Sunday, April 15, 2012

What every boiler owner should know about indirect water heaters

Indirect water heaters have been around since the 1970’s in this country, but somehow, even after all this time, they don’t seem to be very well understood. They get their name from the fact that they’re heated “indirectly” by your boiler. They’re connected via piping to your boiler and circulate relatively hot (usually 180 to 200°F) water from your boiler to a heat exchanger within the water heater. The water surrounds the coils of the heat exchanger to produce your domestic hot water. This is in contrast to the typical gas- or oil-fired water heater that heats water through the use of a “direct” flame or heat source within the water heater.

If your home is heated by a boiler — any boiler (hot water or steam, oil or gas, mid- or high-efficiency) — you have every reason to heat your domestic hot water with an indirect water heater. Some of the benefits include:
  • High efficiency When you use your boiler as a heat source to produce your hot water, the water is heated at the same efficiency as your boiler. Some high-efficiency boilers reach 96%. The average gas water heater is about 60 - 70% efficient.
  • Reduced heat loss An indirect water heater is very well insulated and loses very little heat during long stand-by periods (at night or while you’re away). A gas water heater is always losing energy up the chimney.
  • High performance The performance of an indirect water heater is a direct result of the boiler it’s connected to. Given the size of most residential boilers, it’s not unusual for an indirect water heater to produce two to three times the amount of hot water as a standard gas water heater.
  • Longer life — Most indirect water heaters have a lifetime tank warranty. It will likely be the last water heater you’ll ever need. The manufacturers can offer this warranty because their tanks are not subject to the abuses that a direct-fired gas water heater is. And many of them are made from stainless steel to prevent corrosion.
  • Hot water storage. Available in sizes ranging from 30 - 200 gallons or more, hot water can be stored for high-volume flow-rate usage when you need it.
 The photo at right shows a cut-away view of a typical indirect water heater, with the coil located at the bottom. Boiler water is circulated through the coil and surrounded by the domestic hot water in the tank.

“But Wayne,” you may ask, “doesn’t this mean I need to run my boiler all summer now, too? Won’t that cost me a bundle?” Au contraire, my energy-conscious friend. The only time the boiler fires is when you need hot water. And when it does fire, it’s producing hot water at a higher efficiency rate than a typical water heater. Other than that, it sits quietly and waits. The belief that the boiler is running all summer may be a throw-back to the days of tankless coils in older boilers. They had no storage capacity, so the boiler needed to stay hot all the time to produce hot water on demand.

“This is all well and good,” says the the intrepid Internet traveler, “but I’ve been hearing that the new tankless heaters are the greatest thing since Apple went public. Can’t I save a lot more money with one of those?”

Well, speaking of apples, this is really an apples vs. oranges comparison. A tankless heater usually has little or no storage capacity, meaning it needs to heat the water instantaneously. And it can do that — with some limitations. Older tankless heaters drop the temperature at high flow rates (two fixtures running). Newer models limit the flow rate to maintain the delivery temperature. An indirect heater can handle that high flow rate without reducing the temperature or flow. And, depending on the size of your boiler, it can do it while delivering almost limitless hot water.

Better tankless heaters have efficiency ratings in the 80 - 95% range but typically last just 15 - 20 years. An indirect water heater connected to a 15-year-old cast-iron boiler will deliver hot water at 80 - 82% efficiency. And one connected to a modern modulating/condensing boiler can deliver 96% efficiency. So while tankless water heaters are efficient, they can't beat indirect water heaters.

Indirect water heaters can also reduce your maintenance costs. Having only one gas- or oil-fired appliance means less service. A tankless heater needs to be serviced every year. If not, you can count on reduced hot water production, possible heat exchanger failure and loss of warranty coverage. An indirect water heater requires little additional maintenance beyond your annual boiler safety and performance check-up.

The next time you’re in the basement, take a look at your existing standard water heater. If it's a little worse for wear, you may want to remember that the typical water heater life is 12 years. Wouldn't it be nice to replace it — once and for all?

