Tempstar 40VA Transformer for T8MPT100F14B1 — 115V to 24V Control Power | Ships Today
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Overview
This OEM control transformer (Part #1172810) provides the 24-volt power that operates the entire control circuit of your Tempstar T8MPT100F14B1 furnace. It converts 115V line voltage down to 24V at 40VA, feeding the control board, thermostat, two-stage gas valve, and blower relays. When the transformer fails, the low-voltage side of the furnace goes completely dead: the thermostat stops responding, the board loses power, and no heat call can be initiated. Transformers fail from a shorted winding, an overloaded 24V circuit, a power surge, or insulation breakdown over time. Watch for a blank thermostat, a dead control board, a low-voltage fuse that blows on power-up, or a faint electrical-burn odor at the furnace. This is the exact 40VA OEM replacement for the F14B1.
Specifications
| Spec | Value |
|---|---|
| Part Number | 1172810 |
| Type | Step-Down Control Transformer |
| Brand | Tempstar (ICP / Heil) |
| Primary Voltage | 115V |
| Secondary Voltage | 24V |
| Rating | 40 VA |
| Fit | OEM Replacement |
Compatibility
Designed for the Tempstar T8MPT100F14B1 gas furnace. The same 115V-to-24V 40VA transformer is used across many ICP-family furnaces (Tempstar, Heil, Comfortmaker, Arcoaire) of this generation. Confirm the original part number and the primary/secondary voltage printed on your existing transformer before installing.
Installation Guide
- Safety First — Disconnect power at the switch and breaker, then verify zero voltage with a multimeter at the transformer terminals.
- Access — Remove the furnace control/blower compartment service panel.
- Document — Photograph all primary (line) and secondary (24V) wiring before disconnecting.
- Remove — Disconnect the leads and unbolt the transformer from its mounting bracket.
- Install — Mount the new transformer and reconnect the primary to line voltage and secondary to the 24V circuit exactly per your photo.
- Test — Restore power, confirm 24V across the secondary, and verify the board powers up and the thermostat calls for heat.
Signs You Need a Replacement
- Thermostat and control board are completely unpowered.
- Furnace will not begin a heat cycle.
- Low-voltage fuse blows immediately on power-up.
- Burning smell or visible discoloration on the transformer.
Shipping & Returns
Ships same day before 3 PM CST. 30-day returns. Backed by the National HVAC Parts fitment guarantee.
Shipping Information
- Orders placed before 3PM CST ship same business day
- Standard delivery: 2-5 business days
- Express shipping available at checkout
- Free shipping on orders over $75
- Tracking number emailed upon shipment
Return Policy
- 30-day returns on unused parts in original packaging
- Electrical parts (capacitors, contactors, control boards) are final sale once installed
- Email info@nationalhvacparts.com to initiate a return
- Refunds processed within 5-7 business days