Properly venting a Wei-McLain CGi-4E boiler into a flue?

Discussion in 'Boiler Forum' started by gellfex, Jan 28, 2010.

  1. gellfex

    gellfex New Member

    Messages:
    56
    Location:
    NJ
    I had licensed plumbers install a Wei-McLain CGi-4E a few weeks ago. The venting problem was it goes into a flue along with a standard 50gal water heater. With my old boiler (an HE3), the 3" went into a 4" manifold that received the WH in a wye, and this worked fine. This new boiler is more powerful and they used just a Tee to connect the WH, now the boiler exhaust is coming out the WH hood.

    I've contacted them about this, but since they're obviously challenged by this, I'd like to hear some ideas about how it really should be done, short of the obvious solution of cutting a separate hole into the brick flue for the WH. There so much piping right there that's a big hassle.

    Ideas?
  2. dcelite

    dcelite Plumber

    Messages:
    132
    Location:
    Los Gatos, CA
    Any pictures? What do you have to work with?
  3. gellfex

    gellfex New Member

    Messages:
    56
    Location:
    NJ
    Hope these clarify. This goes into a 15' cinderblock flue on the blank side of my brownstone type building. I know it's not to code, but it's the way we bought it 12 years ago and apparently is grandfathered in. Street grade is a couple of inches above the bottom of the joists. My confidence is not too high in these guys, I watched the journeyman who actually installed the boiler bleed the crap out of expansion tank, and when I asked why, he said it was to get the air out of the system!! The other thing I'm not sure is right is how the vent rises straight out of the fan, so the condensation between there and the drip tee he installed drips back into the fan. The old boiler ran horizontal into a tee so condensation ended up in the dead end of the tee.

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  4. export!

    export! DIY Member

    Messages:
    90
    Location:
    Ontario, Canada
    I don't know enough to call it right or wrong but I do know that I would want a CO detector in the area until I sorted it out. If you don't have one install one today.
  5. Dana

    Dana In the trades

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    You can't vent an atmospheric-drafted appliance into the same flue as a forced-draft unit like a CGi-4E without exactly this problem! You might have thought you were getting away with it with the HE3, but in all likelihood the same issue was present, just less obvious. Unless you're tapping into a separate flue, banging a separate hole for the WH solves nothing- just moves the Tee from the metal vent to the masonry.

    And at the 85% AFUE efficiency of the 4E a condensation tolerant flue liner or side-venting (not using the flue) might be necessary, if it's not already lined. (83% combustion efficiency is about the limit before flue condensation becomes a real issue.) If you side vent it you'd then be stuck with an "orphaned hot water heater" problem (google it.) But if it's lined with clay liner only (or unline) you may be in for extensive chimney repair in short years.

    Whether the CGi is side-vented or vented into a properly lined flue, the "right" solution to the venting of the hot water tank is probably to de-commission the tank and install an indirect-fired HW heater run as a separate zone off the CGi when all is said & done. It won't be cheap, but it should last forever in low water-hardness areas with minimal maintenance, and improve your overall AFUE.
  6. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    Besides Dana's timely comments, You are NEVER grandfathered for installing gas appliances into an unlined flue. Whoever installed that abortion should be hauled before a judge. I can't believe you paid them for that mess. There is so much wrong there I can't even begin to list it all without getting a headache. Call your lawyer!
  7. johnjh2o1

    johnjh2o1 Plumbing Contractor for 49 years

    Messages:
    1,143
    Location:
    South*East
    Is that thing still growing?


    John
  8. gellfex

    gellfex New Member

    Messages:
    56
    Location:
    NJ
    I appreciate the comments, but I'm still trying to sort them out as to what I can do, vs should do. The venting issue is one reason I chose not to go with a higher efficiency unit. I can't direct vent out because this is in the basement. I don't quite get why a second pipe into this large flue would still get backflow from hot rising exhaust.

