Heating Guys

[skeets]

I have been fighting with a leaking chimney for several years and I still cant get it fixed, leaks out from between the bricks at the mortar joints,,,,
With that being said, I was talking to my Lil Bro bemoaning the fact that this freekin leak is giving me no end of grief. He said you got a new boiler in a couple years ago right,, yeah,, and you took out the electric water heater out a couple years before that right,,, well yeah it was 200 years old,,,
He said when they put in the new gas boiler did they line the chimney,, I said it is lined,,, with clay flue liners,, He said nope with pipe,, why the hell would they do that??
He said a guy he worked with was having the same problem and it turned out the new furnace he had put in was so efficient that when it ran the flue wouldn't get hot enough to drive off the moisture and it condensate in the chimney and caused his leaks. And I have both a newer hot water heater and newer boiler.
Now I never heard of such a thing before though I guess it sounds reasonable,,,, So I am ASKING has anyone ever heard this before? If so please let me know cause I am grasping at straws here

 

[aeblank]

Yeah, ss lined. They pull a tube through and put light weight concrete around it to fill the gap.

Sent from my XT1254 using Tapatalk

 

[Fro65]

Yep, I've seen it many times. Modern boilers tend to not like the old 'everything into a common chimney' approach.

Todays high efficiency boilers (ones vented in PVC) will condense like crazy and must be plumbed all the way to the exterior. And, modern lower efficiency boilers (ones vented with metal pipe) tend to require specific flue diameters and not exceed a maximum length in order to draft properly.

Other variables come into play as well. Like, atmospheric v.s. power burner, LP v.s. natural gas etc.

Sounds like poor installation practices. My bigger concern if it is a draft issue would be carbon monoxide. A unit that isn't drafting properly isn't burning properly. Keep yourself safe and have someone do a flue gas analysis.

 

[rob82]

I am an HVAC Tech and this is true. The old chimney I would guess is 8X8 terracotta that is going to be too large for the new boiler to draft right. I would guess you would need to use a 6" liner so it can draft properly. If the chimney is to large it may never get hot enough to draft right. Think of a fireplace, it needs to get hot before it starts drafting. If the chimney is on an outside wall (3 sides exposed to the cold) it is code that it be lined. Some towns here in NJ require it be lined when going from oil to gas regardless if its on an outside wall or not.

 

[skeets]

OK soooo your saying that the flue should have been lines with SS pipe? How is that done how is it sealed how is the exhaust tied in to the SS pipe along with the hot water tank?? And about how much a foot????

 

[olthumpa]

What everyone has already said.

I have 2 - 7X11 terracotta flues which are 26 years old. 1 for an oil fired boiler and 1 for a wood stove. Insurance company wants me to reline them with SS. Like others have said, the new furnaces break down the terracotta.

 

[Diydave]

Check out THis old house's site, they have shown several installations.

http://www.thisoldhouse.com/toh/video/0,,20802896,00.html

This is for a fireplace liner, but a furnace is similar, with exception of the damper.

 

[OldeEnglish]

Skeets, is it an interior chimney or exterior? Like the guys said before vent size is very important. What also is important is if it's an exterior chimney it needs to be sleeved with an insulated vent pipe. If the vent gasses lose too much temp it won't draft properly, therefore the insulated vent pipe will keep the heat in the exhaust.

I'll give an example of a no no... Ever see those heat reclaimers you can add onto a wood stove vent pipe that exchanges the heat from the exhaust pipe into the room? Well those should never be used in gas or oil.

The older style boilers need to heat to raise the exhaust out, sometimes they use a power vent to help.

New high efficiency boilers don't exhaust much heat out of them, that's where they gain their efficiency among a few other things... That's why they are vented with PVC, CPVC, or PPE pipe.

What make and model is your boiler? How tall is the chimney? Interior Or exterior? What is the flue size? Square or round flue?

Rob, sleeving is code in MA now too as well as insulated sleeves for exterior chimneys and even interior if it passes through an unconditioned space.

 

[skeets]

Ok I guess I did leave a few details out,,, the house is about 90 years old, the chimney goes up through the middle of the house, and is exposed about 6 feet over the roof line and maybe 3 feet in the attic.

As far as I can tell, I am thinking either 6 or 8 inch square clay liners from top to bottom. total height is around 35 to 40 feet from bottom to top.
Was designed as a coal flue, coal furnace was modified to a gas boiler some time in the 50s I would think. ( And from the gas bills before I had the new boiler installed I think heating the flue was not a problem).
And like I said I took the OLD electric water heater out and put in a new gas one, maybe 10 years ago and the new boiler maybe 5.

