I just installed a 3 ton packaged and a 2-ton split Carrier GT-PX (Climatemaster Tranquility 27).  It is an open loop standing column well system.  Everything is running well, but my last concern is what protections do the units have if the well pump or breaker fails.   

As I was testing the unit startup and monitoring its performance weeks ago, I noticed a sudden change in the flow meter slowing to a trickle and water temp was very low.  I shut it down immediately and found the sediment filter (a Rusco spin-down) was clogged with fine silt.  Luckily I was standing right there.  I realized my new well return line must have gotten some mud in it during install, which was brought back up by the pump.  Since then its been fine with the normal (barely any) sediment.  I cleaned the filter and tested water flow before starting back up.  The flow through the geo unit was a trickle, and slowly gained volume to normal flow.  Did the significantly reduced flow get so cold it iced inside the pipes?

But, this made me realize that the unit seems to have no protection in the event of insufficient water flow.  I thought the integrated 30 degree low temp sensor setting was for this but I guess not.  Is this correct?  So if the pump or pump breaker fails, it could wreck my units.  If so I plan on putting a low pressure switch on the outflow so if pressure falls under 30 psi it will shut down the system.

Thanks.   

I expect both units have a High Pressure and a Low Pressure Switch in the compressor refrigerant loop. If the water flow becomes too low for any reason the rise in compressor head pressue will open the HPS and lock out the unit before any damage occurs.

You can test the operation of the switch by manually throttling the  water flow  until the lock out occurs. If it works as designed, turn the water back on and cycle the breaker to reset. If you can't get it to work call your installer.  Bet it works.

Dick

"Bet it works." What if it doesn't?

I would have a discussion with your installer before you do anything that might void your warranty.

Low pressure and high pressure switches come with unit to interupt operationin the event of a variety of defficiencies (water flow,air flow etc.) 
Joe

See page 32 of your manual for a description of the HP switch operation.
http://www.climatemaster.com/downloads/97B0045N01.pdf

Have a Happy Turkey Day too!
Dick

There is also a freeze protection sensor that protects the coax from freezing in heating mode.