    Replacing the 11 year old 50 gal HW heater with an exchanger has already occurred to me. I actually have one in a tenants apt that's part of a completely overdone heat system with a cast iron boiler for the 450 sg/ft unit. I could pull the boiler & heat exchanger tank out and replace them with a Bradford White water heater that also does the baseboard, as is working fine in 2 other identical units. I doubt my cost would be much higher than just getting a new one for myself and I would stop having cleaning issues with that damn boiler (not a DIY btw). My problem with this idea is that it seems like using that indirect tank system is horribly inefficient in summer, the room with the utilities is always too warm from passive losses even after I insulated all the zone piping to the tank.

    But doing the above tank is probably much cheaper than running a new lined SS flue pipe the 45 ft up to the roofline, as I understand would be required to be truly to code.
  9. Dana

    Dana In the trades

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    Location:
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    An 85% efficient gas boiler's exhuast just ISN'T all that hot compared to an 80% efficient gas boiler. At 80% you'll have a net-stack temp differential of ~400F+, for an exchust temp right out of the boiler of 450-500F, whereas at 85% it'll be under 300F, with much lower buoyancy. With a high-efficiency condensing gas boilers the stack temps are under 200F, and plastic venting can often be used (but never a clay-lined flue.)

    If the flue is SO oversized that it won't pressurize and force backflow to the water heater when the forced draft boiler is running it's way oversized for the load and needs to be narrowed to have sufficient draft to avoid flue condensation/rot issues. You would need a HUGE natural stack-effect draft to overcome this issue (maybe you could add 100 feet to the chimney height for better draft? :) )


    Side venting is almost always an option, even from basements, but it may require moving the installation to where it can meet clearances from doors & operable windows and avoid a long lateral vent run inside the basement. (Mine had to move from the south wall where the chimney is to the north wall 40' away to get a code-legal side vent, but it made it.)

    An indirect with a 90k boiler behind it runs better than 40% efficiency in the summer. See:

    http://www.nora-oilheat.org/site20/uploads/FullReportBrookhavenEfficiencyTest.pdf

    The standby loss can be reduced dramatically by insulating the boiler loop to the tank to at least R4-R6 Better yet, insulate all of the near tank potable plumbing (including temperature/pressure valve outflow) to R4 at the same time. The smaller, less-massive the boiler, the lower the cycle loss- the CGi 4 will do better than any of the non-purging non-condensing boilers tested in that document. Also the lower you can keep the setpoint on the indirect, the lower the overall boiler/indirect standby will be. There may be lag issues at high flow from a lower-temp indirect on an initial cold start where the boiler needs a minute or three to come up to temp. This can be tweaked up for performance if need be, but storing 30+ gallons of water at 180F all summer is silly with a 90K boiler behind it, which is enough boiler to run a 2.5gpm shower 24/7. Start at 125-130F, and work your way up in 5F increments if the early morning shower has an intolerable lag on boiler warmup.

    If the room is too hot in summer from standby losses, you must be keeping the boiler hot rather than cold-starting it whenever the indirect calls for heat, which would be as-inefficient as an internal-coil, or you have a mini-coil type indirect with sub-10gallon capacity. If it's over 30gallons and it won't cycle very often, so the boiler cools completely. The last thing you want to do is to use an internal "tankless" coil in the boiler, which requires the boiler to remain hot all summer. Running the indirect as a zone, the boiler should only fire when the tank is calling for heat.

    A 50 gallon atmopsheric-drafted beast struggle to make 60% efficiency all year long unless you're a high-volume user (more than 60gallons per day, every day.) See: http://www.aceee.org/conf/08whforum/presentations/1a_davis.pdf This too can be much improved with near-tank insulation on the plumbing.

