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Boiler Change Out - Low Mass vs High mass plus brands

ChrisP Member Posts: 6
Hi everyone,

My 1988 home in Southern Worcester County, MA is in need of a boiler replacement within the next few months. The current heating system is based off of a 23 year old Burnham RS-115 Oil boiler with Tankless Coil.

Right now, we have 4 zones hanging off this system (1 for the first floor, 1 for the second floor, 1 for the finished basement room 10x15, 1 for the four season porch 12x14).

Overall square footage of the house is 2200sq feet and I've decided boiler plus indirect is the way to go. We have no option but to use oil.

My oil company has recommended a Burnham MPO-IQ 147 with a 37 gallon indirect. They just looked at it and gave me a price.

A small oil burner outfit that is up and coming has taken the time to do a full heat loss calc and is in process of recommending two options

1.) Trio Low Mass Boiler (I think this is a re-labeled Biasi) with Super-Stor tank

2.) Buderus 115 with Super Stor Tank

My questions are as follows:

Should I have any brand preference including Weil-Mclain or Peerless from someone else?

Should I go low-mass on the boiler? Is this proven?

Any recommended installers on the Mass/RI border

Thanks in advance.


  • Greg Maxwell
    Greg Maxwell Member Posts: 212
    Low Mass all the way

    Use either a Biasi, or Buderus boiler with SSU-45. Low mass is proven, and savings are big. We have been doing it since the 80's. Do yourseld a favor, and incorporate a Honeywell AQ251 reset / zone control. Along with the cold start boiler, you will see big savings.
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    I agree with Greg..

    btw....unless the first contractor can prove it to you via an accurate heat loss/load, no way you need mpo 147.  My house is slightly larger and the 115 is a little oversized

    There was an error rendering this rich post.

  • meplumber
    meplumber Member Posts: 678
    The debate continues.

    The debate between high mass, low mass, and what I consider mid mass boilers has gone on for years.  I have had great luck with all of the boilers that you mentioned. 

    The Burnham MPO-IQ, the Trio, and the Buderus are all triple pass boilers.  That is definitely the way to go.  I agree with Steve, the 147 sounds a little big for 2200 sq ft.  A heat loss calculation is required by state code here in Maine for all boiler replacements.  There is a reason for that.  It is necessary.  When your original boiler was installed, software wasn't readlily available and heat loss calculations were done by hand.  They took forever.  Equipment was regularly oversized.

    It sounds like you are on the right track.  Remember that the right installer is the key to the whole thing.  A great installer can make up for a lot of slight variances in the equipment.  Do your research on the guys and trust your instincts.  Ask for some references and call them.

    Good Luck.
  • carl_nh
    carl_nh Member Posts: 27
    Consider Buderus G125

    You will spend a little more but get the tiger loop, 2107 controller, outdoor reset, the blue flame boiler and $1500 back from the Feds since its 90% eff boiler. Its the same boiler as the 115 but with a Buderus burner and all the controls are included. I looked at the 115 and with the additions it came within $500 of the 125.

    The blue flame is the best out there, clean, and burns clean year round. The only consideration is you need to either have a central chimney or a lined flue, or do a direct vent with PVC out the side of the house.

    We have saved 400 gal annually (900 vs 500 now) for the lasat two years so do yourself a favor and look into the G125.

    On sizing, unless you have poorly insulated house, the smallest unit G125-21 should work for you (it heats our 2800 SF with heat loss @ 75KBTU).

    So you must do a heat loss calculation - you can do you own and compare to contractor - spreadsheets are on line.. I would bet you are somewhere around 70-85KBTU for 2200 SF, .If you are over that, then tighten up the house. add insulation, seal the gaps etc as you are thowing $$ out the window with any heating upgrade.
  • Mac_R
    Mac_R Member Posts: 117

    The 115 is a really good boiler.  I have seen anywhere from 45-70% savings by installing them.  The only thing that worries me is the indirect tank they want to install.  If you are going to use the Logamatic 2107 control.  I hope you do.  You really need to use the Buderus indirect tank for DHW.  There is something about other indirect water heaters that the control does not like and will not keep the tank at a constant temp.  They are using the super store because it is cheep.  For a little extra money you can get the Buderus tank and have no problems.  You just need to have the anode rod checked annually and replaced if necessary.  The G125BE is an awesome boiler.  However the price of lining the chimney usually is not worth the little difference in efficiency between it and the 115.  Don't give me that **** about not having to line the chimney.  Your flue gasses are well below 350.  It is going to condense in the chimney.  That equals acid.  The boiler can take it.  The chimney can not. 
  • Mac_R
    Mac_R Member Posts: 117
    Venting the G125BE

    You can not and must not vent the G125BE with PVC!  You still need to use smoke pipe for a chimney vent or L vent for direct vent.  I use a peace of Z flex for direct vent.  Even in the manual it tells you not to use PVC or CPVC.  
  • Robert O'Brien
    Robert O'Brien Member Posts: 3,542

    Unfortunately,the $ 1500 tax credit is now $150 and will be gone at the end of this year
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • Robert_25
    Robert_25 Member Posts: 530
    They all work, but the installer makes a big difference.

    It sounds like one company wants to sell you oil, the other wants to sell you a heating system.

    Any of the boilers you mentioned would do the job, but Buderus would be my choice. Ask about their Logamatic control.
  • JimmyQ
    JimmyQ Member Posts: 3
    Boiler water capacity

    I'm a little late to the discussion, everyone has provided great advice. My 2 cents is while the Buderus is a great unit, the boiler holds a lot of water, almost 9 gallons. some one mentioned Biasi, same sized unit holds about 3.5 gallons. The AFUEs are almost identical, but at the end of the day the Biasi has to come out more efficient. Why? Takes less BTUs to heat less water. I think the tank capacity is an over looked consideration.
  • Ironman
    Ironman Member Posts: 7,379
    Another Way to Look at it

    This poster has at least 2 small zones that will cause short cycling with a low mass boiler.

    Having a larger mass will give some buffer and extend run times. That will result in better efficiency than short cycles. If he simply had one large zone, then the lower mass might have a slight advantage. The Buderus has a 3 " insulation blanket so standby losses are minimal.

    Either way, I'd recommend the Buderus G-115 with the Logamatic 2107 control, but any of the three are good boilers. The installer/servicer is the most important factor.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • JimmyQ
    JimmyQ Member Posts: 3
    Short cycle?

    My house has two zones, the Biasi was my choice if I had to stay with oil. Fortunately I was able to convert to natural gas. I have a Burnham Alpine which holds .6 gallons of water. My other issue was sizing. One installer I got a quote from wanted to install a unit that was too large, which will cause short cycling. Not sure how a smaller amount of water in the tank will cause the boiler to short cycle. I agree the Buderous is a great unit, especially with the logimatic control, but I can tell you I wouldn't have put it in my house.
  • Mac_R
    Mac_R Member Posts: 117
    Buderus mass

    The Buderus G115ws/3 only holds a little over 5 gallons.  the G115/5 does hold a little over 8 gallons.  
  • JimmyQ
    JimmyQ Member Posts: 3
    Buderus capacity

    According to the Buderus web site that model holds 8.7 gallons. The "5" holds 12.9! That's a lot of water. I found the specs here;

This discussion has been closed.