Designing Commercial Sewage Lift Stations Part 1: How To Determine Flow Rate

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By Chris Edmondson

Sometimes codes just aren’t very helpful.  Take Section 712.4.2 of the International Plumbing Code (IPC) and its insight into the selecting flow capacity for a sewage and ejector pumps:

712.4.2 Capacity. A sewage pump or sewage ejector shall have the capacity and head for the application requirements.

(Thanks, IPC….)

Clearly, having the proper flow is necessary to efficiently discharge wastewater from a commercial plumbing system – but how do you determine the flow rate for the sewage system so you can properly size the pump? 

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“What Pressure Do I Pre-charge My Hydropneumatic Tank To?”

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 In our last blog we talked about how to properly size a hydropneumatic tank – but the engineer’s work doesn’t end there.  He or she also needs to specify the appropriate pre-charge on the drawings.  Otherwise the tank will not be set properly at start-up and will not provide the intended energy savings.
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How To Size A Hydropneumatic Tank in A Pressure Booster System

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 Properly sized hydropneumatic tanks are a non-negotiable element in a domestic water pressure booster system--including variable speed systems.  Without a hydropneumatic tank, pumps will short cycle on and off during no flow periods.  Even a leaky faucet can cause pumps to operate unnecessarily without this pressurized reserve of water.    
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ASME Hydropneumatic Tanks Play An Important Role in Pressure Booster Systems

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 “Do I really need a hydro-pneumatic tank on my variable speed pressure booster?”

 It’s a question many engineers will ask, particularly after ASHRAE 90.1 – 2010 takes effect in commercial building codes as early as October of this year.  As we discussed in an earlier blog on variable speed pressure boosting, the new ASHRAE standard no longer permits pressure reducing devices to reduce the pressure of water supplied by booster system pumps.  This essentially puts an end to constant speed pressure boosting, which brings variable speed to the forefront.  But since the whole point of variable speed pumping is to more accurately align demand with supply, why would hydro-pneumatic tank still be required?

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ASHRAE Pipe Sizing Requirements Are Changing – System Syzer Makes It Easy!

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Bell & Gossett’s System Syzer does all the piping calculations necessary to meet ASHRAE 90.1 and 189.1 requirements. JMP is committed to getting all our customers up-to-speed on ASHRAE 90.1 – 2010. We’ve already covered some of these topics in previous blogs, including changes to pressure booster design.  Today’s blog focuses on the portions of 90.1 - 2010 that dramatically impact the selection of pumps and associated piping.

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