However this brings some thing else to light, the last couple winters ( I live on a hill top with lots of wind) on the leeward side of the chimney there was ice. I never gave it much thought I figured it was snow or what ever melting off the chimney cap and refreezing.

 

[OldeEnglish]

Shoot me the make and model of the boiler. Try to find the exact size dimensions of the flue, its very important. Does the boiler and wh use the same chimney?

I'm assuming the chimney is being used for both appliances. That's not a common practice today and is frankly dangerous. You have a few options that sadly should have been thrown at you in the first place.

Option 1 - Do away with the gas fired WH and have an indirect water heater piped into the boiler as a primary (which means when the WH calls for heat, any heating zones running at the same time will shut off and all of the boiler power is sent to the WH until it is satisfied. Once satisfied, the heating zones will turn back on). Sleeve the chimney, and insulated vent would be best but a non insulated will work. The sleeve needs to be piped directly to the boiler out the chimney to keep all gasses inside the vent.

Option 2 - go with an electric WH, there is new electric models that act like an AC compressor that actually compresses the water to help heat it, along with a couple heating elements. They are very efficient and should have a hefty rebate that brings the cost way down. Sleeve the chimney like I stated above for the boiler.

Option 3 - the most expensive but the most efficient... Doing this will drastically reduce your gas bill to the point where it pays for itself in a few years. Do away with the boiler and WH and have a high efficiency system installed. It will be direct vent with plastic pipe out the side of the house and do away with using the chimney. An inexpensive way is with a Navien combo boiler that makes hot water instantly. They run about 92% efficient and work great, super quiet too. Go with the 200k BTU model because you want the most BTUs for making HW. Don't worry, the boiler will not use all of that power for heating because it throttles itself up and down depending on what the supply and return water temp difference is. I believe it ranges from 20k BTUs to 200k BTUs. These require routine maintence that you can do yourself. A lot depends on your water quality, high calcium content will scale up the heat exchanger and it needs to be flushed with vinegar.

You can also use a Lochinvar, or Vieseman boiler. They are expensive but are good quality. What ever is used you want it with a Stainless Steel heat exchanger, not aluminum because the condisation the boiler creates is very acidic and the stainless will last longer. Combine that with a good Indirect water heater like a super store or a squire (same tank, same manufacturers, squire is slightly cheaper). I suggest no less than 150k BTUs for using an indirect water heater. 100k will work but will not keep up with a large hot water demand. Vieseman have their own style indirect WH and they also work well, but you can also use a different stand alone tank.

Option 4 - get a direct vent WH that vents just like the boilers, they come in tank or tankless style. Tankless are the most efficient, somewhere around 97% and there is a bunch of manufactures.

All the new high efficacy equipment comes with hefty rebates, some more than others depending on the efficiency rating. There is also tax rebates from Uncle Sam that help pay you back.
Feel free to ask any questions, I'll try to explain the best I can.

 

[Lil Foot]

You know, it's always a pleasure to read posts from people who obviously know their err, stuff.

 

[skeets]

OK here it is,,, LAARS Mini-Therm JVi and looking at the clay liner with out getting on the roof still to cold and I really don't want to break any shingles up it appears to be a 6 inch, it is square,,, There now you got everything I know

 

[OldeEnglish]

I apologize skeets, few more question.... How many BTU's is the boiler?

Is the smoke pipe going to the chimney single wall or double?

How many ft of smoke pipe is there from the boiler to the chimney?
How much of that is running horizontal?
What size is the smoke pipe coming off the boiler?
How many 90's or offsets from the boiler to the chimney?

Sorry it been a long time since I sized an old school boiler vent, had to break out the revised code.

 

[OldeEnglish]

Here is three of many charts used to size vents. This is for educational purposes only, only a licensed/insured pro should install it.

This is the chart that your working with right now except this is for a single appliance. I believe your boiler is fan assisted. As you can see under the fan min and max btu rating, there is NA across the board, that means it can not be used.

Here is the chart that is for what your working at the moment having both vented into a masonry chimney.

This chart is assuming you have a single wall smoke pipe to the chimney from the boiler. If a corrugated chimney sleeve is used, you have to minus 20% off of the btu max. If you use B vent that is smooth and double walled, you do not have to deduct 20%. Type B is very expensive! Only use stainless not aluminum pipe.

I would highly recommend only venting the boiler through the chimney. A common vent can be used but very difficult to actually install in an existing chimney and getting both connections air tight. Sleeving the chimney is a pain in the ass any way you look at it. If there was no masonry chimney and just smoke pipe all the way up, piping both appliances in would not be a problem.