Heidronically yours,

Wayne

127 comments:

  1. Really why can't you use it for heating the house? as well! Really the ideal thing would be to prevent the boiler from cycling on and off as often and using the indirect like a slave or backup for recirculating the heat through the base boards or radiators. Now you would be talking an increase in effeciency and or fuel savings. When your thermostat calls for heat the water comes from a recirculating pump from the indirect water heater first before the boiler is activated to kick on. Sort of like making a match burn twice. This is sort of what I am looking for or too accomplish. With the price of fuel oil maybe it is time to rethink and that is what I amn doing! And why I am looking into in direct water heaters or combinations there of. To help reduce my fuel oil costs as I live in a big old house sort of like a caretaker.

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    1. that would actually be very inefficient. The baseboards radiators would "use up" the heat stored in an indirectly heated storage tank in minutes if not seconds, compared to the long amount of time it takes to heat the water in the tank. There are ALWAYS losses in exchanging heat from one location to another, and it's simply much more efficient to heat water from your boiler and circulate it directly throughout the house without heating an entire tank of water, having heat loss from the tank not only during the time it's actually circulating thru your house but even when it's sitting there idle, and then have the energy stored in the tank be expended within a couple minutes while circulating, and have to reheat itself over the next hour (give or take) to be ready for the next time. Might want to rethink this process.

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    2. Wow what a Great Information about World Day its very nice informative post. thanks for the post. residential boiler

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    3. I wanted to know if I can replace my Weil-Mclain indectic tank for an eleltic water heater

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  3. I have an indirect tank, and just replaced the boiler. Now I'm seeing the boiler pressure steadily rise over a period of a week or so. I turned off the boiler autofill, but it is still happening. I think the boiler must be pulling water back from the direct tank, but I'm not sure how. Is this possible, and how could I fix it?

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  4. When I was in chelsea I and wanted to get boiler system for my new apartment and as well as wanted repair my old boiler too. I didn't know the proper idea regarding all that's why I had to boiler repair chelsea engineer to fix all. After getting above tips I am sure, next time it'll help me a lot.

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  5. solar water heater system has to be further researched to be made commercially more viable. It is still so priced, at initial investment, to be affordable to few.

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  6. A combi boiler provides heat for your radiators and domestic hot water on demand. ... No immersion heater, so no back up if there is a problem with the boiler. heating engineer Birmingham

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  7. We've seen an average of 25-30% fuel savings by switching from tankless coil to an indirect. All systems are different and your's is no exception. Depending on the type of system you have and the way you make hot water, you can see a payback in 3-5 years. so it's definitely worth looking into.

    However, considering the fuel dependency of this heater and the cause of it to the environment, I'll prefer to Solar water heater.

    Thanks,
    Pool Solar Heating

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  9. Thank you for sharing. Did you know the life expectancy of the average water heater is 8 to 12 years?
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  12. Why would i would I go hours without jot water from my indirect superstor and the get hot water

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  13. That is a really long time to be doing water heater repairs. I bet it has been really interesting to see all of the changes and innovations that have happened over the years. Regardless, it is good to take personal ownership and be as aware as possible.

    http://www.pennyplumbing.com/services/

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  14. Some of the information here is incorrect. A condensing boiler only has the efficiencies listed when producing water at low temperatures. When a condensing boiler is producing 180 to 200 degree water as suggested here it won't be condensing and therefore wouldn't operate at a higher efficiency than a standard boiler. Wayne needs to open a boiler catalog and look at the outlet temperature versus efficiency and see that boilers don't condense until you get down to around 140 degrees outlet temperature.

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    1. Hi Thomas. Thanks for your comments. While you're partially correct that a condensing boiler won't produce its highest efficiency if it's not condensing, it will always see higher efficiencies than a non-condensing boiler and much more than a tank-type water heater. If you're running a boiler at 140F outlet temp it will be condensing almost constantly. A boiler condenses when it's RETURN water temperature is below the flue gas dew-point which is generally considered to be about 135 - 140F for natural gas. Since most modern modulating/condensing boilers require a flow rate that creates a delta T of 30 - 40F, I have seen plenty of boilers condense when in DHW mode. My personal experience has been that I rarely set the boiler's DHW supply temp as high as you suggest. With the large heat exchanger surface of an indirect water heater, supply temps over 150F or 160F are rarely needed. And at these lower supply temps you'll see return temps plenty low enough to put the boiler into condensing mode. It's a great balance between recovery rate and efficiency.

