Chimney help

[SHOZ]

I had an oil furnace with a 6" double wall stack, looks like 8" for the outside pipe. It also carries the propane water heater 3" flue.

I replaced the oil furnace with a propane one that has a 4" flue. So now I have the 4" and 3" tee into a 6" and up the chimney.

The internal 6" pipe in the old chimney must have a hole in it as I get water dripping out when the water heater is running.

So, I'm thinking of just running a smaller pipe up though the old 6". I can get 5" pipe to 'reline' the old one but would rather use 4". So can 4" be used for both the furnace (80k btu and seldom used) and the water heater? Should I use a smaller tee where the two join together?

 

[LazyDog]

Let your fingers do the walk and look at a minimum venting for the appliances, they are charts. I would pay for some one to design and tie the vent pipes properly.

Keep a Carbon Monoxide alarm in the same room to notify you of any problems.

 

[Ausfahrt]

You need to hire a professional.

 

[zzyzzx]

 

[SHOZ]

You need to hire a professional.

Professionals installed it......

 

[Ausfahrt]

Professionals installed it......

Based on your pic, that's a chickenshit job. You need to get a refund and then hire some real professionals.

 

[SHOZ]

Based on your pic, that's a chickenshit job. You need to get a refund and then hire some real professionals.

No kidding. I can do a better job myself. That's why I'm asking. It seems pretty simple and Menards has all kinds of pipe. I even have the vent pipe flow needs for the furnace.

Just though someone might actually know something.

 

[Rob_Roy]

The water heater alone is not enough to keep the chimney above the dewpoint of the flue gasses. You are getting condensation, which will quickly ruin the chimney.

Have an insulated stack put up that is properly sized for the two units.

 

[SHOZ]

Looks like the AmeriVent B line gas venting pipes Menards carries will do the job for about $100. Just using 3 and 4 inch pieces an going up through what I have.

I don't want to take the existing chimney out as it would leave a much bigger hole that what I need.

 

[manicrodder]

Used to be my trade. An old rule of thumb was to use a framing square. For example connection for combined 3" and 4" measured accross square makes 5". Even mechanical engineers would use it in the field. This is basic formula fo making a square corner by plumbers and others.

 

[BituminousCoal]

so, you replaced an oil furnace with an 80% propane? Modern oil to modern 80%propane you would have been much less $$ per btu to stay with oil. You also likely wouldn't have had to reline the flue.

Yes, not enough heat in the stack and/ or not enough dilution air to let it dry between cycles. need a smaller liner or insulate (wrap) the exposed portion in the attic, that may help.

 

[manicrodder]

so, you replaced an oil furnace with an 80% propane? Modern oil to modern 80%propane you would have been much less $$ per btu to stay with oil. You also likely wouldn't have had to reline the flue.

Yes, not enough heat in the stack and/ or not enough dilution air to let it dry between cycles. need a smaller liner or insulate (wrap) the exposed portion in the attic, that may help.

Increasing vent height might help too.

 

[SHOZ]

Propane is around 40% of fuel oil cost. I will not be using the furnace for heat except for times when the crawl space gets close to freezing.

 

[BituminousCoal]

Propane is around 40% of fuel oil cost. I will not be using the furnace for heat except for times when the crawl space gets close to freezing.

I would be surprised if that were the case per btu. In most areas it is not.

In my experience, many customers think that it is "cheaper" because they seem unable to grasp that you nedd 1.4-1.6 (depending on appliance efficiency) gallons of propane to equal 1 gallon of heating oil.

For example, in your situation:
A new 80% efficient propane furnace burning propane at $2.49/gal

To be the same cost with
A modern oil furnace at 86 %

You would pay $ 4.06 per gallon

If you pay less (which you would because oil is not at 4.06/gallon) you save money.

Sounds like your hvac salesman gave you bad advice and a poor install. At the very least he should have suggested going with a 95% unit. You never know when illness or injury will mean you have to rely solely on "automatic" heat.

 

[SHOZ]

I'm only paying 1.45 for propane and I doubt if I use 25 gallons a year in the new furnace.

 

[Dinoburner]

NFPA pamphlet 54 will have venting tables that will describe proper venting. The OP should call the licensing board over the cluster shown in his post. I agree a competent installer should be called.

 

[SHOZ]

I'm just gong with single wall 3"+ 4" to tee to 5" up the stack and out the roof.