Proper Venting

Unknown

The picture looks like it is okay. The single wall pipe going through the wall is using a thimble which allows for proper clearance.

Some older water heaters did not require a spill switch (blocked vent switch) it depends on your local code. If they add one they will have to change the thermocouple to one with a junction block. This will allow the spill switch to be inter connected with the millivolt circuit. This can present other problems sometimes which is that the switch actually robs millivolts from the water heater control pilot safety system causing nuisance pilot outage.

With two natural gas systems you can use a TEE to connect the two appliances together as long as they are sized correctly. They did increase the size on the water heater which is a good idea they should have used an increaser at the draft hood connection on the water heater 3" to 4". We would like to see a "Y" connection but the TEE is okay. With oil we want the smaller appliance (Water Heater gas) above the oil or use a "Y" connection. You should not get into sizing unless you have had training on how to size venting. If you do a pressurization test on the house and the boiler and water heater still maintain a draft it should be okay. Shut all windows and doors and bring on every fan in the house, close fireplace damper, make sure the dryer is also running. Then bring on all the equipment, after about ten minutes running time check the draft at each draft hood with a match it should be pulling the match flame up into the draft hood. If it is blowing back you have a negative pressure condition in the house. At that point they would need to hire someone to do a blower door pressurization test to determine actual pascals and size make up air or whatever to oversome the problem. Mark Hunt can enlighten you on that.

There is a "Rule of Thumb" for sizing vents, not that it is the most accurate method but for your use it will suffice it is:

The venting system should be sized to the area of the largest vent connector plus 50% of the area of the additional connectors (area in square inches) Formula is

A = 3.1416 x radius squared

Beyond that you need training on venting. I have a maunual on venting and also for the next several months will be running a series on venting in HVAC Insider paper.

Always here to help Arlene call anytime.

October Home

Is this OK?

Natural Gas New Yorker Boiler, Rheem Nat Gas Hot water heater. The chimney is metal.

I sited the hot water heater draft hood because its loose and there's no spill switch and the flue pipe going through the wall is single walled. But, am I right when I think that the hot water heater flue shouldn't connect to the boiler's flue pipe instead of to the chimney? I've got the National Fuel Gas Code (1999) but can't find a reference.

Timmie?

Yours in learning, Arlene

Jack Smith

Common venting

of natural draft appliances is perfectly acceptable, if, like anything else it is done properly. For example, is the diameter of the pipe of sufficient size to handle the connected load. Also, that single wall pipe going thru the wall, is it really going thru the wall or is going into a masonry chimney built into the wall and cover with a plaster material, which would make it pefectly legal?

October Home

No Masonry Chimney

Its metal.

Thanks for your quick response. Don't Wetheads ever sleep?

Best wishes, Arlene

Unknown

Common venting

I think the sizing tables are in chapter 10, and the common venting rules are in 7, in that year's codebook.

Noel

Boilerpro_3

One common prooblem with water heater venting...

Is the vent pipe diameter is too small. When taking a look at those sizing tables alomost every time a water heater is vented into the same chimney or breeching as another appliance, the vent pipe needs to be 4 inch. Almost all water heaters are equipped with 3 inch draft hoods and installed with 3 inch vent in homes. FYI

Boilerpro

Alan R. Mercurio

According to NFPA 211-2000 Table 6-8 Interconnections (Chimney Connector and Vent Connector)

6-8.1 Connectors serving appliances operating under natural draft shall not be connected into any portion of a mechanical draft system operating under a positive pressure.

6-8.2 Unless listed for such connection, solid fuel-burning appliances shall not be connected to a chimney flue serving another appliance.

6-8.3 Gas utilization appliances and appliances burning liquid fuel shall be permitted to be connected to one chimney flue through separate openings or shall be permitted to be connected through a single opening, provided they are joined by a suitable fitting located as close as practicable to the chimney and provided both of the following apply:

(1) Sufficient draft is available for the safe combustion of each appliance and for the removal of all products of combustion.


(2) The appliances so connected are equipped with primary safety controls and all appliances are located in the same room.

6-8.4 If two or more openings are provided into one chimney flue, They shall be at different levels, and the smaller connection shall enter at the highest level consistent with available head room or clearances to combustible material.

Arlene, I may stand corrected but I think the flue pipe from the water heater shold be connected VIA "Y" not a "Tee"


Your friend in the industry,

Alan R. Mercurio

Oil Tech Talk

[Deleted User]

does your area of jurisdiction

accept all that different materials making up the water heater relief valve drain?

Glenn Harrison

I was thinking that too.

In my area it's supposed to be against code to have ANY plastic pipe on a relief valve.

October Home

Hoo Boy

More to think about. Strickly speaking though, I don't site code. If I do, then I've become a code inspector and have to site code for my entire report. I can say "not in compliance with generally accepted practices."

I'm interested in the safety of my client's health and their pocket books. So if the relief valve tube is PVC and it will still do what its suppose to do, then that's OK. I don't site code.

Thank you, wetheads.

Arlene

Glenn Harrison

O.K. so you just write

that it is not a general or safe pratice to use plastic pipe on a relief valve based on the probability that the pipe could deform or melt in the event of 210º water coming out of it. That should cover you and keep you from being a "code enforcer", and keep your customers safe. There is a saftey reason why this is code, as I just listed above.

Hope this helps you out, Arlene

Glenn