    Not measured in an efficiency test, the heat loss from the builiding due to infiltration induced by the open draft hood of the water heater adds up to 1-5% of the total heating bill (depending on a whole lot of factors.)
  10. gellfex

    gellfex New Member

    Messages:
    56
    Location:
    NJ
    Dana, thanks for an awesomely informative post! I've got to reread it a few more times. I think what I have is a 40 gal, what would the reset time be like on that off my boiler? I have a family of 4 with 2 full bathrooms. Could a plan be to use a mixer and raise the water temp in winter when there's a greater temp rise needed, to decrease reset and increase capacity? The apt is about 1300 sq ft, can I assume the CGi has the capacity to heat it and the HW?

    I just had the plumbers here and discussed the options for over an hour. The option of the indirect aside for the moment, the question was whether if the CGi4 and the WH were connected with a wye rather than a tee, would the blower in the CGi create suction on the WH line rather than the exhaust diversion we have with a tee. I guess you've already said NO.

    More info on my flue/chimney. For the 1st time in the 12 years I've owned this place I climbed up a ladder to look down that flue, and found it was capped! What they did was cut back though the brick building wall and into the bank of inside chimmneys (there are 4, building is >100 years old). The exterior flue is lined with 8X8 clay, the chimmneys as far as I've seen are unlined.

    One last thing, what I don't get about the "orphaned hot water heater" issue is the fact that the WH in those cases was already an orphan for the half the year that the boiler wasn't in use, wasn't it?
  11. Dana

    Dana In the trades

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    I can't quite get my head around a licensed heating contractor offering up a non code-compliant wye as even a potential solution, since it doesn't meet code (let alone the dubious aspects of whether it could actually WORK), and doesn't address the flue-damage factor from the mid-efficiency boiler's cooler exhaust. In an unlined chimney you're likely to be driving exhaust gases & moisture into other parts of the house, since the power vent puts the chimney at postive pressure relative to the rest. You seriously need to be talking to a different (and competent) contractor to recommission the whole shebang (ask Peter for details when his headache subsides.) Take more pictures, get some quotes/suggestions for remediation from other contractors, and get your town's building inspector involved (and likely a lawyer, if you ever hope to get paid for the recommissioning costs.) These guys aren't just cowboy-plumbers- they're dangerous to both your health and the structural integrity of the building.

    During the summer the temp of the masonry is typically higher on average than the dew point of the HW heater's hood-diluted exhaust, reducing chimney damage risk, but there still could be backdraft issues that must be tested for safety.

    A 30 or 40 gallon indirect with a 90KBTU boiler behind it will produce ~100 first-hour gallons at 130F, which is 20-40% more than your 50-gallon standalone. The cold-start time is a function of the boiler's mass & cold-temp, and how short you need it to be is a function of flow out of your tank and it's setpoint. At 10gpm out of the tank, if your tank is set to 130f you're much more likely to find it running cold, but at 5gpm (two 2.5gpm showers), not so much. Starting at 130F and raising it as-needed should you find it runs cold sometims keeps the return-water temp to the boiler high enough that you won't end up with condensation damage to the boiler, and minimizes standby loss. Odds are good it'll never need to be above 140F unless you have a large soaking tub that you're trying to fill.
  12. Dana

    Dana In the trades

    Messages:
    2,841
    Location:
    01609
    I can't quite get my head around a licensed heating contractor offering up a non code-compliant wye as even a potential solution, since it doesn't meet code (let alone the dubious aspects of whether it could actually WORK), and doesn't address the flue-damage factor from the mid-efficiency boiler's cooler exhaust. In an unlined chimney you're likely to be driving exhaust gases & moisture into other parts of the house, since the power vent puts the chimney at postive pressure relative to the rest. You seriously need to be talking to a different (and competent) contractor to recommission the whole shebang (ask Peter for details when his headache subsides.) Take more pictures, get some quotes/suggestions for remediation from other contractors, and get your town's building inspector involved (and likely a lawyer, if you ever hope to get paid for the recommissioning costs.) These guys aren't just cowboy-plumbers- they're dangerous to both your health and the structural integrity of the building.

    During the summer the temp of the masonry is typically higher on average than the dew point of the HW heater's hood-diluted exhaust, reducing chimney damage risk, but there still could be backdraft issues that must be tested for safety.

