I ordered a new HERMS coil awhile back and it will not be delivered until next Monday. I was itching to have a brew day so I used my plate chiller to maintain the mash temperature. Working vary well!
This worked great in the pinch I was in to brew at the time. I recirculated until the flow from the mash tun was clear and the connected to the heat exchanger. Before I used it to chill the wort after the boil , I back flushed it first to make sure it was not clogged. I brew with whole hop cones and the false bottom in the boil kettle keeps the heat exchanger clear. Small particles make it the screen but not enough to clog the plate chiller/heat exchanger.
A counter flow coil would work even better because of the larger diameter of the copper coil, to control the mash temp and to chill.