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Originally Posted by rgatlin

I'm going to jump in on this thread, from an on going personal experience. I have two 1000 ton Trane Centra-Vac's. (lead lag/weekly rotation) My building just completed it's 8th year of operation. My chilled pumps have always been on VFD's and my Chillers have VFD's. For the life of me, I didn't understand why my tower pumps were soft start using auto-transformers tapped at 80% then to 100% about 10 to 15 seconds later. So here we go, 125 hp vertical pump, slamming into a 40% open triple duty (instant head). Pumps were within temp specs but extremely warm to the touch and running full load of (going from memory) about 139 amps. This was all done at start up to maintain Chiller Condenser Delta P. (Chiller VFD's and Vanes taking care of Load)
My background is residential. I only have 8 years in building plant management. Back to my pumps......
We installed VFD's on our tower pumps. Working with my programmer, we installed pressure differential transmitters on the chiller condensers. (no more changing failed paddle flow switches for me) Opened the triple duty's to 100% open and now controlling the pumps to maintain condenser delta P. (demand option referenced of course)
This is the result. My pumps are running somewhere around 68 amps. My pumps are cool to the touch. We're saving in the neighborhood of $24,000.00 a years in operating cost.
This again is my experience in one building. We have added VFD's to supply and relief blowers and have seen a 12 to 14% reduction in operating cost even running at 100%. Our resident master electrician was so baffled, he contacted the VFD mfg and talked to their engineering department. Their explanation seems quite simple. The difference is going from utility to "conditioned" power. I can testify that what I've been told in VFD seminars has become reality. If you can reduce your motor to 80% with a VFD, you reduce your operating cost by 50%. I'm not an engineer and I can't explain all the why's and what for's but I can tell you that it works. The proof is in the electric bills.
I'm a firm believer in VFD's. Installing them are a plus in my book even if you run at 100%. Work with your programmer, work with the engineers and I'm confident that you won't regret installing the VFD's. It opens the doors to a lot more opportunity to meet demand and save energy/money at the same time.
Just my humble opinion.

It is more a function of simply running the system itself more efficiently, than it is any electrical magic. In the case of your condensers, it is far less efficient running a pump that is too big for the flow, then throttling the flow down with the triple duty valve, than to simply only run the pump at the capacity you need. The same can be said for air handlers, where running a fan at full speed, and then controlling duct static with dampers is far less efficient than running the fan at just the right speed and letting dampers be full open.

In either case, and especially in the condenser case, if you've got a fixed load (in the condenser case, a fixed condenser water flow), then the MOST efficient option is to have the pump sized exactly right for your system load. An exactly correct sized pump, running across the line, is still going to be more efficient than the wrong sized pump, running through a VFD. However, because it is often near impossible to accurately predict system losses, most times engineers simply design pumps a bit oversized, and count on throttling to balance things. This is why vfd's still save on single load systems, because the single load systems were never designed right from the beginning.

I'm going to jump in on this thread, from an on going personal experience. I have two 1000 ton Trane Centra-Vac's. (lead lag/weekly rotation) My building just completed it's 8th year of operation. My chilled pumps have always been on VFD's and my Chillers have VFD's. For the life of me, I didn't understand why my tower pumps were soft start using auto-transformers tapped at 80% then to 100% about 10 to 15 seconds later. So here we go, 125 hp vertical pump, slamming into a 40% open triple duty (instant head). Pumps were within temp specs but extremely warm to the touch and running full load of (going from memory) about 139 amps. This was all done at start up to maintain Chiller Condenser Delta P. (Chiller VFD's and Vanes taking care of Load)
My background is residential. I only have 8 years in building plant management. Back to my pumps......
We installed VFD's on our tower pumps. Working with my programmer, we installed pressure differential transmitters on the chiller condensers. (no more changing failed paddle flow switches for me) Opened the triple duty's to 100% open and now controlling the pumps to maintain condenser delta P. (demand option referenced of course)
This is the result. My pumps are running somewhere around 68 amps. My pumps are cool to the touch. We're saving in the neighborhood of $24,000.00 a years in operating cost.
This again is my experience in one building. We have added VFD's to supply and relief blowers and have seen a 12 to 14% reduction in operating cost even running at 100%. Our resident master electrician was so baffled, he contacted the VFD mfg and talked to their engineering department. Their explanation seems quite simple. The difference is going from utility to "conditioned" power. I can testify that what I've been told in VFD seminars has become reality. If you can reduce your motor to 80% with a VFD, you reduce your operating cost by 50%. I'm not an engineer and I can't explain all the why's and what for's but I can tell you that it works. The proof is in the electric bills.
I'm a firm believer in VFD's. Installing them are a plus in my book even if you run at 100%. Work with your programmer, work with the engineers and I'm confident that you won't regret installing the VFD's. It opens the doors to a lot more opportunity to meet demand and save energy/money at the same time.
Just my humble opinion.

