Wait on Liner?

Damian418

Hello all! I have a 17 yr old house with same age clay lined chimney flue. I'm in the process of researching replacement boilers for my 17 year old Burnam vs111 oil fired hot water boiler that has a cracked fire box.



My question is if I get a higher efficiency boiler, I understand that I should line my flue with SS, but can I wait a few months to line? The chimney was inspected a little over a year ago and the clay was intact. Can I upgrade boiler now, have it vent into clay flue and install a liner in a few months? Heating season (hopefully) is ending soon...with spring/summer heating and reduced use should I be ok until the fall?



Thanks!

icesailor

Clay Tiles:

I was under the possibly mistaken impression that a clay tiled chimney is considered to be "lined". If it has been inspected and found to be in good shape, if you are replacing a oil boiler with the same type of oil equipment, you do not need to add a new liner. Only if the clay tiles is badly cracked or broken.

If you are adding a category 3 condensing gas appliance, you will need to change it.

Damian418

Could be mistaken as well...

I was under the impression that with a higher efficiency, 3-pass boiler that the lower stack temps will (could) lead to condensation which erodes the clay tiles hence why a SS liner is recommended.



Maybe it would help if I shared the boilers that I am looking at? My short list includes: Burnham MPO-IQ, Buderus G115WS, New Yorker CI-WGS - all in the 87% AFUE range. Also installing a Triangle Tube Smart 40 Indirect DHW heater.

icesailor

Vent Category's:

What are the vent category's on all of those oil boilers?

billtwocase

I would

do them both now. That is an RS111 boiler that you have now? Replaceable chamber if need be, until you make a decision.

Damian418

Thanks!

I went and looked again, and the name plate on my current one actually says Model: RSH-111. It says 120 MBH DOE and 104 MBH Net IBR.



Icesailor, where would I find that info? I looked through the manual for the Buderus and Burnham and didn't see that specifically mentioned. They both say chimney venting...



And I know I should do them both now, but the economics would be easier if I can delay the liner. I guess what I am asking is CAN I wait on the liner a few months. Or...as icesailor suggests, perhaps I don't have to at all.



Thanks again.

icesailor

Category venting:

I'm not disagreeing with anything.



The oil boilers you have mentioned are all CAT. l non-positive draft, non condensing appliances. A clay tile flue liner in good condition is acceptable for venting Cat. 1 and Cat. 2 appliances if after a proper inspection, they are deemed to be in acceptable condition. The flue width and overall length and location must be considered. There are vent tables that tell you what parameters you need to be in. Flues can be too small and they can be way too big. Too small and you may not have enough draft velocity. Too large and it may be too slow and the heated gasses may not heat the flue properly to make good draft.

Putting a 100,000 BTU oil boiler into a 16" X 16" clay tile flue that is 150' long does not qualify. Putting the same oil appliance into 6" round clay tile flue chimney or a 6" corrugated liner 150' long probably isn't either. But somewhere in the middle and/or not a 3 sided outside chimney. You'll never heat up a 3 sided outside chimney if it is 20 degrees outside.

If the house is 100 years old with no clay tile flue liner, you will need a liner if it is a Cat.1 appliance. If the chimney is 17 years old, and has a tile liner that has been inspected and approved by someone with qualifications, you should be able to continue to use it. But it must be inspected.

If you have a 8" X 8" tile liner, I would like to watch someone put a 6" CSST liner down it. And have the flue qualify for something over 100,000 BTU's on the average oil burner boiler input.

Do I think that CSST flue liners are a bad idea? ABSOLUTELY NOT!!!!. Most masons I have worked with wouldn't know how to build a proper multiple flue chimney if they were paid to do it. Their worst complaint is that they leak. They're talking about water. They DO leak. Draft vacuum between the flues and the outside. If the appliance flue is connected to a fireplace base and fireplace, it is a concrete block base with a brick façade.

Have the chimney inspected. Install the CSST liner if you are planning to go to a Cat. 2 or Cat 4 appliance. There are no Cat 3oil appliances that are sold in the USA.

If the above oil boilers are condensing in the flue, the flue is too large. The point of properly sized flues is to keep the flue gasses hot enough to warm the flue and stop condensation. 

Correct me if I'm wrong.  

icesailor

NFPA's

Gas and oil have different NFPA codes and for chimney flues I think.

The real expert here is Tim McIlwaine.

In my 2011 Massachusetts CEU to keep my licenses, most of the morning session was covering flue and vent sizing for gas appliances. I've never has a class on oil venting so I don't have true information on it. It should be close though. The CEU classes and courses are set by the State Board of Plumbers and Gas Fitters so they can get everyone in the Commonwealth on the same page as to what is allowed and what isn't. This includes inspectors. It only covers gas. But the theory is the same. For example, if you have a properly sized flue with a oil burning appliance and a gas domestic water heater in it, and you remove the oil burner for a direct vented gas heater, the flue is probably too small because a 36,000 BTU water heater probably doesn't warm up the chimney enough to make it work properly.

Not all chimney "Specialists" know what they are talking about.

Bob Harper

suitable venting

The chimney must be suitable for the class of service. When changing appliances, it must be inspected. NFPA 211 dictates the levels and scope of inspection. If there is a single mortar joint failed or missing, you would need to reline even if all the flue tiles were visually found to be intact. Finding debris in the cleanout base means material is now missing above and thus compromised.



Your typical "8x8" flue tile measures about 6.5" ID. Now, factor in offsets, misaligned tiles and protruding mortar and yes, it gets fun pulling a 6" ID liner down one but it is done every day with no problems.



A corrugated stainless steel liner typically must be de-rated 20% plus an additional 20% for any offsets. There are a few smooth wall liners available to buy back 20% when you're too close in your sizing.



Use a listed liner meaning UL1777 and install to the mfrs. listing and your codes. Usually insulation is not required for oil and gas but recommended. I use air insulation and it works better than blankets IMHO.