cooling a small server room

[john dalton]

Dear Thehumid1,

This is from the Bard link you furnished above, page 4, top of page:

This states the TWO modifications, system capacity control AND head pressure control….BOTH ARE NECESSARY….and DEPENDENT upon one ANOTHER…..do you see my friend…two different animals.


Respectfully Submitted,
John J. Dalton

[john dalton]

Dear Thehumid1,

Like I posted before, Serverroomcooling’s load is almost constant, but in order to lower the room’s setpoint below 70 degrees F to his requested 65 degrees F would require BOTH the head pressure control and the evaporative coil control that your own Bard literature says IS required for a complete system. Check out page 4, top of page, and paragraph one. Both are needed and work TOGETHER>

Respectfully Submitted,
John J. Dalton


[Edited by john dalton on 01-22-2005 at 06:02 PM]

[john dalton]

Dear Thehumid1,

Sit down friend, although I totally agree with you regarding your option that when worst case scenarios are present involving wind that is blowing across the condensing coil, condensing coil flooding is the preferred, best, most logical, most reliable form of condensing coil reduction. Having said that, and not knowing the weather patterns in this area of Florida, I would use the flooded condensing coil method of reduction if the wind was a factor.

Now, with that said, Serverroomcooling,: I know you have never seen your condensing unit on the roof, but I wonder if the wind has the ability to flow through the condensing coil unobstructed or is there structural members of the building that would hinder or prevent that?

If the wind can blow through the condensing coil, unobtrusively then I would recommend the flooded condensing coil methods to control your capacity reduction in this section, if on the other hand, the wind was not a problem, then I would recommend the JC P66 condensing fan controller for the reduction of capacity control for this section.

Is this a satisfactory statement Thehumid!......and what about the installation of HGB on the evaporator so Serverroomcooling could lower his setpoint to 65 degrees F ?

Respectfully Submitted,
John J. Dalton

[john dalton]

Dear Thehumid1,

Have to leave the office again………..will continue this discussion later this evening or on Monday morning…..have a great weekend…what’s left of it that is…..lol

Respectfully Submitted,
John J. Dalton

[thehumid1]

Originally posted by john dalton
Dear Thehumid1,

Sit down friend, although I totally agree with you regarding your option that when worst case scenarios are present involving wind that is blowing across the condensing coil, condensing coil flooding is the preferred, best, most logical, most reliable form of condensing coil reduction. Having said that, and not knowing the weather patterns in this area of Florida, I would use the flooded condensing coil method of reduction if the wind was a factor.

Now, with that said, Serverroomcooling,: I know you have never seen your condensing unit on the roof, but I wonder if the wind has the ability to flow through the condensing coil unobstructed or is there structural members of the building that would hinder or prevent that?

If the wind can blow through the condensing coil, unobtrusively then I would recommend the flooded condensing coil methods to control your capacity reduction in this section, if on the other hand, the wind was not a problem, then I would recommend the JC P66 condensing fan controller for the reduction of capacity control for this section.

Is this a satisfactory statement Thehumid!......and what about the installation of HGB on the evaporator so Serverroomcooling could lower his setpoint to 65 degrees F ?

Respectfully Submitted,
John J. Dalton

For this system they may be dependant on each other yet they do say they have two distinct functions.
One can be installed without other independantly depending on what the application calls for. If I install the hot gas bypass head pressure(low ambient) control in a system like serverroom where the load is constant it would work without an evaporator pressure regulator. and vice versa in an area where low ambient was of no concern the epr cold be installed with no low ambientHBG.

They also say fan cycling controls should NOT be used to control head pressure......

Still unable to convert you I ask you this:

1)When a fan cycles off does the compressor pull more amperage as the head pressure rises? If it does ...is this beneficial to the compressor motor and windings?

2)Does this happen with the Hgb low ambient valve?

3)Does a fan motor pull more amps continously running all day or shutting on and off 100 times a day?

4)Which reduces motor life more stoping and starting or having the motor continuously running?

5)Besides the obvious wind drawback do you believe the sudden high side pressure changes caused by fan cycling have no adverse effects on the TXV? You do not think it causes the TXV to start seeking as well which while it is seeking takes away from the system efficiency?

Ok ........this getting to be like chess again.

[Edited by thehumid1 on 01-22-2005 at 07:23 PM]

[thehumid1]

and what about the installation of HGB on the evaporator so Serverroomcooling could lower his setpoint to 65 degrees F ?


well depends what the valve was set at but greater delta t would be achieved on startup by setting this at the lowest possible pressure before icing would occur but with r-22 you come pretty close to the icing stage as a 65 degree supply temp normally indicates a 45 degree coil temp. If you set the epr too at a constant pressure equal to 35 degrees this should stop icing and pull the 65 degrees in my humble opinion.

