makeup water system connected to water supply for closed chiller system 1

[hollandhvac]

Gents,

We are in the process of designing closed chiller that will be connected to teh water supply system. To prevent back flow I have been going through some document on the internet, but I noticed that there is a requirement for a double check valve. I also have an existing system here, but I do not want to copy it as I noticed this one does not contain a double regulation valve and could have the possebilty of back flow.
I have two questoins;

1) can you tell me how to design a makeup system that is direct and perminent connected to the water supply.

2) see attached pictures, would this be acceptable system or are there difficulties?

 

[PEDARRIN2]

You need to determine what the code allows, but typically when you connect the drinking water (potable) system to a HVAC (non potable) you would be required to use a reduced pressure zone backflow preventer (

http://media.wattswater.com/ES-009.pdf).

I would recommend a separate shut off valve upstream of the backflow preventer, with a strainer (to prevent any particulates which could foul the backflow preventer). Some would put a check valve upstream of it to mitigate any pressure swings upstream of it (to keep the backflow from sputtering.

 

[EnergyProfessional]

In general code will require it and your local water Utility usually inspects those. Where I'm the State also requires annual testing of backflow preventers. You should check what your JHA wants. but either way do what Pedarrin2 said.
Water Utility calls this cross-connections since it connects your chilled water (with toxic corrosion inhibitors etc.) with their water system and they want to make sure you don't spill back the toxic materials.

 

[Drazen]

in EN-based legislation this device just needs upstream strainer and two isolation/service valves as it already contains two check valves plus discharge valve.

though, when i see this photo, i recall good old times when i used hammer as engineer's supervision tool - to destroy things like this on the spot, without discussion this "janitor" hose clutched upstream of water meter is particularly fancy.

moreover, i am not sure what this central device presents. is that pressure reducer? you likely need to reduce pressure from water network - in german-based specs testing pressure of water supply systems is 10 bar, for chilled system it is 5 bar.

anyhow, this is not a way to establish pressure control in your chilled water system. you are on the right track to not copy old system, so continue that way and do not copy concept of this old system.

direct automatic make-up would be acceptable only for some rugged industrial systems where there are no other options. you do not want to plan for system which will leak all around and have automatic make-up - that is finally not closed system at all, isn't it?! if maintenance guys complain to thoughts like these ones, fire them.

if you cannot live without automatic make up, than you need electronic controller-based pressure control system with digital output for solenoid valve which will open make-up when needed. backflow preventer serves only to protect potable water supply.

 

[RossABQ]

There should also be a pressure relief valve(s) on downstream side of make-up train to protect the cooling system components (the expansion tanks in particular) in the event the make-up regulator sticks open.

 

[Waramanga]

Err, document on the internet?? I think you are in trouble designing the chilled water system if you are struggling with the make-up....ask a local plumbing consultant for advice on this, money well spent mate!