Make-Up Air required for Direct Vent Fireplaces?

[sirrox]

I have installed two direct vent propane fireplaces. Both Regency models P40 and P36. I have a boiler going in the garage to avoid that combustion appliance in the house. However my HVAC technical advisor says I will need a make up air system to keep the house less than -5 Pa when exhaust fans are used as the fireplaces have no 'rating' or tests done to prove they can withstand any negative pressure so they are assumed to be the same as a classic wood burning open fireplace with a chimney (the ones you stoke and poke....).

I have searched high and low for something in the ANSI or CSA regarding tests but he claims they only test for internal pressures caused by the gases themselves not external pressures caused by negative pressure in the building envelope.

Can anyone shed any light on this or put a nail in the coffin which will force me to install a make up air system?

 

[chilled]

Put the question to the local building and gas inspectors.

 

[willard3]

Consider the house a control volume: if you remove air with combustion, you're going to have to put it back in somewhere.

Because you can't see air doesn't mean it doesn't have mass and follow physical laws. Put in a make-up air system or remove the fireplaces.

 

[walkes]

Let me know if you find anything, in the past I have put direct-vent appliances in to ensure that there is no issue with downdrafting when an exhaust fan is turned on.

Direct-vent appliances keep the combustion process out of the environment and should not be affected by any exhaust fans. Combustion air is drawn directly to the burner by a separate duct,to the sealed combustion process and out the chimney, no interaction with room air.

 

[4everlearning]

Sirrox:
I also installed a direct vented propane fired fireplace in my own house a few years back. The combustion air is supplied via the termination fitting which is connected to the double wall flue (aka "B-vent" I believe). The annulus is the path of the combustion air.
I've built several homes with direct vented natural gas fireplaces. One code official made us connect the optional air inlet ducted (4") directly to the outside air, another code official in a different jurisdiction did not require a separate connection.
Check with your fireplace manufacturer as well. Since it typically is a very minor cost to install and in the case your code official sys he wants it, consider just doing it to maintain good rapport.