No More Constant Speed Pressure Boosting Under ASHRAE 90.1 - 2010

By Mark Bingham

“Constant speed pressure boosters are DEAD and GONE TO HEAVEN!”

That was the prevailing message recently from Chris Edmondson, CEO of JMP, as he briefed the folks here at about the upcoming mandatory changes under SECTION 10.4 of the new ASHRAE 90.1 – 2010.

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How To Size A Hydropneumatic Tank in A Pressure Booster System

 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

 “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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