Honeywell Vr8205S Gas Valve; High Altitude Operation; Checking Temperature Rise - International comfort products N9MP1 Service Manual

Single Stage Multi Position Furnace
The VR8205S Gas Valve is a REDUNDANT type valve.
This means that it consists of two (2) valves (internally) with
independent operators (solenoids) that both must be ener-
gized before gas can flow through the valve. This redundan-
cy provides an added safety measure. In case one of the
valves sticks open (Mechanically), the second operator will
close preventing the flow of gas.
If the valve does not open, check for 24 Volts across the two
These furnaces are designed to operate in the majority of
the country without modifications. At altitudes over 2,000'
above sea level, however, certain measures need to be tak-
en to insure continued, safe reliable operation. For exam-
ple, units must be de−rated for altitude (by adjusting man-
ifold pressure and/or changing orifice size) based upon the
type of fuel (I.E. Natural Gas or L.P. gas), Btu content of the
gas, and installed altitude.
Altitudes over 4,000' may require a different air proving
pressure switch than the one installed at the factory. Check

Checking Temperature Rise

Figure 9
Thermometer:
Return Air Temp.
Air Flow
Return
Air Flow
Temperature Rise Check
The blower speed MUST be set to give the correct air tem-
perature rise through the furnace as marked on the rating
plate. Temperature rise is the difference between supply
and return air temperatures.
440 08 2011 00

HONEYWELL VR8205S Gas Valve

HIGH ALTITUDE OPERATION

CHECKING TEMPERATURE RISE
Supply
Thermometer;
Supply Air Temp.
wires to the valve during a call for heat. This check MUST
be made IMMEDIATELY following the igniter warm−up peri-
od (17 seconds). 24 Volts will be present ONLY for a period
of 7 seconds after the igniter warm−up if flame is not proven.
If 24 Volts is present during the above check and the valve
will NOT open, then replace the valve. If 24 Volts IS NOT
present, problems are indicated in the control and/or wiring
to the gas valve.
parts list for pressure switch and consult your distributor for
part number and availability. In Canada, provincial codes
may govern installation or switch. Check with governing au-
thorities.
When servicing a unit installed at altitudes above 2,000' in-
sure that it has been properly modified to operate at that alti-
tude. See the sections on Gas pressure (Page 10), and
pressure switches (Page 15) to obtain specific information
for you particular installation altitude.
To check temperature rise,use the following procedure:
1. Place thermometers in supply and return air registers
as close to furnace as possible, avoiding direct ra-
diant heat from heat exchangers.
2. Operate furnace continuously for 15 minutes with all
registers and duct dampers open.
3. Take reading and compare with range specified on
rating plate.
4. If the correct amount of temperature rise is NOT ob-
tained, it may be necessary to change blower speed.
A higher blower speed will lower the temperature rise.
A lower blower speed will increase the temperature
rise.
NOTE: BEFORE CHECKING TEMPERATURE RISE BE
CERTAIN THAT MANIFOLD PRESSURE IS PROPERLY
ADJUSTED.
ALLOWABLE TEMPERATURE RISE ALL MODELS
Model
50, 80 Mbtu
75, 100 & 125 Mbtu
Example:
Supply Temp.
Return Temp.
Temperature Rise 100
Solution: Increase Blower Speed
Service Manual
Range
35°F − 65°F
40°F − 70°F
170
°
70
°
= Too High
°
13