Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Replacing old coal boiler with standard 82 %

John B_2
John B_2 Member Posts: 46
in THE MAIN WALL
The old boiler has 3 inch supply then down to 1 -1/4 after the air scoop and check flow valve. Three tees to for supply runs in 1 1/4 with a check valve on each.

Returning to the boiler each has its own Grunfos circ pump which are connected to relays. Each relay has it's own thermostat.

From there into a 3 inch header which goes back into the boiler at two places.

Do I need to beware of downsizing the piping with the new boiler?

Would you keep things the same or would you move the circ pumps to the supply in order to "pump away" from the expansion tank.

The new boiler (250,000 btu), has a circ pump on the return Taco 007, do I even need it? Since each zone has it's own pump?

I'm not doing the work myself but want to make sure that the people I'm paying do this in a way that would be acceptable on this site.

Comments

  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    I'm sure this has never been asked of you before, but...

    Has anyone bothered to do a heat loss calculation? Or are they just matching like with like.



    The coal system was most probably originally gravity, and required as little resistance to flow as possible, hence the monster piping on the boilers near boiler piping. Pumps change everything. Pipe size is dictated by required flow, which is dictated by heat loss, which dictates boiler size.



    Got heat loss???



    ME

    There was an error rendering this rich post.

  • John B_2
    John B_2 Member Posts: 46
    yes heat loss done

    old boiler is much bigger. Taking in about 330,000 btu measured at the gas meter.

    New boiler smaller.
  • John B_2
    John B_2 Member Posts: 46
    forgot to mention building is one story only

    Thanks
  • Brad White
    Brad White Member Posts: 2,399
    So, what is

    the actual heat loss you calculated? Inquiring minds want to know.



    Let's find out! :)
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • John B_2
    John B_2 Member Posts: 46
    lol. I used a heat loss calculator.

    the building was originally built as a motel with 10 units. Each is about 16 feet wide and 28 feet deep. A living room and bedroom in each. From previous posts, I've learned that each unit has was built with too much fin tube (about 40' 3/4 inch per unit) Two sliding windows per unit. Flat roof. Poorly insulated. One entry door each. Boiler is in center. Three zones. 2 zones have about 160 feet radiation one has about 100.

    Everyone wanted to replace the same size at about 300,000.

    i had to do the heat loss myself since no one else would.

    I mean I know now that there are companies that would for a fee, but I didn't know that before becoming a member here and begin my education at this stuff.
  • Brad White
    Brad White Member Posts: 2,399
    Mrs. Bates?

    Ah, the old run-down motel story strikes again.



    What is somewhat encouraging is that the place was not insulated yet you say it has too much radiation. This is good news! It means a lower water temperature will heat the place, especially once you tighten it up.



    So, how many BTUs per hour do you need?
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • John B_2
    John B_2 Member Posts: 46
    lol, again

    i calculated at around 200,000 btu /hour this time.
  • Brad White
    Brad White Member Posts: 2,399
    edited October 2010
    As a benchmark figure,

    how many SF is the final building? Just to get a "BTUH per SF" figure, to see if the sizing is rational. (Just a check-figure, not a design outcome.)



    Has the boiler been purchased? Just trying to sort out where you are in the process. Also, has the insulation, air sealing and/or window work been done yet? In other words, those factors have been taken into account in your heat loss and are in place now?



    If you already own the boiler and it is 250 input (I think you said that), this is in range for what you are doing. Not enough difference to quibble about. But there is much you can do to protect your investment as noted above, by separating the boiler circuit from the radiation circuits (primary-secondary pumping). This will also allow outdoor reset control, better comfort and fuel savings, which is the idea.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • John B_2
    John B_2 Member Posts: 46
    building is about 5500 sq feet

    no new insulation or upgrades yet
  • Brad White
    Brad White Member Posts: 2,399
    At that floor area

    the 200 MBH works out to about 36 BTUH per SF.



    Was that 200 MBH heat loss an "after insulation" number, or as it is now? I would hope that you could get that number down a bit, but then, I do not know where this building is located. If in the Boston area, for example, with a design cold temperature in the single-digits, getting to 30 or less in an improved structure is possible. If in upstate NY, Canada or Michigan, 36 might not be a bad number. Unimproved structures could be in the 50, 60 or 70 range for comparison.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • John B_2
    John B_2 Member Posts: 46
    not sure i'm following

    im near detroit michigan.

    the heat loss calculation is for today's conditions. am i still over-sized right now with the new boiler?
  • Brad White
    Brad White Member Posts: 2,399
    edited October 2010
    Let's sort this out.

    If the current boiler has 330 MBH input, say 264 MBH output at 80% efficiency, that is 48 BTUH per SF. Detroit has a 99% heating design temperature of 3 degrees F. close enough to Boston for discussion purposes. So your benchmark of 48 BTUH per SF is reasonable. I was worried that you might be under-sized. Still, I would get cracking on insulation but air sealing before that. Why wait?