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  15. Hi! Really enjoyed your post, and hope you have some insight! We just bought a house this week which has an indirect, off-boiler water heater. Every time we take a shower, it cycles from coldish to hotish and back. It's very unpleasant, considering the temperature outside is much less than freezing. Any insight you may have is appreciated!

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    1. Hi Kimberly. Congratulations on your new home purchase. I'm sorry to hear you're having problems with your indirect water heater. It's tough to say what the problem is without more information but I'd check first to be sure your indirect is set up as a priority circuit over space heating. After that, I'd look at the cold water inlet dip tube (if there is one) to be sure it's intact. The older Amtrol units were notorious for this one. Also, if your indirect has a thermostatic mixing valve on the outlet, it may be acting up. It could also be caused by a missing or fouled check valve on a hot water recirculation line. And finally, if your shower has a thermostatic mixing valve, it could also be contributing to the problem. I hope this helps. Good luck.

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    2. Thank you! You've given us a few good places to start!

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  16. Wayne, great blog. Just had a significant failure on a 10 yr.old Buderus indirect. They are having problems with their anode rods, and the fact that (according to their rep.) their installation/maintenance technicians aren't aware of proper maintenance. Also they just changed from a limited lifetime warranty to a limited 6 yr. warranty on the same tank. My service company estimates that it will be about $300 annual labor to drain and visually inspect the anode (according to new specs) and about another $300 to replace the rod. Also Buderus just increased the specs for replacement frequency of the anode. Although an efficient tank/system; I'm not sure I can continue to afford the maintenance! Any suggestions for my next tank?

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    1. I'd suggest you think about stretching out your anode rod inspection frequency to reduce your maintenance costs. You may want to check it on year 2 or 3 and make a judgement about subsequent service based on how much life appears to be left on the rod. Another strategy is to just plan on replacing the rod (rather than inspecting only). Anode rods aren't very expensive when compared to the labor to access it. If you stay on top of the anode rod you may find you never need to replace that tank. But if you DO need to replace your indirect, I'd highly recommend a stainless steel model.

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  17. Off oil-burner 10 + year old hot water unit is leaking in basement. Shut-offs not working so off at main resulting in shutoff of boiler also. NO HEAT or WATER in MA...It's snowing....
    I have good exposure and room for solar but lack money and as you can see, Time, for such an installation right now.
    How do I have a new Hot Water Tank Plumbed, Placed to add my DIY solar connections in future and what Capacity, Type-Manufacturer and other Considerations are appropriate for a smooth and inexpensive completion of this project? I will want this to qualify for Tax Credits if possible?

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  18. Hi Wayne,

    Great post! Very informative to us laymen. I do have a couple questions for you. My family and I have bought a multi-family building and we're presently in the middle of a full gut renovation. This will include new separate heating and hot water systems for each of the three apartments in the building. I was leaning towards a TriangleTube Prestige boiler w/ one of their smart series indirect water heaters. My question is, in your opinion, with this kind of system do you need a larger capacity water tank or can we go with something smaller? Two of the three apartments are roughly 825 sft 2 bedroom 1 bath. You'll probably have no more than two people living in them at any given time. Each will have a dishwasher and laundry. The third unit is a duplex 1.5 bath with dishwasher and laundry. We'll have three people in this apartment, but could go up to four. Anyways, I'm trying to determine what size tanks to go with... 30 gal. 40 gal. or 54 gal.?

    Thanks for any help you can give!
    James

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    1. Hi James,

      Congratulations on your purchase and your decision to use a hydronic heating and domestic hot water solution. I wonder if you've considered using one central boiler and indirect for the entire building? Your initial equipment costs would likely be lower than separate systems for each unit. That said, there are many variables that help determine the best system design for your particular situation so I couldn't possibly make a specific recommendation from where I sit. I would suggest that you work with your hydronic contractor, designer or supplier for help with the design and equipment selection. Another resource you may find helpful is the Wall at HeatingHelp.com. Lots of sharp people participate in that forum.