What would have to be looked at is if running the evap that cold would cause too much cycling as obviously the set point will be reached quicker.

[serverroomcooling]

I saw the condensing unit on friday, it is on the roof, in plain sight, the roof has a concrete wall, so I'm not sure if the wind can go through the unit....my guess would be that it could.

the best thing that could have happened to me in this thread is that someone could have said "Get a Liebert!!"

but that's fine, because I don't think it would have happened anyway....it needs to fail before I really get the funds, that's just the way it is. Unfourtunate, but that's life sometimes.

The Liebert guy is coming in on Wed with his boss, I will get all of the readings from him, and I hope he can get me all of them, and they will be reliable readings!!!

I will ask him to fit me with a Liebert unit and I will keep that in my back pocket and figure out what I can do....Again, if the current system can not keep the room at 70 degrees in the summer, I will demand a liebert system!!!

[serverroomcooling]

Sunday night we are having a freeze warning....South Florida is getting some arctic air

[twcpipes]

http://www.sporlan.com/90-40.pdf

[Diceman]

Originally posted by john dalton
Dear Diceman,

Would you permit me a question or two?

Do you think anyone who has either posted to or viewed this thread has learned any fundamental or specialized information that has come from this thread?

Do you think anyone who has either posted to or viewed this thread has walked away with any useful information that he or she might use on their next HVAC job?

Do you think, after working all day, all night, and maybe all week in this crazy, hectic, dangerous, and stressful industry that maybe a technician or two has found some amount of joy, humor, information, or maybe just plain old entertainment in our thread here?

And finally, in this day and age, when freedom, liberties and personal aspirations are being undermined by tyrants, thugs, and terrorists around the world, do you think you should go around and thwart or hinder the efforts of a few fellow colleagues in their efforts to help someone, to spread the technician information they have worked so hard to obtain, to relay their own personal experiences, their preferences, or even their efforts to bring some humor to this thread, or do you think, as you have posted here before, your posts are humorous in nature. I think not sir. I see no one here amused by this type of humor, but have found several posts pointing out the distain and haphazard comments you have posted regarding this thread.

In conclusion I would say, you of course have just as much as a right to be here as any of us, but I would point out the fact that it’s still a privilege to post to this forum, and like I inform my children at home, with all privileges comes an equal amount of responsibility, and in my own option, I think your responsibility here is wavering my friend.

Thank you for reading this post.

Respectfully Submitted,
John J. Dalton

PS: 17,510 posts…….I bet you have some knowledge, experiences, and stories to share on this forum that we ALL would like to hear, why don’t you post them?

I already did, go read them.
Whether you think I, or others in here, are humorous or not only shows how uptight you are. Unfortuantely not too many guys have had the fortitude to read and digest this entire life history of one small, poorly designed and underbudget job. As for me, I have seen and worked on enough of them to know the ultimate end of the story.
Tyrants, thugs and terrorists?????????????
And in case you didn't notice, the only "enjoyment and humor these hard working techs" get is from guys like me...........not you......
When you are at parties, do people yawn and and tell you they have to go the bathroom or get a drink, never to return for more stimulating conversation?

[Edited by Diceman on 01-23-2005 at 12:38 PM]

[Diceman]

And how the hell did you work the preamble of the constitution in here.

[Diceman]

All kinds of people like me..........just look.

http://hvac-talk.com/vbb/showthread.php?threadid=69069

[thehumid1]

Originally posted by Diceman
All kinds of people like me..........just look.

http://hvac-talk.com/vbb/showthread.php?threadid=69069

That was hilarious.... but scary too... reminded me of the time I was in Boyscout camp and got abducted by aliens and woke up with my elbows and knees scuffed up and a condom in my butt...but the alien kinda looked like that... except with a scoutmasters uniform on...I guess he must have been a prepared alien.

[Diceman]

hmmmmmm This guy did appear out of nowhere, I wonder...

[john dalton]

Dear Thehumid1,

Hold on for a moment my friend, I think we have another two issues of confusion to clarify before we go any further with our discussion..

First of all, let me make four statements and then look at them and we cam discuss condensing reduction control again:

1. When the project calls for some form of condensing capacity reduction, and the wind can blow through the condensing coil without the condensing fan running, I prefer a flooded condenser type of system.

