Water to refrigerant HX cleaning?

[refmet]

I went to a service call in a DQ last night on a walk in freezer that was not cold enough. Room was at about 20f and compressor was running and constantly tripping on HPS; hooked my gages and read a high side of 260psi and a suction of 20 Psi; the dual pressure control was a ranco with adjustsble low pressure cut out but there seems to be a fixed high pressure cut out factory setted at 300psi. I replaced the dual control and restarted the compressor to read RLA which was over by 10%; checked the run and start capacitor and relay; replaced an open run capacitor and restarted the compressor which was now 15 % under RLA. I tried to adjust the penn valve(water regulating) to obtain a lower liquid line pressure(about 225) and I cranked it open and nothing happened; the water comes out cold but the liquid line is still at about 95f with a screwdriver holding the stem fully open in the valve. I am thinking that the HX might be dirty on the water side; the flow is good but the exchange is slow. Right now system runs at about 270psi head pressure and does not trip on HPS anymore as I have setted it to 340psi; of course liquid line is still hot (100f) and I would like input on how to clean that HX and could it need cleaning on both sides. Is it bad to run the compressor with such a high head pressure. I am running the unit with city water and from my experience the flow of water I have is plenty enough to cool such a small unit(about 3gpm at 48f). Anyways as I said the water that comes out of the condenser with a full flow is at about 55f and the liquid line will still be hot to the touch(about 100f). Can I flush the water side of the condenser using descaler and small circulation pump? Any help would be appreciated! Compressor model is Copelametic EWA2-150-CAB. Also the exchanger is mounted underneath the compressor and seems to be a tubular heat exchanger; it seems to be manufactured with the unit by Copeland.

[Six]

its scale that your trying to remove so you need to use a scale remover and monitor ph.

Its pretty common.

[refmet]

The water running through the condenser is city water and has constant PH of 7.0. I know that heating water will precipitate the minerals; so I was thinking that the lower I set the water regulating valve; the less scale I am going to have in the condenser. System has R408A and I was wondering what would be the lowest correct head pressure to set the water regulating valve knowing that I have a balanced port TXV. Is it really an advantage to run the system at a lower head pressure and will it prevent or reduce scaling effect? Is it common to have scale on equipment using city water?