      Hope that helps. Best of luck.

      Wayne

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    2. Hi Wayne,

      Thanks for the reply. We thought about the one boiler/one water tank option and the equipment cost savings... however, I think we opted for dedicated systems so everyone is paying their own bills. I'll definitely reach out to some of those folks you suggested.

      Thanks again,
      James

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  19. If your home is heated by a boiler — any boiler (hot water or steam, ... hotwatertank.blogspot.com

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  20. Hi Wayne, this is a great post for someone in the market for a new water heater who knows very little about them. My 40 gallon tank is leaking and needs to be replaced. My plumber suggests upgrading to an 80 gallon tank. He recommends amatrol boiler mate as a brand. The difference in cost to me between the 40 and the 80 is $715. I have a family of four and we live in a four bedroom house. Do you think this makes sense? Are there any brands you particularly like or that outperform others? Thanks so much for any insight you can offer!

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    1. Hi Jenny! Thanks for reading my blog. To your question, an 80 gallon indirect water heater sounds awfully large for a family of four unless you have some unusually large usage pattern (like everyone takes half-hour showers back-to-back or you're filling a large whirlpool). I rarely recommend more than 40 gallons for a family of four, sometimes 30. Depending on the size (gas Btu/hr input) of your boiler, you'll have three or four times the recovery rate of a standard gas water heater. Ask yourself if you were running out of hot water with your old 40 gallon heater. As for brand, I'll tread lightly here and just say Amtrol has had their share of issues over the years. They may have resolved them. (Full disclosure ... I'm living with an Amtrol right now but will replace it with something else when it fails.) I like stainless steel indirects like the HTP or Utica (ECR). If you're heating with a steam boiler, you'll want one with a low coil and side boiler connections. Good luck!

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    2. Thank you for your reply, Wayne! The plot keeps thickening and something I neglected to mention is that we are on well water and chloride is an issue. In my research, I've learned that stainless steel may not be the way to go with chlorides, although we do have a water softener. The plumber has recommended Vaughn, cemented lined, or Alliance, porcelain lined, both of which get pretty bad reviews. Further research says that some SS tanks are okay -- the Superstor and Triangle. Do you have any thoughts on this? I never knew buying a water heater would be quite this complicated, but with such a huge purchase I don't want to mess up! Thanks again for your help! Jenny

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    3. Jenny ... The compatibility of a particular stainless steel indirect heater to water with elevated chloride levels depends on the type of stainless steel, the level of chlorides and the water temperature. If I were you I'd have my water tested to determine the chloride level and call Heat Transfer Products and Triangle Tube to get their recommendations. It may not be as much of a problem as you have been led to believe. All the best, Wayne.

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    4. Thanks again! Will do just that.

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  21. Hi Wayne - great post, thank you. Question. We have an indirect water heater with a gas fired boiler. Just now my daughter went to take a shower and there's no hot water. What should we do first to either try and fix or at least diagnose the problem? Thanks.

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  22. Hi Wayne,
    Great blog, thanks! Your trailing question "Wouldn't it be nice to replace it — once and for all?" is appealing indeed. But under what conditions is this true? Or maybe the better question is: Are there conditions under which this won't be true?

    I have a 40 gallon HTP Superstor indirect water heater which is coming up on 20 years old. Just recently, it developed a drip from the temperature/pressure relief valve. I had a guy come to take a look. He said he could replace the valve, but he didn't think that the valve was the problem. He said the valve was doing exactly what it should be doing. The problem, he said, was that the coil inside the water heater have gotten so gunked up over the years that the unit has to work extra hard to heat the water, which causes the pressure to rise, and the valve to relieve the pressure by dripping... and he'd happily replace the unit for $2400. Does his diagnosis hold water? And even if it does, is there a cheaper remedy then replacing the entire unit?

    (A couple of side notes: I haven't noticed any lack of hot water, or insufficiently heated water. Also, the water entering the water heater is treated by a water softener, but I don't know how effectively.)

