Raypak 266 btu ng. Understanding this chart for venting

[uxbridgechris]

If I install this in a shed, I understand the flue had to be vented and the shed needs to have vents for combustion air. Not really understanding this chart.

If all air is from outside of building vent size =
if all air is from inside of building vent size =

The air is clearly coming for the inside of the building via a vent to the outside of the building is it not? Lol.

page 17 here I’d you can’t read the chart. Thanks

https://www.heritageparts.com/media...jkzOTY4MDkzOTVlYTc3MTYyODE4NjBlODhjM2RjNWU3NQ

 

[Bama Rambler]

All Air From Inside The Building:
Each opening shall have a minimum net free area as noted:

This statement assumes that there is no direct ducting between the unit and the outside. It assumes that the unit gets it's combustion air through indirect air sources already present for the room. And if that's the case the net (total) area of all the air inlets has to be the sizes listed in the smaller chart. It assumes that some of the ventilation through those openings will also be used for air exchange in the room.

All Air From Outdoors:
When air is supplied directly from outside the building, each opening shall have a minimum net free area as noted:

What this note is saying is that if there's a through wall duct between the combustion air intake and the outside it has to be the sizes listed in the lower chart. It assumes that there will be a single source of combustion air.

 

[uxbridgechris]

So I need a total of 67 sq" hole in the building?

 

[Bama Rambler]

If it's a screened or screened and louvered opening then you need 101in² or 134in². That's due to the restriction that screens and louvers impose on the opening.

I assume you're running a dedicated exhaust vent stack out of the building.

 

[uxbridgechris]

If it's a screened or screened and louvered opening then you need 101in² or 134in². That's due to the restriction that screens and louvers impose on the opening.

I assume you're running a dedicated exhaust vent stack out of the building.

Yes, raypak exhaust vent with b vent thru roof.

 

[Teald024]

From the first para on that page, a hole near the ceiling for vent air and a second hole near the floor for combustion air. Each sized per the appropriate chart.

 

[uxbridgechris]

From the first para on that page, a hole near the ceiling for vent air and a second hole near the floor for combustion air. Each sized per the appropriate chart.

Each size to the sum of the chart I assume? so if I need 100sq"

I need one by the floor @ 50sq" and one at the ceiling @ 50sq".

I want to have enough but not too much because in the late fall, I may want to heat the shed.

 

[Teald024]

Vent at ceiling can be one or multiple holes (round, square, oval, tropical tree shaped) but needs to be sized so sum matches chart.
Combustion at floor can be one or multiple holes (round, square, oval, tropical tree shaped) but needs to be sized so sum matches chart.
These are totally separate and serve different purposes so you cannot combine areas for them.
My interpretation is that you use the top chart if you just have holes in the wall. I believe this is the scenario if you have a heater in a room inside of a larger building.
If there is a specific duct that brings air from outside the building to the heater (room) area then you can use the bottom chart.
In your case I think it is a moot point since the building has only one room with no additional partitions in it. Therefore you can use the bottom.
FWIW, I am not an expert, Just my interpretation of what you posted and trying to understand it’s purpose.

 

[Bama Rambler]

Since you're venting it through ducting through the roof, you just need the one opening near the floor. I'd go a little bigger than needed because the draft hood will draw a little fresh air into it as it exhausts out of the building.

 

[Teald024]

Since you're venting it through ducting through the roof, you just need the one opening near the floor. I'd go a little bigger than needed because the draft hood will draw a little fresh air into it as it exhausts out of the building.

The wording from the manual says:
"The heater must have both combustion and ventilation air. Minimum requirements for net free air supply openings are one opening that is 12 inches from the ceiling for ventilation, and one opening that is 12 inches from the floor for combustion air as outlined in the latest edition of the National Fuel Gas Code, ANSI Z223.1(Canada-CAN/CSA-B149) and any local codes that may have jurisdiction."

In this case, I believe the vent isn't the flue exhaust gas vent, but instead ventilation air to keep the room air from overheating. This assumes that you will also have a ducted flue gas exhaust to atmosphere.

 

[uxbridgechris]

The more you guys help me, the more I get confused. hahahaha
But i do appreciate it.