electronic expansion valves

[habs]

I am converting a dx coil from thermostatic valves to electronic. Currently there are 4 25 ton valves on the system , I want to put two 50 ton valves to replace them. I am installing a new compressor on the system that will control two valves but not four, I need a external board to control four valves. Will it be a problem replacing the four with two?

[airworx]

not till it unloades.

[Carrene #2]

How is it, that the compressor controls anything?

I just spent last week in Windsor, not such a bad place for a mud flat. Kind of reminds me of Saskatchewan, only more trees.


[Edited by r718 on 04-16-2005 at 11:22 PM]

[airworx]

becuase when they unload, capacity and pressures change.

i do wish i had customers that would spend money like this.
i dont believe it will work and youll need more than a control board.

[Carrene #2]

I figure it's my job to prevent customers from spending money, like this.

That may be an unfair statement, since I don't know the full story.
The who, what, where, when, and why, would be nice to know facts.
Don't worry about the "where", I really (to be honest) dislike Windsor ( mudflats of Ontario ).

I am curious though, to find out how this will work.

[Edited by r718 on 04-17-2005 at 12:34 AM]

[habs]

I'm putting in a turbocor, it controls two valves but not four.
What were you doing in Windsor, you are right it is pretty flat and dirty but we still call it home>

[Carrene #2]

Last night, I couldn't grasp what you were trying to do (must have been the beer).
It's clearer this morning.
I stayed in Windsor, but was actually working out in Amherstburg. In one of the plants there.

[habs]

I grew up in Amherstburg it is a nice town. Not much to do unless you are tourist though.

[CityHvac]

Originally posted by r718
Last night, I couldn't grasp what you were trying to do (must have been the beer).
It's clearer this morning.
I stayed in Windsor, but was actually working out in Amherstburg. In one of the plants there.

yup.....Windsor...you can cut the humidity with a knife in the summertime. I worked there one summer in '73...no A/C in the truck....thought I would die.

[habs]

Gotta have the truck with ac in it or you are in trouble down here. We are the banana belt of Canada you know!!

[overtimeman]

this will only be a problem if you have a varible cfm or loads less than the 50% load. unless you have hot-gas or unloading capabilities.

[habs]

The compressor is on a vfd but the air flow is constant. I am worried about even refigerant flow to each circuit but don't see any real problem with it.

[joeywpittman]

are there four txvs on one coil. or is there more than one coil; if so are the coils in different rooms?

[habs]

Four valves on one coil

[john dalton]

Dear Cardinal ac,

I thought all but two of you Cardinals were in the Sistine Chapel servicing out your conclave. I guess you must be one of the two sick cardinals that stayed home……that would explain the extra time you have on your hands for this thread. Sorry, had to get the humor out of the way first.

Seriously though, you can convert your existing four circuit TXV evaporative coil assembly to a two circuit EEV if one of either issues are meet first. First if the existing evaporative coil assembly is divided into two equal circuits each having a dual inlet liquid line inlet and a single suction line manifold outlet, then this is possible with a minimal amount of refrigeration piping. Second, if you didn’t mind installing four separate EPR valves on the four separate suction lines, then you could accomplish almost the same result from it.

My guess though is your trying to control your liquid line solenoid valves from the Turbocor’s onboard electronic circuits. If you, or the Client has already made up your minds about converting over to EEVs, then my recommendation would be to stay with four separate EEVs and control them from a new DDC controller monitoring both the return and supply plenums of your system. This would increase your evaporative capacity control steps and take better advantage of your Turbocor’s infinite steps of capacity and efficiency control. Either way, be sure you install a large enough suction line accumulator in the system regardless of what the Turbocor representative suggests based upon their complete dislike of any liquid refrigerant back to the compressor.

Just my suggestion based upon my own research of other HVAC contractors failure of this compressor, namely scramble caused by liquid slugging.

Respectfully Submitted,
John J. Dalton

[habs]

I am going to control the liquid line solenoid with the turbocor but only until the compressor reaches 18000 rpm for motor cooling. I talked to our rep today and he says the best way to go is to put in four valves, he got this from one of the owners of turbocor which means they have tried this before and the best way to go is four valves.
As far as the accumulator goes the compressor should close the guide vanes if any liquid is getting back to it, they were not too concerned about liquid getting back during our training at the factory. They don't even reccommend the oil seperator anymore to get rid of the excess oil.
This is my first install and I am pretty excited about it , the compressor is pretty cool.

[Dowadudda]

Let me ask.

Typically on what I work on, or use to I should say. If you got four coils. Isn't that doing capacity control. Like stage 1 through 4 to maintain discharge air. How are you going to gain any tighter control by taking it down to 2 stages? You may be screwing yourself. I can picture a scenario where, your under light load with a moderate ambient to boot, and you can't keep the pump from cycling cause she acheives discharge air quick. On and Off on and off.

I don't want to pretend that I know the set up you got, but if this system is set up the way I am thinking, I would not mess with ability of capacity control.

The EEV's want to see superheat target. There not simply just going to allow less gas as the dishcharge air drops. I am interpreting you thinking that the EEV will modulate. It won't do that.

[Dowadudda]

I think the coils are for staging. Then you ramp up or down the freeq based on suction. Just like normal mechanical or hydraulic unloading.

[Carrene #2]

cardinal ac,
Sorry, you're right, there's no place like home, no matter where it is.
I was workin' at the Honeywell plant. The system I was workin' on holds 30,000 lbs (no typo) of R-134a. I was doing more Millwright and Pipefitter stuff, than refrigeration related work.
Good luck with your project, it's out of my league.

[habs]

I have heard that is a pretty nasty place, I knew the guy who used to do it for Honeywell .

[westcoast refer man]

Hey cardinal ac,

If the refrigerant distributors used are the kind with removeable orifices, you should proceed with caution. Nozzle type distrbutors can only tolerate half loading before they become oversized. If your system unloads below 50% and all four electic tevs are still on, then you've reached the lower limit of loading on the distributor. It's quite possible under these circumstances that you'll have unequal refrigerant distribution through your evap coil sections. This can lead to poor superheatr control even with electric valves.

I'd look into this more closely if your system runs this way.