1.Complete System Check
With thermostat contacts closed and gas cock dial in the “ON” position, the main burner should ignite. Measure the reading between the 2 & 3 terminals. If the reading is more than 100MV, replace the gas valve.
2.System Resistance Check
With thermostat contacts closed and main burner “ON”, measure the millivolt reading between the 1 and 3 terminals. The reading should be less than 80MV. If not, recheck the thermostat leads and connections. Replace with new or heavier gauge wires if necessary. If the reading is still greater than 80MV, replace the thermostat.
3.Automatic Pilot Dropout Check
With the thermostat contacts open, hold the gas cock knob depressed with the pilot lit until the maximum millivolt output is observed between the 1 and 2 terminals. Then extinguish the pilot and observe the meter. The sound of the pilot magnet dropping should be audible. This dropout should occur between 120MV and 30MV. If it occurs outside these limits, change the gas valve.
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| TH |
| TH |
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| TP |
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THTP | 1 |
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| 3 | TH |
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| TP | TP |
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Millivolt Operator
Terminal Panel (Robertshaw)
| Test |
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| Meter |
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| Meter Leads |
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| Acceptable |
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| Setting |
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| On Terminals |
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| Results |
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1 |
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| MV |
| 2 | & | 3 |
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| <100MV | |||
2 |
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| MV | 1 | & | 3 |
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| <80MV | ||||
3 |
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| MV | 1 | & | 2 |
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HONEYWELL SYSTEM CHECK
1.Complete System Check
With thermostat contacts closed and gas cock dial in the “ON” position, main burner should ignite. If not, measure across terminals 2 and 3 as indicated in the diagram. If the reading is more than 180MV, replace the gas valve.
2.System Resistance Check
With thermostat contacts closed and main burner “ON”, measure the millivolt reading between terminals 1 and 3 as indicated in the diagram. The reading should be 220MV or less. If not, recheck thermostat leads and connections. Replace with new or heavier gauge wires if necessary. If the reading is still greater than 220MV, replace the thermostat.
3.Automatic Pilot Dropout Check
With the thermostat contacts open, hold the gas cock knob depressed with the pilot lit until the maximum millivolt output is observed between terminals 1 and 2. Then extinguish the pilot and observe the meter. The sound of the pilot magnet dropping should be audible. This dropout should occur between 110MV and 36MV. If it occurs outside these limits, change the gas valve.
4 |
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| 1 |
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| PP |
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3 | TH |
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| PP | 2 |
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| Millivolt Operator |
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| Terminal Panel |
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Test | Meter | Meter Leads On | Acceptable | ||
Setting |
| Terminals |
| Results | |
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1 | MV | 2 | & | 3 | <180MV |
2 | MV | 1 | & | 3 | <220MV |
3 | MV | 1 | & | 2 | |
