I spent another day on ERV controls. It is unbelievable that these controls are taking so much time. I was gratified that I finally got the variable speeds to work with the Lutron Caseta wifi dimmer and the GRX-TVI control box. I decided to hook the Nest back up to the boost control on the ERV circuit board and to hook up the Dehumidistat for the family room bathroom.
Both of these are attached to the boost and to the line input.
ERV Boost Wiring
It is obvious here that the two controls should be wired in parallel, but I tried wiring them to the same input and output. The dehumidistat works great but the Nest has a wiring error. So I will have to separate those wires and follow the instructions.
The next connection I spent time on was the control for the furnace fan. Unfortunately I couldn’t understand the instructions for using the Nest to control a dehumidifier with typical furnace controls. I found instructions last year to use a separate relay. But I didn’t see why the Nest couldn’t just use the furnace blower connections directly.
Furnace Air Handler to ERV Wiring
Since I have radiant heat, I don’t have the furnace control board illustrated in the relay diagram. So it made sense to me that I could hook up the fan wire and a common directly to the furnace air handler connections and skip the relay.
Nest with Relay
But when I removed the jumpers (JP6 and JP7), all the other controls stopped working and the Nest fan setting didn’t run the ERV. Then I noticed in the printed manual, an extra jumper setting for a furnace air handler.
Printed manual jumper setting
Despite the fact that I had removed the furnace air handler wires from the board, I reconnected them to try this extra setting. This was time consuming because the wire screws don’t seem to hold the wires very well, and I had to try several times to get a tight connection. Moving this jumper J6 to position 1 didn’t change the outcome. So I removed the wires, probably for the third time and replaced the JP6 and JP7. I thought I moved J6 back but when the ERV tried to run with the Lutron switch it stopped immediately. I rechecked the jumpers and when I reset J6 the ERV was able to run again. J6 is described in my printed manual as a control to set the furnace tie in to a minimum of 70 cfm in position 1, but in the electronic manual, J6 sets the wheel options for the heat wheel rotation. Two different functions for the same jumper can’t be right. I’ll have to call support to figure this one out.
When I was finished for the day I had accomplished hooking up the dehumidistat and getting it to control the ERV. This was a very simple connection according to the Honeywell 8908D manual. But it took me most of the day to end up with one more working control.
Dehumidistat to ERV Wiring