    Marty

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  23. Hi Marty,

    If the relief valve on your indirect is leaking it's important to determine the cause. As you stated, the relief is a temperature / pressure valve. That means it's leaking due to an over-pressure or over-temperature condition. This can be determined by monitoring the pressure and temperature with a thermometer and pressure gauge while it's operating.

    I find it hard to believe that the problem is related to "coil gunk". That would only slow down the rate of heat transfer and you'd be experiencing slow recovery and have less hot water.

    If the issue is pressure related, you may need a pressure reducing valve (or your existing one has failed) or you may need a potable water expansion tank.

    If the issue is temperature related you'll want to look at the controls, especially the tank aquastat on your indirect.

    Best of luck,

    Wayne

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  25. This is in contrast to the typical gas- or oil-fired water heater that heats ... ewaterheater.blogspot.com

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  26. Pretty good post. I just stumbled upon your blog and wanted to say that I have really enjoyed reading your blog posts. Any way I'll be subscribing to your feed and I hope you post again soon.

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  28. A hot water coil in a boiler is expensive to run in the non heating months.I think indirects make sense for a family with heavy hot water needs. If you don't use a lot of hot water it's awfully hard to beat a standard gas hot water tank. My 40 gallon gas tank heater uses 5-6 therms a month (in the summer) - very little money.

    By the time you install an indirect with a bronze pump you are looking at several thousand dollars between labor and material. They can last a long time but they will eventually need replacing and the pump will not last forever.

    It's best to look at domestic hot water heating from all angles to make sure you select the method that works best for your situation

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    1. Hi Bob. Thanks for your comment. I believe you're referring to a tankless coil that requires the boiler to be kept in a state of constant readiness (hot) to provide hot water on demand. Indirect water heaters, however, are usually installed with a "cold-start" boiler that requires no stand-by energy use. A boiler with indirect will produce hot water with an efficiency much higher than a standard tank-type heater. Most indirect tanks are supplied with a lifetime warranty and modern cartridge circulators last many years before needing replacement. And even then, the replacement cost of a circulator is minimal. And a bronze pump is not necessary because it is circulating "boiler water" that is not oxygenated like potable water. I agree with you that it's best to look at DHW heating from all angles. For an owner with a boiler, a long-term, objective analysis will show the indirect as a hard-to-beat option.

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    2. everything you said is true, but do you need it? Last time I checked bronze circulators cost a lot of money.

      If you need a lot of hot water the indirects make sense, if you don't look elsewhere.

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  29. I've always wanted to add an indirect to my Burnham series 2 and today my electric water heater crapped out. After reading your comments it appears that the series 2 is not a "cold start" boiler as when I run it during winter it runs at a constant 180. Would this system be sub optimal?

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    1. Hi Jim. Thanks for your comment.

      A "cold start" boiler is one that is fired only when there is a call for heat. It will cool down between cycles. Many cold start boilers are set to control at a high limit of 180F. This is in contrast to a boiler with a tankless coil that requires the boiler to be warm constantly, even between calls for heat. Either way, there's no reason why you can't use an indirect.

      Best of luck,

      Wayne

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  31. Nice post.
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  32. Is there a brand of indirect tanks you recommend? i'm going tonhave to replace mine at high cost and would like a great one

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  33. Great blog. Appreciate all the effort that went into it.
    They are installing my indirect tank and we a trying to find the best spot for it in my storage room. The least intrusive place is about 5 feet away from the boiler but requires the plumbing from the boiler to run overhead as it is a walkway for the storage room and cannot put it on the floor. Is this OK or should I find a spot that can have it run along the floor without traffic going by. BTW Traffic is low and it is a 9 FT ceiling. Thanks in advance.

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  38. I went with an Lochinvar Squire 40g indirect a year ago and I am extremely satisfied with performance and cost. My gas bill runs $24-$28 during the summer months when my boiler is only running to heat water, so minus the transmission charges its only costing me $12-$15 a month for hot water for a family of 4. I can't imagine anything would be cheaper than that. Plus hot water seems to be endless. I would highly recommend going with an indirect.

