Connecting Trane Water chiller to air handling unit

[celtictech]

Hi All,
I am looking for some advice on a chilled water piping layout , to connect a trane RTAB chiller (cooling capacity 269kW) to an air handling unit for a cleanroom with a cooling coil of 106KW. The room is 27 metres x8 metres x 3 metres high.
I have been told that a buffer tank of at least 2000litres should be installed with the circulation pump sucking from the tank pushing the water through the chiller evaporator and from the evaporator to the air handler cooling coil.

The chiller, pump and tank are on the ground and the ahu is on the first floor upstairs. I really need to know the correct layout to connect all this together and what valves, fittings ,test points, and accesories should be fitted ( and where) in the system .
A diverter valve is already fitted to the cooling coil which will allow the chilled water bypass the coil when the room is at the set point temperature. The ahu is all that the chiller is cooling for the moment.
Thanks.

[bruceboldy]

celtic tech,
it is always fun to read this blog for new ideas and problems.
I am with Trane and and I am currently doing a similar job with chilledwater for a storage and humidity application.
I am using the cgaf chiller and multiple air handlers The chiller I am using has multiple scroll compressors instead of the RtAB with only one screw compressor.
My application does not include a storage tank, but I would suggest a tank for your application. If your system becomes satisfied the chiller unit will shut down on a low temp safety... this can lock out a restart thus causing you a room temp problem. The tank will act as a buffer for up and down requirements of the air handler.
Remember you will need a pump for the tank and one for the system. A VFD on the pumps might be helpful with your load profile. It can be tied to water flow and temps.
The system may need a humidistat and sensor along with
the standard temperature controller to maintain proper conditions. You also may need some reheat on the air handler to temper the air after the dehumidification.. The 2 position three way valve assembly should work well for you. but the difference in cap. of the air handler vs the chiller may cause some un wanted shutdowns.

Hope some of this is helpful, send me an email if you need to discuss

[Electrocoolman]

Hi Celtictech,
Presume the room is in use 365 days so demand is year round.
I would consider putting in two pumps...duty and standby and as previously suggested a VSD on pumps.
I've used plastic pipework and fittings in the past...easy to work with, and you can get it preinsulated if need be.
Trace heating on outside parts also needs to be considered.
Air bleed and drainage points at highest and lowest points.
You will also need a safety expansion valve point.
Would also suggest filter, and temperature and pressure gauges to indicate water flow and temperature. Also consider 'binder' test points.
Isolation valves for maintenance purposes to avoid unnecessary draindown of complete system. Don't forget a system fill point.

Hope this covers some points to consider.

[celtictech]

Thanks guys thats useful advice, what is a binder test point?

[Electrocoolman]

I thought you mighht ask that.....its a type of gland that allows insertion of a thin probe into the pipe to measure water temp and or pressure (and possibly flow). They seal on withdrawing the probe.

[US Iceman]

Here is a link to review for additional information:
http://www.petesplug.com/index.html

If I remember this correctly I think Trane used to have a small paragraph in their chiller brochures/manuals that stated a chiller should be used with a buffer tank if the system volume was to small to prevent short cycling or loss of temperature control.

I don't remember all of the details, but you might look on the Trane website for additional information too.
http://www.trane.com/Commercial/Training/Default.aspx?i=877

[wkd]

Using the buffer tank will depend on load and temperature variations along with the total volume of the system.my suggestion is to have a look at the installation and commissioning manual for any of the main manufacturers of chillers as they usually show a schematic of how they recommend the system to be configured including valves ,strainers test points etc.The manual should also tell you a minimum volume of system you need to operate the chiller.You might also want to consider adding a small percentage of glycol to the system for frost protection,this will reduce the capacity of the chiller slightly but you look to have more than enough in hand.Happy hunting.

[malik55]

Celtictech
If chiller is with single compressor then you will have problems with chiller operation as its capacity is more then double then the load, why not you go for a chiller with 2 circuits then at least you will have a 100%
standby system, Many installation works with out buffer tank actually that all depend on the cost and design requirements,
malik55

[frank]

Hi Celtictech

The use of a buffer tank on a chilled water circuit will smooth out the start / stop of the chiller providing the chiller is operating on return water control.

The Binder points, usually installed either side of the orifice plate/valve, allow you to connect a manometer to measure the pressure drop across the orifice plate/valve. By plotting the dp on the valve chart you can adjust the flow rate to match the chiller requirement.

[celtictech]

Hi,
Thanks for the help , the chiller and equipment was purchased second hand so I've been told we have to use it , its probably not ideal having such a large chiller on a small load.

[Electrocoolman]

Hi Celtictech,
Does your site have off peak tariff electricity?
This is just a thought but with such a large surplus of capacity available, could you incorporate an ice bank storage facility? This could be charged up during the night on cheap rate electricity, then instead of running chiller during the day you draw on the ice bank for cooling.
I dont know if the ice bank could fully replace the buffer tank requirement, but it would at least load the chiller and make it more efficient. What about hot water requirements on site...heat recovery from the chiller?