cooling towers

Jim M · June 2006

> Hello I am having some really bad news with a 
> cooling tower problem in Winnipeg. The problem is 
> the cooling tower in question according to 
> Balimore Air Coil ;the maker of the cooling tower 
> is good for 42 nominal tons of cooling. The tower 
> is a BAC FXT 42 and it is being used on a cooling 
> load of 110 nominal tons. Prior to the 
> installation of the tower the condensing units 
> were on city water and ran very well. The design 
> engineers { I use the term loosely} have sized 
> the system to use three pumps one two horse, - 
> two one and one half horse; directly before the 
> condenser inlet. The condensing units are one 
> sixty ton Trane, one thirty ton Carrier, and one 
> Trane twenty ton. I have written BAC for some 
> engineering guidence and I am still waiting for 
> help. I require some solid advise to give my 
> customer. I am of the mind the only way to have 
> this system work; is to take the Trane units off 
> the cooling tower and put them back on city 
> water. Then put the thirty ton Carrier on the FXT 
> 42 ton cooling tower after altering the piping 
> and pump supplying the Carrier to allow proper 
> operation of the condensing unit.The tower is 
> piped in three inch PVC and the lonest run to the 
> Trane unit[sixty ton] is over three hundred feet 
> in length. The units are air bindng and to the 
> best of my knowledge; the cooling has not worked 
> in this building since the cooling tower has been 
> installed and the units taken off city water ; 
> this is five years ago. I need some engineering 
> backup very badly!!!! The help I have requested 
> from BAC is taking entirely too long. I am asking 
> for help from the HVAC communiy at large and I 
> have never been let down in the past when I have 
> asked for help in a serious vain. 
> 
> Please send 
> your advise asap and I an so desperate my email 
> aaddress is jackmartin@shaw.ca 
> 
> Thankyou for 
> the help Jack Ennis Martin -- All the best

JackEnnisMartin · June 2006

Cooling tower problems

Hello
I am having some really bad news with a cooling tower problem in Winnipeg. The problem is the cooling tower in question according to Balimore Air Coil ;the maker of the cooling tower is good for 42 nominal tons of cooling. The tower is a BAC FXT 42 and it is being used on a cooling load of 110 nominal tons. Prior to the installation of the tower the condensing units were on city water and ran very well. The design engineers { I use the term loosely} have sized the system to use three pumps one two horse, - two one and one half horse; directly before the condenser inlet. The condensing units are one sixty ton Trane, one thirty ton Carrier, and one Trane twenty ton. I have written BAC for some engineering guidence and I am still waiting for help. I require some solid advise to give my customer. I am of the mind the only way to have this system work; is to take the Trane units off the cooling tower and put them back on city water. Then put the thirty ton Carrier on the FXT 42 ton cooling tower after altering the piping and pump supplying the Carrier to allow proper operation of the condensing unit.The tower is piped in three inch PVC and the lonest run to the Trane unit[sixty ton] is over three hundred feet in length. The units are air bindng and to the best of my knowledge; the cooling has not worked in this building since the cooling tower has been installed and the units taken off city water ; this is five years ago. I need some engineering backup very badly!!!! The help I have requested from BAC is taking entirely too long. I am asking for help from the HVAC communiy at large and I have never been let down in the past when I have asked for help in a serious vain.

Please send your advise asap and I an so desperate my email aaddress is jackmartin@shaw.ca

Thankyou for the help Jack Ennis Martin -- All the best

Brad White_79 · June 2006

Jack, you cannot wish a 42 ton tower

into the 110 ton category. No way that is going to happen.
Perhaps that is why BAC is not responding- they do not know what do do short of selling you another tower or two. Hey, wait a minute, why are they not calling you and beating down your door?

I do not know what the city water situation is up there, but here we can no longer do that for new installations.

The PVC is of concern too in that your temperatures have to be higher coming out of your condensers when all is loaded. How they function at all and not go out on high head is best left to faith in a higher power.

I do not know what else to tell you but that you need more tower and condenser water pumps...

Jim M · June 2006

At standard design of 3 gpm/ton at 95 in and 85 out and a 68 WB you would need an FXT 68. before you think about going back to a once through system, look at the condensers, they are probably not sized for cooling tower standards of 3 gpm/ton at a ten degree split. the condenser water piping if not properly sized will never carry the flow rates.

good luck

Marty · June 2006

Air binding ? if they are really doing that you have more problems than just an undersized tower. I'd be kinda curious if when a pump comes on if the sump level is dropping enough to pull in a slug of air.

JackEnnisMartin · June 2006

cooling tower

Hello
Thank you for your input concerning my cooling tower problem. The tower is ,as you have pointed out, much too small in size and the capacity is not there. I read with interest the suggestion the condeners are in fact sized for 47 degree water and will not have the capacity required even if the tower is added onto:another unit is installed in tandem. I can only assume the design engineers [ yeah right ] went on the idea of; one gallon of water per ton. However, even if we take that as a possiblity ,the tower is still grossly undersized. The pumps as you say are too small to say the least. I have spent alott of my HVAC life in the ammonia sector and I have never seen a tower designed without a central pumping station? The pumps would be okay if there only purpose was to overcome the resistance of the condensers. I have been told and I have not seen this for myself; the tower sump has a vortex in it as the water is sucked down into the basement! The pipe sizing as you have remarked is incorrect and this baffles me. The trade has no end of very good piping programs to use for pipe sizing and yet the people doing this did not avail themselves of the service? In an effort to bring some levity into a very sad job, one "brain" enlarged the supply from the tower to six inch to help circulation. God help us all. I would ask the forum to tell me if they know of some good sites I can quote from when I present this mess. I will use the imformation so graceishly given here as a starting point. As an engineering fact ,the net suction head for this system is --- 10 psig max. Now, if we do the math with the pumps, it gets siller and siller. Why BAC is not getting back to me is strange ,after all, they make a very good product and what it is used for after it leaves their factory is not thier concern, surely.
Well ,thank you ,and please if anyone would like to make further suggestions ;I am more than ready to listen. Unlike some engineers I could name. I would like to state, I have had worked for ,in my opinion, the smartest refrigeration engineer in Winnipeg -- the old sod up and retired; good for him. I wonder if he would come out for one more round of fun and games?
Jack Ennis Martin

cooling towers

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