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  40. Hello, I know this is an older post, but I thought it was a great read, thanks for the info. I have a Triangle Tube Prestige Solo 175 (I think that is the model) condensing boiler I use for my hydronic heating system. I currently use a traditional gas fired water heater for domestic hot water. I've been thinking what to do when that has to be replaced. My installer recommended going with an indirect setup with my boiler. They also do tankless systems as well and I was convinced that was the way to go (partly because everyone raves about them), but now I'm not so sure. Since this post, would you have any comments on tankless water heaters vs. indirect off a boiler? My installer uses Rinnai tankless systems. The real problem I have with tankless is finding a place to put two more holes in the side of the house for a tankless system. I'm also thinking about adding a circulation pump/system to improve hot water delivery times to the furthest fixtures. Thanks.

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  41. Thanks for sharing information about indirect water heater. Love that article.

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  43. Great post, thanks for all the good info. A couple questions. First, wouldn't it create inefficiencies when using an older cast iron boiler (80+ efficient) during summer months? To heat up the entire cast iron boiler takes quite a bit of energy which seems quite inefficient to only run for maybe 45 minutes to an hour a day to heat water in the tank. (I heat with propane and currently have a 40 gallon propane water heater, we have low hot water usage with only a couple people in the household normally, and I currently run the hot water heater for about 45 minutes at night (or an hour at most if more hot water will be needed),and it lasts us for showers and what we need thruout the day most days. To run a boiler to do this seems like so much energy is wasted in heating up the boiler system for such a short amount of time needed. Seems to me that would only be efficient if more hot water was needed or during winter when boiler will already be needed to be heated up.
    Second, you mention most indirect tanks can last a lifetime. Is this the case even when using well water which is very hard (not softened) and which has very high sediment levels? We get very high levels of caking and scaling on everything our water touches. Wouldn't the inside of tank and associated coil etc become a problem over time from this? Also, Is there a way to flush these tanks like normal water heaters without requiring special skills/tools etc?

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  44. I'm still trying to grasp the truth here with respect to the real efficiency possible with high-efficiency condensing boilers when used with an indirect tank. From my understanding, condensing boiler efficiency only approaches the 96 percent range when the boiler return water temperature is around 80 degrees F. At a boiler return water temperature of 120 degrees F, the condensing boiler efficiency is around 88 percent, and continues to drop to it's nadir of 86 percent at a return temperature of 140 degrees F. Given the slower rate of exchange of heat energy when an indirect tank coil is run at lower temperatures to maximize condensing boiler efficiency, how well would a indirect tank system really function? Granted the efficiencies at 86 percent are still an improvement over conventional non-condensing boilers, but the 96 percent figure seems unattainable to me in a real-world system unless there is something I am not understanding here. Thanks for any light you can shed!

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  49. Great info. Ty! Seems I have an indirect system. Finding the hot water temp extremely hot when boiler is working and lukewarm when not. Trying to understand why? Thx!

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  50. If you want to be able to heat an enormous amount of water within a short period of time, you can do well to take advantage of the marine tankless water heater. Pleas shop with Us We are the leading manufacturers of Water Heater In UK.

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  51. The belief that the boiler is running all summer may be a throw-back to the days of tankless coils in older boilers.Fred

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  52. Hi, ran across this informative older post so I hope you are still monitoring! We have an 80 gal HTP Stainless indirect water heater running off an oil burner in a house we purchased a year ago. For a few months we have been running out of hot water after 10-12 min with 2 showers running. We have replaced the circulator with a higher flow pump 12 gal/min, replaced the aquastat is working properly set at 123 deg, and confirmed the boiler runs between 180-200 degrees. With all faucets off it takes 20 min to recover from 99 to 130 deg. We conclude it's a heat transfer problem in the water heater. Lifetime warranty only applies to original owner. Is there a way to dissolve any accumulated deposits on the coils that are impeding heat transfer? Other suggestions?

