Wanting some method of dehumidifying our GMC living area when it is cooler than what would require the aircon compressor to stay running I came up with this mod. The heat strip installed is not listed for our aircon but it can be made to fit. The plan was to use the original thermostat to control the heat element with an inverting relay. A side benefit would be the option to use it for dehumidifying by alternating the compressor and heat.
Not listed to fit our aircon but it will by drilling a couple holes. All of this can be done from the bottom no need to go on the roof.
Duotherm circa 1975
Element installed, two holes need drilled and some trimming on the screen
Grainger 5Z484 relay with pigtails soldered on 120vac coil 15 amp SPDT. Any like rated relay would work. This was Ebay 10$ and will fit in the electrical box.
Relay out of focus and in the box
Paper pattern of the proposed switch box
Aluminum cut and ready to fold up for the real box
Folded up ready to install
Installed switch box.
Operation is cool on heat off - just cools, heat on cool off -just heats, Cool and heat both on - compressor and heat alternate on the thermostat thus dehumidifying. We like it.