My condo is equipped with 2 heatpumps climatemaster model # is 81630GNPKSCOK.
One the units compressor lock out and the CXM controller indicates:
HP Fault-Code 2
There are 4 possible causes (According to Functional Troubleshooting Table).
1-Reduced or no water flow (very likely)
2-Water Temperature out of range in cooling (very unlikely)
3-Overcharged with refrigerant (very unlikely since the refrigerant is factory sealed and has not been touched)

I called a qualified tech today here is what happened:
My diagnosis was right and there is water flow problem.
The CXM controller is working properly.
The Temperatures at inflow and outflow are OK.
He vacuumed the inflow and outflow and some rusty water was drawn out of the coil.
The Problem did not fix
He did more vacuuming and more vacumming...
Still the problem did not go away
Here is his recommendation:
He thinks the flow regulator is stuck and not working (my question is is there really a flow regulator, I kind of doubt it. My Google search does not return anything)
He says replacing the flow regulator is a major work. It will take him a couple hours to replace the regulator since it is silver welded. He said he also has to locate a climatemaster regulator which might cost around $300-$400 (parts only). He will also have to run acid through the coil and that will take couple more hours. The total will run around $1100 to $1500.
Does this sound right?
Please advise...
Thanks

That number seems like a serial number, not a model number - can you get us the full model #.

I take it that this is connected to a building boiler/tower loop system, rather than open loop or closed loop geo.

 In that case, there may be a motorized 24v zone valve inside the unit that controls the flow of water through it. If that's the valve needing replacement, it may well be manufactured by a third party supplier like Taco. It may be possible to just twist off the motorized valve actuator from the valve stem and replace only that one component - your local plumbing supply store would be able to provide the part for maybe $100 or so. If the valve is fouled up internally and needs to be unsoldered and replaced, then that's gonna cost more for parts, and take significantly more labour.

Vacuuming sounds like a pretty inefficient way to clean the heat exchanger coil. I've heard a little about acid flushes here, but I'm not sure whether that'd be a DIY option with something mild like vineagr or CLR (lactic acid), or something you'd need a contractor to do with a stronger product like muriatic acid or ice-machine cleaner.

Any one else wanna chime in here?

Hello jml,
Here is some information I found regarding the unit:
816= Model Type Chassis
30=Unit Size
G=Voltage (208-230/60/1)
N=Options
P-Control CXM
K-6GPM Automatic Flow Regulator
S-No Water Valve
C-Copper Coax
O-Standard
K-Revision Level
So according to these numbers there is a 6GPM Automatic Flow Regulator and there is no water valve or secondary pump in this unit.
Now the question is "Is the Automatic Flow Regulator really bad? and Is it really welded?"

I'd want compressor current as additional supporting data. Restricted water flow should drive compressor current to or above rated FLA or RLA

If water flow is severely restricted then I would expect leaving water temp to be NOT ok - should be quite high in cooling mode as the unit attempts to reject heat into a comparatively low flow of water.

I agree with the thought that some sort of heat exchanger flush may be in order

Here is some very interesting progress I made on water flow issue.
I wanted to get a second opinion so that I could be sure before spending the $1500 cleaning and replacing the water flow regulator. Here is what happened. I brought in an electrician to check the controller. The controller checked to work what it is supposed to do. Then we tuned off the inflow and outflow valves and opened the fittings. Then we pulled out the chassis. Then we got a bucket and released the inflow water valve into it. The high pressure water rushed out into the bucket. The only problem was the water is dirty black and full of sediments (sand and tiny metal particles). The water was so much polluted with sediments and metal that we had a hard time closing the valve (basically the sediments were ceasing the valve). The bottom 3rd the bucket is full of sediments. So the problem is the water coming into the system. It probably has already damaged the regulators, valves or what so ever inside.
So the conclusion is:
It is the HVAC water tower for the building that caused my unit to go bad.

C-Copper Coax
This is bad news!  I would have put in a cupro-nickel coil.

There is such a thing as a flow regulation, the individual controls would be- solenoid, flow rater, flow meter. It sounds like you are referring to a solenoid. You would find geo solenoids easier to identify with a search engine. Taco (take-o, not the popular food) is very popular. This is an electric water valve that closes to prevent flow when unit is not in use. A flow rater would determine GPM flow of an open loop system The repair quote sounds somewhat pricey, but I don't know what's left out of the job description (such as a lack of isolation for the solenoid causing contractor to interupt service to all your neighbors while doing the repair) so i'll pass on the price question.

While it certainly matters what is in the water, insulation of the heat exchanger is not caused by every sundry contaminant.
I'm also not a believer in 2 problems occuring at once. That means that one or the other is causing your lock-outs (that doesn't mean that both can't be true, just that both did not occur simultaneously and one isn't shutting the unit off).

If you didn't ask the condo association, they will sometimes be responsible for the water system. They may also have a contractor they recommend who is most familiar with your system.

good Luck,
Joe