(206) 949-5683, Top Rated Plumber, Seattle
Page 3 of 5 FirstFirst 12345 LastLast
Results 31 to 45 of 66

Thread: Boiler help

  1. #31
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    Location
    New England
    Posts
    21,405

    Default

    Well, one way to look at it is if you go with the 150K unit, they'll be seeing you again to replace it when you short-cycle it to an early death.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  2. #32
    In the trades Dana's Avatar
    Join Date
    Jan 2009
    Location
    01609
    Posts
    2,720

    Default

    With his high-mass radiation even a 150K unit probably won't short-cycle itself into an early grave- it'll probably go at least 15-25 years, whether you want it or not, (and maybe even 40) but it'll run at ~70-75% net efficiency rather than it's rated 83%/whatever AFUE.

    At his load, short of a mod-con I'd rather pay for a cheap 50-60K cast-iron beast, (preferably a forced draft side vented unit, since the chimney is obviously way oversized for a smaller boiler) and have the thing operating on at least SOME substantial duty cycle, living on the knee of the regression curve rather than on the shin. It doesn't take a whole lot in the way of near-boiler plumbing to set it up for lower temp at the radiation (== lower distribution losses, steadier radiation & room temps) without compromising the boiler with condensing return water temps.

    OTOH, the excess standby losses of the 5x oversized unit mean the boiler room will stay warmer- it might even be the warmest room in the house, so maybe you could make the boiler room the living room, or maybe even the sauna !? :-)

  3. #33
    Master Hot Water Mpls,MN BadgerBoilerMN's Avatar
    Join Date
    Mar 2011
    Location
    Minneapolis
    Posts
    285

    Default

    Over-sized radiation; GOOD. Over-sized boiler; BAD.

    High-mass radiation with a low-mass condensing boiler is perfection in a box.

    Nobody wants a cast iron boiler, some can't afford a good boiler and some don't know any better but if you have natural gas and radiation already in place...

    I would rather have a boiler that was properly sized to the load. If we get the 10 year or 20 year record freeze, I will put on a sweater for the week that it may last and be happy to have the place way down to 66F instead of my usual 68F. Or, I might even turn on the lights or oven or televisions to make up the difference. For the other decade or two my properly sized boiler will purr along happily making all the hot water and space heating I can stand at half the cost of your "lazy man's" over-sized boiler.

    I swear, my head is going to explode!

  4. #34
    In the Trades Tom Sawyer's Avatar
    Join Date
    Nov 2010
    Location
    Maine
    Posts
    2,940

    Default

    I'm pretty impressed with Buderus, Biase and Crown cast iron boilers.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  5. #35
    Master Hot Water Mpls,MN BadgerBoilerMN's Avatar
    Join Date
    Mar 2011
    Location
    Minneapolis
    Posts
    285

    Default

    A condensing boiler that does not need to condense?

    I don't discourage people from installing condensing boilers. In fact, I have been encouraging them to buy them for all hydronic heating systems, but more especially low temperature systems including cast iron radiator and radiant floor systems.

    But, as in all things, personal responsibility is the first rule. If you, in fact, can't find a qualified installer, ModCons are not for you.

    In any case, a load as small as yours should be handled by a storage-type condensing water heater for the ultimate in combination efficiency. Installation is much easier and more forgiving while service is much simpler as well.
    Last edited by BadgerBoilerMN; 07-31-2013 at 09:31 AM.

