ReplyAre these the kind of units that have a small compressor and a large compressor?
Regular Guest
Hi my name is Javier Borges I am from PR right now I am installing 20 Tons Chilled water system using 4 Trane 4TTZ060 condensing units and 2 10 tons plate HX. Right now I have trouble deciding which DDC Controls to use should I use Trane Controls (++++++++++ Expensive) or my trusted control supplier which supplies Trend Controls. For those of you that do not know these trane units have two compressors inside of them and requiere a special wiring harness to connect them to any control either Trane or Trend. Please reccommend thanks.
Professional Member*
Are these the kind of units that have a small compressor and a large compressor?
Professional Member*
Sounds like fun although I'm not familiar with either control systems you mention. Are these units 2 stages? Seems to me like you need something that will the number of stages in addition to a leaving water sensor, freezestat, and all that. How are you going to control the pump? What kind of application is this going to be used it?
Professional Member
is it just me or do the txv external equalizer lines look like they are going to the wrong suction line?
"Right" is not the same as "Wise".
Don't step on my favorite part of the Constitution just to point out your favorite part.
Just because you can measure it, doesn't mean it is important. Just because you can't measure it, doesn't mean it isn't important.
Professional Member*
Has that apearance.Originally Posted by jayguy
Pretty cool project though
Professional Member*
I'm pretty sure those circuits cross over in that BPHE.
Regular Guest
Looks like a clean job.
Who makes that pipe isolator for the uni-strut clamp?
Have you thought of adding a liquid line solenoid valve to prevent migration. Does that condenser have a suction accumulation to prevent liquid slugging on start up or is it even necessary?
As far as Trend goes they make a good control as long as you have the support.
Regular Guest
The units are the one that have the double compressor and they are going to be used on high end residence for chilled water. I have already consider a freezestat, and every other sensor in that need to be done. The pumps will be controlled with the same DDC controls that will be installed with DPS and Transmitter for bypass valve. This is my third system that I have built but never with these condensing units. The hx suction and liquid connections are crossed blow them with nitrogen before doing installation.
Those isolators are electrical PVC Pipe cut at 3"
Professional Member*
I don't know your condensing unit's exactly but it my understanding that only one compressor runs at a time correct and not a true two stage?
Professional Member
Interlock your pump with the flow switch and set up a freeze protection. I don't guess it wouldn't much matter what controls you use. As far as staging goes, looks like x controls will just bring on more compressors in order to compensate for the load. Good stuff.
Last edited by txhvac; 10-14-2012 at 08:34 PM. Reason: Wrong spelling
Sic Semper Tyrannis.
Professional Member
So you are looking at 9 binary outputs, 2 binary inputs, 5 analog inputs, 1 analog output. Are you isolating the heat exchangers from each for low load conditions? Did you provide head pressure controls on the condensing units? How about a flow meter instead of DP?
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New Guest
The fan contact will run the water pump. Hopefully the condensing units are equipped with essential safety
devices and solenoid valves( not essential in this kind of a system). Make sure the the pump
is off delayed. Cheers
Professional Member
There is more then four stages here, each condensor has two stages.
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New Guest
Anyway, you can use an aditional 4 stage simple thermostat. Don't worry about the head pressure control
of the comps. it's probably in the condense units.
I forgot to mention that you must install a seperate water pump with a check valve on the discharge side
for each heat exchanger and please don't forget the safety devices such as water flow switch and freeze protector
for each heat exchanger. Cheers
Professional Member
And your thoughts on the bypass valve???
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Regular Guest
I am using a DDC based control system because it gives me the best control of the system, and the fancoil units in the house. I already have done all things for protecting the system including: freezestat, dp switch (is more accurate than a flow switch), on/off control valves for HX when full load is not neccesarry, planning on putting high and low ref pressure sensors to communicate to the controler. These CU start using the big compressor and when the load is acheived the small compressor starts that is the way the units saves energy. The thing with the CU is that if you do it wrong the compressors start failing and after a couple of failures Tranes does not warranty them at least locally this is my main problem. Have known of this problem from an early experience from another contractor but the system was with a multiple cu units split system.
New Guest
What bypass valve?
Professional Member*
Looks like fun, sounds like you've got it covered. Ive done a few retrofits but never just built my own chiller.
Let us know how it turns out.
Regular Guest
Due to the system been built with two way control valves the system needs a bypass with a proportional control valve to relieve system pressure when valves start to close.
Professional Member
Please read the whole post and you will find mention of a bypass valve.
You will find out that if you come to this forum and only read the first post and then comment without reading all that your opinion will eventually become null and void because people will learn that you are not paying 100 percent attention to what you are reading.
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