An interesting debate today about what the definition of "vertical" and "horizontal" is. Is it as clear as it should be in the standard? The question asked was, if the unit is clearly below the window but not "directly" below does the 1500 rule still apply from the corner of the flue to the opening of the window? Or because the unit is not directly below the window the 1500 rule wont apply? For example the range of clearance for LPG bottles is clearly defined by the "cone", (In the image bottles are to close to an opening and dont comply) whereas this is not 100% clear with the window opening. So whats your definition of J and N, especially around the corner??

Logic would suggest that the 1500 rule would apply "above" the flue in all directions making the following installation non-compliant. Whats your thoughts?   

Linkback: https://www.plumbers.nz/instantaneous-water-heaters/67/flue-clearance-on-instant-water-heaters/1936/

I think the note at the bottom of the diagram that says "Shading indicates prohibited area" answers the question. 

Sure, but the question still remains, if I put the unit directly below the window and as per the "definition" of j (or the shading) only 300 mm horizontally (fan assisted over 150 MJ/h = 1500 mm value n) to the side putting the flue diagonally just over 300 mm away from the opening window that flue gasses wont enter the room while someone is in the bath? I honestly don't think so. I think "below" needs to be better defined as the whole point of having these prescriptions is to prevent harm.

Im aware the drawing is from the old standard but because the clearances are the same I didn't see an issue. 

I have attached an example drawing with reference to the heater (not window) of how this could look like. This is certainly a grey area.

Hi Guys

Just a question on vapour barriers around LPG bottles. If you look at the pic above doesn't the basement door for a entry or egress into sub floor area for any LPG leakage that may occur? and is defiantly inside the cone referred to above?

As for the vertical and horizontal distances I have always worked on the measurement to the side ie 300mm and draw a line straight up from there 1500mm and if there is a window or vent in that area its a no go.