Technical question

[SIGNSTU]

On a system with twin recips. flooded chiller (717) pumping glycol where wuold be the best place to measure the subcooling temp. and the superheat temp.

[NH3LVR]

On a system with twin recips. flooded chiller (717) pumping glycol where wuold be the best place to measure the subcooling temp. and the superheat temp.
Hi Sinstu:)

Is this the same system you were having problems with earlier with the uneven discharge temps? Was that issue resolved?

The subcooling is measured at the outlet of the condenser. It can be a bit tricky on some systems without a equalizing line, as the sewer type of flow can cause problems measuring. What is correct can very widely.
I usually take my IR thermometer and take readings from the condenser outlet down into the engine room, at the receiver itself, and at the receiver outlet. It gives me a better picture this way.

The superheat is measured at the suction line leaving the accumulator for the chiller, assuming it is not a pump recirculated system. You can also measure at the compressor suction. It will be a bit higher there, depending on several factors, but will give you a idea. (If you have a long poorly insulated suction line it can be meaningless.)

A little more information about you system would be of help to give you better advice.

Pumped, or flooded by an accumulator?
Evaporative or water cooled condenser?
Receiver installed or just using the condenser of liquid storage.

[SIGNSTU]

Yes it is the same system.The problem is resolved it was a combination of the by pass valve and a bad sensor.It is flooded by use of a henry foat valve on the return line from the evp cond.There is no receiver but a chiller barrel 1/2 full of liquid ammonia. THANKS NH

[NH3LVR]

This makes it simple.:)
Just measure the Temp of the Liquid upstream of the float valve for the subcooling. Unless the area is extremely warm it should be fairly accurate. Make sure the float is feeding while doing this.
Convert the head pressure to temperature using your temp-pressure chart. Subtract the temperature you measured from this and you have your superheat.:)

IR is the easiest way. If you use a conventional thermometer fasten it to the pipe with some insulation over it. IR is not always as accurate.

Is this an evaporative condenser?

As for the superheat, just measure the temp of the suction line leaving the barrel as I mentioned.

Simple;)
Let us know what you find.

[SIGNSTU]

Thanks, the numbers just dont seem right. The temp in front of the valve is 68 deg. f The head presure is 125 that is 68 deg f which gives me a superheat of 7 deg ? and yes it is an evap condencer. Somthing is not obsorbing it must be my head !

[NH3LVR]

If your head pressure is 125lbs (8.6BAR), the condensing temperature is 75F (24C).
If the liquid leaving the condenser is 68F (20C), you have 7F subCOOLING, not superHEAT. The superheat is measured at the evaporator suction outlet.
It can be a difficult concept to understand initially.
It just take a little time. Once you have it it becomes second nature.
Are you having a system problem? If so describe it for us.

[SIGNSTU]

Iam just trying to understand a problem i had last season. The glycol in the tube nest was turning into slush and i lost suction presure. the glycol was good to -10 (f). The temp at the suction valve was 6 deg f (5 feet from the exit of the flooded chiller, insolated line) what would the temp be in the chiller.I understand 3/4 of the tube nest is in liquid 717 & 1/4 above in vapor

[Andy]

Iam just trying to understand a problem i had last season. The glycol in the tube nest was turning into slush and i lost suction presure. the glycol was good to -10 (f). The temp at the suction valve was 6 deg f (5 feet from the exit of the flooded chiller, insolated line) what would the temp be in the chiller.I understand 3/4 of the tube nest is in liquid 717 & 1/4 above in vapor

The freezing point of a glycol mix differs from the mimimum operation temperature, people confuse these;)

before freezing solid the glycol will crystilize at higher temperature.

What is happening is the glycol is below it's minimum operating temperature for that mix, but it has not yet reached the freezing point of the mixture.

Hope this helps.

Kind Regards Andy:)