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Interested in new high efficiency boiler for old steam heat system

Evanka Member Posts: 19
edited August 2021 in Radiant Heating
I have a small 4 plex built in the 1920s with about 16 steam radiators. It currently uses a natural gas Weil-McLain Model number EG-55-PIDN, series No 4, 200,000 BTU which vents through an old chimney that goes up about 40' from the basement.

The boiler was installed in 1994 and is heating well except that it is not venting properly. The basement where it is located started to feel humid at the end of last season.

I have an estimate from a chimney sweep to reline the chimney. But I hear that a high efficiency boiler might be cheaper to vent (like maybe through PVC instead of Stainless Steel) and maybe it would cost less to run.

I do not know much about any of this. I have one of the few Heating contractors that works on radiant systems coming to look at it for replacement next week and I suppose they will answer a lot of my questions. But I wanted to see what advice I could get from the forum here.

Also, the building is definitely not efficient. I also don't know how long I will own the building, so not sure how much to invest in it.



  • pecmsg
    pecmsg Member Posts: 2,898
    There is NO boiler for Steam that can be vented thru PVC.

    200K is HUGE!

    Tightening the envelope is your best return on investment. Keep the heat from moving out! Then you can reduce the size of each radiator, in turn the EDR and use a much smaller boiler.
  • Jamie Hall
    Jamie Hall Member Posts: 18,953
    And furthermore... if you basement was starting to feel humid towards the end of last season, I'd be very very suspicious of some steam leaks. One other clue to that would be how much water you have to add to the boiler -- anything over a gallon a week is really excessive, and actually that boiler should use less than a gallon a month.

    And any steam that leaks is steam which isn't heating your building!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Evanka
    Evanka Member Posts: 19
    Thanks for the feedback. I have not had to add water to the system. Maybe it is steam. A tech that came to look at it said it was the venting. If a high efficiency unit can't be vented easier, then I may as well get the chimney re-lined. I'm trying to get this resolved before the winter but hard to tell if it's steam or exhaust with out the boiler running. One thing is the CO2 alarms are not going off.
  • mattmia2
    mattmia2 Member Posts: 5,533
    Please edit to remove the price of the chimney lining.

    The cost of retrofitting it to something else or even replacing that boiler will be far more than the cost of repairing the chimney. If you make sure the system is leak free that boiler could last decades more. The important thing is to make sure the system is not leaking and if it is, fix the leak or leaks, the fresh water will kill the boiler quickly but with a leak free system half a century or more is not uncommon for that type of boiler.
  • pecmsg
    pecmsg Member Posts: 2,898
    Be advised UL Listed CO alarms are dangerous at best. 
    They are designed to prevent nuance alarms at a higher Levels then all health officials advise. 
    70 PPM for over 1 hour is dangerous. 
    Keep at least 1 low level CO detector in the home. 
    HVACNUT Member Posts: 4,594
    Can you posts some pics so everyone has s better understanding of what we're talking about?
    You seem unsure if its actually a steam boiler.
    JUGHNE Member Posts: 9,765
    Could you post pictures of the boiler showing all the piping floor to ceiling,
    include the exhaust venting into the chimney, please.

    Also a couple shots of the radiators that show both ends of the units.
    Are they all about the same size?
  • Evanka
    Evanka Member Posts: 19
    I will post some pictures soon. I am sure it's a single pipe steam heat system. Thanks
  • Evanka
    Evanka Member Posts: 19
    Here are some pictures of the system. The radiators are single pipe steam. Pressure is set very low, but I do not have a low pressure gauge installed. There is a gas water heater also venting through the same pipe BUT it is no longer in use. I know it may be creating a back draft issue with the exhaust. I plan to have it removed once I figure out my next steps. It’s venting through the chimney on the left. The radiators are various sizes, although most are similar. There’s one in the basement apartment that is on the ceiling though, and that’s totally different. Thanks for your help!

    EBEBRATT-Ed Member Posts: 12,010
    Well, the boiler is piped almost right. I have seen much worse. I would have the chimney investigated looks like flue gas condensation or water coming down the chimney.

    Either way with an outside chimney you will need a liner
  • Jersey2
    Jersey2 Member Posts: 103
    I thought a stainless steel liner was a must for gas heaters. Your system looks uncomplicated which IMO is great. What do you use for hot domestic water?
    I'm not a plumber or hvac man and my thoughts in comments are purely for conversation.
    JUGHNE Member Posts: 9,765
    It looks as if you have a condensate water accumulator/reservoir tank on the back side of the boiler (it sits on 4 pipe legs).
    Could you post a couple of pictures, one of each end of that tank showing the piping? Needs more light on the right hand end of the tank.
    I am in the process of building one for my project and always looking for design ideas.

    It puts more water in reserve for slow condensate return systems.
    Like having a larger boiler with more water, but no fire under it.

    In any event you will need the chimney liner.
    That mess of water stains is most likely flue gas condensate water which will eat up mortar joints and the piping. You have a "3 side cold" chimney that cools the exhaust gases down before they make it to the top.