What are the specs for this Transformer?

The correct replacement for Tempstar model T8MPN100J20B2 — 115V to 24V | 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 T8MPN100J20B2 — 115V to 24V | 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 40VA Transformer for T8MPN100J20B2 — 115V to 24V | Ships Today

Name: Tempstar 40VA Transformer for T8MPN100J20B2 — 115V to 24V | Ships Today
Brand: Tempstar
SKU: 1172810-GEN
Price: 28.95 USD
Availability: InStock

SKU: 1172810-GEN Brand: Tempstar

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Overview

This genuine OEM 40VA control transformer (part number 1172810, "TRANS 115>24 40VA") supplies the 24-volt control power for the Tempstar T8MPN100J20B2 gas furnace. It steps the 115-volt line voltage down to 24 volts AC to run the thermostat, gas valve, control board relays, and blower/fan circuits. A failed transformer is one of the most common causes of a completely dead furnace: no display, no thermostat response, and no blower or ignition. Typical failure symptoms include a buzzing or burnt-smelling transformer, repeatedly blown low-voltage fuses, intermittent 24V, or zero output on the secondary even with 115V present on the primary.

Specifications

Spec	Value
Part Number	1172810
Description	Transformer, 115V > 24V, 40VA
Type	Step-down control transformer
Brand	Tempstar (ICP / Heil family)
Primary Voltage	115V AC
Secondary Voltage	24V AC
Rating	40 VA
Fitment	OEM — exact replacement

Compatibility

Built for the Tempstar T8MPN100J20B2 100,000 BTU gas furnace and shared across many ICP / Heil / Comfortmaker furnaces that use a 40VA 115-to-24V control transformer. Confirm your existing transformer is rated 40VA with a 115V primary and 24V secondary before ordering. This is a direct OEM replacement for 1172810.

Installation Guide

Safety First — Disconnect power at the furnace switch and breaker, then verify zero voltage at the transformer leads with a multimeter.
Access — Remove the furnace control-compartment service panel.
Document — Photograph all primary (line) and secondary (24V) wire connections before disconnecting.
Remove — Disconnect the primary and secondary leads, remove the transformer mounting screws, and lift out the old transformer.
Install — Mount the new transformer, reconnect the 115V primary and 24V secondary leads exactly per your photo, and secure all connections.
Test — Restore power and verify 24V AC across the secondary and normal thermostat, ignition, and blower operation.

Signs You Need a Replacement

Furnace completely dead — no thermostat response or blower
Repeatedly blown 3A or 5A low-voltage control fuse
Transformer buzzing, overheating, or smelling burnt
115V present on the primary but no 24V on the secondary

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 40VA Transformer for T8...

$28.95

Frequently Asked Questions

Does this Transformer fit my Tempstar T8MPN100J20B2 — 115V to 24V | Ships Today?

Yes. This is the factory-specified OEM transformer for the Tempstar T8MPN100J20B2 — 115V to 24V | 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 T8MPN100J20B2 — 115V to 24V | 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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