Evap Cooler Piping

[Fett]

Does anyone know how to calculate the size and pitch of PVC piping to get X amount of water flow.

I have 41 coolers in my warehouse and a few do not get enough water and I think its because of the way they piped them. I have a 10HP Armstrong pumping the water up. It is a 32 foot rise. They go from 4 inch pipe to 3 inch down to 1 inch by the time it gets to the unit. The 1 inch is a 4 foot rise up through the roof with a single ball valve at the top. The units that are not getting enough water are NOT farthest from the pump.

Every intersection is a "T" and the only elbows in the system are on the main supply line.

[cadwaladr]

Does anyone know how to calculate the size and pitch of PVC piping to get X amount of water flow.

I have 41 coolers in my warehouse and a few do not get enough water and I think its because of the way they piped them. I have a 10HP Armstrong pumping the water up. It is a 32 foot rise. They go from 4 inch pipe to 3 inch down to 1 inch by the time it gets to the unit. The 1 inch is a 4 foot rise up through the roof with a single ball valve at the top. The units that are not getting enough water are NOT farthest from the pump.

Every intersection is a "T" and the only elbows in the system are on the main supply line.
not sure but why not have tanks to supplybanks dedicated to an amount of coolers,just a thought.

[US Iceman]

Fett,

Is this for water defrost supply or carrying away the water from the drain pan?

It makes a difference if the piping is gravity fed or pumped.

[Magoo]

Have you tried balancing each take-off point, may be a case of too much at the first section and not enough at the last take-offs.
Just a thought.
magoo

[lowcool]

Does anyone know how to calculate the size and pitch of PVC piping to get X amount of water flow.

I have 41 coolers in my warehouse and a few do not get enough water and I think its because of the way they piped them. I have a 10HP Armstrong pumping the water up. It is a 32 foot rise. They go from 4 inch pipe to 3 inch down to 1 inch by the time it gets to the unit. The 1 inch is a 4 foot rise up through the roof with a single ball valve at the top. The units that are not getting enough water are NOT farthest from the pump.

Every intersection is a "T" and the only elbows in the system are on the main supply line.
gday fett i have no idea about calculations but by the sounds of it pipework configuration maybe the issue,i think along the lines of liquid line teeing to multiple evaporators if not done correctly some will starve.a schematic will make things clearer.dont suppose cavitation maybe occuring generating air in your lines lessening water delivery.are sumps dry,inlet valves restricting?

[MrMark]

Don't know if the OP ever got an answer, but this is fairly simple to solve.

1. What is the consumption or use rate of each evaporator in GPM or GPH?
2. What does the pump curve (pressure vs volume) look like?

For example (And it's been awhile since I looked at anything like this) - 32 feet elevation is going to be about 13 pounds of water weight to overcome by the pump. So if the pump is capable of 20 GPM at 14 psi, then there will be 20 gpm available to split among the coolers.

It's important to answer the 2 questions above first, then we can move forward to solve the problem from there. And to note, in all likelyhood the existing piping is oversized for the job, but no reason to take it out. It will still work. But it sounds like the pump (@ 10HP) has got a problem, or something is restricting it's output, or starving it's input.

[Fett]

Thank you for the input. Sorry for the lack of information.

They are evaporative coolers. The pads are 6 inches thick and are 5 feet by 5 feet. They have a 5 hp baldor electric motor that belt drives a 5 blade fan. They move roughly 60-70,000 cubic feet of air a minute. The 41 coolers are divided up by North (20 coolers) and South (21 coolers). There are two central pump stations, one for the north and one for the south (the two do not connect). There is a 10HP Armstrong centrifugal water pump at the base of the storage tank. The storage tank is a 2000 gallon stainless steel tank. It has a conductivity controller on it so that when there is too much minerals in the water it starts replacing the water.

Bassically on the south side there is a section of coolers (6 coolers to be exact) that are fed from a single 1 inch pvp pipe. The rise from the pump is almost 28 feet and then it branches from 3" pipe to 1" 3/4" pipe with another 4 foot rise. It then curves (90 degrees) and downsizes to 1 inch pipe. It goes straight for 150 feet serving three coolers. About 75 feet into the 150 feet it branches off with a T and carries to another three coolers. This is where my problem is because the first three coolers on the straight away get enough water and the last three off of the T branch do not.

I will take some pictures tomorrow so you guys can see a little bit more.

[Magoo]

Do the evaporative coolers have float/ level controls?.
Do you know the the water feed requirements for each unit ie., gpm.
That 1"pipe worries me over such a long run. Could still be a water balance problem. General comment is a 10HP pump and the vertical rise plus line losses, you not going to get a lot of water at the last take-off.
Interesting problem.
magoo

[Fett]

Do the evaporative coolers have float/ level controls?.
Do you know the the water feed requirements for each unit ie., gpm.
That 1"pipe worries me over such a long run. Could still be a water balance problem. General comment is a 10HP pump and the vertical rise plus line losses, you not going to get a lot of water at the last take-off.
Interesting problem.
magoo


It boggles me as well because the north side has no water issues at all yet on the south side people are sweating because of it. The coolers do not have floats or pumps inside them because the 10hp pump keeps pressure up in the lines. The only thing regulating water flow to the top of the pads is a ball valve. I have the manual from the manufact.. but its more of a generalized one size fits all manual. It does say NOT to allow more than 1.5 GPM per SQ FT over the top of the pads. I'm not sure this applies to my units because they are so big.

On the north side at the very end of the line (cooler farthest from the pump) there is still enough pressure and water flow to flood the sump pan in less than a minute. Contrary to the south side the 6 units are pretty close and three of them I have the ball valve fully open and it can barely maintain an inch of water in the sump pan.

