Adding indirect water heater on older ('82) weil-mclain HE-5

Discussion in 'HVAC Heating & Cooling' started by brainbone, Aug 26, 2008.

  1. brainbone

    brainbone New Member

    Messages:
    7
    Goals: We are remodeling the basement, and are looking to try to increase available space as much as possible, as cost effectively (cheap) as possible.

    Situation:
    We currently have a gas fired water heater that needs replacement for multiple reasons (age, clearance required around it for operation take up too much space, too many cold showers in the morning, etc.)

    We're thinking about replacing the water heater with a Triangle Tube "Smart 40" indirect water heater, attaching it to the HE-5. This would be stuck in a small closet, running off a new, 3rd, priority zone.

    Currently, we have a Weil-mclain HE-5 (133 btu in, ~82% claimed efficiency when new) installed somewhere in the mid 80's (before we owned the home). Running 2 zones, 1 for (2) Myson kick-space heaters in the kitchen, 1 for the rest of the house.

    We have an older home (1910). Typical 4 square, 2 story, ~1500 sq. feet., with an additional ~650 to be added when the basement is finished.

    We will have 2 bath (with a 3/4 possibly being added in the near future). 4 person household.

    Located in Minnesota. (cold winters, but since replacing our windows, the HE-5 keeps things comfortable)

    I would like to avoid replacement of the HE-5 at this time. (don't really want to spend $3,500+ on a new mod. boiler.)

    I will be doing the installation myself. Material costs for installing the water heater aforementioned are ~$1300-$1400.

    Questions:
    Will the HE-5 be up to the task?

    Any real negatives that an indirect water heater brings to the table, especially when run with an older, non-modulating boiler?

    Any other options that may be better than an indirect water heater for such a situation that would cost the same or less?
    Last edited: Aug 27, 2008
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    It should work fine. The only disadvantage is that the boiler will need to continue to run throughout the year. Not familiar with that particular one, but many of them, when on, cycle between the max and min settings, so there would be some standby losses. An indirect is pretty efficient and that boiler is probably 2-3x bigger burner than a typical standalone waterheater, so it should work fine. Since these things have the wholel boiler to reheat water, you usually can end up with a smaller tank than with a standalone. The thing to check is the first hour delivery. Some of them are available with SS tanks, and should last essentially forever. Mine is a SuperStor Ultra. I can dump 40 gallons into a big tub and be doing wash and dishes at the same time. My boiler only has 80K BTU. The tank is insulated well enough so that the boiler only runs once or twice a day...but I'm the only one using it - more people, more use.

    One thing that adds to the complexity is you should also install a tempering valve - it's required here, and a very important safety feature. So, figure that into your costs - plumbing it in adds to the complexity.
  3. nhmaster

    nhmaster Master Plumber

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    Na. you can hook it right in just like it was another zone. The HE does not have a low limit aquastat on it so it will cold start just like any other heat zone. Piece of cake.
  4. Southern Man

    Southern Man DIY Hillbilly

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    Location:
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    I agree it should. Page 12 of his manual shows this as a cold start boiler, so it will only run when there is a call for heat.

    Brainbone, you probably only have one zone now and will be adding a second. Figure 9 on this attachment shows how this is done with an aquastat controlled gas boiler and multiple zone relays. http://customer.honeywell.com/techlit/pdf/60-0000s/60-2278.pdf
  5. hj

    hj Moderator & Master Plumber Staff Member

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    heater

    Jut remember this is not "free hot water". The boiler has to have enough capacity to heat the house AND the hot water.
  6. brainbone

    brainbone New Member

    Messages:
    7
    jadnashua, nhmaster, Southern Man, hj; Thank you for your input.

    It seems unanimous that the HE-5 should be up to the task of both continuing to heat my home, while also providing hot water via an indirect water heater on a priority zone.

    A few more questions:

    - Any opinions on the Triangle Tube "Smart 40"?

    - Is the 36 gal. capacity of the Smart 40 enough for the typical 2 3/4 bath, 4 person, home?

    - The HE-5 is around 24 years old. How much efficiency do these things tend to loose over time? How much more life might I expect out of the boiler?

    - Should I entertain the idea of an electric water heater instead of an indirect? (I've had a few contractors push me in this direction)

    - Tempering valve. A good idea in any case?
  7. nhmaster

    nhmaster Master Plumber

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    It's a pretty good unit. I like Super Store but probably because I get a better deal on them. :D
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    A tempering valve is required by code where I live and is a good safety feature anywhere it isn't as well. It will add over $100 in parts, though. How much is one trip to the emergency room? It's good insurance. If you keep the water in the tank at 140, it provides more useable hot water as well (and keeps the tank from growing nasty things!), and that's too hot for a typical home, so the tempering valve makes that volume become bigger since you usually set the valve to around 119 (code says 120 and that gives a little tolerance).

