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(Commercial) Your opinion on replacement boilers

Mike_SheppardMike_Sheppard Posts: 549Member
I have a customer that wants new boilers. They currently have an old Kewanee firetube, 5 million btu, and two 2 million btu condensing boilers. The boilers never condense. They run their domestic hot water off a shell and tube heat exchanger. They have to send 160-180 to the heat exchanger to make hot water year-round. The DHW load is so small that one 2 million btu boiler short cycles all summer to maintain it. These condensing boilers have a 20:1 turndown, even at 100,000 btu input at low fire they short cycle during the summer.

My original suggestion was lets gut this and re-do it all. Install water heaters so that we could actually use condensing boilers or a hybrid condensing/non-condensing boiler setup. I was informed that they want to go as cheap as possible, no exceptions. They have listed a few different boiler brands that they want, all of them are condensing boilers and all of them only have a 5:1 turndown, which means even more short cycling during the summer.

Since removing the DHW heat exchanger isn't an option, what would you do in this situation?

I am leaning towards two cast iron sectionals. Added mass would hopefully limit summer short cycling. They'd last a lot longer than condensing boilers and cost less to maintain.

Thoughts?
Never stop learning.

Comments

  • Steve MinnichSteve Minnich Posts: 2,465Member
    edited July 25
    HB Smiths or Weil 88s with Industrial Combustion burners are what I see the most of as replacements.

    And I see them commissioned and firing. Nice set up.
    Steve Minnich
    Tell me I can't, and I'll show you I can.
  • Mike_SheppardMike_Sheppard Posts: 549Member
    > @Steve Minnich said:
    > HB Smiths or Weil 88s with Industrial Combustion burners are what I see the most of as replacements.
    >
    > And I see them commissioned and firing. Nice set up.

    The last company I worked for was an IC rep. The most common burner around here is PowerFlame.
    Never stop learning.
  • Steve MinnichSteve Minnich Posts: 2,465Member
    Most of the PowerFlames around here that I see are being replaced with ICs. Strong IC support here.
    Steve Minnich
    Tell me I can't, and I'll show you I can.
  • RayWohlfarthRayWohlfarth Posts: 756Member
    Mike I like using modular boilers and typically see a 20-25% reduction in fuel costs. In addition, there would be some backup in case of a failure. The modular boilers limit the cycling and since they are isolated with primary secondary, you lower the standby losses. I like the Triad model for the Superior boilers.
    Ray Wohlfarth
    Boiler Lessons
    Click here to take Ray's class.
    Click here to buy Ray's books.
  • Steve MinnichSteve Minnich Posts: 2,465Member
    I jumped the gun on your post. I saw Kewanee and 5000 MBH and assumed steam.

    Cascaded Lochinvar FTXLs or Laars NeoTherm and MagnaTherm are popular around here.
    Steve Minnich
    Tell me I can't, and I'll show you I can.
  • Mike_SheppardMike_Sheppard Posts: 549Member
    edited July 25
    @Steve Minnich those are popular around here as well. But they’re trying to go as cheap as possible. I’d love to throw in a bunch of small condensing boilers with lower inputs but they’re not gonna pay for it. The best thing I can come up with is two non-condensing sectional hot water boilers, both for price and for life longevity.
    Never stop learning.
  • Steve MinnichSteve Minnich Posts: 2,465Member
    I also see the Weil SF boiler but that wouldn’t be my first choice.
    Steve Minnich
    Tell me I can't, and I'll show you I can.
  • Mike_SheppardMike_Sheppard Posts: 549Member
    @RayWohlfarth I’ve seen those setups in a few boiler rooms. One had 16 burners.
    Never stop learning.
  • Solid_Fuel_ManSolid_Fuel_Man Posts: 1,598Member
    Weil 88s, with power flame if you want to go cast iron. Is there any way to cove DHW with a condensing on demand, or even electric if really small load? I see a lot of commercial building with the only DHW load is hand washing and light dish washing, then they have an indirect and the boiler room is 120F all summer.
    Master electrician specialising in boiler and burner controls, multiple fuel systems, radiant system controls, building controls, and universal refrigeration tech.
  • Mike_SheppardMike_Sheppard Posts: 549Member
    @Solid_Fuel_Man I'm going to keep working on them to see if they will give in on the DHW. But as of right now they don't want to change it.
    Never stop learning.
  • SteamheadSteamhead Posts: 13,117Member
    Any technical reason for the HX, for example, water pressure exceeds the usual water heater rating?
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
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  • Mike_SheppardMike_Sheppard Posts: 549Member
    edited July 26
    @Steamhead I will double check on Monday. Building is only 7 stories.