    A 30 or 40 gallon indirect with a 90KBTU boiler behind it will produce ~100 first-hour gallons at 130F, which is 20-40% more than your 50-gallon standalone. The cold-start time is a function of the boiler's mass & cold-temp, and how short you need it to be is a function of flow out of your tank and it's setpoint. At 10gpm out of the tank, if your tank is set to 130f you're much more likely to find it running cold, but at 5gpm (two 2.5gpm showers), not so much. Starting at 130F and raising it as-needed should you find it runs cold sometims keeps the return-water temp to the boiler high enough that you won't end up with condensation damage to the boiler, and minimizes standby loss. Odds are good it'll never need to be above 140F unless you have a large soaking tub that you're trying to fill.
  13. gellfex

    gellfex New Member

    Messages:
    56
    Location:
    NJ
    Yikes, it sounds like even if there is no WH, the existing flue is not appropriate. So, since clearly I need to be better informed when dealing with these guys (other licensed heating specialists have worked on this system and not raised the flue issue when it was a HE-3), what would the best solution be for the circumstances?

    This is a 4 floor multifamily brick "brownstone" with the boiler for my unit along a side wall about 6' from the rear of the basement. There's ground floor windows on the back about 2' from the corner and a side window 15 from the corner. What are my options: could I simply drop a double wall 4" liner down the ~12 ft outside masonry chimney and vent it there rather than have it return inside to the chimney? The plumbers said the code was 5' from a window, but I had thought it was further. 45' of double wall to bring it all the way up the outside to the roof would be pretty expensive.

    BTW, the guys that did the CGi were chosen because they could do it on a saturday after the HE-3 died during a 20 deg cold snap. I don't think they're heating specialists. But like I said, the guys who are one of the bigger hvac contractors here did maintenance work and added a zone for me before this without commenting on the venting. I'm a pretty DIY guy, but the only thing on there I did is the pex zone for suspended radiant under my kitchen.
    Last edited: Jan 31, 2010
  14. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,015
    Location:
    New England
    The first thing I'd do is look at the installation manual that came with the unit. If you don't have it, you may be able to download it from the manufacturer's website. Most local codes require installation to be per the manufacturer's specifications. If you did not have a permit and inspection, that's an issue, right there. The installation manual will normally show the various approved methods of how their unit must be installed to work properly.

    The permit and inspection are your safety net to ensure this sort of thing doesn't happen. Too many people avoid them, and more than a few get bitten either from a substandard installation or other issues later on when it comes time to sell the house.
    Last edited: Jan 31, 2010
  15. gellfex

    gellfex New Member

    Messages:
    56
    Location:
    NJ
    I'm certain you're right that inspectors are your friend in most places, but I live in Hudson County NJ, where building inspectors, among other officials, are regularly jailed for extortion. You wouldn't believe some of the stories I've heard 1st hand, like restaurants having openings delayed literally for years. Recall the FBI corruption arrests here last July that made national news? I've shaken hands and chatted with 4 of the 30 odd officials indicted.

    Combine that with the fact that as owner of a multifamily I can't even legally hang a cabinet or build a closet without a contracting license & a permit, never mind do simple DIY level plumbing and electric work, and you have the reason I'm inspector shy. And not just me, I've never had a contractor who voluntarily pulled permits, they'll always ask me if I want one! Like I'm the expert on whether that particular job requires one. It's like a game of cat and mouse, except the contractors and inspectors are both the cats and I'm the mouse.

    I do have the manual, I'll study it.
  16. Lightwave

    Lightwave New Member

    Messages:
    98
    Location:
    Vancouver, BC
    Can you find another heating contractor?

    Have someone who knows what they're doing install a code compliant direct vent exhaust (this boiler can be direct vented) somewhere else. Ditch the HWT for an indirect and abandon the existing chimney when you have the opportunity. Don't keep messing around with your existing chimney unless you have to.
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