Daikin ARQ Installation Manual

Also see for ARQ: Installation and maintenance manual

Daikin ARQ Installation Manual Manual pdf 23 page image

IM 1083 Self-Contained WSHP Unit Ventilator Models ARQ, ERQ, GRQ Page 23 of 42System BalancingThe recommended method, and the one most commonly used, forbalancing a system is called "proportionate balancing." Figure 41shows a water system consisting of reverse return mains feeding threebranch mains. Branch A and Branch C are designed as reverse returns,while Branch B is designed as a direct return upfeed riser. Each of thebranch circuits has a balancing valve in the line going back to the systemreturn main. In addition, each unit has a balancing valve in its returnline. The prescribed method of proporationate balancing is as follows:1. Open all valves fully.2. Beginning with Branch A, take readings to determine theGPM flowing to each unit in the branch.3. Determine the ratio of the actual/design flow for each ofthe coils in Branch A. This is called the proportionate flowrate. For instance, if Coil A-1 had a design flow rate of 10GPM and the measured flow rate was 15 GPM, then itsproportionate flow rate would be 1.5.Figure 41: Typical System Balancing CircuitFigure 40: Typical Piping Through Grommets in Back ofUnit4. Assume Coil A-1 has the lowest proportionate flow rate, A-2 thenext lowest, and so on. Leaving the balancing valve to Coil A-1wide open, begin to throttle the balancing valve on A-2 until thetwo coils have the same proportionate flow within an allowedtolerance. (This usually is set by the balancing contract at around5 percent.) Proportionate balance now has been achieved betweenthese two coils.5. Proceed to Coil A-3 and establish proportionate balance betweenit and Coil A-2 by the same procedure. Coil A-2 need not be read.It will change in direct proportion to the change in A-2 and willremain in balance with it.6. Adjust the balancing valve in Coil A-4 until it is in proportionatebalance with Coil A-3. Likewise, bring Coil A-5 into proportionatebalance with Coil A-4. This is the end of Branch A. All coils onthis branch will be proportionately balanced and any increase ordecrease in the total system GPM, or the branch, will increase ordecrease the GPM at each coil proportionately. They will remainin balance with one another.7 By the same process, achieve a proportionate balance of all coilson Branches B and C.8. The next step is to balance the branches. To do this, select at randomone coil on each of the three branches. Use the same procedureas for coil balancing and proportionately balance the branchesagainst one another, using the selected coils. Note the balancingvalve on the lowest proportionately flowing branch will be leftwide open.9. The final step in the procedure is to adjust the flow from the pumpto the system to bring all coils to their design flow rate. As waspreviously discussed, this can be done by imposing additionalresistnace at the pump by means of a balancing valve and throttlingthe system back until the flow rates are equal to those called forby the design, or decreasing the output of the pumpTypical water system consistingof reverse return mains feedingbranch circuits