Friedrich VERT-I-PAK VHA18K34RTQ User Manual

28 PB
External Static Pressure can best be described as the pressure difference (drop) between the Positive Pressure (discharge) and the Negative
Pressure (intake) sides of the blower. External Static Pressure is developed by the blower as a result of resistance to airow (Friction) in the
air distribution system EXTERNAL to the VERT-I-PAK cabinet.
Resistance applied externally to the VERT-I-PAK (i.e. duct work, lters, etc.) on either the supply or return side of the system causes an
INCREASE in External Static Pressure accompanied by a REDUCTION in airow.
External Static Pressure is affected by two factors.
1. Resistance
2. Blower Speed (Changing to a higher or lower blower speed will raise or lower the External Static Pressure accordingly).
These affects must be understood and taken into consideration when checking External Static Pressure/Airow to insure that the system is
operating within design conditions.
Operating a system with insufcient or excessive airow can cause a variety of different operating problems. Among these are problems
such as, reduced capacity, freezing evaporator coils, premature compressor’ heating component failures, and/ or other air local distribution
issues..
System airow should always be veried upon completion of a new installation, or before a change-out, compressor replacement, or in the
case of heat strip failure to insure that the failure was not caused by improper airow.
Checking External Static Pressure
The airow through the unit can be determined by measuring the external static pressure of the system, and consulting the blower
performance data for the specic VERT-I-PAK.
1. Set up to measure external static pressure at the supply and return air.
2. Ensure the coil and lter are clean, and that all the registers are open.
3. Determine the external static pressure with the blower operating.
Use a digital manometer to measure. Measurement should be taken roughly 3-6” from the Vert-I-Pak collar and the center of the
indoor coil with the lter installed.
4. Refer to the Air Flow Data for your VERT-I-PAK system to nd the actual airow for factory-selected fan speeds.
5. If the actual airow is either too high or too low, the blower speed will need to be changed to appropriate setting or the ductwork
will need to be reassessed and corrections made as required.
6. Select a speed, which most closely provides the required airow for the system.
7. Recheck the external static pressure with the new speed. External static pressure (and actual airow) will have changed to a
higher or lower value depending upon speed selected. Recheck the actual airow (at this “new” static pressure) to conrm speed
selection.
8. Repeat steps 7 and 8 (if necessary) until proper airow has been obtained.
EXAMPLE: Airow requirements are calculated as follows: (Having a wet coil creates additional resistance to airow. This additional
resistance must be taken into consideration to obtain accurate airow information.
EXTERNAL STATIC PRESSURE
Determining the Indoor CFM
MODEL VHA 09/12 VHA 18 VHA 24
FAN SPEED LOW HIGH LOW HIGH LOW HIGH
ESP (“) CFM
0.0” 470 520 730 800 755 805
0.05” 460 510 670 735 700 750
*0.10” 430 490 630 675 660 700
0.15” 410 470 595 640 615 665
0.20” 360 440 550 600 575 625
0.25” 310 400 505 550 525 580
0.30” 260 350 455 500 485 540
0.35” -- -- 400 445 450 500
0.40” -- -- 345 400 415 465
Table 401 (Determining the Indoor CFM)
* values indicate rated performance point

Friedrich VERT-I-PAK VHA18K34RTQ Specifications

General

Brand	Friedrich
Model	VERT-I-PAK VHA18K34RTQ
Category	Heat Pump
Language	English