  6. #36
    DIY Junior Member Steve Lanham's Avatar
    Join Date
    Jul 2013
    Location
    Maryland
    Posts
    17

    Default

    Hey gentleman....I was wondering why someone would want their boiler to run for longer periods of time. I'm not sure what my water volumn is but lets say its 100 gal..If a 150k boiler can heat the 100gal. say in 15 minutes but a 50k boiler would take 45 minutes how much energy would I save. If the boiler took 45 minutes that means the t-stat was calling for that long, which means my house was cold or cooler then I wanted it for that length of time. The house reaches temp. and shuts off the boiler. The boiler will remain off until the t-stat again calls and it would repeat the cycle. When this house was built in 1932 it had a 180k boiler. Its still functionable !! I'm starting to wonder if maybe you guys are super GREEN and not interested in keeping your family as comfortable as you can temperature wise. Badger talks about wearing a sweater for a week and having the house be 66 degrees instead of 68. Personally we,re a 70 to72 type family..Trust me when I say I'm not trying to offend anyone...Thanks !!!......
    for Badger.......Nobody wants a cast iron boiler, some can't afford a good boiler and some don't know any better ....Does this mean they don't make good cast boilers...how much does a good boiler cost...and as many cast boilers that are sold somebody has to know alittle something...PS...My cast boiler in my house was installed in 1932 with hardly a hiccup in 80 years. At least for the 30+ years I've lived here. You might want to rethink your statement !!
    Last edited by Steve Lanham; 07-31-2013 at 07:15 PM.

  7. #37
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    Location
    New England
    Posts
    21,405

    Default

    There are hundreds of thousands of boilers installed where the IWH is a priority zone (probably millions). Their houses do not get cold when the WH needs to be reheated! Mine works this way, and I've never noticed it cooling off while needing to reheat water, and I've got a deep 6' tub that gets filled up on a regular basis, so you'd think I'd notice. The point is more, size the IWH for your anticipated load. A boiler setup to treat it as a priority zone will fire to max temp while reheating the indirect. It rarely would need to be on full fire (assuming it is a mod-con) when heating the house. If you're really worried about the IWH as a priority zone, don't treat it as one. If you size the IWH properly, it will easily be hot by the next big use you require of it. Keep in mind that an indirect is much more efficient at being reheated than a typical stand-alone WH - you'd probably have lots more BTU for it, and you'd be heating it with a MUCH more efficient boiler.

    Any boiler is more efficient running constantly. It will last longer, too. It's the start/stop cycles that have it coming up to temp (just like the first few minutes of your car's operations - try running lots of short trips and see what your mileage is!), then, you're wasting the heat it has after it satisfies the call while it returns to idle state; might keep your basement warmer, though.

    There are lots of hacks out there...the easiest thing for them is to specifiy a boiler that is too big...the house is always warm, no call backs, damn the efficiency. A right-size boiler does not mean you have to compromise on comfort...that comes from a qualified installer, proper install, design, and setup.

    It's sort of like buying a MacLaren supercar to run errands in town...a big waste. As you've already said from your energy use, you don't need much of anything for your design day worst temp. The smallest boiler you can buy is bigger than that. You will not be uncomfortable if it is installed properly. Buy the bigger one, sleep well, pay more for the install, and forever...it's your money, but you're wrong to think you need a 150K BTU boiler for your house!
    Last edited by jadnashua; 07-31-2013 at 07:30 PM.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  8. #38
    Nuclear Engineer nukeman's Avatar
    Join Date
    Nov 2009
    Location
    VA
    Posts
    696

    Default

    What you are forgetting is that the efficiency is really a steady-state number. The more that you cycle on/off, the lower that number gets. Badger was stating an example. Based on your numbers, Dana has already calculated an upper bound of what you need (based on your previous use). If you got that exact size, you would never be cold. The worst that could happen is that a record 100-year cold snap hits and maybe it will be one or two degrees colder in the house than normal (may just be a few hours out of a 100-year period), but even the smallest boiler that you will buy will probably be oversized to some degree and will even keep up under these conditions.

