Reline oil burner chimney?

[jatoxico]

So before I have my insert installed this Sat I had the chimney swept. While I was at it I had the chimney swept that exhausts the oil fired boiler and water heater. $30.00 bucks a piece.

The sweep said the fireplace flue was in good shape but the one supporting the oil burner is bad. The clay liner is going (he says bad bad) and mainly because there is no device to make sure both the boiler and water heater don't fire at the same time.

I can see the "volume" issue causing excess deposits but not so much how the simultaneous firing should hasten deterioration of the liner. The liner may very well be bad as the house was built in 62', but I'm hoping for a little insight. Does the deposition of soot "eat" the liner? I'm aware that Sulfer and Nitrogen to some extent can generate acids but anyone heard of this scenario?

His suggestion is to add a unit to prioritize one system over the other so they don't fire at the same time then install an SS liner. Wants $1000.00 to install and the liner he wants to use is very good. I've had my hands on it and it is heavy gauge (0.018" I think) and smooth so no problem there. Excepting a total failure allowing gases to reach the masonry what is the major issue, poor draft, anything else?

 

[btuser]

That's a really good price for the liner depending on the height. The hot water heater and the boiler should have seprarate flues, not a trick to make sure they don't fire at the same time. That being said I don't think its an over-abundance of flue gas that causes the build up, rather a hot water heater venting into too large a large chimney. That will cause condensation which will in turn cause soot particles to stick on the tile. Soot + more moisture (either condensation or even rain) will form acid and you end up where you're at. I relined my chimney and I'm glad I did it. My new boiler is a little too efficient and the exiting flue gas is barely 300F at the breech and about 150F at the height of the stack.


Is it a gas HW heater or oil?
What is the dimension of the current flue?
What are the dimensions of the appliances you're venting?

 

[jatoxico]

That's a really good price for the liner depending on the height. The hot water heater and the boiler should have seprarate flues, not a trick to make sure they don't fire at the same time. That being said I don't think its an over-abundance of flue gas that causes the build up, rather a hot water heater venting into too large a large chimney. That will cause condensation which will in turn cause soot particles to stick on the tile. Soot + more moisture (either condensation or even rain) will form acid and you end up where you're at. I relined my chimney and I'm glad I did it. My new boiler is a little too efficient and the exiting flue gas is barely 300F at the breech and about 150F at the height of the stack.


Is it a gas HW heater or oil?
What is the dimension of the current flue?
What are the dimensions of the appliances you're venting?

They are both oil. The flue is standard? . Guess its 8". The boiler is a big old unit but the water heater is a relatively new Bock w/ Beckett burner. In this case each unit is exhausted into gal pipe, these tie in together before entering the chimney.

He called the "trick" a Preferential Relay Switch. Sounds like a real thing.

BTW the chimney is 25', considering the quality of the materials I think it's a pretty good price.

 

[peakbagger]

I have an 8 inch flue and a fairly efficient oil boiler. I never had any deterioration until I put a chimney cap on for a year or so. When I was checking the flue next season the top tile was starting to flake. I expect the slight amount of added resistance was just enough to get the exhaust slowed down enouhg that it got below the dewpoint. Many of the hihg efficiency boiler like the system 2000 recommend a SS liners as they dont put out enough exhaust gas volume and exhaust at a low temp. I just had the chimney replaced down to the roof line and the only bad tiles were above the roof line.

The amount of sulfur in heating oil was ramped down a few years ago, so acid precipitation should be less of an issue.

 

[maverick06]

If you burn enough wood you shouldnt have to worry about this.....

I burn 30 gal/year and havent ever looked in my oil chimney since i got my wood stove....

but the idea of timing the devices so they dont run at the same time just sounds like a workaround, not the right solution.

 

[btuser]

I would still re-line (seeing how its necessary at this point) but would get rid of the oil-fired HW heater and install an indirect. Because you have an open flue on a direct-fired hot water heater there is a tremendous amount of standby loss. That way you wouldn't have to share a flue.

Of course, one has to run the numbers to see if it makes sense, but oil-fired hot water heaters are more maintence and nowhere near as efficient as an indirect DHW heater.

 

[jatoxico]

I have an 8 inch flue and a fairly efficient oil boiler. I never had any deterioration until I put a chimney cap on for a year or so. When I was checking the flue next season the top tile was starting to flake. I expect the slight amount of added resistance was just enough to get the exhaust slowed down enouhg that it got below the dewpoint. Many of the hihg efficiency boiler like the system 2000 recommend a SS liners as they dont put out enough exhaust gas volume and exhaust at a low temp. I just had the chimney replaced down to the roof line and the only bad tiles were above the roof line.

The amount of sulfur in heating oil was ramped down a few years ago, so acid precipitation should be less of an issue.

Had System 2000 in my old house, very nice unit and used 40% less oil. Could not believe it. Damage to flue may have been done long ago but interesting about the cap. I should upgrade my system sooner than later.

 

[jatoxico]

If you burn enough wood you shouldnt have to worry about this.....

I burn 30 gal/year and havent ever looked in my oil chimney since i got my wood stove....

but the idea of timing the devices so they dont run at the same time just sounds like a workaround, not the right solution.

Right! Gotta get more wood! Seriously, I won't be completely supplanting my oil system or I don't think I will (this will be first year with EPA insert) just trying to supplement and be more comfortable. Not sure what other solution there would be besides a preference relay except running a whole new flue and chimney. I don't think that's how it's done at least around here but I'm no expert.

Very possible the flue is shot, mostly just curious if anyone ever heard of 2 sysytems causing premature flue failure. I'm not convinced I think it just went from age but if I put a 6" liner in the sweep insists you need a relay or void any warranty since 6" is just too small for both appliances to run at once.