What are the specs for this Transformer?

The correct replacement for Tempstar model T8MPN125J20B1 — 115V to 24V 40VA | Ships Today is this exact part. It is the factory-specified replacement with exact OEM specifications. Using a part with different specifications can cause equipment damage or void your warranty. You can verify this by checking the data plate on your Tempstar equipment which lists the model number T8MPN125J20B1 — 115V to 24V 40VA | Ships Today.

Is this transformer compatible with Bryant or Payne systems too?

Many Tempstar parts are cross-compatible with Bryant and Payne systems since all three brands are manufactured by Carrier Global Corporation. The same physical part is often used across multiple brand labels with different model numbers. To verify cross-compatibility, check your Bryant or Payne equipment service manual for cross-compatible part numbers, or contact info@nationalhvacparts.com with your model number for confirmation.

Tempstar

Tempstar Transformer for T8MPN125J20B1 — 115V to 24V 40VA | Ships Today

Name: Tempstar Transformer for T8MPN125J20B1 — 115V to 24V 40VA | Ships Today
Brand: Tempstar
SKU: 1172810-GEN
Price: 32.00 USD
Availability: InStock

SKU: 1172810-GEN Brand: Tempstar

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Overview

This OEM control transformer (part number 1172810) steps line voltage down from 115V to 24V to power the low-voltage control circuit in your Tempstar T8MPN125J20B1 gas furnace. Rated at 40VA, it supplies the thermostat, gas valve, igniter control, and relays. A failed transformer is one of the most common causes of a furnace that will not respond to the thermostat. Symptoms of failure include a completely dead control board, no 24V at the thermostat terminals, a tripped low-voltage circuit, or a transformer that hums, buzzes, or smells burnt. Because it carries the entire 24V load of the furnace, a short anywhere downstream can take it out, so always check for shorted wiring before installing a replacement.

Specifications

Spec	Value
Part Number	1172810
Type	Step-Down Control Transformer
Brand	Tempstar
Primary Voltage	115V
Secondary Voltage	24V
Rating	40VA

Compatibility

Direct OEM fit for the Tempstar T8MPN125J20B1 gas furnace and other ICP/Heil/Tempstar/Comfortmaker N9/T8 series furnaces using the same 115V-to-24V 40VA control transformer. Always confirm the part number on your existing transformer before ordering.

Installation Guide

Safety First — Disconnect power at the furnace switch and breaker, and verify zero voltage with a multimeter.
Access — Remove the furnace blower/control compartment service panel.
Document — Photograph all primary and secondary wire connections before disconnecting.
Remove — Disconnect the 115V primary leads and the 24V secondary leads, then unbolt the transformer from its mounting bracket.
Install — Mount the new transformer, reconnect the primary and secondary wiring exactly per your photo.
Test — Restore power and verify 24V across the secondary terminals and proper furnace response to the thermostat.

Signs You Need a Replacement

No 24V at the thermostat or control board
Furnace completely unresponsive to thermostat calls
Buzzing, humming, or burnt smell from the transformer
Repeatedly blown low-voltage fuse after wiring is verified good

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

Tempstar Transformer for T8MPN12...

$32.00

Frequently Asked Questions

Does this Transformer fit my Tempstar T8MPN125J20B1 — 115V to 24V 40VA | Ships Today?

Yes. This is the factory-specified OEM transformer for the Tempstar T8MPN125J20B1 — 115V to 24V 40VA | Ships Today. It is a direct drop-in replacement that fits without modification. Always verify the model number on your equipment nameplate before ordering.

How do I replace the transformer on my Tempstar T8MPN125J20B1 — 115V to 24V 40VA | Ships Today?

Difficulty: Medium (30–45 min)
Step 1: Turn off breaker. Step 2: Photo wiring connections. Step 3: Disconnect wires from old transformer. Step 4: Remove mounting hardware. Step 5: Install new transformer, reconnect wires matching voltage ratings. Step 6: Verify 24V output with multimeter.

My thermostat has no power. What failed?

Thermostat with no display = failed 24V transformer (or blown control board fuse). Check the 3A/5A fuse on the control board first ($1–$5 fix). If fuse is good but no 24V output from transformer, replace transformer.

Is this transformer compatible with Bryant or Payne too?

Many Tempstar parts are cross-compatible with Bryant and Payne since all three brands are manufactured by Carrier Global Corporation. The same physical part is often used across brand labels with different model numbers. To verify: check your Bryant or Payne equipment service manual for cross-compatible part numbers, or email info@nationalhvacparts.com with your model number.

Should I use OEM or aftermarket for my Tempstar transformer?

OEM recommended for reliability and warranty compatibility. OEM parts match exact factory specifications for proper fit, performance, and safety. While aftermarket alternatives cost less upfront, the risk of improper fit and reduced lifespan usually makes OEM the better value long-term.

How fast does National HVAC Parts ship?

Orders placed before 3:00 PM CST ship the same business day. Standard delivery is 2–5 business days anywhere in the continental United States. Express shipping available at checkout. We ship from Houston, TX to all 50 states. 30-day return policy on all parts.

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