2. When the project calls for some form of condensing capacity reduction, and the wind is not an issue, then I prefer a variable speed condensing fan type controller such as the JC P66.

3. Then the project calls for some form of condensing capacity reduction, and the wind is not an issue, I NEVER recommend a fan cycling control for several of the same reasons you’ve already outlined along with several more you’ve left out.

4. The JC P66 condensing fan controller is a variable speed controller that controls the operating speed of the condensing fan motor, while monitoring the pressure of the system’s refrigeration liquid line. The controller utilizes a closed sensor loop algorithm type system to match the speed of the condensing fan motor to maintain precise and constant liquid line pressure. This controller does not harm the condensing fan motor, extends the useful life expediency of the motor, saves energy, is relatively inexpensive, is reliable, rouged, and has a great track record in the industry.

Second, by your most previous posts I believe you do not understand the method and basic operation of the hot gas bypass (HGB) in terms of evaporative pressure regulating. Be honest, have you experience with this type of HGB? If so, I do not make sense and I do not know what you asking in terms of using this type of control. This exact situation of Serverroomcooling is what this HGB system was made for. Please post your reply so we can discuss this issue further.

Respectfully Submitted,
John J. Dalton

[john dalton]

Dear Thehumid1,

If on the other hand, you need a little help on understanding the operation and methodogy of the HGB in regards to evaporative pressure regulating, don’t feel bad, less than ½ of 1% of HVAC technicians every get a chance to work on this type of system.

Respectfully Submitted,
John J. Dalton

PS: Of previous posters here on this thread, I would say less than 3 or 4 know how this type of system works with any degree of experiance.

PSS: Before you post TWCpipes,I know you know.


[Edited by john dalton on 01-23-2005 at 09:14 PM]

[hvac-alan]

I am certainly one who has no experience in working on hot gas bypass. But---then again that is why I am reading this thread--to learn a little more. Do not appreciate the cheapshots at those who have took the time to read this thread, ask questions and give comments. To all those who keep criticizing the contributors of this thread for repeating themselves and making this thing to long. Why are you still reading it then??? Does the thread have something more to offer you OR are you grinding out some personal grudge. The latter is no place on this website. Give it a rest.

I did, however, think that I knew what Hot gas bypass was. There is a valve (sporlan is apparently prefered), a receiver. When the head pressure gets to low, hot gas is bypassed into the receiver without going through the condenser. This raises the temperature/pressure of the refrigerant travelling to the metering device. Hence, the necessary 100psi diferential over the metering device is maintained. This is what I thought the gold standard was???

I faintly know of another type of hot gas bypass, but I thought that was used in ice machines or in other refrigeration applications that required a defrost of the evaporator coil.

An evaporator pressure regulator, I thought was a valve (ok we can use sporlan again) that maintained a certain pressure in the evaporator. This valve was after the evaporator coil and modulated shut to increase the pressure in the evaporator. I thought this application was used in supermarkets when you had multiple evaporators on one circuit that required different temps. Though, I suppose it could work here to prevent freezing on the evap??

Hummid1-

I hope that I was not included on your list of folks who were repulsed by HGB. I was not..., just trying to use my little brain to come up with a different solution to solve any potential problems (easier and cheaper). I did not dispute you or Dalton on Hgb as the best solution, just thought that it maybe a little overkill for a unit that so far appears to be working ok (dispite the sketchy readings from the dubioius installer)

Please. If I am off base on the above assumptions or understandings. Let me know. Do not talk down to me just at me.

[john dalton]

Dear Hvac-alan,

Regarding your post:

“am certainly one who has no experience in working on hot gas bypass. But---then again that is why I am reading this thread--to learn a little more. Do not appreciate the cheapshots at those who have took the time to read this thread, ask questions and give comments. To all those who keep criticizing the contributors of this thread for repeating themselves and making this thing to long. Why are you still reading it then??? Does the thread have something more to offer you OR are you grinding out some personal grudge. The latter is no place on this website. Give it a rest.’

My point exactly….thank you.


“I did, however, think that I knew what Hot gas bypass was.”

First and foremost, you have to know that hot gas bypass (HGB) is a generic term used in our industry to describe one of several different valves and processes within the refrigeration cycle. Each of these processes is piped differently and provides different functions within the refrigeration cycle. The term HGB simply means that “some or all” of the hot discharge gas from the compressor is bypassed from the inlet of the condensing section, through a specific type valve, to a different part of the refrigeration system. The type of valve the hot gas discharge goes through along with the location of where this discharge hot gas is reintroduced back into the refrigeration system defines the type of hot gas bypass (HGB) that is being used.

