Chimney Venting

Alex Giacomuzzi

Timco..

The boiler is a Weil McLain WGO-4 which is a Natural Draft oil fired hot water boiler with a 1.2 gph burner capacity.
I believe that works out to 168K btuh for the input.

The vent from the boiler is sized at 7 inches diameter and mates with a rectangular liner inside of the clay flue tile. I am not at the property presently and do not have the dimensions on that vertical section --- sorry. The chimney height is approx. 18 feet high.

The boiler manual, which I have in hand, states the minimum chimney size is 6 inch diameter and 15 feet high.

The hot water heater, which I do not presently have, will have an input rating between 37K -- 40K btuh. This is my assumption.

Thanks for the help... Regards Alex

Alex Giacomuzzi

Chimney Venting Question

I have a code and practicality related appliance question regarding chimney venting..

Just purchased an existing home that has oil heat with an existing 51 year old buried oil tank under the front stoop.
The tank tested out fine, but at that age anything becomes a concern. The boiler is relatively new WM(5--7 years old) and is in good condition. It has a 150K btuh input capability. The existing chimney has a clay flue with masonry around the exterior with a metal liner inside the clay flue.. The existing venting appears to be in good condition..

The city just installed a gas line to the property. This gives me a future option of going to gas with my boiler in the future if I chose to do so. Presently it gives me the opportunity to take my water heater off of electricity.

I would like to change my existing electric hot water heater to a gas fired hot water heater and vent it into the existing boiler venting flue stack. The hot water heater would be around a 40K btuh input. The flue size is adequate for both appliances, and my question is does the code allow me to combine both these exhausts?? One from the oil fired boiler and one from the gas hot water heater?

The exhaust pipe from the boiler over to the chimney is galvanized steel. Gas appliances normally would use aluminum. I am not certain of the metal inside the clay flue. It is either stainless or galvanized.. I will have to check that out. What are your thoughts?? Can I safely combine them? Thanks.

Timco

What is the model of your WM boiler? Need to know the venting catagory (fan assist? Mod/Con?) and the existing vent size, as well as the aprox total vent height. Also, need proposed BTU of water heater. Galv steel is standard for all gas fired equipment.

Scott04

Better yet

why not spend the extra money now and hook an indirect water heater to the boiler. It is an investment now, but it will cost less to heat the water, and the indirect will last longer than the gas water heater. If you decide down the road to switch to a gas boiler, the indirect can still be used.

And, you don't have to worry about venting!

Scott

Ken_40

Unless your area...

has a different code than NFPA-54, you CAN vent the gas W/H into the same chimney.

To do so, you must make a second penetration ABOVE the existing one for the W/M. There are dimensional issues however with regard to:

1) the distance from the existing penetration and the one you must create above it.

2) The distance/clearance from the new gas vent from the bottom of the floor joists above.

3) Whether or not you use or required to use single wall or 'B' vent for the connections from the W/H to the new chimney penetration needed.

4) Additional "combustion air" issues for the gas W/H.

If all 4 above are good to go, it is a viable project. However, given the falling prices of oil and major downspin of NG, you may want to consider keeping your ~85% efficient boiler and NOT switching to a NG W/H and doing as Scott suggests; use an indirect for stiorage and use a TIMER to allow the boiler to fire in summer once or twice a day - period!

The advantages of the far better efficiency of your boiler (as opposed to the ~60% efficient W/H typically sold these days) is the best bang for your buck.

The timer is cheap, would assure minimal summer-time boiler firing and reduce the fuel consumed to the lowest possible quantity, short of changing everything.

When the W/M goes south, consider fuel costs and go with the same indirect, with either gas or oil-fired boiler, and enjoy all the hot water imaginable!

Alex Giacomuzzi

Thanks

Ken & Scott:

Thanks for the good advice on the Indirect opportunity.
Our present (not the one I am asking about above) home has an indirect and you are correct, you can not run it out of hot water.. Truly a joy. It presently does not have a timer on it for summer usage, but that might be a good option. Thanks for the thought.

Part of my reason for asking about gas, is with the service coming into the oil heated house, there will be a nominal fee whether it is used or not. Therefore the thought of a gas hot water heater which is much more economical compared to an electric which presently occupys the space.

Again --- thanks much for the information.. Regards Alex

Reed

You can't go wrong

with installing an indirect. As said above even if you decide to go with nat gas in the future the indirect can be used and also no venting issue.

Mark Hunt

Ken is right


you can vent gas and oil into the same chimney but I am not so sure that you will be able to make a connection to the liner inside the chimney. Even if you could get a hole in it, I doubt you would be able to seal it properly.

I think that the indirect is the best option for you here.

Mark H

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