    I've worked in many other buildings in the area, including the two buildings next to this one and they both have water heaters and cast iron sectionals.
    Never stop learning.
  • EBEBRATT-EdEBEBRATT-Ed Posts: 5,914Member
    @Mike_Sheppard
    a buffer tank would reduce the short cycling in addition to the water capacity in the boilers you choose
  • Mike_SheppardMike_Sheppard Posts: 549Member
    @EBEBRATT-Ed I was thinking that as well. I did some rough calculations with estimations and ended up with a pretty darn huge buffer tank. I’m sure it wouldn’t be cheap.
    Never stop learning.
  • ScottSecorScottSecor Posts: 260Member
    @Mike_Sheppard I think we have worked for similar owners, small budget and want expensive equipment...

    Around here most jobs with private owners (Apartment Houses, Churches, etc.) are fitted with Powerflame burners. Most public jobs (Schools, City Halls, etc) are fitted with IC burners (now owned by the Cleaver Brooks parent company I believe). Used to be easy to get parts for either brand around here, now Powerflame is a little easier and IC is nearly impossible. I always felt IC was a superior product. Even the burner housing seemed much more heavy duty. I think we may have worked on every Heav-E-Oil atomizing oil burner in NJ at one time years ago.

    Back to your question, if there is any way you can install numerous large indirect tanks, you may be able to reduce the short cycling. With massive amounts of storage we have been able to harness the "large horsepower" with deeper cycles and a mixing valve.

    With regard to CI boilers we have had fantastic luck with Weil McLain 88 series and Peerless TC series. IF Powerflame still offers the HTD (high turn down) version of the 'J' or 'C' burner you might want to consider them. This way you will get that much needed high turn-down ratio.

    About ten years ago we were asked to design a new oil heating and dhw system for a roughly 80 unit apartment building. We do not install too many oil fired systems anymore, but the owner was "protecting" the tenants for the future in case natural gas was shut off for some reason. This heating system load is roughly 1.5 million BTU and the DHW load is roughly .5million BTU. We installed two W/M 80 series boilers with on/off oil burners and a W/M WGO "house" boiler with an on/off oil burner. For approximately eight months of the year they only run the small "residential" oil boiler for both the heating and the dhw system. As a matter of fact, they turn the two 80 series boilers off on April 1st and turn them back on November 1st (just in case). In the event the small boiler fails, two guys could swap it out relatively easily (and it's stocked locally).

    I realize the system I describe is likely about one fifth the size of your project, however I think you can see how this type of system might make sense. I cannot stress enough how well this type of system works. Might want to consider two large cast iron boilers and one relatively small (say 350,000 BTU) cast iron or better yet condensing boiler for dhw and heat under light loads.
  • hot_rodhot_rod Posts: 11,665Member
    What type of heat emitters? What SWT temperature is required. If lower operating temperatures are possible, you may leverage condensing technology enough to consider that option.

    https://www.caleffi.com/sites/default/files/file/idronics_25_na.pdf
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Mike_SheppardMike_Sheppard Posts: 549Member
    edited July 26
    @Hotrod they have fan coil units. They lowest temperature heating water they supply to the building is 120 degrees via 3-way valve. I will verify on Monday what they’re sending out for domestic water, but it comes out of the heat exchanger to a mixing valve to step it down to 120-130. Boilers are set for 170 degrees supply to heat exchanger all summer.

    @ScottSecor I was thinking of that as well, using a smaller boiler for light load and DHW. I will verify on Monday what the ratings on the shell&tube heat exchanger are for DHW. I’d like to accurately calculate what size buffer tank they’d need too.

    I sent them an email and explained my concern with installing 2 million btu boilers with 5:1 turndown due to short cycling in the summer. They said they will rethink and consider adding water heaters.
    Never stop learning.
  • ScottSecorScottSecor Posts: 260Member
    @Mike_Sheppard I doubt you can do this practically, but could you or a trusted staff member try lowering the dhw temp and/or boiler water temp for the next week or two to see what you could get away with? I realize it's a crap-shoot but I'm betting with the short cycles that you could probably lower the bwt by at least 20 degrees and the dhw temp by 10 degrees, especially during the summer months.
  • Mike_SheppardMike_Sheppard Posts: 549Member
    @ScottSecor I don't think it would have much effect. I think they need to install water heaters or a couple smaller boilers for shoulder season / DHW service.

    Ideally water heaters and condensing boilers would be a good fit here. A couple water heaters aren't that expensive, especially when we're talking increase life of the boilers and condensing efficiency savings.