Most service technicians knows of al least one, or maybe even two different types of hot gas bypass (HGB), because they rarely, if ever, have the opportunity to work on this process. There are several different types of hot gas bypass (HGB), all of which serves different and diverse functions within the refrigeration cycle. I will not try to outline or define them here; there simply isn’t enough room or time tom do so. But if you are interested in them, please investigate the following website for a complete and though explanation of the majority of these different processes. And yes, it is a Sporlan site:

http://www.sporlan.com/downloads.shtm

After reading the above information, and there is a lot of it, you should posses a wealth of information at your fingertips regarding hot gas bypass (HGB). But……remember, just reading it makes you as much an expert at it, as a homeowner reading a HVAC text book makes him an expert at our trade. Only experience and time will take you to the level of proficiency that you would like to obtain.


“There is a valve (sporlan is apparently prefered), a receiver. When the head pressure gets to low, hot gas is bypassed into the receiver without going through the condenser. This raises the temperature/pressure of the refrigerant travelling to the metering device. Hence, the necessary 100psi diferential over the metering device is maintained. This is what I thought the gold standard was???”

Read the above posted information, and we can discuss it if you’d like, by the way, there is no “gold standard” in our trade, because every project’s requirements are so diverse that any of the HGB processes could be the right chose for that particular project, making “it” the gold process for that particular project.


“I faintly know of another type of hot gas bypass, but I thought that was used in ice machines or in other refrigeration applications that required a defrost of the evaporator coil.”

Yes, this is indeed another form or process of hot gas bypass (HGB), it is known as hot gas defrost and involves the application of hot gas from the compressor backwards through the evaporative coil assembly so it can either partially melt the ice on the surface so it can fall off, as such as one way of harvesting in ice machines, or completely melt the ice , such as in refrigeration to remove the buildup of ice on this surface.


“An evaporator pressure regulator, I thought was a valve (ok we can use sporlan again) that maintained a certain pressure in the evaporator. This valve was after the evaporator coil and modulated shut to increase the pressure in the evaporator. I thought this application was used in supermarkets when you had multiple evaporators on one circuit that required different temps. Though, I suppose it could work here to prevent freezing on the evap??:

This is not a form of hot gas bypass (HGB) since it doesn’t bypass the hot gas anywhere. This is used exactly as you’ve outlined, as form of evaporative coil temperature control for the purpose of maintaining several different temperatures within a single multiple compressor rack system, such as used on supermarkets, as you pointed out.

Respectfully Submitted,
John J. Dalton

[thehumid1]

Originally posted by john dalton
Dear Thehumid1,

If on the other hand, you need a little help on understanding the operation and methodogy of the HGB in regards to evaporative pressure regulating, don’t feel bad, less than ½ of 1% of HVAC technicians every get a chance to work on this type of system.

Respectfully Submitted,
John J. Dalton

PS: Of previous posters here on this thread, I would say less than 3 or 4 know how this type of system works with any degree of experience.

PSS: Before you post TWCpipes,I know you know.


[Edited by john dalton on 01-23-2005 at 09:14 PM]

Hey you side stepped my questions I did not ask what you do....but nice move lol.

But I will answer yours ffearlessly:

No I never installed one of this valves and if I had been famaliar with them obviously I would have realized TWC PIPES was referring to a completely different animal as you put it ...EPR,CPR,IPR' valves I have installed and used to control suction pressure.

But it seems pretty cut and dry how it works or correct if i am wrong similiar in nature to a TXV it senses the suction pressure from the suction line leaving the evap if it is below a minimum setpoint the valve opens allowing hot gas from the discharge line to enter between the TXV and distributor on the evap and then as the coil temp rises back above the setpoint it closes again.

Now for my own future reference....

I would like to know from you.....

What I would see as a big advantag in using this kind of HGB valve would be in conjunction with a EPR valve. The EPR to mainain an constant evap temp of lets say 30 degrees and the evap HBG to prevent the coil from icing which is kind of the idea I was getting at in my post to the original question. So the coil would always be as cold as possible and this kind of HBG would prevent it from icing. I would think using the two together would then easily maintain serverrooms 65 degree desired temp easily.

[Diceman]

Originally posted by john dalton
thread, ask questions and give comments. To all those who keep criticizing the contributors of this thread for repeating themselves and making this thing to long. Why are you still reading it then??? Does the thread have something more to offer you OR are you grinding out some personal grudge. The latter is no place on this website. Give it a rest.’

My point exactly….thank you.

Lighten up girls.