Small Chill Water System

[gatt]

I am trying to put together a small chiller system for an existing in-row cooling unit in a server room. We are keeping the in-row cooler. Is it acceptable to purchase a 3 ton residential type condensing unit and then match it with an indoor refrigerant to water brazed plate heat exchanger with all the necessary pressure, temperature, flow and refrigerant controls.

I understand that I will have to include some kind of low ambient control on the condensing unit.

I am also installing a buffer tank and small expansion tank on the chillwater side.

There are complete systems available - both glycol and split - but they are cost prohibitive.

Any tips would be appreciated.

 

[tys90]

I'm a little surprised all that equipment is that much less cost than a 3-ton in-row Liebert split system. Is low ambient control on a residential type unit going to be good enough where you are? Where I am, that wouldn't work, we need control down to -20F.

 

[gatt]

We presently have an APC In Row chilled water unit that is supplied from our main building chiller system. Works great until the power goes down. The building chiller is not on our generator circuit. I am going to keep the APC unit and supply chill water from a different source that is supplied from our generator circuit.

I'm going to 0F for low ambient. Indiana. We've been using our building chiller all winter anyway - that can't be good.

I haven't paid enough attention to low ambient until I started to research this project. I've been quoted refrigeration units to cope with the low ambient.

 

[Shophound]

Two challenges with running a resi/light commercial condenser in low ambient conditions: oil return and head pressure control. Fan cycling wears the condenser fan motors out more quickly. There are single phase controls that can turn the condenser fan into a variable speed, responding to condenser pressure or temperature. Hot gas bypass would be an additional low ambient aspect on top of controlling the condenser fan; using that depends on how steady the heat load is in the conditioned space, and whether or not you can maintain at least 100-105°F condensing temperature in the condenser during your coldest weather.

There's also a device on the market called a Rawal valve that is supposed to offer some form of condenser capacity control as well. I haven't really studied how that device works but I know it's been around awhile. Could be similar to a "headmaster" control used in commercial refrigeration.

 

[Shophound]

Also, have you thought about not completely unplugging from the chilled water supply of the building's central plant? In other words, if your little 3 ton resi condenser craps out, would you have the ability to switch over to building chilled water to tide you over until the three tonner is repaired?

 

[MintJulep]

You might be better off starting with a walk-in cooler condenser unit. Likely already has provisions to work in low ambient.

 

[gatt]

Thanks everyone.

We will keep the in row unit connected to the building chill water system. We'll just open the isolation valves if needed.

I do have a vendor that can put together a standard residential condensing unit with low ambient control(s). I am already seriously considering a walk in cooler type unit. It has the head pressure control that has been referred to.

 

[KiwiMace]

Why don't you buy a small chiller rather than trying to make one out of parts? Trane CGA/VGA, York YLCA...