Originally Posted by ZeroTolerance

Yes, there are manual valves on each side of each of the pumps. There are so many manual valves, it would be hard for me to identify them all lol.

Luckily, Manual valves can become automatic valves rather easily.

Yes, there are manual valves on each side of each of the pumps. There are so many manual valves, it would be hard for me to identify them all lol.

Are there no valves on the pumps for service? It would be more appropriate if the isolation boundary included the chiller and associated pumps (this would aid in implementing my above shown example system, also).

The Bray Automatic Valves are located on each chillers, chilled water supply and condenser water return right at the chiller. There are no automatic valves yet on the chiller in the bold outline, but will be once it is replaced with the new chiller

Somthing that piping diagram doesn't show is valving. Where are the isolation valves located for the chillers?

The proposed chiller is in the bold outline on the plans and will have VFD's on both pumps and compressor:
You can right-click the image and save it to your computer, so that you can rotate it clockwise 90° for easier reading/viewing.

Sorry that was my mistake, we run the Tracer™ CH530 on the chillers and they use the UCP3 board. We also have a comm4 board in them for communication with the Tracer Summit BCU.

Russ, you state you run several towers/chillers off one condenser pump. If I am reading what you are saying correctly, you run one big pump for the chilled water and one big pump for the condenser water, and these two pumps can accomodate several chillers?

Our setup is a bit different if that is in fact what you are stating, we run individual pumps for each of our chillers. I will post a print of our plant setup here in a few.

I don't think you will have near the problems you anticapate.

Back in the late 90's I had some engineers show up for my new chiller plant. They wanted variable speed chillers with variable speed pumping through the evaporator. No 3 -way valves...no decoulping loop....nothing to maintain minimum flow through chillers......just one huge chill water pump on a VFD and nothing else.

Made me more than a little nervous....even made York real nervous. I was used to Tranes, primary/secondary pumping, decoupling loops, 3-way valves, and all of that stuff. We argued, we fought, we even flew around the country together looking at equipment.

Now that plant design has become the norm. I do things I never thought I could have before. Under the right conditons I run entering condenser water within a few degrees of leaving chill water.....I run several towers off one condenser water pump....and I can get an easy 1,500-2,000 tons out of a 750 ton machine at kw/ton rates that would make me feel like a liar if I quoted them.

You need a team you can work with and you need to pick chiller barrels and cooling tower designs that work with your climates and loads. IMHO ragging on engineers cuts both ways. I don't think an operating engineer can look himself in the mirror and feel pride if they are still advocating constant volume, 3-way valve, chill water systems. Sure such systems are easy to keep operating but they are wasteful of natural resources to the point of being negligent.

And yes, expect to become more proficent at BAS programming than your vendor....just no way around it.

Is "ucp4" street slang for the AdaptiView panel?

I think most issues begin right there....noone works there way up anymore, out of college and right to a supervisor postion. no hands on.. In other countries part of the education process is hands on work in the field working on yours and others designs, Why that cannot be done here is beyond me

Originally Posted by CraziFuzzy

...This conversation DOES make me glad our plant has 2 separate towers. We've got 2 1985 vintage CVHE-750's on one tower, and 3 1990 vintage CVHE-1250's on the other. We are in the planning stages of replacing the 750's with some newer 750's, but since they are on a separate tower and can run colder, the VFD's are a no-brainer.....

i would agree with you here. earlier, i was thinking of 3 way valves on the towers instead of on the individual condenser pumps...working in the heat had gotten to me. that i also like and it may work if the controls are set up properly and left alone. it does add for individuallity of the condenser water temperatures per chiller. i have had trane chillers that lost all of their oil with entering condenser water temperatures below 84F and i have had trane chillers that never lost a drop at 65F. individual control allows for age differences and mechanical issues. i would be concerned about being able to write a proper sequence and maintaining it. i don't have that kind of faith in the industry.

it used to be that the experienced mechanical techs moved into the BAS field...now it is mostly young punks who grew up playing video games and don't know what dirt under a fingernail feels like.

