I'm thinking I need one UPB phase coupler, on one of the panels downstream of the generator transfer switch. But I'm open to a second opinion 
We have a 400A service into the house (geothermal HVAC requires standby electric heat!). This is split into two 200A main panels, one directly connected to utility power and the other behind the automatic transfer switch for a generator. Each of these two main panels has sub-panels beyond it.
Am I right that I need just the one phase coupler on any one of the panels fed by the transfer switch? It will always couple the two phases provided by the transfer switch, regardless of whether the power is coming from the utility or the generator. And, when the transfer switch is connected to the utility, it will also couple to the utility-fed panel since the wires meet at the meter.
There is no need for a second phase coupler on the utility-fed panel, and we definitely don't want the phase coupler connecting the utility-fed and generator-fed panels together -- that could lead to accidentally energizing the grid from the generator and killing some poor linesman. Right?
We have a 400A service into the house (geothermal HVAC requires standby electric heat!). This is split into two 200A main panels, one directly connected to utility power and the other behind the automatic transfer switch for a generator. Each of these two main panels has sub-panels beyond it.
Am I right that I need just the one phase coupler on any one of the panels fed by the transfer switch? It will always couple the two phases provided by the transfer switch, regardless of whether the power is coming from the utility or the generator. And, when the transfer switch is connected to the utility, it will also couple to the utility-fed panel since the wires meet at the meter.
There is no need for a second phase coupler on the utility-fed panel, and we definitely don't want the phase coupler connecting the utility-fed and generator-fed panels together -- that could lead to accidentally energizing the grid from the generator and killing some poor linesman. Right?
