Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Is pumping away from chillers technically okay?

Is pumping away from chillers technically okay?

Is pumping away from chillers technically okay?

I'm working on a remodel project where they're redoing most of their hydronic piping in the building but keeping the existing pumps and chillers. In their current setup the pumps are pumping away from the chillers. The piping is on the roof and has aluminum jacketing so it would be expensive to redo this piping configuration. Is it okay to keep it this way? Would I just have to make sure the pressure is high enough in the closed system? This is on a 13 story building and the pumps and chillers are on the roof. Thanks in advance.

RE: Is pumping away from chillers technically okay?

It complicates your NPSH estimate.

Heat exchangers have convoluted flow paths with many sites turbulence can occur at. Under suction conditions this turbulence can cause cavitation and erosion in the heat exchangers.

RE: Is pumping away from chillers technically okay?

I see no issues with this.

RE: Is pumping away from chillers technically okay?

A diagram would help but from your description yes, you just need to maintain enough pressure in the chillers to prevent vacuum conditions.

If it works now then there is no reason why it shouldn't in the future, even if it is a little strange.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Is pumping away from chillers technically okay?

I fyou keep both chillers and pumps and it works, then it should be fine. Obvioulsy confirm it actually works fine and if you do other hydraulic changes to the system it may be different....

IF you installed a new chiller, I'd consult with that manufacturer.

RE: Is pumping away from chillers technically okay?

Yeah, that's some of the issue is they've never had a system that works well in the building (heating or cooling). They fired their maintenance guy that had been there for years so we have no way to ask specifics. The non-engineers just say that it's never worked great but they don't have any details. The current piping in the building is full of gunk and almost closed off in some places, the fan coils never had circuit setters or strainers, there's a lot of issues. We're doing new fan coils and new piping so I think I'll be able to solve most of their issues; I've just never had chillers on the suction end of the pumps so I'm a bit worried about that. These are all existing chillers but I'm going to check their manuals and see if they say anything about it.

I attached a preliminary schematic that I put together. Happy to take any feedback.

RE: Is pumping away from chillers technically okay?

Based on the location of the expansion tank, you are still pumping towards the chillers....they are just at the end of the loop.

Can I assume that you have very low delta-T with this system?

RE: Is pumping away from chillers technically okay?

Oh, I didn't realize that. It's 55 deg F return and 45 deg F supply.

RE: Is pumping away from chillers technically okay?

To be ok the following must be met: the NPSH at the pump inlet must be greater than the pump minimum NPSH requirement; air in the piping must be automatically vented by automatic air vents located at all high points of piping; the expansion tank initial pressure must be set such that minimum 10 ft height of water pressure would be available at the highest point of piping in the building to allow automatic venting of air in the piping.

RE: Is pumping away from chillers technically okay?

The pump away from chiller configuration is used in installations where the plant room is at the ground level of a high rise building. If you put the pumps ahead of the chiller s in such an installation the pressure exerted on chiller tube will be static height + pump outlet pressure. This is a determination that needs to be made in consultation with the vendor.

In a closed loop circulation system NPSH has no relevance(assuming you do not have a globe valve at the pump suction).Therefore I do not see any issues with the pump being located on the chiller discharge side but make sure all flow throttling is done at the pump outlet.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close