    I'm not super green or anything, but you don't need that boiler unless you keep your windows open all winter. You can do what you want, but you will see many threads in here with people in Alaska getting boilers less than half your size. It all starts the same way. The installer wants to put in some huge beast, we educate and show them the real numbers. They end up with something 1/3 to 1/2 the size that the installer wanted to put in and they still stay nice and warm. They save money now and for all the years that they have the boiler. Why you wouldn't want that?...I'm not sure. You have to also remember that when you are heating the house, you aren't starting from "cold". Maybe you have a setback and the house cools to say 64F and night and you want it 70F in the day. It only has to gain 6F. It isn't like you are letting the house get to 20F every night and then wanting to heat it to 70F in the day. For that kind of climb, you would need something bigger. However, the temperature is really mostly constant (maybe vary a few degrees if you use a setback). As such, the boiler only is balancing the heat lost out the windows, walls, etc. and that is the number that Dana was giving you.
    Last edited by nukeman; 08-01-2013 at 05:56 AM.

  9. #39
    In the Trades Tom Sawyer's Avatar
    Join Date
    Nov 2010
    Location
    Maine
    Posts
    2,940

    Default

    Well it Dana.

    Badger, the firebird is a condensing, oil fired boiler that will condense with 180 degree return temperatures.

    http://www.qhtinc.com/firebird-products/
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  10. #40
    In the trades Dana's Avatar
    Join Date
    Jan 2009
    Location
    01609
    Posts
    2,720

    Default

    When the house was built in 1932 odds are it had NO insulation, single pane windows (no storms), and the 180K boiler was STILL oversized for the heating load. The net efficiency of that 180K boiler was likely 70-75% steady state, maybe less, and retrofitted with a post 1980 flame retention burner might have hit 80%.

    Apparently you didn't actually read the Brookhaven effciency report I had referred to in a prior post, nor looked at the regression curves to ponder just how big the true efficiency hit is at gross oversizing levels. You might also want to download the FSA Calculator from the NORA site which uses the data from lab testing several different boilers & types, which would also estimate what your actual operating efficiency would be in comparison to a more right-sized modern oil boiler with heat purge controls. The tool also estimates your heat load, and would tell you fairly accurately how much you'd waste by going with the 150K Columbia vs. a 60K Burhham vs. a 50K mod-con, if you figure out to use the tool correctly. (It's not bug free or particularly user friendly, but it works.)

    At your heat load a 50K barely-legal 82% AFUE cast iron boiler would literally never leave you cold enough to be reaching for a sweater any time before the next ice age, and would yield higher comfort and higher average efficiency than a 150K 86% AFUE cast iron boiler. Set it to 72F and forget it, it'll keep up just fine and use less fuel than the 150K boiler would using a deep setback strategy, and it would pretty much hit it's AFUE numbers, whereas the 5x oversized boiler wouldn't come anywhere close unless retrofitted with heat purge controls.

    A 76KBTU/hr condensing Vertex hot water heater would still have 40-50K of burner to spare for the hot water load when it's -2F outside (like it did briefly 101.5 years ago), and would use 15-25% less fuel than the 50K cast-iron boiler, and 30-40% less fuel than the 150K Columbia, in rough terms.

    Green? I definitely have a green side, but recommending a 50-60K 82% AFUEcast iron beast wouldn't exactly put me in anybody's Super Green club. You actually have enough radiation and a low enough heat load & operating temp to run with a Daikin Altherma high efficiency modulating air-water heat pump, which would cost slightly less to operate than a condensing gas-burner and alsoe with a somewhat lower carbon footprint at MD's grid source average. But spending 20 grand or so just for some marginal green-cred isn't exactly cash-green, eh? ;-) Even for the carb counter Super Greenies there would be much cheaper carbon reduction to be had out there than the upcharge between a cheap right-sized 82% gas boiler and a high-efficiency heat pump. (Don't even get me started on how ridiculous and expensive ground source heat pumps are, and how heavily they are subsidized!)

    At a low enough load (and you're getting close) the absolute efficiency matters a lot less. My recommendation here are far more about comfort & upfront cash than it is about any environmental stuff. Seriously- I'm heating my own house with an ~82% efficient burner. But it's a modulating burner operated at or below the design condition heat load during heating-only calls, ramps up to about 2x the heat load on very long showers if there is a simultaneous call for heat, but that's it. It replaced a still functional 4x oversized cast iron boiler, and the comfort levels have improved, not diminished.

