Broan HRV90H Service Manual download pdf (Page 24)

9.4 BALANCING PROCEDURE

1. Set the unit to high speed.

Make sure that the furnace blower is ON if the installation is in any way connected to the ductwork of the cold air return. If not,

leave furnace blower OFF. If the outside temperature is below 0°C / 32°F, make sure the unit is not running in defrost while

balancing. (By waiting 10 minutes after plugging the unit in, you are assured that the unit is not in a defrost cycle.)

2. Place the magnehelic gauge on a level surface and adjust it to zero.

3. Connect tubing from gauge to flow collar (or “Flow Measuring Station”) in exhaust air stream at

location A. Be sure to connect the tubes to their appropriate high/low fittings. If the gauge drops

below zero, reverse the tubing connections.

NOTE: It is suggested to start with the exhaust air flow reading because the exhaust has typically

more restriction than the fresh air, especially in cases of fully ducted installations and

exhaust ducted installation.

Place the magnehelic gauge upright and level. Record the readings.

4. Move tubing to FRESH air flow on the other side of the unit (location B) and note readings.

Adjust the fresh air balancing damper F until the reading at B is approximately the same as

the reading at A. If the reading at B is less than the reading at A, then go back and adjust the

exhaust balancing damper G to equal the fresh air flow.

5. Secure both dampers in place with tape or with a

fastening screw.

6. If you are using flow collars, remove them, reconnect the duct and seal with duct tape. If you are using “Flow Measuring Stations”,

remove them and seal the holes with duct tape. Write the required air flow information on a label and stick it near the unit for

future reference (date, maximum speed air flows, your name, phone number and business address).

NOTES: Most flow collar kits provide a conversion chart located on the collar which enables you to convert magnehelic gauge

readings to equivalent cfm values.

The unit is considered balanced even if there is a difference of ±10 cfm (± 0.015 in. w.g.) between both air flow

readings.

If you are only using one flow collar or one “Flow Measuring Station”, then, after completing the first reading, transfer

this measuring device to the other side of the unit and take the second reading.

LOW HIGH

FLOW

VP0004

9. AIR FLOW BALANCING (CONT'D)

LOW

HIGH

FLOW

VP0003

VD0069

VD0052

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Broan HRV90H Service Manual Page 24