That diagnostic is usually caused by no flow through the barrel. Throttle the leaving water butterfly valve, if so equiped to see if you hear water flow. If it doesn't get really turbulant sounding, you don't have flow. Put gauges on to check for pressure drop to see if you have flow.
A lot of Trane screw machines have a built in freeze protection where if the entering water temperature of the evaporator is cooler than the leaving and the chiller is enabled it will fail.
In my country, if this occurs it is because the chiller, controls the pumps and the enable signal is given to the chiller. When the pumps are started the protection is enabled and if there is a cool pocket of evaporator water in the circuit and the reversed temperatures occur the unit faults. To prevent this from occurring, start the chilled water pump at least 5 minutes before the chiller is enabled. Circulating the water evens out the temperatures in the circuit and since the chiller is not enabled, the protection is not active and the fault will not occur.
Take time to think through the problem at hand, don't rush.
Similar issue just the other day. Except w/a hi ent water temp
Fault. Techn. Is new to chiller work, chiller started w/a hot loop.
Piping not well insul. Sun baked, water at 88.7' intake, so it shut
Off. So I told him call BAS to open valve and try in 20m.
Stable at 64',go ahead &start chiller & log readings. This was
After him starting & resetting sev. Times. Explained to him what
Occurred and advised for him to repeat where necessary.
This might seem like a crazy question are you sure those sensors are not reversed?
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ent and leave water sensors reversed?
they are the same sensors, dont think this would be a problem
Originally Posted by zw17
I just was thinking about it and if you switched around the EEWT and ELWT sensors in the right way and under the right conditions (which I believe you are) you run a very real risk of freezing the barrel.
Stop what you are doing, put things back the way they were, and call for some help.
i was taught if someone ever replaces a sensor that it is best to run the wire all the way back to the board,
i am under the understanding if one cuts a sensor that it changes the resistance,
now, i ran across something the other day.,.,
was working on a RTAA1404 , going off on water temp, i changed the temp sensors in the ent and leave wells in the water lines at the machine., theses sensors tied in to the 695, come to find out i replaced the wrong one., i was supposed to change the water temp sensors on the barrol,.
question, why sensors on the cooler barrol,.(because factory mount safetys i would think) and external water temp sensors, in the water lines, more safetys?
Last edited by milkyway; 04-19-2012 at 07:04 AM.
no signature blast'em man blast'em
!!!KILL THE TERRORIST!!!
If it's an RTAC, the entering water temp sensor can be bound as the leaving water temp sensor and vice versa. If it's an RTAA, it's easy to switch them up at the plug on the chiller module.
I had an after hours call recently where the customer had pulled all of the wires out of the MTA plugs to clean the connections. When he put them all back, he got the saturated evap temp. sensor and suction temp. sensor for one of the circuits mixed up. The circuit would pump itself down into a vacuum. Being an RTAA170, it did not have a low pressure switch. I think it would eventually fail on high pressure or low superheat, can't remember which... Probably lucky the compressor didn't lock up.