    With high mass radiation the rads don't change temperature very quickly even with a monster burner behind it, and with a right-sized burner you can narrow the hysteresis on the T-stat to something very small without short-cycling the sucker (not so with the monster-boiler). With an outdoor reset control and a PID algorithm T-stat and continuous flow you can keep the indoor temps at an amazingly tight temperature range (like 0.2 F) if you really wanted to, but that would cost more money. Right-sizing the boiler and long burn times on high mass systems means it never overshoots the setpoint, and the radiators never actually get cool- they stay within a range, and the heat emission is very very steady, even as the boiler fires on & off.

    In the spirit of Jim's McLaren analogy, if you only need to get home from the store in 10 minutes to keep the missus happy and you know to a dead certainty you can get there in a cheap & reliable Ford Focus in 6 minutes without snapping your neck, there's simply no point to buying the 5 liter Mustang that could get you there in 2 minutes burning more fuel to no good end. (That is unless you get some thrill out of the roar of the bigger burner, and the extra operating & upfront costs get filed under "entertainment value." :-) ) I personally don't find the roar of a 150K burner all that appealing. YMMV.

    I'm dead serious about just how grotesquely oversized a 150KBTU/hr boiler is- it's tough to convince people just how low their heat loads really are, especially when swapping out an oversized behemoth like yours. But to replace it with another oversized behemoth does literally NOTHING for you other than drain your wallet faster. It costs a few hundered more now, and a hundred or so every year thereafter. If you want more comfort, right-size it, (or get at least as close as you can- your heat loads are on the very small end of what's rightly served by a boiler), and spend the few hundred on nicer controls like a PID algorithm thermostat or a outdoor reset controlled mixer or something.

  11. #41
    In the Trades Tom Sawyer's Avatar
    Join Date
    Nov 2010
    Location
    Maine
    Posts
    2,940

    Default

    Damn auto correct, I meant to applaud your post. I agree, 150k is 2/3rds more boiler than required here and as he already has high mass radiation it is the perfect fit for almost any properly sized mod-con. My only caveat here would be the possible need to change some of the existing piping for zoning reasons or flow concerns.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  12. #42
    DIY Member
    Join Date
    May 2012
    Location
    Brooklyn, New York, United States
    Posts
    46

    Default

    Just as an example, I did install 120,000 Btu boiler in 6 apartment building, 220,000 btu in 18 apartment building, and there were no complains when weather hit 6F. This oversizing Buisiness is just ridiculous. Anybody of your contractors used manual J ?

  13. #43
    In the trades Dana's Avatar
    Join Date
    Jan 2009
    Location
    01609
    Posts
    2,720

    Default

    Quote Originally Posted by gennady View Post
    Just as an example, I did install 120,000 Btu boiler in 6 apartment building, 220,000 btu in 18 apartment building, and there were no complains when weather hit 6F. This oversizing Buisiness is just ridiculous. Anybody of your contractors used manual J ?
    Yeah.... RIIIIIGHT! :-)

    Even the worst implemented Man-J on an 1800' house with a design temp of +15F wouldn't come up with a 150K boiler with 125K of output, a whopping 70 BTU/hr per square foot of conditioned space- which would be the heat load of an 1800' tent @ 15F with a flap left open.

    The lazy rule of thumb guys in my neighborhood use 25BTU/ft for an older home with at least some insulation and storm windows, 35BTU/ft for uninsulated houses with single pane glass (twice what the 150K boiler recommendation implied). Design temps around here are 0-5F, and these rules of thumb reliably oversize the units by a substantial margin. Applying the 25BTU ft to this house would still only be 45K, and barely-legal efficiency 55K-input boiler would cover it, but it would in fact be about 2x oversized, given how generous the fuel-use calculation was on boiler efficiency. (There's simply NO WAY a 1932 vintage 5-6x oversized boiler with a retrofit oil burner is hitting anywhere NEAR 85% efficiency!)

