Lifebreath CAF-02-MB Bedienungsanleitung PDF herunterladen (Seite 25)

It is necessary to have balanced air flows in an

HRV. The volume of air brought in from the outside

must equal the volume of air exhausted by the

unit.

If the air flows are not properly balanced then:

• The HRV may not operate at its

maximum efficiency

• A negative or positive air pressure

may occur in the house

• The unit may not defrost properly

• Failure to balance the HRV may

void warranty

Prior to balancing, ensure that:

1. All sealing of the ductwork system has been

completed.

2. All of the HRV's components are in place

and functioning properly.

3. Balancing dampers are fully open.

4. Unit is on high speed.

5. After taking readings of both the stale air to

the HRV duct and fresh air to the house duct,

the duct with the lower CFM ([L/s] velocity)

reading should be left alone, while the duct

with the higher reading should be dampered

back to match the lower reading.

6. Return unit to appropriate fan speed for

normal operation.

Balancing Procedure

The following is a method of field balancing an

HRV using a Pitot tube, advantageous in

situations when flow stations are not installed in

the ductwork. Procedure should be performed

with the HRV on high speed.

Choose the straightest section of duct between

the HRV and the weatherhoods. This will be used

for both the supply and return ducts.

Drill a small hole in the duct (about 3/16"), three

feet downstream of any elbows or bends, and one

foot upstream of any elbows or bends. These are

recommended distances but the

actual installation may limit the amount

of straight duct.

The Pitot tube should be connected to a

magnehelic gauge or other manometer capable of

reading from 0 to 0.25 in. (0 - 62 Pa) of water,

preferably to 3 digits of resolution. The tube com-

ing out of the top of the Pitot is connected to the

high pressure side of the gauge. The tube coming

out of the side of the Pitot is connected to the low

pressure or reference side of the gauge.

Insert the Pitot tube into the duct, pointing the tip

into the airflow.

For general balancing it is sufficient to move the

Pitot tube around in the duct and take an

average or typical reading. Repeat this

procedure in the other (supply or return) duct.

Determine which duct has the highest airflow

(highest reading on the gauge). Then damper that

airflow back to match the lower reading from the

duct. The flows should now be balanced.

Actual airflow can be determined from the gauge

reading. The value read on the gauge is called

velocity pressure. The Pitot tube comes with a

chart that will give the air flow velocity based on

the velocity pressure indicated by the gauge. This

velocity will be either feet per minute or metres

per second. To determine the actual

airflow, the velocity is multiplied by the cross sec-

tional area of the duct being measured.

Pitot Tube Air Flow Balancing

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