Quick answer: A heat kit is electric backup or supplemental heat that installs in the air handler. It does not replace the heat pump. It adds heat on very cold days and for emergency heat. Choose a kit your system allows, then match it to your climate. Confirm the size with a Manual J load calculation.
This guide covers the MRCOOL VersaPro 2nd Gen, Hyper Heat 2nd Gen, Universal, and TruInverter central systems. The kit sizes each air handler allows come from MRCOOL's install manuals. The climate picks below are Chill's general guideline, not a MRCOOL chart. Your installer should confirm the size with a Manual J calculator.
What is a heat kit, and what does it do?
A heat kit is a set of electric heat strips that go inside the air handler. The heat pump still does the main heating. The kit adds extra heat when the outdoor air is very cold, or when the system is set to emergency heat.
MRCOOL's VersaPro and Hyper Heat heat kit manual and Universal heat kit manual say to size the optional module for the heat load and electrical needs of the installation. The TruInverter (Signature) heat kit manual says to confirm the size based on the room load at the lowest outdoor temperature.
New to these product lines? Start with our comparison of Universal, Hyper Heat, and VersaPro central systems.
Which heat kits fit VersaPro, Hyper Heat, and Universal systems?
These three lines share the same allowed kit sizes by tonnage. The VersaPro and Hyper Heat central install manual lists them by system size. The Universal heat kit manual lists the same matches for its air handlers.
The 1.5 ton (18K) row applies to VersaPro in the current lineup. Chill does not currently list an 18K Hyper Heat or Universal system.
| System size | Compatible kits |
|---|---|
| 1.5 Ton (18K), VersaPro | 5, 8, 10 kW |
| 2 Ton (24K) | 5, 8, 10, 15 kW |
| 2.5 Ton (30K) | 5, 8, 10, 15 kW |
| 3 Ton (36K) | 5, 8, 10, 15, 20 kW |
| 4 Ton (48K) | 8, 10, 15, 20 kW (no 5 kW) |
| 5 Ton (60K) | 10, 15, 20 kW (no 5 or 8 kW) |
A 2 ton VersaPro system can take 5, 8, 10, or 15 kW. A 4 ton VersaPro system starts at 8 kW, because a 5 kW kit is not approved for that air handler.
Which heat kits fit a TruInverter system?
TruInverter (Signature Series) uses a different set of kits. There is no 8 kW kit. A 5 kW kit is allowed on the 4 ton and 5 ton air handlers. These sizes come from the Signature heat kit manual and match the Heat Kit options on Chill's TruInverter product pages.
| System size | Compatible kits |
|---|---|
| 2 Ton (24K) | 5, 10 kW |
| 3 Ton (36K) | 5, 10, 15 kW |
| 4 Ton (48K) | 5, 10, 15, 20 kW |
| 5 Ton (60K) | 5, 10, 15, 20 kW |
How much heat does each kit produce, and what breaker does it need?
The U.S. Energy Information Administration lists 1 kilowatthour as 3,412 Btu. So 1 kW of electric heat produces about 3,412 BTU/h. Output is lower when the supply voltage is 208V rather than 230V or 240V.
The breaker sizes below are the 230V maximum overcurrent values from the VersaPro, Hyper Heat, and Universal heat kit manuals. The TruInverter manual lists the same 230V maximum fuse or breaker sizes. MRCOOL says the specification can differ by model, and to use the indoor unit nameplate and local code.
| Kit | Approx. heat output | Electrical at 230V |
|---|---|---|
| 5 kW | About 17,060 BTU/h | 1 circuit, 30A max breaker |
| 8 kW | About 27,296 BTU/h | 1 circuit, 45A max breaker |
| 10 kW | About 34,120 BTU/h | 1 circuit, 60A max breaker |
| 15 kW | About 51,180 BTU/h | 2 circuits, 30A + 60A max breakers |
| 20 kW | About 68,240 BTU/h | 2 circuits, 60A + 60A max breakers |
A licensed electrician should confirm breaker and wire sizing from the air handler nameplate and local electrical code.
What size heat kit should I pick for my climate?
MRCOOL does not publish a kit size chart by climate. The table below is Chill's general guideline. It uses about 3 kW per ton for moderate climates and about 5 kW per ton for extreme climates, then rounds to the nearest kit that air handler allows. Ties were rounded up. For mild climates, the guideline is no kit, or the smallest approved kit for emergency heat.
