. It will out perform amtrol and if you need it superstor will honor the warrentee. Amtrol- good luck.
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