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Gravity System convert with OLD condensing cast iron boiler, Help, Question

JACKBLACUS Member Posts: 2

I live in Queens NY and currently have a Weil Mclain Series 6 CGM-7 210,000 BTU boiler. I have owned my house for the last three years. I don't know how old the boiler is, however a service tag attached dates back to 1997. Heating bills are very high in NYC and cost 500+ a month in winter which is what got me doing research on boilers. The house is an old Victorian, however R19 insulation has been added to all exterior walls and new modern doors and windows replaced on all.
Currently I have a old Gravity system with cast iron rads which was converted with the addition of a Bell & Gossett circ pump series 100. I have cast iron rads with a total EDR of 892. The house three stories, has an unfinished basement, two living floors, and a finished attic with heat rads in all locations. Total square footage of house is 3100 sq feet. Rads get to about 100-110 degrees with FLIR.

I was doing research into new Con/Mod HE boilers when I realized that this boiler has, ALWAYS?, been condensing which is bad for corrosion. The boiler heats the house well running for about 30 minutes between cycles of 1.5 to 2 hours depending on temps in December, in colder months longer. I used a FLIR ONE recently with electrical tape (for reading accurately) on the supply and return pipes. With 30 minutes of run time the temps are 110, 100 return. With run times of an hour the temps are 120, 110. I have never seen the temps approach 140 or above, but also I haven’t checked the pipes in January/February.

There is NO temperature return mitigation on this boiler, clearly being plumed incorrectly. Even the original manual for installation talks about return mitigation.

My questions are, why hasn’t this boiler failed after so many years of usage in this configuration? And can anyone suggest a new boiler for a converted gravity system for this house.
Thank you in advance.

PHOTOS attached. https://www.flickr.com/photos/197086861@N02


    EBEBRATT-Ed Member Posts: 14,560
    You can use another CI boiler if it is piped correctly. Adding return temp protection is very easy to do.

    Or you can us a mod con boiler which will be more efficient with your old system if installed right

    Mod cons are more efficient, cost more to purchase and have more sophisticated controls and the life expectancy is probably 15 years. Replacement parts are more $$$$ and are sometimes a struggle to get and you need a better service technician to tune it and set it up properly

    CI boiler usually last longer and are less expensive, parts are less expensive and usually in stock less efficient (on your system) and more forgiving to adjust and tune.

    The choice is yours.

    I would factor in how long you plan to live there among other factors
  • pedmec
    pedmec Member Posts: 828
    I don't know if a piece of tape would give you the correct reading. i would spray the area your testing with black spray paint. I'm personally not a fan of infrared thermometers as they give plenty of incorrect measurement. I could be wrong about the tape but have not ever measured it that way. i like to use a strap on thermometer with a cooper kit. Way more accurate and you can the thermometer with a cold water bath for accuracy.
    JACKBLACUS Member Posts: 2
    edited December 2022
    Thanks for the idea, however I think the temp is accurate as I can touch the pipe when it's 110 and it's about the same temp as hot water from faucet. Also without tape it's about 8 degrees lower, I've also used electrical tape and same temp as painters tape.