VersaPro, Hyper Heat 2nd Gen, and Universal
| System | Mild | Moderate | Extreme |
|---|---|---|---|
| 1.5 Ton (18K) | No Heat Kit, or 5 kW | 5 kW | 8 kW |
| 2 Ton (24K) | No Heat Kit, or 5 kW | 5 kW | 10 kW |
| 2.5 Ton (30K) | No Heat Kit, or 5 kW | 8 kW | 15 kW |
| 3 Ton (36K) | No Heat Kit, or 5 kW | 10 kW | 15 kW |
| 4 Ton (48K) | No Heat Kit, or 8 kW | 10 kW | 20 kW |
| 5 Ton (60K) | No Heat Kit, or 10 kW | 15 kW | 20 kW |
Rounding notes: a 1.5 ton system at 5 kW per ton is 7.5 kW, and 8 kW is the nearest kit. A 2 ton system at 3 kW per ton is 6 kW, and 5 kW is nearer than 8 kW. A 2.5 ton system at 5 kW per ton is 12.5 kW, which is halfway between 10 and 15, so this table uses 15 kW. A 3 ton system at 3 kW per ton is 9 kW, halfway between 8 and 10, so this table uses 10 kW. A 4 ton system at 3 kW per ton is 12 kW, and 10 kW is nearer than 15 kW. A 5 ton system at 5 kW per ton is 25 kW, which is larger than the 20 kW max kit, so the table caps at 20 kW.
TruInverter
The same kW per ton math applies. The compatible set is different, so two mild climate picks change.
| System | Mild | Moderate | Extreme |
|---|---|---|---|
| 2 Ton (24K) | No Heat Kit, or 5 kW | 5 kW | 10 kW |
| 3 Ton (36K) | No Heat Kit, or 5 kW | 10 kW | 15 kW |
| 4 Ton (48K) | No Heat Kit, or 5 kW | 10 kW | 20 kW |
| 5 Ton (60K) | No Heat Kit, or 5 kW | 15 kW | 20 kW |
On TruInverter, a 4 ton or 5 ton system may use a 5 kW kit for emergency heat in a mild climate. On VersaPro, Hyper Heat, and Universal, those sizes cannot take 5 kW, so the smallest approved kit is 8 kW on 4 ton and 10 kW on 5 ton. A 5 ton system in an extreme climate is still capped at 20 kW.
Not sure which fits you? As a rough guide, Mild is IECC zones 1 to 3, Moderate is zones 4 to 5, and Extreme is zones 6 to 7. You can look up your county on the IECC climate zone map.
This is a general guideline. Your installer should confirm the size with a Manual J load calculation.
Still shopping?
Browse VersaPro 2nd Gen, Hyper Heat 2nd Gen, Universal, and TruInverter systems, or shop heat kits in central unit accessories. One example is the heat kit for VersaPro central systems. Size the house first with our free Manual J calculator.
Not sure? Call (888) 231-8920.
FAQ
What is a heat kit on a MRCOOL central heat pump?
It is electric heat that installs in the air handler. It adds backup or supplemental heat on very cold days and for emergency heat. It does not replace the heat pump.
Can I put a 5 kW heat kit on a 4 ton VersaPro?
No. The VersaPro, Hyper Heat, and Universal manuals do not approve a 5 kW kit on a 4 ton (48K) or 5 ton (60K) air handler. The smallest approved kit is 8 kW on 4 ton and 10 kW on 5 ton. A 4 ton or 5 ton TruInverter air handler may use 5 kW.
What size heat kit does a 2 ton system need in an extreme climate?
The Chill guideline for a 2 ton system in an extreme climate is 10 kW. That is 5 kW per ton, and both the VersaPro family and TruInverter allow a 10 kW kit on 2 ton. Confirm with a Manual J calculation.
How many breakers does a 15 kW or 20 kW heat kit need?
Two circuits. At 230V, the manuals list a 15 kW kit as 30A plus 60A, and a 20 kW kit as 60A plus 60A. A licensed electrician should confirm the final breaker and wire size.
Is the climate table from MRCOOL?
No. MRCOOL does not publish a kit size chart by climate. The climate picks in this post are Chill's general guideline. MRCOOL says to size the kit for the heat load and electrical needs of the installation.
Does a heat kit replace the heat pump?
No. The heat pump remains the main source of heat. The kit adds extra electric heat when the outdoor air is very cold, or when you need emergency heat.
Do I still need a Manual J calculation?
Yes. Use our Manual J calculator and have your installer confirm the result. The climate table is a starting point, not a substitute for a load calculation.