    Was this the 3 degrees F. figure you used for the calculations? Say 3 degrees or even zero outside temperature and maybe 68F or 70F inside?



    When you DO insulate it, what will the heat loss drop to? That is the most important number long term.



    You mentioned earlier that you have a 007 circulator on the boiler. If the boiler has an output of 200 MBH, that is 20 GPM. A 007 will deliver 20 gpm but only against 2.5 to 3.0 feet of head. It is way out on the far end of the curve. What I mean by this is that you can keep the 007 as a boiler circuit circulator and let your zone circulators be specialists for their own zones, but do not use the 007 to feed outward beyond the near-boiler piping.



    I have attached a rudimentary diagram to illustrate the basic concept. From the other discussions and in light of this, I suggest that your boiler loop be a full 2 inches to keep the pressure drop down and the pressure differential between the closely spaced tees, to a minimum.   The diagram is not intended to show every device, relief valve, drain, etc.  but rather just the concept.



    Similarly, I would make the outgoing headers to the circulators 2" size also, if you are making them new. I do not want the circulators to affect one-another by having them on too small a line. I presume most of the circuits will be close enough in pressure drop.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • John B_2
    John B_2 Member Posts: 46
    Brad the current boiler is an old coal converted to gas

    by use of a conversion burner. Everyone says that they'd be surprised if it was 60% efficient. I mean, I really dont know, but it's about 5 feet tall 4 feet wide. The exhaust is about 12 inches.

    The circs right now are on a return header. So they should be moved?

    Can I still use the 1 1/2 air separator if I use 2"
  • Brad White
    Brad White Member Posts: 2,399
    edited October 2010
    No where to go but up!

    I would move the circulators to the supply header because that allows a single point where the expansion tank can connect.  When all circulators are on the return, the question is, "which one gets it so the others can suffer?" So a single common point is better. We can explain why, later.



    There may be a debate as to if one puts that on the suction side of the boiler circulator or the suction side of the collective group of system-side circulators. I would opt to keep most circulators happy -especially those with higher system pressure drops. So upstream of the new (moved) supply header is what I would do.



    For the air separator, 1.5" should be fine. Velocity will be just over 3 FPS. But go back to 2" pipe for the traveling size once you can, to keep pressure drops low. Double check with the exact model you are using. Scoops versus micro-bubble resorbers have different requirements, but in general, being at 3 to 3.5 fps does not concern me.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • John B_2
    John B_2 Member Posts: 46
    I might be using spirovent JR 150 TM

    I looked at brochure but am not good at understanding tech stuff (yet). Would you mind helping? I'm pasting to spirovent. http://docs.google.com/viewer?a=v&q=cache:3T2A3wwzCF8J:www.spirotherm.com/docs/brochures/Air-1B.pdf+spirovent+jr+150&hl=en&gl=us&pid=bl&srcid=ADGEESiO7D4gt0UIagfPmzwgRHKc1QZgKauBj-wY7FwYDQPYJz3hedGo_-klowheUyc-8r3Bg4x56MbJrQ8JSQGrdXHipdq_jB7_kIYrlS-rNVSalmjLfrRBdK43cxN51RJ0tF_jzYce&sig=AHIEtbQlOXJULK47ZhevsY9T_JzKqiA1OAg

     
  • Robert_25
    Robert_25 Member Posts: 549
    Extra zones?

    I agree that the efficiency on a gas-converted coal boiler would be terrible...but the exact number is a mystery, so base your boiler sizing off the heat calculation.  Have you considered splitting the units up into individual zones?  Additional zones would spare some boiler capacity; especially if some of the units are ever empty and could be turned down to ~50 degrees.



    Take a look at Bell & Gossett's Inline-air-separator.  They work well, and the 2" model should run you about $40.
  • John B_2
    John B_2 Member Posts: 46
    can you recomend the type of check valves on the supply side?

    I mean do they need to be balancing or anything like that? Supply is 1 1/4"
  • Brad White
    Brad White Member Posts: 2,399
    The VJR 150

    seems like a good selection to me. 
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • Brad White
    Brad White Member Posts: 2,399
    Taco

    in general is a good place to start. There are other manufacturers and the functions are similar.  They would not be the balancing type although such are available (triple-duty valves, which are check, balancing and isolation in one).



    Personally, I do not like them and prefer separate devices for each*, but acknowledge the appeal when tight spaces require them.



    *The reasons I am not a fan, are that each function with the possible exception of check valve function, are compromised to an extent. As check valves, "OK", but as a shut-off, too restrictive and for balancing, not nearly as accurate as a good wye type with proper straight pipe. OK for rough balancing, but I like accuracy.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • John B_2
    John B_2 Member Posts: 46
    So is a flow check valve the same as a

    simple check valve?

