12
7.2.1.3
Then set the controller at this resultant temperature; the step controller should maintain nominally half
of the steps on. Setting the OUTDOOR RESET CONTROLLERS basic information is shown in
Table 1
below
.
Table 1
SETTING THE TEMPERATURE CONTROLLER
Reset Ratio: 1:1-1/2 (IE: 2/3:1)
Outdoor Temperature: 40°F
Boiler Water Temperature: 130°F
Step ‘A’
Difference between outdoor temp and 70°F
70 – 40 = 30°
Step ‘B’
Multiply 30°F times the Reset Ratio 2/3 (and then)
30 x 2/3 = 20°F
Subtract 20°F from the Boiler Water Temp 130°F
130 – 20 = 110°F
Step ‘C’
Set the Controller at 110°F
Note: If the Outdoor Temperature is above 70°F, add the difference in Step ‘A’, multiplied by the
Reset Ratio, to the Boiler Water Temperature.
See Honeywell manual for specific details.
7.2.2 Solid State Dual Input Reset Controls
(Honeywell T775J controls)
These are dual sensor reset controllers with adjustable reset ration and outdoor reference temperature. The
‘reset ratio’ is the ratio of the change in the temperature at the secondary sensor to the opposing change in the
control point. If the reset ratio is 2:1, every 2°F change at the outdoor sensor will cause an
automatic inverse
change of 1°F at the control point.
NOTE: Refer to the applicable vendor literature provided on both the setpoint
controls and
step controls
installed in your boiler.
8.0 PREVENTIVE MAINTENANCE
8.1 General
Electrical immersion heating element boilers and water heaters are automatic, quiet and safe. Consequently,
they are all too often neglected. Like any piece of electrical / mechanical equipment, they require care and
maintenance to keep them in top working condition.
If electrical connections are allowed to become loose or dirty, there is danger of an electrical fault. If the
elements are not inspected periodically for leaks, the water from leaking elements can leak onto adjacent
elements, causing external element damage and resulting in blowing of load fuses in the boiler electrical panels.
If the boiler water is not properly treated, element failure could occur due to the formation of scale.
Treat the boiler with respect.
CAUTION:
Always work on the boiler with all electrical power sources disconnected
.
8.2 Water Treatment (Boilers Only)
Boiler water should be periodically checked through a sampling procedure. Properties should be maintained in
accordance with
Table 2
at the end of this section. For consultation relative to water treatment, please contact
a reputable water treatment firm.