    They operate the heating water at 120 on the low side and 170 at the high side with fan coil units. There is at least some condensing capability there.

    None of this is going to happen until the get the asbestos abatement done anyways lol. I will be there on Monday and Wednesday and will be making an existing piping diagram etc if anyone is interested in following along.
    Never stop learning.
  • The Steam WhispererThe Steam Whisperer Posts: 383Member
    What is the actual load on the boilers? I suspect you have the regular heat load plus ventilation load. If the ventilation system is set up well, it will only be running when the building is occupied, so you should have a significant offset on your heat load from internal gains to help cover the ventilation loads.

    I pulled a 3.7 million input boiler and 4- 199,000 input water heaters in a nursing home and was able to replace them just 2 250,000 input mod cons. Definitely check the loads. The kind of firepower you have now is enough to heat some good sized downtown buildings here in Chicago. That would work out to about 300,000 to 350,000 sq ft of heated space with a design temp of -5F ( not including ventilation loads).

    Probably the cheapest solution is to calculate the heating load on the typical winter day ( usually about 90% of the heating season), which is usually about 60% of the design ( less if you have large internal gains), and baseload the heating plant with some simple step fired atmospheric boilers to meet this load ( if the load is light enough) or a couple on/off power burners. Keep the big Kewanee just as a peak load boiler that is usually only needed a few days a year, so it just sits there cold the rest of the year.

    You can certainly run the fan coils cooler than 120F unless there are issues with cold drafts. However, be aware that the cooler the water temperature, the more the blower motors run, sucking up a lot of expensive electricity. What you save in gas by running lower water temps, will be at least partially if not completely offset by blower motor power usage.
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  • JUGHNEJUGHNE Posts: 5,778Member
    I have a small hospital that is only a fraction of your fire power.
    They had a 80 HP, 2.65 million btu boiler running at about 7 PSI 24/7/365 for 40 years. Steam insert coil in 365 gallon tank. No working temp valve, tank set at 120 or less.
    In the summer the boiler room could be the same temp as the water they supplied.

    Replaced 40 year old tank/coil with 2 HTP Phoenix SS WH's .
    The boiler room is now tolerable in the summer.
    No steam needed for half of May and all of June.
    Savings not as predicted as I was unaware of the need for re-heat for chiller cooling.
    But there is definitely NG savings and they got an upgrade for DHW equipment .

    This is small potatoes compared to your job but it was an easy sell. The board was made aware of the old DHW heating method and were glad to approve the upgrade.
    The two HTP's have interchangeable components and have a cross over pipe to work on one tank if needed.

    I also pointed out the Legionella danger of having 365 gallons of barely 120 degree in a hospital.
  • Mike_SheppardMike_Sheppard Posts: 549Member
    @The Steam Whisperer

    I don’t know the actual load of the building. And I don’t even know where to start with doing a load calculation with a building of this size. I’d love to do a load calc but it’s not something I’ve had a chance to learn yet on this scale.

    I’m sure they have way more firepower here than they need, but this is pretty small compared to a lot of what I work on lol.

    My favorite plant to work at is a research facility that has almost 200,000,000 btus of boiler. 3 boilers total.
    Never stop learning.
  • Mike_SheppardMike_Sheppard Posts: 549Member
    edited July 27
    They have no website or information online other than the building was built in 1962. After counting the condos online from Zillow there is about 26 condos per floor and there are 7 floors. Approximately 182 condos. Average square feet approximately 900 per condo. Approximately 163,000 sq/ft of condo space - not counting common areas and the basement level.

    No RTUs. No outdoor air ventilation systems. No heating or air conditioning in the hallways. Typical of buildings in this particular area.

    If you guys know of any load calc methods / software / classes / books etc that relate to large apartment buildings please share. Definitely something I want to learn.
    Never stop learning.
  • ZmanZman Posts: 4,995Member
    Commercial gas meters in my area log consumption daily. If you are able to access those records, you can dial in the boiler sizing for the design day, typical day and DHW only days. Then you can design a new plant very accurately. Heat loss calcs are good, 3 years of daily data logs is the best.

    I don't know why folks get hung up on shell and tube instantaneous DHW over indirect storage tanks. It forces you to run everything at max just in case they get a big demand. Tanks allow you to make hot water much more efficiently.

