TS-17: Troubleshooting the 24Vac Transformer

The transformer is located near the Sage2 control

Verify the power switch to the boiler is on. Is there a green light illuminated on the Sage2 control?

Yes No

#B9

Unplug the L3 harness (see diagram) from the transformer with the Brown and Pink wires. Meter the brown and Pink wires from the transformer for 24Vac. The reading should be between 21 and 30Vac. Do you have a good reading?

Yes No

Back

#B15

Unplug the line voltage wire L2 (see diagram)harness to the transformer with the black & white wires to the transformer. Check the harness end not going to the transformer but the harness end from the boiler junction box for 120Vac. Do you read 120Vac +/- 10%?

Yes No

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#B23

Check for 120Vac on the line voltage PC board at terminals P3-3 & P3-12 (blue circle). Is there 120Vac present?

Yes No

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#B31

Transformer is good

Done

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#K9

Replace transformer

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#K23

Replace harness between line voltage PCB board and transformer

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#K31

The transformer is good but there should be a green light on the Sage2 control. Check the fuse on the low voltage PC board. To check the fuse, remove fuse from control and check continuity with an electrical meter . Do you have continuity?

Yes No

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#P23

Replace fuse

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#P31

Check for 120Vac on terminals L & N on the line voltage PC board. Is 120V +/- 10% present?

Yes No

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#B39

Check terminals L to G on the line voltage PC board. Is 120Vac present

Yes No