How to protect HUM and EAC circuit?

[windeye]

It's likely a stupid question, but please bear with me.

My Trane XV95 furnace control board has a HUM terminal and an EAC terminal. I use the HUM terminal (per manual it's 120VAC at 1A max) to power the humidifier via a 24VAC transformer. The HUM terminals feed the 120VAC to primary side of the transformer, and the 24VAC goes to humidistat (Honeywell) and then to water valve. I also use the EAC terminal (also 120VAC at 1A max) to power two inline booster fans in the ductwork via a relay-in-a-box (RIB1C).

It's been a few years, and it works well. One thing on my mind is to protect both HUM and EAC circuits from overcurrent (coil shorting in relay or transformer). Am I over thinking? I can't seem to be able to find 1A, 125VAC fuses that can be used for this even if I wanted to. There are some surface-mount fuses on digikey.com, but they can't be easily mounted. I know I can't use DC fuses.

Does the control board (CNT05160) have fuse protection for these two circuits? please let me know what you think. Thanks.

[VTP99]

The relays low voltage side will be protected by the fuse on the board.
As for those contacts no.

[windeye]

just wanted put a closure on this topic. I read quite a bit on fuses since I posted this thread, actually found properly rated 1A fuses at just one homedepot store, 1A, 250VAC fact acting fuses. EAC is powering my inline booster fans thru a RIBU1C (relay in a box), and HUM is powering a 10VA step-down transformer which goes to humidistat and then to humidifier solenoid, so had to worry about in-rush current. Main purpose of fuse is to protect against shorts. I also found properly rated inline fuse holders, 250VAC, 10A rated holders made by Littel Fuses (mouser.com). So one fuse on each circuit, and I also added a 5A automotive style fuse on the secondary side of the transformer to protect against shorts on the solenoid. The control board uses the same fuse. all done.

Note: Trane's EAC and HUM are 120VAC, not tied to fuse (5A) on board. The 5A fuse is on the 24VAC side.

[beenthere]

1 amp at 120 volts=120 VA.
5 amp at 24 volts=120 VA.

Low voltage fuse is too large.

[windeye]

1 amp at 120 volts=120 VA.
5 amp at 24 volts=120 VA.

Low voltage fuse is too large.

Thanks. What would u recommend for the fuse size on the load side? The solenoid is rated 24vac 0.5 A. What about solenoid inrush current?

[windeye]

OK. found the label on the solenoid itself (was obscured from view), it's rated at 2.3w, so 24VAC, the holding current is 0.1A. The label on the humidifier body says 0.5A (which I mistook as holding current) seems to be more likely to be inrush current rating (5x). so I should replace the 5A fuse with a 1A fuse (ATC style), if I can't find one, I know I can find 2A fuses.

Again, thanks for prompting me to think and do some research.

[windeye]

[windeye]

Click here to see the pictures of the labels. https://drive.google.com/file/d/1n1w...ew?usp=sharing

[mgenius33]

I just read you other post. You’re trying to protect a 10va transformer from shorting with a 5A fuse?

[beenthere]

Any fuse that is at or below the transformers VA rating, will protect the transformer.