Originally Posted by ZeroTolerance

Our other chillers were put in in August of 2007, so they are fairly new. They are both CVHE 600-tons running ucp4

Then they have the refrigerant pumps and can take the lower condenser temps.

My opinion ( for what it is worth) is that all of these mechanical design engineers need to start paying for their mistakes and experiments. They have become just like doctors, they cover for each other and admit no mistakes. Seems like every start up i go into has the same old stupid mistakes. You would think that by now they should now what to do with head pressure controls. Maybe it's my impatience, but i get tired of the same old arguments. I have however seen a few good enginnered projects, but they are getting less frequent.

My statement does not ascertain that service engineers and building engineers are smarter than desigb, but sometimes i think they need to listen to the voice of experience.

In your case it would seem that a serious discussion needs to occur. Reading these posts indicates the answers are available, it simply is a matter of everybody getting on the same page and planning well ahead of time, especially the controls.

Originally Posted by Dallas Duster

So most likely it will be running balls to the wall all the time.

That would depend on the other chillers setpoints.

Originally Posted by CraziFuzzy

Well, the way they control the compressor speed in most cases is to run just above the point of surging. Keep in mind, we're not talking about 'warm' condenser water, just not 'cold' condenser water. It shouldn't be any closer to surging than a constant speed compressor - and and part load, it should have no problem backing off speed a bit, improving part load efficiency.

Still, if the other chillers are that new, and not likely to be replaced, then the other part of my argument is invalid - unless of course they are new enough to receive VFD upgrades in the next few years.

This conversation DOES make me glad our plant has 2 separate towers. We've got 2 1985 vintage CVHE-750's on one tower, and 3 1990 vintage CVHE-1250's on the other. We are in the planning stages of replacing the 750's with some newer 750's, but since they are on a separate tower and can run colder, the VFD's are a no-brainer.

One recommendation I have is, if they DO end up putting in the VFD chiller, perhaps it might be worth it to see what it would take to add a 3-way, or a pump return bypass, on one or two of the constant speed chillers. You might be surprised how little it would cost, and the gains would be huge.

So most likely it will be running balls to the wall all the time.

Since you already have dedicated pumps for each chiller (I think you said that), getting variable temp condenser water to each chiller may only require cutting in a simple modulating valve across each pump take-off like so:

This way, the pump is just concerned with the right GPM through the chiller, and the bypass valve will vary to regulate the temperature of the water into the chiller.

Originally Posted by Dallas Duster

I have a feeling it will not be running at part load with warm condenser water, it just might surge.

Well, the way they control the compressor speed in most cases is to run just above the point of surging. Keep in mind, we're not talking about 'warm' condenser water, just not 'cold' condenser water. It shouldn't be any closer to surging than a constant speed compressor - and and part load, it should have no problem backing off speed a bit, improving part load efficiency.

Still, if the other chillers are that new, and not likely to be replaced, then the other part of my argument is invalid - unless of course they are new enough to receive VFD upgrades in the next few years.

This conversation DOES make me glad our plant has 2 separate towers. We've got 2 1985 vintage CVHE-750's on one tower, and 3 1990 vintage CVHE-1250's on the other. We are in the planning stages of replacing the 750's with some newer 750's, but since they are on a separate tower and can run colder, the VFD's are a no-brainer.

One recommendation I have is, if they DO end up putting in the VFD chiller, perhaps it might be worth it to see what it would take to add a 3-way, or a pump return bypass, on one or two of the constant speed chillers. You might be surprised how little it would cost, and the gains would be huge.

Our other chillers were put in in August of 2007, so they are fairly new. They are both CVHE 600-tons running ucp4