York Predator MagnaDRY DR090 Series Installation Manual

Also see for PREDATOR MagnaDRY DR090: Technical guide Installation manual

264276-XIM-B-120846 Johnson Controls Unitary Products1. Turn off all power to the unit.2. Using the outlet pressure port on the gas valve, connecta manometer to monitor the manifold pressure.3. Remove plastic cap covering HI and LO pressure adjust-ment screws.4. Turn on power to the unit.5. Set thermostat to call for second stage heat and start fur-nace.6. If necessary, using a screwdriver, turn the second stageadjustment screw (adjacent to the “HI” marking on thevalve) clockwise to increase manifold pressure or coun-terclockwise to decrease manifold pressure. Be surenot to over-fire the unit on second stage.7. After the high manifold pressure has been checked,adjust the thermostat to call for first stage heat.8. If necessary, using a screwdriver, turn the first stageadjustment screw (adjacent to the “LO” marking on thevalve) clockwise to increase manifold pressure orcounterclockwise to decrease manifold pressure. Besure not to under-fire the unit on first stage.9. Once pressure has been checked, replace the plasticcap covering the HI and LO pressure adjustment screws.NOTE: When using natural gas, the manifold pressure forsecond stage (100% input) should be 3.5 IWG ±0.3. The manifold pressure for first stage (60%input) when using natural gas should be 1.5 IWG ±0.3.CHECKING GAS INPUTNATURAL GASThis unit has two stages of gas heat. The first stage is 60% ofthe full fire input and is considered the minimum input for thefurnace. The intended input for each furnace is shown in thetable below. The following Table applies to units operating on60 Hz power only.To determine the rate of gas flow (Second Stage).1. Turn off all other gas appliances connected to the gasmeter.2. Turn on the furnace and make sure the thermostat iscalling for Second stage (100% input) heat.3. Measure the time needed for one revolution of the handon the smallest dial on the meter. A typical gas meterhas a 1/2 or a 1 cubic foot test dial.4. Using the number of seconds it takes for one revolutionof the dial, calculate the cubic feet of gas consumed perhour. (See example below).5. If necessary, adjust the high pressure regulator asdiscussed in the section “Manifold Gas PressureAdjustment”. Be sure not to over-fire the furnace onSecond stage. If in doubt, it is better to leave the Secondstage of the furnace slightly under-fired. Repeat Steps 1-5.To determine the rate of gas flow (First Stage)1. Turn off all other gas appliances connected to the gasmeter.2. Turn on the furnace and make sure the thermostat iscalling for first stage (60% input) heat.3. Even when the thermostat is calling for first stage heat,the unit will light on second stage and will run on Secondstage for 1 minute. Allow this one-minute time period toexpire and be certain the unit is running on first stage.4. Measure the time needed for one revolution of the handon the smallest dial on the meter. A typical gas meterhas a 1/2 or a 1 cubic foot test dial.5. Using the number of seconds it takes for one revolutionof the dial, calculate the cubic feet of gas consumed perhour (See example below).6. If necessary, adjust the low pressure regulator as dis-cussed in the section “Manifold Gas Pressure Adjust-ment”. Be sure not to under-fire the furnace on firststage. If in doubt, it is better to leave the first stage of thefurnace slightly over-fired (greater than 60% input).Repeat Steps 1-6.TABLE 32: GAS HEAT STAGES# of Burner Tubes2nd StageInput (100%Btuh)1st StageInput (60%)Btuh4 120,000 72,0006 175,000 105,000