The UL98 test standards for disconnects are stringent with regard to the number of operations under load. In reality, UL98 does not differentiate between GD and HD, the test standards are the same. I believe it is 6000 total operations at rated load, something drastic like that, and then up to 4000 operations unloaded, but being operated once every 20 seconds or so (it's been a long time).
The difference between GD and HD is about two things: maximum withstand capacity and long term reliability. The GD switches are intended for residential / light commercial use so are typically limited to 240VAC, and with the right fuses, can be used in 10kA-100kA AFC applications. HD switches can go up to 600VAC and up to 200kA AFC with the right fuses. Basically, GD switches are made cheaper for those who would hardly ever use them and never abuse them.
Both meet the MINIMUM standards, the HD versions exceed those standards.
You didn't say the voltage, so ASSuming 240VAC single phase (because you said GD switch), a 30A fused switch would be fine for this. I'm not saying it's a good idea to not have more control over it than a simple safety switch, but at a bare minimum, that would be acceptable.