    Or does having the word "flow" make it different?
  • Brad White
    Brad White Member Posts: 2,399
    No

    A flow check is not the same thing as a regular (flap type) check valve.



    A regular check valve has (usually) a machined metal to metal seat and can, under some conditions, make a "clacking" or "chattering" sound.



    A flow check has a lift type seat guided on a stem. The flow enters the bottom and lifts it, allowing water to flow into the upper chamber and out of the valve on the other side.



    This lift seat and stem can be adjusted, even closed down in some cases, or "released", actually lifting the disc off the seat, to leave the valve wide open. But in normal operation, the disk has some weight, some resistance so that gravity flow is stopped, but the circulator, when on, can lift the seat and establish flow.



    Mark Etherton wrote about this in another thread, not sure that was yours, but with pictures.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • John B_2
    John B_2 Member Posts: 46
    ok got it, thanks found it.

    It's made of iron.
  • John B_2
    John B_2 Member Posts: 46
    Is it ok

    that the oo7 is reduced to 1 1/4 at the return?

    Also, is the just a circ pump or does it adjust to temp changes?
  • John B_2
    John B_2 Member Posts: 46
    So if I

    add the boiler loop, Can I then run the boiler at, let's say 145 F then not worry about condensation? Is there a device in the bypass that you attached?
  • Brad White
    Brad White Member Posts: 2,399
    You can run the boiler

    at any temperature sufficient to heat the spaces. It may well need to be higher than 145F as the building is now, on the coldest day.



    Once you insulate and air seal the place, that boiler temperature might well be below 150F, even below 140F. But 145F is a safer bet, allowing some margin. The key temperature is 135F at the return and even a 20 degree delta-T system often runs at half that, so at 145F supply, you are likely to keep the return at 135F or higher.



    The RIGHT way to do this is to have a bypass mixing valve or bypass circulator responding to the return water temperature, diverting supply water to the return automatically in response to boiler return temperature. Obviously, you understand about boiler condensation.



    The diagram I posted was a simple primary-secondary loop system without a mixing valve in play, either on the boiler side or the system side. Rather it is just a way to keep the boiler hot and circulating, drawing from it as each zone calls and allowing some uncontrolled but effective mixing in the tees.



    IF a true system responsive mixing approach were to be done, given that your radiation is all of one type (fin tube I believe you said), AND the radiation lengths are proportional to each room's heat loss, you could use a single mixing valve. This would be a three-way or four-way, to decouple the boiler circuit and keep it warm but also allow the radiation side temperature to go as low as you please.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • Brad White
    Brad White Member Posts: 2,399
    The 007

    is a circulator, plain and simple.

    There ARE variable speed versions available from Taco.



    I had a 007VS used to maintain a constant Delta-T in my radiation loop at my last house. (My heating system has been called, "Dr. Frankenstein's Lab", because I use it as a test bed for different pumping strategies, part of my education, you see.)



    The 007VS ran at very low speeds to maintain 20 degrees drop, considering that the system typically ran at 8 to 10 degrees, even on a cold day, with a Grundfos 15-58 on Speed 1... Even so, I was pumping 2 to 2.5 times the water I needed to.



    As for size, that is a function of the flanges. A 1.25" flange is common and you may find 1.5" flanges. Personally, I go for isolation/purge flanges such as by Webstone. The 007 can be fitted to any flange size available in that 2-bolt pattern, typically 0.75" to 1.25" and maybe higher. Might even be a 2". Still, a short reduction will not hurt things.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • John B_2
    John B_2 Member Posts: 46
    I'm having difficulty understanding how a mixing

    valve in the bypass will know what to do? Won't it need some type of sensor on the return? I mean, I've installed a watts mixing valve on a public sink and understood that concept of keeping the hot side limited. But this I'm finding myself pondering over and over without it clicking in. You see it woke me at 2:45 am, it's obviously bothering me :)
  • Brad White
    Brad White Member Posts: 2,399
    edited October 2010
    Try This

    Here is a diagram I did for my own house, using Taco iValves (simple and elegant ODR control with return water monitoring and protection). The valves do not have all of the features I would want, but for the cost, do most of what I need.



    Anyway, the blue linework is the control layer, showing outdoor temperature, HWS and HWR temperatures.



    But you picked up on that, the need for a sensor! This is the fine line between specifics and theory. :)



    EDIT: After several tries I could not get the PDF diagram to "stick", so if you write me off-line, I will e-mail it to you.



    bewhite at rcn dot com
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • John B_2
    John B_2 Member Posts: 46
    Brad, I just shot

    you an email.
  • John B_2
    John B_2 Member Posts: 46
    Ok, the supply house carries Tekmar 356

    any thoughts?
This discussion has been closed.

Categories