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100 year old system, new mod/com boiler install

maybemark
maybemark Member Posts: 1,131
As many of you know, i live in a house between 90 and a 100 years old. At one time, it had a gravity system, which has been replaced with my existing boiler. The existing is 35 years old, way too large for my house, and costs a fortune to heat my house. I still have some 3" and all my 2" mains. I have a 2 pipe hot water system, with at the moment i have 14 large radiators. Possibly I will install 2 more units in the basement. i have a feeling, the only good thing about the existing boiler is, it keeps my basement warm about 55 when it's in the teens outsidewithout having any radiators down there.

I did many upgrades to my house that i don't feel I need to get into on this post, did a heat loss, and with you great people out there i was able to decide on getting a Lochinvar whn-85 and a Squire indirect water heater for my house. (thanks for helping me decide)

I see in the manual many different ways the system can be piped. I have talked about this with several people here on this site. I have only 1 heat zone and then have the DHW

Many people say, go with the single boiler full flow, zoned with circulators, DHW piped as priority ( in my case i will only have the 1 zone and DHW, rather than multiple zones.

My question is simple, and i am not trying to say no for doing it this way, rather than have a seperate circulating loop for the boiler then the single zone and DHW. i was told both will work fine for me. My question is WHY, go this way. Is it more effecient? is it simpler to do the piping, 1 less pump? Is it because of the massive 2 pair of 2" pipe i have running in my basement for my main runs?

I never questioned why, I just chose i will do it the way that many have told me.

The more i learn since i have come to this site, and i thank many of you for helping me learn, (I'm not saying i am any kind of boiler professional, just saying i have learned.) Well, i guess i want to learn more. WHY is this the best way for me?
thanks all
mark

Comments

  • GW
    GW Member Posts: 4,691
    Mark, it may be me, but I don't fully understand your question. Your question is 'why pipe it like the manual says?' What is your opposing idea? Your system is newly installed and you're now questioning the installers piping methods, even though it's illustrated in the manual?

    Gary
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    gary@wilsonph.com
  • maybemark
    maybemark Member Posts: 1,131
    Gary
    thank yu for looking at my post today.
    I have several post, that i don't remember seeing you participating. but i sure am glad you are today.

    Ist, the boiler has not been installed yet. this spring my plumber will be installing it.

    2nd, I am saying there are several ways in the manual on how they recommend the boiler and tank to be installed.
    The 1st way shown is with a seperate boiler loop. With talking to many of you kind, and smart people on this site, it was suggested by many, to eliminate the boiler loop, and just have the 2 pumps. This is in the manual also, but the drawing is with several zones (mine is 1 zone and DHW). This is not here nor there. I am taking the suggestions from most.

    I am just asking WHY is this the best for me. I don't think i ever asked why, just accepted it.

    I hope this helps you a little more on my question.
    thanks again for reading my post
    Mark
  • Paul48
    Paul48 Member Posts: 4,469
    When possible, pumping through the boiler eliminates the problem of trying to match the boiler gpm to the system gpm . All the heat goes to the system.
  • maybemark
    maybemark Member Posts: 1,131
    Paul, thanbk you for your comment, so, I guess your saying (correct me if I am wrong) it is simpler this way. Less steps to try to correct a possible problem?

    Is doing it this way, more effecient?

    Thank you very much for your comment, it does make sense.
    Mark
  • Paul48
    Paul48 Member Posts: 4,469
    No more efficient....just easier.
  • maybemark
    maybemark Member Posts: 1,131
    Paul
    cool, thank you very much
    I doesn't make it less effecient I hope.
    Mark
  • Paul48
    Paul48 Member Posts: 4,469
    No less efficient.....Just right... :smile:
  • maybemark
    maybemark Member Posts: 1,131
    great
    thank you very much
  • GW
    GW Member Posts: 4,691
    This is a modulating condensing boiler you're asking about? A dedicated boiler pump is the standard, at least for me, here's a pic of a job completed yesterday
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    gary@wilsonph.com
  • maybemark
    maybemark Member Posts: 1,131
    Gary
    Thank you for your pictrures and your participation.
    Since i have been on this site, I have learned there are more than 1 right way to do a cod/con install. I have also learned you can have a bad install, and your system and you, will suffer
    thanks again
    mark
  • Gordy
    Gordy Member Posts: 9,546
    edited January 2015
    Strictly speaking mod/cons

    P/S piping, or a hydraulic seperator offers hydraulic separation from the boiler, and the system. Doing this method the piping is a little more material, labor, and adds another circulator on the secondary side so additional operating cost. Not huge if the circs are reasonably sized.


    This method is used when it is known that the system side flow rate can not equal the boilers flow rate So essentially you are hydraulically decoupling the two loops so they can operate at two different flow rates. This need comes into play when the system side can not meet the boilers minimum flow requirements, or the system sides flow requirements are so high that the boiler can not run at an efficient delta t. The wider that delta the more efficient the boiler can be. Paul is,referring to this.

    Depending on the HX design of the Boiler whether it is high head, or low head plays a lot of the deciding factor.

    In a gravity system there is very little headloss in the large diameter piping. So it does lend itself to piping the boiler direct especially a fire tube design. This is exceptable so long as the flow requirements on the system side can be met to,off set heat losses. Emitter type plays a strong role in this. You can afford to run a higher delta with radiators verses say radiant panels.

    So what that means is your flow requirements will be lower for a radiator convector which would fare well with a 30 delta vs a radiant panel which usually seeks lower deltas of 10-15 for a more even heat spread across the panel.
  • maybemark
    maybemark Member Posts: 1,131
    Gordy
    Thank you very much for the explaination. I have learned since i have been on this site, but to be honerst, I haven't learned enough to understand everything you are saying, except the part, this is probably the best way fpr me to pipe my system because of the old gravity fed, and me haviong radiators than other emmiters.

    It's been a while since we conversed, and i thank you for taking then time to help explain. You were one of the 1st ones on helping me, and i truely appreciate it.
    thanks
    Mark
  • SWEI
    SWEI Member Posts: 7,356
    With fire-tube mod/con boilers, the question of flow rates becomes one of design preference rather than absolute necessity (as is usually the case with most water-tube HX designs.) The need for hydraulic separation and two pumps becomes a question of whether the boiler and the emitter system will be happy running at the same ΔT or not. In your case, with oversized cast iron radiators, they will be.
  • maybemark
    maybemark Member Posts: 1,131
    Thanks, what you said is above my head, other than the fact I have many radiators for my house. But I do believe whatr your saying is true