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Perform the following steps and complete the column marked 1st operation in Figure 5.
Step 1. Close valves 1 and 2. Leave valves 3 and 4 open (Figures 2 and 3).
Step 2. Operate the thermal fluid pump.
Step 3. Enter on Line 1 of Figure 5 the value shown on the coil inlet pressure gauge (Figure 4). This is the maximum output pressure of the pump. It should indicate the same psi as the coil outlet pressure gauge.
Step 4. Turn off the thermal fluid pump.
Step 5. Open valves 1 and 2. (Figures 2 and 3.)
Step 6. Operate the thermal fluid pump.
Step 7. Enter on Line 2 of Figure 5 the value shown on the gauge for the coil inlet. (Figure 4.)
Step 8. Enter on Line 3 of Figure 5 the value shown on the gauge for the coil outlet. (Figure 4.)
Step 9. Fill in Lines 4 through 8 of Figure 5 by making the simple calculations indicated.
Step 10. Set the two dials of the Barksdale unit according to the values shown on Lines 7 and 8 of Figure 5.
Note: Figure 5 has extra blank columns marked 2nd operation and 3rd operation for repeating the procedures after you begin to heat the thermal fluid, as previously noted.
After the settings have been made with the thermal fluid at normal operating temperature, allow the heater to operate for several hours under normal operating conditions to make sure the final settings do not cause it to shut down.
Time delay relays may be required
The Barksdale Dialmatic switch can cause an unintended shutdown in certain systems. This can occur in a single line system that has one or more temperature control valves that momentarily shut off flow when opening and closing.
We now use a time-delay relay in the heater controls of HCS (single line) heaters to prevent unintentional shutdown while a temperature control valve opens and closes. We will retrofit a time-delay relay into the controls of any existing HCS heater that experiences this problem.
Do not permanently disable the differential switch to avoid the problem. Disabling the switch will void our warranty on the helical coil.
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Time delay relays not always needed
The shutdown problem does not occur in systems that employ temperature control valves that have proportioning plugs. (These valves are also known as proportional valves.) They do not momentarily shut off flow when opening and closing. All temperature control valves in piping installations now performed by Heatec are proportional valves.
Likewise, the shutdown problem does not usually occur in heaters that have manifolds. Heaters with manifolds always maintain flow through the heater coil.
The shutdown problem does not occur in industrial applications where there are usually other provisions to maintain flow.
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