    You need to look at the spec and see what the first hour rating is in gallons, then figure out what you think you'll be using. Then, see if that size matches your needs. Keep in mind that they usually only give specs for one or maybe two input heat ranges, so you may have to interpolate to get a good answer.

    With the priority zone, when the tank needs heat, you won't be getting any to the house. This isn't normally a problem. It could be if the shower was being run continuously for hours on end, but that isn't typical.
  9. brainbone

    brainbone New Member

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    7
    Is this the correct type of tempering valve for this situation?

    Showing 150 gal. w/90 deg. rise for 1st hour at 200 deg. boiler water supply, 112,000 boiler BTU output (my boiler shows only 109 BTU output max).

    Any recommendations on zone valves?
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Watts is generally a good company, but I don't have extensive experience long-term. If you chose that one, you'd want the L70A, since you'd probably want to set it to 120-degrees or so, which is plenty hot for a home. Your boiler may go to 200-degrees, but they often are set a little lower. You probably wouldn't want to raise the upper limit for this, so your output would be less. At say 2.5-gpm for a showerhead, that's 150 gallons in an hour so you could run one shower continuously for an hour and not run out of hot water. You have to determine how much is going to be going on at the same time, then factor that in to decide if that is enough.
  11. Southern Man

    Southern Man DIY Hillbilly

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    Location:
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    1. Depends on local code. A better option is to keep the tank temperature at 120F.

    2. I just put a 50gal in mine (4 person, 3 bath) and at 120F will not fill my wife’s Jaucuzzi tub. But it will at 125.

    3. Keep it clean and it shouldn’t loose much at all. Gas is a clean fuel so this should be very easy to do.

    4. Depends on the cost of electricity vs. gas. When I lived in NYS my electric bill was a second mortgage (Niagara Mohawk’s excuse: “because we have nuclear powerâ€), so I got a fuel oil fired direct hot water tank and the payback was 18 months. Here in the South the payback period is something like 20 years (Duke Energy’s reason for cheap electricity: ‘because we have nuclear powerâ€).
  12. Southern Man

    Southern Man DIY Hillbilly

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    Location:
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    This would be a different set up then the Honeywell diagram that I showed you, which used multiple pumps and zone relays. I have been told that the pumps work better than zone valves but don’t have personal experience to compare the two.
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    The tempering valve allows for safety and provides a greater supply of water at your desired, lower temp. It also prevents crud from growing inside of the tank. There's a reason organic stuff (food) should be either greater than 140 or less than 40...in between there, stuff grows very well.
  14. Southern Man

    Southern Man DIY Hillbilly

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    I didn't think of the growth issue since mine is on city (chlorinated) water. I like to keep my whole tank low because the dT between it and the boiler water should increase efficiency. Or am I missing something?
  15. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    I have iron reducing bacteria and various mold in my city water. Chlorine inhibits their growth and kills some, but not all; it keeps the levels low. But, then let it sit for awhile at ideal temperatures, and guess what, anything left grows! At 140 you not only maximize the hot water available, but prevent things from growing (and it will kill some of them as well).

    My boiler is set to run at around 140 for heating, but will go to 190+ when it calls for heating the water tank. If the tank is well insulated, the small difference in heat loss is not worth the potential risks. And, since a smaller tank at higher temp is equivalent to a bigger tank at lower temp in delivered water at a typical use, you can get by with a smaller tank. This results in a lower initial cost, and typically, quicker recovery with lower standby losses.
  16. Southern Man

    Southern Man DIY Hillbilly

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    I figured Nashua would have pretty good water. I grew up down the street (metro Boston) and we had great water, from the Quabin Reservoir.

    I didn't know that you could set up a boiler to run at two different temperatures like that. You must have two different aquastats?
  17. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    It's all done with a computer and a temperature sensor...it monitors the water temp and system needs, and adjusts firing as required.

    Nashua used to get all of its water from spring-fed ponds. As the city grew, they augmented it with water from the Merrimack river when needed, which decreased the quality.
  18. nhmaster

    nhmaster Master Plumber

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    Except in very high concentrations chlorene has no effect on legionella bacteria. In fact even raising the tank to 140 degrees and installing a tempering valve at the tank may not achieve the elimination of the bacteria because legionella bacteria are extremely resistant and studies have shown that even with the tank at 140, the bacteria can still propagate in the downstream piping. The only sure way to solve the problem is to go as high as 160 at the tank and then install tempering valves at each fixture as close to the valve as possible. An expensive proposition to be sure but I would look for it to be adopted by the code within 10 years.
  19. Southern Man

    Southern Man DIY Hillbilly

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    I would think that you'd have the same problem in the cold water plumbing.
  20. nhmaster

    nhmaster Master Plumber

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    Nope, legionella doesn't like cold water.
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