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Bugster

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Discussion starter · #1 ·
I apologize if this is the wrong thread, but its the closest for my question. Are there any codes for the sharing of a fuel oil boiller flue and LP boiler flue within the same stack? Both flues go above roof line, but share the same rain cap. The LP is primary and fuel oil is back-up only. Any verification from NFPA or ASHREA would be helpful.

Thank you,
 
#2 ·
maybe

NFPA 211 and the 2009 IRC both allow common venting or interconnection between gas and oil. Solid fuel must have its own separate flue.

You refer to same 'stack', which is confusing. They appear to share the same flue. Are there two separate flues within this one chimney-one for the oil and one for the LPG but both terminating under one large multi-flue cover?

Those connectors look pretty big. A common vent or flue must be sized for the combined BTUs. Both appliances must have primary safety controls. Both have very little vent rise. I don't see a listed liner but I do see galvanized steel cemented into the wall which is not approved in 211.

I would install a listed liner sized both both appliances and bring it in closer to the ceiling while maintaining clearances to combustibles. You would use type L vent near the ceiling for a 9" clearance to combustibles, manifold it, install separate barometric dampers with spill switches, etc.

Any pics of the top of the chimney?

Move this to Pro section and we can discuss sizing and other details.
 
#3 ·
This looks like a commercial or institutional installation. If that is the case, there may be other codes or standards that come into play by municipality and state.

What is the building's usage?
 
Discussion starter · #4 ·
Hearthman and Meplumber,
Thanks for your timely responses. I will post a couple more photos for referencing; though crude.. they may assist with increased defining of use. The heating water is used for a large garage with docking access.
 
#6 ·
You have a problem there with that draft inducer/ power venter. It can generate positive vent pressure, which is not allowed in either vent system. Positive vent pressure can only be on one appliance regardless of fuel type and the venting must be listed for positive vent pressure. Just gooping joints with red RTV silicone does not count. Besides, in this application, it could easily vent from the WH back through the boiler into the room if the top of the chimney is blocked.

Do you have a photo of the chimney taken from this county? A little far away...
 
#7 ·
hearthman said:
You have a problem there with that draft inducer/ power venter. It can generate positive vent pressure, which is not allowed in either vent system. Positive vent pressure can only be on one appliance regardless of fuel type and the venting must be listed for positive vent pressure. Just gooping joints with red RTV silicone does not count. Besides, in this application, it could easily vent from the WH back through the boiler into the room if the top of the chimney is blocked.

Do you have a photo of the chimney taken from this county? A little far away...
Click to expand...
not to hijack, but a similar question/situation;

a NG natural draft H2O heater with an Iron Fireman oil furnace. Is the I.F. considered a power venter or induced draft and therefore okay? I have questioned this for years, have 3 homes this way of which 2 are former company owners homes.
 
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#8 ·
PAC, your answer is not from the mfrs. propaganda but your manometer. If you read positive pressure in the vent connector, then you must treat it that way. This is under 'steady state' (as if that truly exists) or after 5-10 min. of firing.

Note in the pic all the red RTV downstream of the inducer/ blower. Shouldn't be needed if nat. draft. If it truly just induces and vent pressure goes neg. then its ok for a minute or so......unless its dumping gobs of CO into the CAZ.
 
#9 ·
pac. The I.F. oil furnace is not positive draft. At least I have never seen one that was. As long as the flue is of the appropriate size and the smaller btu appliance (the water heater) connects to the chimney above the larger, then you are alright.
 
#10 ·
neg draft pressure from I.F. 'furnace'?

Apparently, we need some more info. here.

Pacnw, can you provide a model I.F. burner? Also, this burner is on a furnace and not boiler?

MEPliumber, all but one of the burners I saw on the I.F. site were forced draft according to the mfr.

I have seen plenty of power burners and induced draft burners that end up with a negative draft pressure.

I still say always test with a manometer to be sure then full combustion analysis to ensure it is burning properly and venting effectively.
 
#11 ·
All of the iron fireman oil products are considered unassisted draft. According to NFPA 31, if the burner provides all of the necessary draft to overcome the static pressure of the vessel, then it is not considered to be a positive draft situation.

There are literally thousands of this combination all over New England. All legally installed and operated. Oil fired Furnaces with regular old tank type natural draft gas water heaters venting into the same flue. As long as it is common vented as I mentioned before, it is legal per NFPA 31, 211, and 54.
 
#12 ·
Not looking to pick a fight meplumber--just curious about your source of info. on the I.F. being nat. vent. As I stated, I went on their website and about 90% of their units were listed as "forced draft" which means positive vent pressure. If you have a reference that contradicts this such as possibly for older units in the field, that's fine.
 
#13 ·
No reference on their newer stuff. All of the I.F.'s that I service are at least 15 years old. Many much older. The only reference that I have is just my experience. I will try and take a couple of pics the next time I service one. I might get lucky and find an old I & M lying around.

I just looked at their newer specs. Your right. Learn something new everyday. To be honest I wasn't sure that they were still in business.

Thanks.
 
#14 ·
I think I.F. made a broad shift in their product line because I agree with you on the oldies being naturally vented. You don't see their advertising hardly at all anymore but then again, they seem to be focusing more on commercial than residential, which is totally different marketing.

Back to the focus of my original point I would like to reiterate that inspite of ANY mfrs. claims, I prefer going by what my instruments are telling me rather than their propaganda.

Another problem is, there are devices and gizmos for sale that generate positive vent pressure and are being sold to a market who are lead to believe it is ok with traditional galv. pipe. Some even say to goop the joints with red RTV out of a guilty conscience, such as most pellet stove venting. All pellet stove venting in the US is technically illegal. I'm working on changing that.
 
Discussion starter · #15 ·
Thank you

Gentlemen or persons,

Thank you for the great responses and information. The discussion was very professional and better than some of my posts on the Controls side. Not sure if the maturity was an issue with some of them or what.. :bump: Maybe I should have stayed in the plumbing & HVAC industry.

I will share this with the associated personnel working on the issue.

Thanks again,
 
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Bugster
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