Yes, more details are always helpful....
I will be using a 2 stage heat pump connected to a RCS ZCV4. The ZCV4 will be controlling 4 zones. My concern is that when only 1 zone is calling for heating/cooling, the air handler will be trying to push too much air into only one zone. The back pressure in ducting will be harmful to the air handler and possibly ducting. This is a common scenario and one common solution is to install a barometric bypass damper that will automatically open up when the pressure becomes too high and shunt air from the supply plenum back into the return plenum. Unfortunately when the bypass damper is open, the air handler coils can become over heated/cooled and the air handler can either ice-up or overheat. To prevent the ice-up/overheating conditions, many zone controllers (e.g. Honeywell TotalZone and Robert Shaw SlimZOne Deluxe) use a "discharge air temperature" sensor to measure the temperature of the air in the supply plenum. If the air gets too hot or too cold, the heat pump compressor(s) will be turned off until the temperature returns to a safe value again.
Looking at the RCS ZCV4 "INSTALLATION AND OPERATION MANUAL", I see a nice wiring diagram (on the last page of the manual) that shows a "leaving air temperature" sensor connected to the ZCV4. I'm guessing that this sensor is the same as what the other manufacturers are calling a "discharge air temperature" sensor. The manual even gives a part number for the sensor - "LAT6". The problem is that I can't find the LAT6 sensor for sale on-line nor is it mentioned in the text of the manual.
The RCS ZCV4 is attractive because it and the RCS TS40/TS16 tstats appear to be the least expensive zone controller and tstat solution that interfaces to the Elk M1. If I use one of the other zone controllers I mentioned above, I would have to use more expensive tstats (e.g RCS TR40/TR16).
I'm hoping that someone has been down this path before, found a source for the LAT6, and verified that the ZCV4 actually uses the data from the sensor to prevent icing and overheating.
Thanks.