When it comes to buying appliances with the GPC; the primary concern is the purchase of kitchen related appliances, the Comptroller General and DoD Regulations place limitations on purchases of that kind.  However, we don't consider a vacuum to be a kitchen appliance.

Therefore, we can only assume this is a local/organizational/installation policy as we could find no regulation at the Department of Defense level that prohibits the procurement based on your scenario.  We also assumed your GPC is being funded with an O&M appropriation.  Sources reviewed:

1) The Department of Defense Government Charge Card Guidebook for Establishing and Managing Purchase, Travel, and Fuel Card Programs (special emphasis on A.1.2.4. Prohibited Purchases).

2) DoD Financial Management Regulation.

3 The FAR and DFARS

While we did not research agency level regulations (e.g. AFI 64-117), we're quite positive these would not prohibit your purcahse either.