Manifold Gas Pressure Adjustment; Two Stage; Adjustment Of Temperature Rise - York Sun Select YV28 Manual

EXAMPLE
By actual measurement, it takes 19 seconds for the
hand on a 1 cubic foot dial to make a revolution
with a 200,000 Btuh furnace running. To determine
rotations per minute, divide 60 by 19 = 3.16. To
calculate rotations per hour, multiply 3.16 • 60 =
189.6. Multiply 189.6 • 1 (0.5 if using a 1/2 cubic foot
dial) = 189.6. Multiply 189.6 • (the Btu rating of the
gas). For this example, assume the gas has a Btu
rating of 1050 Btu/ft . The result of 199,000 Btuh is
3
within 2% of the 200,000 Btuh rating of the furnace.
Manifold Gas Pressure
Adjustment

Two Stage

About this task:
This gas furnace has two heat stages. Therefore, the
gas valve has two adjustment screws located under
two cover screws. The second stage adjustment
screw is adjacent to the "HI" marking on the valve
and the first stage adjustment screw is located
adjacent to the "LO" marking on the valve.
Manifold pressure adjustment procedure.
Adjust second stage first, then adjust first stage
pressure (refer to Physical data
plate.
1. Turn off all power to the unit.
2. Using the outlet pressure port on the gas
valve, connect a manometer to monitor the
manifold pressure.
3. Remove cover screws covering HI and LO
pressure adjustment screws.
4. Turn on power to the unit.
5. Set thermostat to call for second stage heat
and start furnace.
6. If necessary, using a screwdriver, turn
the second stage adjustment screw
(adjacent to the "HI" marking on the valve)
clockwise to increase manifold pressure
or counterclockwise to decrease manifold
pressure.
7. After the high manifold pressure has been
checked, adjust the thermostat to call for first
stage heat.
or the unit rating
Johnson Controls Ducted Systems
8. If necessary, using a screwdriver, turn the first
stage adjustment screw (adjacent to the "LO"
marking on the valve) clockwise to increase
manifold pressure or counterclockwise to
decrease manifold pressure.
9. Once pressure has been checked, replace the
cover screws covering the HI and LO pressure
adjustment screws.
Figure 70: Two Stage Gas Valve
Item Description
A Outlet pressure tap 1/8 in. - 27 NPT
B Outlet
3/16 in. x .032 in. thk. male spade terminal - 2nd
C
stage coil
D External jumper
1/4 in. x .032 in. thk. male spade terminals (2) -
E
common
F Inlet
G On/Off switch
H Inlet pressure tap 1/8 in. - 27 NPT
Regulator cover screws (reg. adj. beneath these
I
screws)
Adjustment Of Temperature
Rise
The temperature rise (the difference of temperature
between the mixed air entering the furnace and the
heated air leaving the furnace) must lie within the
range shown on the unit rating plate and the data in
when the unit is operating as full input.
Air temperature rise should be determined when
the furnace is firing at full input. Two stage furnaces
require a second stage thermostat call. Modulating
furnaces require a second stage thermostat call
and the Modulating Furnace Control must be in
COMMISSION mode to maintain full input.
After the temperature rise has been determined, the
CFM can be calculated as follows:
Installation Manual: YORK
®
Sun™ Select YV28 to YV50 91