    I have a client that has one that is about 35yrs old and keep they dumping $$$'s into it and I can't talk them out of it. They really only perform well with high temp, high mass systems.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • The Steam WhispererThe Steam Whisperer Posts: 383Member
    What Z-man said. Look at the gas bills and work backwards from there. Subtract the summer gas usage from the winter bills to get about what the fuel usage is for heating. Start with the coldest months gas bills. I just divide the gas input by the number of days for the month to get the therms per day then divide by 24 for therms per hour. Then take a look at the average temp for the month and subtract it from 62F ( probably about the temperature that heating is needed) to get your delta t. Divide the therms per hour by the average temp to get therms per F degree. Now comes the intuitive part.... just how efficient is the heating plant running? If they are running the modcon only, then its probably about 88%. If the Kewanee is also on, I'd do a combustion test for starters and then drop the efficiency from there, depending on how heavily loaded the heating plant is. If the combustion test comes out around 80%, you can probably safely figure the efficiency around 75% due to standby losses.
    Once you get a heat loss per F degree I add about 15% for the non-linear increase in heat loss due to air leakage.

    You will probably be quite surprised at the number you get. I would design the heating plant for maximum efficiency at the 60% heating load plus some extra for water heating. If your weather is like Chicago, you probably only need about 2 million btu input for the typical day.
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  • Mike_SheppardMike_Sheppard Posts: 549Member
    Here are a couple of bad drawings of what I am dealing with. Kewanee boiler from 1965 (boiler 3). And two Aercos (boiler 2 and 1).

    Aerco 2 does DHW only during summer. The other ones can be used in an emergency. The two 2 million btu Aercos (4 million total) carry the heat load and DHW load all winter with no problems. If one goes down, the other one cannot carry the load by itself. The Kewanee boiler has an output of ~ 4.1 million btu (at 80% efficiency) and can also carry the load by itself in an emergency.

    They want to go as cheap as possible. Don’t want to remove the Kewanee because they got a quote today on asbestos removal and it was big money. The Aerco boilers are on their last leg so they want to replace only the two Aerco boilers. They don’t want a buffer tank and they don’t want to install water heaters. They don’t want a sectional boiler because they can’t fit 4 million btu worth of sectional boiler in there where the Aercos are sitting. They don’t want Aercos with a 20:1 turndown because they don’t like Aerco. They don’t want to modify any piping. They want Aercos out, new boilers in in place of the Aercos and hooked back up to the piping.

    Looks like the one and only option is to slap in two 5:1 turndown condensing boilers and let them short cycle themselves to death all summer / shoulder seasons. Not sure if I even want to be a part of this job lol.

    In the pictures: on the winter picture green is the DHW piping for the heat exchanger and orange is heating water. On the summer picture orange is the DHW piping and blue is chilled water. I did not draw this. I am currently drawing a prettier isometric version.
    Never stop learning.
  • Mike_SheppardMike_Sheppard Posts: 549Member
    edited July 29
    And here’s a horribly drawn isometric close to what they actually have there (minus the chiller and other pumps and storage tanks). Poorly planned as I ran out of space on the right...
    Never stop learning.
  • ScottSecorScottSecor Posts: 260Member
    Lochinvar Crest boilers? Two million BTU at high fire and 80,000 BTU at low fire. Likely less costly than the Aerco model.
  • Mike_SheppardMike_Sheppard Posts: 549Member
    @ScottSecor I was looking at those as well. Saw the 25:1 turndown. Those may be an option. I would want to consult the reps first to make sure the install would be kosher and would be no issues with warranty.
    Never stop learning.
  • The Steam WhispererThe Steam Whisperer Posts: 383Member
    Since you only need at most 4 million BTus to carry the building, Id' just put in a 2 million btu boiler and run it as a lead boiler. The kewanee would only be cycled on a couple days a year and you would still have 100% back up for typical winter days where you only need 2 million btu and freeze protection for pretty much any weather.

    It's sounding like this is a customer that should be fired.
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  • Mike_SheppardMike_Sheppard Posts: 549Member
    @The Steam Whisperer I think I am going to suggest keeping the Aercos for another year and saving the budget until they can knock it all out at once.

    The Aercos are in bad shape but it’s also because they’ve never been maintained properly. Assuming I get the maintenance contract I may able to convince them to do this.
    Never stop learning.
  • TimcoTimco Posts: 2,927Member
    http://www.htproducts.com/literature/elite-xl-brochure.pdf

    We have larger versions in development as well.
    Technical Support Manager, HTP Comfort Solutions.
  • HenryHenry Posts: 914Member
    I saw the XL and 4million at the plant 3 weeks ago. They have a low pressure drop with the new heat exchanger. BTW the I & O manual had a few errors that will be corrected shortly.
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