June 2015
TIMMIE'S TIPS
TIMMIE'S TIPS
by Timmie McElwain
Replacement Controls Part 15
Universal Part 15
Since back in the 1990’s Universal Controls have been available for various mod- ule systems, gas valves and recently Electronic Fan Tim- ers and Integrated Furnace Controls.
They offer to the techni- cian a single control that can be stocked on their service vehicle and used to replace a diverse number of controls.
In this Part Fifteen we will continue to look at Universal Replacement Controls but will shift over to Universal Re- placement Gas Valves.
The valve we will address is the Robertshaw720-079 Universal Electronic Ignition Gas Valve Uni-Kit .
It is important to know that all redundant (dual seated) gas valves from Robertshaw are identifi ed by the RED HANDLE controlling the on-off-pilot on the gas valve.
These valves are a great truck stock item as they cover so many different applications of gas valves on the new elec- tric ignition systems.
We will also cover some of the characteristics of gas valves that are very important when making sure the defec- tive valve you are removing is being replaced with one hav- ing the same characteristics. Robertshaw 720-079
Universal Electronic Ignition Gas Valve Uni-Kit
The 720-079 is designed to work equally well on Intermit- tent Pilot, Direct Spark and Hot Surface Ignition.
FEATURES
• Dual automatic valves (redundant)
• Wiring connections, manual selector and adjustments on top of the valve
• Meets all codes requiring dual valve safety shutoff
• Reduces service truck stock-freeing up valuable space and saving money.
The 720-079 shown in Fig- ure 15 features; manual se- lector, wiring connections and adjustments that are all easily accessible on the top of the
valve. The 720-079 Uni-Kit has 1/2" side outlets and a pres- sure regulator that is preset at 3.5" W.C. for natural gas. For L.P. gas applications the valve can be converted by using a pressure regulator conversion kit that is included.
The 720-079 incorporates a manual valve, pilot valve (dual automatic valves) and a main gas pressure regulator all in a small compact valve with a swing radius of 3-9/16". The small size of the 720-079 lends itself to replacing many O.E.M. and competitive valves. The 720-079 is multi-position and can be mounted in any posi- tion, except upside down.
The red manual selector arm easily identifi es the 720-079 shown in Figure 16; in fact all Robertshaw 7200 series valves with this arm are dual seated valves. The valve also features side outlets, which can be plugged if not used. Also illustrated are the inlet and outlet pressure taps and the regulator adjustment cap.
Figure 17 illustrates the capacities for different inlet and outlet sizes for the 7200 series. The 720-079 as shown in the ordering data is ½” x ¾” valve with a capacity of 150,000 BTU’s.
The cross-reference above covers White-Rodgers and Honeywell Valves.
Figure 18 illustrates the installation instructions and wiring for intermittent pilot ap- plications.
Figure 19 is the wiring and instructions for hot surface ignition applications. The pilot plug must be in place as there is no need for a pilot. It can be either local sense using the igniter as a sensor or remote sense with a separate fl ame sensor.
New England HVAC Insider
Figure 20 illustrates the wir- ing and instructions for direct spark ignition either remote or direct sense.
OPERATING INSTRUCTIONS
1. Turn the wall thermostat to its lowest setting. Remove burner access panel(s). Selector arm must only be op- erated by hand see illustration Figure 21. Do not use pliers, wrenches or other tools to operate the arm. The selector arm cannot be moved into the “off” position without fi rst de- pressing the lever in the “on” position. 2. Move selector arm to the ·off position. 3. WARNING: Wait at least 5 minutes to allow any gas in the combustion chamber to vent if you then smell gas in the appliance area or near the floor, STOP and follow warning instructions. Failure to do so may result in fi re or explosion. 4. Move selector arm to the “on” position, and set room thermostat to desired tempera- ture. Allow burner to cycle on and off. 5. Leak test with a soap solu- tion after installing with main burner on. Coat pipe and tubing joints, gasket, etc. with soap solution. Bubbles indi- cate leaks. 6. Replace burner access panel.
PRESSURE REGULATOR ADJUSTMENTS
An adjustment of the pres- sure regulator is not normally necessary since it is preset at the factory. It may need to be adjusted however for maximiz- ing combustion effi ciency of the equipment. Field adjust- ment may be accomplished as follows.
NOTE: Manometer attach- ment may be accomplished at pressure tap plug, above control outlet, as shown in Figure 21. It is also a good idea to measure inlet pressure at the tap on the other side of the valve.
1. Manometer or gauge attach- ments may be accomplished at pressure tap plug (D). 2. Remove regulator adjust- ment screw cap (top of con- trol- A). 3. With small screwdriver, rotate adjustment screw (B) ·clockwise· to increase, or ·counterclockwise· to decrease pressure to comply with manu- facturer’s specifi cations.
Page 9D
continued on page 12D
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