The CU 301 system i have seems to work ok when there is a fast short need for water (like Flushing the toilet) The pump will get to its set pressure 50 psi and shut off.But when the shower is run for a few minutes then shut off the pump will climb to about 52 psi and not shut off .What Should I be looking at.

pump is producing pressure so it is ok
loosing pressure indicate pipes leaking or non return valve leaking

Check to see if you have any leaks in the system, check the Foot valve, or check valve.

Usually toilets do not require hot water.
Is the plumbing divided into hot and cold water pipes?
If toilets are hooked to hot water, how many flushes and how many gallons per flush per day.
What is the expected consumption per each worker?
What is the latitude from equator, and expected solar input. Further north, and hazy atmosphere reduce input. Beijing has smog I believe.
How often is the solar panel going to cleaned of smog and dirt for maximum collection?
If the area has hard water, then the entire system is prone to sediment build-up and failure unless water is artificially softened.
Solar water heater temperatures can exceed 180 degrees at times. This temperature will damage storage tank that is not made for that temperature.
Most solar water heater systems have pressure regulating valve and expansion tank to accommodate occasional high temperature and pressure.

A good fellow to contact might be at following website:
http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm

Solar collectors are usually connected to a circulating pump, and then the heated water is stored in a tank.
The pump circulates water continually from solar collectors through a storage tank.
This type of system would use ordinary tank-type water heater for storage.
Most of these systems also utilize a back-up heating element inside the tank.

More complicated systems circulate special liquid through spiral tubes inside the water heater.
This type of heater would be an indirect water heater.
Indirect heaters are used for solar collectors, and used with boilers, or any outside heat source.
http://www.bockwaterheaters.com/Products/products_coil_tank_water_heaters.html
http://www.hotwater.com/products/residential/cirrex_solar.html
http://waterheatertimer.org/images/solar-water-heaters-on-roof_lbiRv_5784111-500x282.jpg

Vibrations were caused by the worn water pump bearings. They could be reduced by reducing the speed of the pump. Vibrations in the water system that is connected to your neighbor may be caused by a change in pressure in the system, if the water pipes are not isolated, and they touch the wall at some oscillation frequency.

Double check that washers inside fittings attached to back of tank, are not wedged or pinched in there restricting flow. Drain tank, relieve water pressure prior, obviously. The other thing is to check that the by-pass is allowing good flow in to tank when in normal operation mode. Have seen those only go half way inside valve, but lever is at wide open setting. If all that checks out, try removing the check valve on tank, and replace it with a 1/2" galvanized pipe nipple, ( or certified plastic/nylon fitting same size) and reconnect water line direct to that, without a check valve. That should do it if nothing else was wrong. Now you have a choice, either change it or leave it out if everything seems ok, but double check that hot water isn't siphoning back to another utility such as toilet if you leave it out and toilet is close. Feeling that cold line (inlet) when water is hot should tell you. I've seen the check valve in both locations, hot (at top of tank) and cold (at bottom of tank -inlet) Not 100% sure why, right from factory that way, but I say, put it on bottom fitting if required at all. Let me know how you make out.

Grundfos is a p. o. s. I have a new system cu 301 and I have had to get it repaired twice by Fogle Pump and Supply. These guys are real rip of artists in Washington State and should be reported to the BBB. Dont Use Fogle if you need a well

The pressure tank psi may be too high. To set it you get the system to pressure up and stop then check that water pressure. Whatever that is, is what the tank should be set at. Too much air pressure and the water pressure will suddenly drop before the pump kicks in.
To set the tank properly turn off the pump, drain all water pressure, then set the air pressure in the tank to the same as the water pressure was. Turn it back on and check again.

sounds like the bladder tank at the well is ruptured this will cause pressure surge, and pump short cycling, and needs to be replaced asap.

This seems to be a case of blockage within the toilet. Check the
Flushholes under the inside-rim of the toilet. they might be partially blocked by debris or deposits. If so, a Wire-Clotheshanger will help.
If the Blockage is in the drain, a Handauger might be helpful to push
blocking objects through or retrieve.
Waterlevel in the Toilet-tank could be too low. It should be about 1"
below the top of the Drainvalve in the middle of the Tank.

Pressure tank should be charged to 2 pounds less than your lowest pressure (ie28psi). Must be set with system under no (0) pressure.