Overview of Primary Product
Page 7
MULTIPLE APPLIANCE SYSTEMS 
When using one PVO power venter to common vent more than one 
appliance, a Control Kit is required for each additional appliance. 
1.  Connect the negative pressure port of each air pressure fan proving 
switch on all Control Kits being used to the provided tee mounted on 
the PVO. (See Figure 4) 
2.  Remove the cap from the branch of the tee and use the ferrule and 
compression nut provided in the small envelope with the PVO to attach 
the connecting tube. 
3.  Refer to the instruction sheet included with each Control Kit for specific 
instructions for that kit, including wiring diagrams. 
ADJUSTMENTS
A
IR FLOW ADJUSTMENT 
NOTE: Before installing, refer to the General Installation Inspection to 
check for negative pressure problems in the building. 
1.  To adjust the power venter air flow, open the choke plate ½ to ¾ of the 
way open. (See Figure 5) Follow the appliance manufacturer’s 
procedures for starting the heating appliance. 
2.  Adjust the thermostat to call for “Heat”. After the system has operated 
for several minutes to stabilize flue gas temperatures, use a draft 
gauge, velocity meter, or match test procedure to check for negative 
draft or up-draft at the heating appliance outlet or air flow into the draft 
hood. 
3.  Adjust the inlet choke damper on the power venter in or out to obtain 
the minimum air flow required to maintain draft. Then increase air flow 
slightly (10% over minimum air flow rate) to ensure proper venting. 
For power burners, adjust draft to proper over-fired draft. 
If using a barometric draft control, use the draft control to fine tune the 
system draft. 
4.  If proper draft has been established, secure the choke plate by 
tightening the screws on the inlet collar. 
5.  Shut off thermostat and check for residual heat spilling from the draft 
hood or draft control. If this occurs, increase the post purge time on 
the timer. 
NOTE: After proper venting has been established, it is recommended 
that a combustion test and a smoke test be performed to ensure 
maximum burner efficiency. Oil burner air adjustments should be set at a 
zero to a trace smoke at the highest or recommended CO
2
% setting set 
by heating equipment manufacturer. 
P
RESSURE SWITCH ADJUSTMENT 
1.  With the venter air flow set and the appliance operating at the best operating 
efficiency, adjust the pressure switch by rotating the adjustment screw 
clockwise until the burner shuts off. 
2.  Rotate the adjustment screw counterclockwise until the burner fires. 
3.  Rotate the adjustment screw an additional ¼ turn counterclockwise to insure 
proper switch setting. (See Figure 6) 
P
OST PURGE TIMER ADJUSTMENT 
To adjust the post purge time, refer to Figures 7 & 8. 
For timer that looks like Figure 7: Rotate the timer adjustment on the 
timer clockwise to increase the operation time. To decrease the 
operation time, rotate the timer adjustment counterclockwise. 
For timer that looks like Figure 8: Rotate the timer adjustment on the 
timer counterclockwise to increase the operation time. To decrease the 
operation time, rotate the timer adjustment clockwise. 
*Typical post purge time should be between 3 to 5 min. 
Figure 6
Figure 5
Figure 4
Figure 8
Figure 7