    Typical heat loads @ +15F for 1930s houses in that area will be well under 15 BTU/ft, and many will be around 10. Odds are pretty good that the true heat load of this one between 20-25K, and cheap 2-plate atmospheric-drafted 50K cast iron boiler would handle his load down to inland-Alaska style design temperatures south of -25F. This worry about a 50K boiler being too small for the space heating is just nuts- most 1800' homes in northern Minnesota can be kept comfortable with a 50K boiler (but 60-70K wouldn't be an efficiency-disaster overkill, for those handful of days every 50-100 years when it hits the -50s.)

  14. #44
    DIY Junior Member Steve Lanham's Avatar
    Join Date
    Jul 2013
    Location
    Maryland
    Posts
    17

    Default

    I have to find out what happens when Columbia tells me I need a 150k based on my cast rad size and I insist on a 50k boiler. I wonder if they will honor the limited life time warranty that comes with the boiler. I also wonder why boiler installers don't have to pass some sort of proper sizing certification so they're not selling units that cost the customer more dollars and waste energy to boot. With all the regulations in this country and the state of Md. I find it hard that the pols missed this one. I'm going to hunt down someone to do a Manual J. I have'nt been cheap when it comes to that. I did'nt have much luck on my casual search. Everything Dana and the others say makes perfect sense except for the talk of longer burns. Longer burns to me means longer time for your t-stat to be satisfied. Which means sitting there listening to your boiler run waiting for your room to warm to desired temp. Thanks for everyones response !!!

  15. #45
    In the trades Dana's Avatar
    Join Date
    Jan 2009
    Location
    01609
    Posts
    2,720

    Default

    A longer burn time is only a "problem" if you're raising the room temp by a large step in temperature. The thermal mass of the water in the system is substantial, but not infinite, and it's emitting constantly, warming the house even if it's not fully up to temp. If the thermostat is set up with a 1F differential it'll take 2x as long as if it's set up with a 0.5F differential.

    Only if you use deep overnight setbacks would you ever be left "waiting room to warm to the desired temp", and even then there are "smart" programmable setback T-stats that "learn" how long it takes to come up to temp based on recent cycle history, and would automatically start the warmup ramps earlier during colder weather.

    Or you could just "set it and forget it", and still use less fuel than the oversized boiler, and adjust differential on the T-stat to 0.5F. Or, with a fancy T-stat that has a PID algorithm the room temps won't vary by more than 1/4 degree, but the radiator temperatures might vary within a 5F differential while the boiler cycles on/off 1-3 times in an hour.

    You'd have to really listen carefully to hear a 50K burner, unless you're in the boiler room. (Have you ever heard the hot water heater firing in somebodies basement while you're on the first floor? You might be able to hear the pumping if you put your ear to the radiatior, but because the setpoint isn't being overshot, the radiators won't be tick-ticking away from metal expansion after having cooled too much with a room-temp undershoot. A 50K mod-con with an outdoor reset control would give you even steadier radiator & room temperatures than a 50K cast-iron, but with high mass radiation it would still deliver pretty even temperatures, even with a cheapo $20 T-stat.

    Right sizing the boiler & getting longer burns reduces the under/overshoot problem- it's MORE comfortable than an oversized boiler that satisfies the T-stat in 2 minutes instead of 10, or 20, creating larger swings in room temp.

Similar Threads

  1. Replies: 28
    Last Post: 01-15-2014, 08:32 AM
  2. Replies: 3
    Last Post: 09-10-2012, 07:21 AM
  3. Replies: 4
    Last Post: 01-27-2012, 03:30 PM
  4. Replies: 7
    Last Post: 11-20-2011, 01:38 PM
  5. Back boiler & oil boiler to twin copper cylinder
    By sheen in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 2
    Last Post: 12-07-2006, 04:34 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •