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Chilled Water System-Pressure Problem

09/13/2017 2:51 AM

hi Guys we chilled water system in one of the high raised buildings, it's running for the last 7 years, the water column height of the chilled water is 92 meters and this is causing a high pressure on the chillers coils and compressor and as the chillers getting old and problem increases, the compressors keeps failing and now the chillers coolers also started failing. any ideas to overcome this issue thanks

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#1

Re: Chilled water system- pressure problem

09/13/2017 4:06 AM

Put the compressor and coils on the roof.

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#2
In reply to #1

Re: Chilled water system- pressure problem

09/13/2017 4:43 AM

it was supposed to be on the roof in the design stage, but now their is no way to take up. it is occupied building

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#4
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Re: Chilled water system- pressure problem

09/13/2017 9:01 AM

it was supposed to be on the roof in the design stage, but now their is no way to take up. it is occupied building

I don't believe that.

a heavy lift Helicopter will do the job. They do that all the time.

abandon and dismantle old chiller and install a new chiller on roof, hire a structural engineer to ensure the roof can handle the weight.

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#5
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Re: Chilled water system- pressure problem

09/13/2017 9:21 AM

Hi Phoenix Since it is occupied building and people are living their, we cant shutdown the system for long time. lifting of chillers can be done as you said; this may be the best solution but it is expensive and time consuming ( we have 5 chillers, 350 tons each). We have contacted York the manufacturer of the chillers we have and they informed me that they have chillers which can handle up to 290 PSI pressure. I am now thinking to replace one of the chillers ( the one failed) with the new York model and see the results. what do you think. one of my colleagues is suggesting to install low- loss header to isolate the chillers from the 92 meter head. what do you think? thanks

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#6
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Re: Chilled water system- pressure problem

09/13/2017 9:28 AM

This is not my expertise,... but what your colleagues mentions is what I had in mind.

Your distributors would also have a good idea, if not at least know of people that are familiar.

Yes it is difficult in an occupied building... but maintenance issues can be expected, the tenants just need to be informed when and for how long the shutdown will be so they can store some water and planned for it.

Don't know your plumbing schematic, but I'm sure you have the piping installed in separate zones.

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#7
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Re: Chilled water system- pressure problem

09/13/2017 12:39 PM

I fail to see what you can really gain with a low loss header. Some part of the system will still be under a considerable head pressure.

Seven years, and we are just now seeing this as a problem? LOL

How is keeping seal condition on high pressure water any easier than on the refrigerant? Granted the low-loss head may help reduce chiller compressor output pressure, so this may save some on energy input per ton of chilling.

You will be forced to provide pumping energy for water that may not have been needed previously, so plan accordingly. You could also plan to install the new unit at the top of the building(s), and still keep the old in service until the moment of switch-over.

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#9
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Re: Chilled water system- pressure problem

09/13/2017 12:42 PM

93 meters is a lot of head...

I think the problem what their seeing now is with the amount of head, it's being to fail...

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#19
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Re: Chilled water system- pressure problem

09/13/2017 3:11 PM

This statement, "it was supposed to be on the roof in the design stage," leads me to believe that this entire project was built as cheaply as possible to maximize profits for the builder, at the expense of safety and good building standards.

Are there earthquakes or high winds in that area?

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#29
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Re: Chilled water system- pressure problem

09/14/2017 1:08 AM

Hi Lyn it is not cheaper to install the chillers in the ground floor, it costs more as the chiller yard is little far away from the building core, and the pumps are also more expensive; I have seen the original design of the building, and found no space to install chillers on roof, that's why it was installed down, but the design and built contractor, the consultant and York distributor did not thing of the high head pressure

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#30
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Re: Chilled water system- pressure problem

09/14/2017 2:59 AM

Good luck. <unsubscribe>

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#3

Re: Chilled Water System- Pressure Problem

09/13/2017 8:59 AM

off the top,...

can you isolate the chiller and compressor with a regulator and backflow preventer, and use the 92 meters of head where its needed.

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#8

Re: Chilled Water System-Pressure Problem

09/13/2017 12:40 PM

Maybe put one or more booster pump stations part way up, with pressure-limiting valves on the way back down.

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#10
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Re: Chilled Water System-Pressure Problem

09/13/2017 12:43 PM

ya, this guys knows...

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#11
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Re: Chilled Water System-Pressure Problem

09/13/2017 1:38 PM

The pressure reduction valves seem problematic to me. I suppose, though, that the pressure will be high enough that any loss through the PRV would not be sufficient to cause a flow issue. Isn't the return side hot vapor returning to the compressor? If so, then the only thing needed is maybe one booster pump on the liquid side.

I know there are high rises higher than the one in question, and they pump water to the top at extreme head pressures. Is the refrigeration equipment at the top, or in the basements of these tall ones?

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#15
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Re: Chilled Water System-Pressure Problem

09/13/2017 2:41 PM

What is being pumped is chilled water (secondary refrigerant), not primary refrigerant. The whole problem is possible excessive pressure on the lower floors. A typical pressure reducing valve entails maybe 2psi pressure drop at rated flow; not a problem in this context.

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#20
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Re: Chilled Water System-Pressure Problem

09/13/2017 3:20 PM

Then why are they losing compressors? Ingress of high pressure water?

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#21
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Re: Chilled Water System-Pressure Problem

09/13/2017 3:25 PM

Seemingly so. The excessive water pressure can rupture the chiller tubes, thereby leaking water into the refrigerant side.

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#22
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Re: Chilled Water System-Pressure Problem

09/13/2017 3:27 PM

wrong

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#23
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Re: Chilled Water System-Pressure Problem

09/13/2017 3:30 PM

could you elaborate?

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#24
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Re: Chilled Water System-Pressure Problem

09/13/2017 3:34 PM

Very emphatically NOT wrong.

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#31
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Re: Chilled Water System-Pressure Problem

09/14/2017 3:06 AM

yes Tornado is right. we have tried installing PRV on one of the chillers returns and it did not help in reducing the pressure on the cooler

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#33
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Re: Chilled Water System-Pressure Problem

09/14/2017 7:22 AM

If a Pressure Regulating Valve (PRV) failed to reduce pressure then either that valve failed or the pressure is not coming from that direction. If the PRV did reduce pressure but the cooler still failed then your problem is not caused by pressure.

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#18
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Re: Chilled Water System-Pressure Problem

09/13/2017 3:06 PM

you don't lose a compressor due to building height, the compressor isn't involved in pumping the chilled water, chiller circ. pumps are.

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#12

Re: Chilled Water System-Pressure Problem

09/13/2017 1:50 PM

you get what you pay for in life

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#13
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Re: Chilled Water System-Pressure Problem

09/13/2017 1:55 PM

I suspect you knew I would reply with this.

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#14

Re: Chilled Water System-Pressure Problem

09/13/2017 2:38 PM

The only thing I can think of is multiple heat exchanger or chillers on intermediate floors to reduce the individual fluid column height.

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#16
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Re: Chilled Water System-Pressure Problem

09/13/2017 2:46 PM

That would be another solution. I don't know how often it is done that way. In the World Trade Center, for instance, the chillers were all in the basement (7 x 5000 refrigeration tons).

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#17

Re: Chilled Water System-Pressure Problem

09/13/2017 2:46 PM

I think I might re-engineer the the coils to handle a higher velocity of water flow then install booster pumps on the supply lines....the return would be limited by pipe size and loops on the way down, the supply velocity increased would then reduce the pressure in the coils...

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#25

Re: Chilled Water System-Pressure Problem

09/13/2017 3:46 PM

You live in Athens and have other 5 buildings in the country plus the 8 buildings I have in the project and work for a billionaire. Billionaires are notorious for being dishonest and not paying their bills, as we know. I'm sure some are very nice people, too.

Make this person pay a reasonable amount for the repairs.

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#26
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Re: Chilled Water System-Pressure Problem

09/13/2017 4:33 PM

You have buildings in Athens? Athens, TX?

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#27

Re: Chilled Water System-Pressure Problem

09/13/2017 4:38 PM

Starting over: High head noted on both the chiller coils and compressor, and on the chill water loop (at the bottom where HX is stationed, I presume).

Maybe you are not moving sufficient chilled water, and this may be causing something unusual, such as surging the compressor (liquid forming during compression), root cause being insufficient evaporation temperature of the vapor due to (1) chilled water not sufficient velocity, and (2) chilled water getting too cold in the local zone of the coils.

The system needs to be re-designed seriously by the professionals at York, and let them show you how this scheme is to be operated in order to get the most out of your equipment. Are you air cooled, or water cooled on the compressor outlet?

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#28

Re: Chilled Water System-Pressure Problem

09/13/2017 8:55 PM

Quit being cheap and hire a local company to solve your problem!

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#32

Re: Chilled Water System-Pressure Problem

09/14/2017 3:17 AM

I am not sure if the space / cost limitations allow for isolating the building's CHS & CHR risers by using a primary (Low pressure - Chillers side) / secondary (High pressure - Risers side) system with a suitable heat exchanger!.

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#34

Re: Chilled Water System-Pressure Problem

09/14/2017 8:25 AM

If it is the chilled water that is being circulated, then the return water column will balance the pumped water column (less pipe friction) and so the circ pumps only need to overcome the pipe circuit resistance (while also containing the 92m static head). If the system wasn't closed, then there would be water spurting out at the lower levels in the building. Introducing PRVs in the return line would create a situation where the pump would face an increased load due to reduced pressure on the inlet side.

The plumbing on the other hand needs to withstand the vertical head.

There would be some loss in efficiency, but what if the system were modified to have two heat exchangers. One where the chillers cool an intermediate heat transfer liquid in a low pressure system. The other where that low pressure system interfaces to the high pressure pipework.

This could be as simple as the chiller coils and the high pressure pipework being submerged in a tank of antifreeze or similar.

This separates the 92m head pressure from the chiller coils and would enable independent servicing of the components. Also wold not involve alteration of building internal pipework.

Just a thought.

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#35
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Re: Chilled Water System-Pressure Problem

09/14/2017 8:54 AM

Where have I heard that idea before?

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#36
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Re: Chilled Water System-Pressure Problem

09/14/2017 5:47 PM

Yes, similar but different. If the building plumbing is not the issue, then single device to isolate the high pressure (and thus thick wall section) water circuit from the relatively delicate heat pump is all that would be necessary.

Maybe if we suggest it often enough the OP will eventually understand.

Intermediate heat exchangers at different floors would need associated circulation pumps and other infrastructure.

Where I saw this in a big way was working at a winery. They had a tank with "tons" of brine (Olympic swimming pool size) as the intermediate. The refrigeration ran flat out. The cold brine was used to moderate the temperature of juice/wine during fermentation.

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#37
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Re: Chilled Water System-Pressure Problem

09/14/2017 9:27 PM

Say, if they used liquid helium for the transfer chilling fluid then they would only have 1/8th of the pressure at the bottom of the column. (I know this is absurd but why not have some preposterous fun. Particularly when you get 2 GA and I get bubkiss. )

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#38
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Re: Chilled Water System-Pressure Problem

09/16/2017 5:50 AM

I'd love to, but unfortunately I trod on a few toes a couple of weeks back. My humour doesn't translate well across the ether.

Though, if there was something that had an adequate simple density differential based on temperature (cold floats on top of warm), then a simple column with a louvred central baffle would enable cooling transfer with no pump at all.

For me, the GA system is sometimes not providing recognition for the quality of the response. There were some that I logged in the last few years where others repeated it days later and got GA's.

Seems like this time it has happened in my favour, next time will be your turn, I'm sure.

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#39
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Re: Chilled Water System-Pressure Problem

09/16/2017 10:07 AM

Don't sweat it. I still haven't found a place I can cash in any number of GA. I vaguely remember the offer a CR4 coffee mug discount for GA but I can no longer find the CR4 store let alone a discount.

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#40
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Re: Chilled Water System-Pressure Problem

09/17/2017 6:56 AM

I always thought the coffee mug offer was from some of the moderators of the time and it was only if you gave them the GA's to boost their score.

I think those are no longer around.

That was back when some participants had multiple avatars and could even give themselves GA's, but that's stopped now, hasn't it?

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