    ReplyDelete
  53. Hi, ran across this informative older post so I hope you are still monitoring! We have an 80 gal HTP Stainless indirect water heater running off an oil burner in a house we purchased a year ago. For a few months we have been running out of hot water after 10-12 min with 2 showers running. We have replaced the circulator with a higher flow pump 12 gal/min, replaced the aquastat is working properly set at 123 deg, and confirmed the boiler runs between 180-200 degrees. With all faucets off it takes 20 min to recover from 99 to 130 deg. We conclude it's a heat transfer problem in the water heater. Lifetime warranty only applies to original owner. Is there a way to dissolve any accumulated deposits on the coils that are impeding heat transfer? Other suggestions?

    ReplyDelete
  54. My weil mclain boiler runs alot in the summer for the amtrol tank.I think way to much than a regular heater would.also down side of extra heat in house from running boiler.This will be the thrid one in 20 years so they dont last forever.Im also now having trouble finding someone who will replace my unit unless i pay$1200 upfront for a unit that is suposed to be free replcement.My last nit cost less than $200 to replace.Why now $1200

    ReplyDelete
  55. My question relates to Mixing Valves. I just had a 60 Gal Superstore Ultra Indirect Fired water heater connected to my oil burner with the optional mixing valve. The documentation mentioned it as optional. I don't believe that either Gas or Electric fired water heaters need them. My question is optimizing efficiency. We got the bigger tank because with the in-line furnace heater we used to have, you could never fill a tub with hot water and we are expanding a half bath to a full bath with a combo tub and separate shower. The wife likes the tub. Although only two of us now live in the house it is a 4-5 bedroom with 3 full baths and I thought for resale value having a big tank would be desirable for resale. To me it doesn't seem to make sense to heat the tank to 140 degrees (the installer said it was set to), then use the mixing valve to mix in cold to drop down to 115-120 and then again at the tub or sink mix cold again to get to "consumption temperature" of less than 100. This makes sense to me if you need massive amounts of water to supply so that 60 gallons of 140 degree water would probably supply 100 gallons or more of less than 100 degree water. For us, I would think that the most energy efficient settings would be to set the water temperature for the tank to 120 degrees or so and set the mixing valve to maximum (no cold water). This would supply 60 gallons of 120 degree water which when diluted with cold at the sink or tub would be more than we would ever need. Lowering it even more might make sense. We never wash clothes with hot water and the dishwasher has a heating coil to increase the temperature. Any ideas?

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  56. Our indirect water heater is making our radiators hot in the summer. Isn't there a way to make the boiler water not circulate through the house in warmer months?

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  59. How would you estimate the energy cost savings for between our system of 10-year old condensing gas boiler fueling our 1907 cast-iron radiators + 80-gallon electric hot water heater VS a new high efficiency gas boiler + 80-gallon indirect hot water heater?

    FYI, our existing boiler needs to be replaced because it's rusted out due to no condensate drain during installation.

    And we have a large 80-gallon tank because the house is a huge triplex with 4 showers, 2 laundry rooms and 3 kitchens.

    Any help would be greatly appreciated!

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  60. I'd probably switch out my old oil boiler to an indirect heater boiler the next time I get a boiler replacement. Seems more efficient than some boilers.

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  65. Anyone know how long a HTP SUPERSTOR should last? Mine is now 30 years old and operating with o problems. I just wonder about replacing it.

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    Replies
    1. I have a SUPERSTOR that's 22 years old and still works fine. Never a problem since I've had it, but was also wondering when I should replace it.

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  66. hey, thanks for sharing this info as an experienced service engineer in one of the best Combi boiler company most of the people don't know about this option the way your explaining is good keep going

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  67. Hi Wayne, Thanks for this great article. We are running two boilers. One to heat the house, the other to heat the water for showers etc.. I am deciding strongly of getting rid of the hot water boiler in favour of the baseboard heating boiler and getting this indirect one. We have a very large home facility and we are looking at ways to cut down on our oil heating bill. This seems to be the solution. My question is: Why are indirect hot water tanks about $1,000.00 dollars or more than a regular heated type water heater? I can pay $500 for an electric water heater, but indirects are like $1500.00 or more. Is there a reason for this? Thanks

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