Retrotec Residential Pressure & Air Leakage - Manual (Page 18)

Page 18 of 75
©Retrotec Inc. 2014
Flame rollout can occur if a vented combustion appliance fires during a depressurization test. This is a very
definite fire and safety hazard. Under no circumstances should a test be conducted if measures haven't been
taken to prevent appliances from firing!
All vented combustion appliances must be disabled prior to the test, including those outside the thermal
envelope being tested (e.g. furnaces and water heaters in buffer zones such as combustion closets, garages,
attics and crawl spaces). Buffer zones are often influenced by pressure changes in the conditioned space and
may also be depressurized during the test.
To shut down fuel fired appliances:
For gas systems, turn the appliance's gas valve control from "On" to "Pilot" and leave the pilot light operating
while the test is being conducted.
For fuel oil systems (with no gas valve), the main power switch can be thrown, or the fuse can be removed or
switched off at the electrical panel.
Although it is best to go to the gas valve or main power switch, furnaces can also be turned off at the thermostat
(if it has a Heat - Off - Cool switch). However, be aware that the homeowner may easily turn the furnace back
on in the middle of the test if only the switch has been changed. Do not rely on turning the thermostat way
down or way up. During a long test, the furnace may still turn on.
In cold weather, it is generally best to turn the thermostat down when first arriving in the home to allow the
chimney to flush itself of smoke and for the flue pipe to cool down, as it may need to be temporarily sealed for a
new home test per R-2000.
Although rare, sometimes a pilot light will go out during the test and must
be re-lit. The furnace pilot is usually easily seen but water heater pilot
lights are not. The water heater should fire right up when it is turned back
on. If it does not, check that the pilot light is still lit by making a pencil
mark on the temperature dial and turning the knob to “HOT”, it should fire
immediately. Return the knob to its original setting, and re-light the pilot if
necessary.
Never leave a home without ensuring that the systems turned off are
reactivated. A simple precaution is to leave car keys or other valuables on
top of the unit, which are only reclaimed once the system is back to
normal.
2.3.3.10. Airtight Wood Stoves and Wood Furnaces
Airtight wood stoves and wood furnaces must not be operating when conducting a depressurization test, as they
can leak smoke into the home. Notify homeowners ahead of time, so that they can ensure that the stove or
furnace is not in use.
If the stove is airtight and is still smouldering, but has no fuel in it, close down the combustion air inlets and
conduct a pressurization measurement. The potential for accelerating the fire in the stove must be minimized
before attempting to depressurize. Disperse any coals in the stove and remove unburned material. When
conducting the test, periodically shut off the Blower Door and monitor the firebox. Do not continue if there is
any risk of over-firing the stove or starting a chimney fire.
2.4 Other Precautions
2.4.1. Suspended Ceilings & Fluorescent Light Diffusers
Figure 8. Leave your car keys on top of the
furnace so you don't forget to reactivate
the system.