DLS and Crossover A2L Safety Fuses

Have you noticed the fuses in the new Carrier Bryant DLS and Crossover equipment?

Historically, in single zone heat pumps there were jumper wires from L1 and L2 on the main terminal block to 1 and 2 on the 1-2-3 terminal block feeding power to the indoor unit. In multi-zone heat pumps, L1 and L2 were wired directly to the main board and each indoor power circuit (A, B, C, D, E) had its own terminal block fed by dedicated 1-2-3 plug connections from the main board.

Just before the shift to A2L refrigerants, the manufacturer added fuses as a safety. The idea is for a fuse to blow before anything in the indoor power circuit throws a spark in the potential presence of a refrigerant leak. The serial range for when these fuses were put into production was approximately 1924V~2124V (*410A equipment included).

See below for fuse type, sizes, and where used:

·      T5H250V are 5-amp 250-volt fuses

  ·     T15H250V are 15-amp 250-volt fuses

In single zone systems, the same L1 and L2 jumper wires now have in-line fuses.

In multi-zone systems, the wiring structure has changed to be able to incorporate the fuses as well. On 18-36K, the L1 and L2 jumpers (with fuses) land on the A or B IDU terminal block and daisy chain to the other terminal blocks. On the 48-55K models, L1 and L2 wire direct to the board, and a wire harness (with fuses) comes from the board to the C terminal block and then daisy chains to the other IDU terminal blocks.

Since the Crossover heat pumps do not power the indoor unit, they are not fused this way. However, 45MBA(DLS) and 45MUA(Crossover) 30-60K fan coils do have the same T5250V (5 amp) in-line fuses in the power wires to the blower motor.



See images for examples of single zone, multi-zone, and Crossover fuses:

Where can you get these fuses? GREAT QUESTION!!!

If you want only the fuses, they can be found online. If you would like Mingledorff’s to sell them at our local branches, then please tell *all* of your sales force (TMs, AEs, DCMs, ISPs) how important it is to you and ask them to relay it to our purchasing dept.

Currently, there is no Carrier part number for the fuses. However, they do have part numbers for the wire harness with the fuses. See charts below:

First up…454 equipment: Click the images to see an expanded view.

Next up is 410 equipment (Made after about 1924V~2124V):

The main question I get asked is “Can I bypass it if it fails?” My response is that we never bypass safeties (except momentarily for troubleshooting purposes – sometimes). But it's an A2L safety, so I do not care if it is bypassed on a 410 unit. However, on a 454 unit, it is a life safety and should never be left bypassed. Then the next question is, “Can I use a blade type fuse?” Yes, you can for temporary purposes, but blade type fuses are not rated for high voltage, so I do not recommend leaving it that way as permanent fix.

Disclaimer: The technical statements, information and recommendations contained herein are believed to be accurate as of the date hereof, but Mingledorff’s does not make representations or warranties, express or implied, as to its accuracy, its completeness, or the results to be obtained. The information is being provided for informational purposes only and is intended for use by persons having adequate skill and expertise regarding the proper selection, use and application of the products and recommendations and at their own risk and discretion.