Pictures will be coming soon.

[Magoo]

Has this always been a problem, or has the problem developed recently. I am still trying to picture the lay-out, is it two systems or a common supply pump?. Do you have pressure gauges on pump/s, have you got a pump curve graph?.[ can be down loaded from supplier hopefully. ]
Can you do a free hand isometric sketch, scan it and post it. With pipe dimensions and approximate lengths. We will/can get to the bottom of this problem with detailed info..
magoo

[Fett]

Has this always been a problem, or has the problem developed recently. I am still trying to picture the lay-out, is it two systems or a common supply pump?. Do you have pressure gauges on pump/s, have you got a pump curve graph?.[ can be down loaded from supplier hopefully. ]
Can you do a free hand isometric sketch, scan it and post it. With pipe dimensions and approximate lengths. We will/can get to the bottom of this problem with detailed info..
magoo

I can do a sketch and pipe dimensions are easy. Getting approximate length is the hard part since all the piping is 30 feet in the air. It is two systems, north and south. There are no pressure gauges anywhere on these systems. I'll have pictures tomorrow. I believe this has always been a problem... this is the first season with this system since we don't/won't be operating it during winter months. All of this is brand new. It sat idle for 6 months and its been running for 6 months, but now that its actually been very hot out its become more prominent. All the motors in this system do run 24/7 from when we decide to turn the system on and off. I've already told my boss that if we turn it on it stays on until the season is over and its time to turn them off. Yeah come to think of it these pump motors have been energized since Feb 1st. Thats roughly 4400 hours.

[Fett]

Our fire wall here at work won't let me get these pictures to a website will have to wait till I get home.

[Gary]

It goes straight for 150 feet serving three coolers.

Is one of those coolers fed off the end of the straight pipe?... or are all three teed off to the side, with the straight pipe dead-ending?

[Magoo]

For approximate lengths of pipe runs, just step it out on the ground. Generally 1 large step is 1 metre.
Magoo

[Chef]

Fett - from your posts to date you seem to have 3 evaporators, each 5*5feet and a maximum flow of 1.5GPM per sq foot. So 3*25*1.5=112.5GPM

That is the maximum and is way too much for a 1inch pipe.

http://gearhob.com/eng/design/calculators/calculator-Fluid_Flow.htm

Go to this site and enter your data, with a 75 foot run to the last 3 evaporators the pressure drop needed to get your flow rate is incredible. You will most likely need a bigger pipe. (the calculator is for copper or steel but the results will be close to plastic to get the idea)

It is also more likely your system is running at 0.5GPM per square foot and that is better but still too high a drop.

If you want to analyse the whole system then go to
http://www.engineeringtoolbox.com/equivalent-pipe-length-method-d_804.html
and download the excel template, here you can add the losses for bends, multiple flow rates etc.

Hope it helps.

Chef

[Chef]

This site may also be useful. It recomends that a max of 5fps velocity in the pipe (plastic this time) and shows what pipe size you will need to your flow rate for a reasonable pressure drop, looks like 1.5 or 2 inch is necessary.
http://www.engineeringtoolbox.com/pvc-schedule-40-pipe-friction-loss-diagram-d_1147.html

Chef

[Fett]

I made the arguement to my boss about the serious nature of our cooling system. So he finally called the company that did the install. They will be out next week to re-evaluate the system to find any shortfalls. I will let you guys know the out-come.

I personally think that it was not plumbed correctly but I am no expert and we shall see.

[US Iceman]

They will be out next week to re-evaluate the system to find any shortfalls.


So...they get to charge you for evaluating the work (which you correctly questioned) they did and then get paid for changing anything they find wrong?:rolleyes:

I would recommend you ask them to explain what they did and why they would change it, and charge again for this service.

[Josip]

I made the arguement to my boss about the serious nature of our cooling system. So he finally called the company that did the install. They will be out next week to re-evaluate the system to find any shortfalls. I will let you guys know the out-come.

I personally think that it was not plumbed correctly but I am no expert and we shall see.


For sure they will find that something is wrong :rolleyes:.... trying to charge you once more... as usual...


What is size of connection for water make up pipe? I believe bigger than 1" - but I can be wrong;)

Also all this sounds very simple ... maybe ...if the pump is giving enough capacity ... then it is a little game trying to close a little all make up valves on the farthest units from the pump ... i.e. starting from the last and coming close to those starving units ... it is like balancing home heating system ...

.... closing outlet valves on radiators close to the pump to keep the water pressure enough high to feed the last radiators too ... this is v.v. close a little the latest valves to get some water pressure/flow on the first units ... seems something is not good with piping slopes ... too big to the far units...


we do not have enough data and all of this is guessing....

I'm sorry my English is not that good and maybe all above is not clear ....

Best regards, Josip :)

[Fett]

I do not think that they will be able to charge us. I have been talking with the contractor that constructed the entire building. This is the contractor that contracted the HVAC/R company. He said that he had been expecting something to come up with our building and will make sure issues such as these will be taken care of without additional cost (our company spend a crap load for this facility).

As for your comment Josip. I do not feel I should need to compromise (starve) other units to get the correct amount of water to another unit.

The north system on this building has enough pressure at every unit to overflow the pan in under 2-3 minutes.

The few units on the south system of the building that are having issues. The valves are wide open and the pads do not recieve enough water and the pan only has about an inch of water in it. Also these units are NOT the farthest from the pump.

So anyways I am still waiting for one of their guys to come out to do the evaluation.

[Fett]

They came out and bassically said that it was installed according to the "plans" and if it has to be upgraded upon that they have to go back to the engineer.