Insteon Thermostat into a 6 wire system?

[koalamotorsport]

I have central air and hot water heat. 2 completely separate systems running separate 24V A/C controls. The Insteon thermostat only has Common and RH connections. Is there a way to make it work with 6 wires? I need Common, RH, RC, W, Y and G. With no RC marked on the Insteon thermostat, I don't think it's viable for my situation. Thoughts? Thanks! Brett

[stusviews]

That's not an unusual situation. The only solution is to use on power supply. Describe the wiring at the current thermostat and at each other end of the thermostat cables. Include the color and what terminal each is connected to (e.g., yellow wire connected to Y at the thermostat). Colors are not always standard, yours may be different. That's OK.

[koalamotorsport]

Thanks Stu. Using a common power supply will be a pain. My house actually has 3 central A/C systems (and therefore 3 zones), a propane boiler, an electric boiler, 8 active heat zones (plus 2 future zones) and, currently, 9 thermostats. Only 2 of the thermostats require 6 wire because they are dual function heat and cool. The other 7 thermostats are either heat or cool, so the Insteon units would work fine in those locations.

[stusviews]

Insteon thermostats can handle both heating and cooling (5 wires). A 6 wire cable is used if you have 2 stages of either heating or cooling and if you have 2 stages of both heating and cooling, then 7 wires are required.

In the case of heating only or cooling only, 3 wires are needed, 4 if you have separate fan control.

Virtually any HVAC system that has different power supplies for each of heating and cooling can be wired to use a single power source without running any additional wires by just changing some connections. If the existing thermostat has a different wire connected to each of Rc and Rh, then you have separate power supplies for that thermostat. A single power supply has one wire and a jumper between Rc and Rh.

[koalamotorsport]

Yes, thank you. I understand that completely. However, when the A/C unit is 80ft from the boiler, it is impractical to try to run fresh wires through a finished structure to switch to a single power supply. Putting RC and RH terminals on the thermostat would have been smarter and far more practical, but the more Insteon products I purchase, the more I realize that most of them are not thought through very well. Huge improvement over X10, but still not where they should be for the price. Tonight, I wired the Insteon thermostat into a cooling only circuit. There was no common connection, the blue wire was being used for cool signal, white wire was unused at both ends. I moved the blue to common at the air handler to get it that much closer to the established standard and used the white wire for cool signal as it was only a 5 wire cable. The thermostat is up and running on that circuit now. I'm glad I didn't buy 9 of these things because it's a major downgrade from my TS9000 units.

[stusviews]

I fully agree. Separate heating an cooling power supplies should be accommodated. OTOH, there is rarely a need to run new wires if the HVAC has separate power supplies for each of heating and cooling. The only need is to determine which wire serves each purpose and re-purpose some wires. The existing wires are almost always adequate. There will be two cables at the thermostat.

[koalamotorsport]

Unfortunately, I'm not that lucky. There are no spare wires at the Tstat in the two locations where I need to control two systems. Somewhere inside the walls, or finished basement ceiling, the single cable to the thermostat splits to two cables, running in different directions, to the equipment. One of the many hack jobs in the wiring and plumbing in this house. Nothing like saving $5 in cable when doing the original install.....