60/Plumbing Engineer February 2020
even broke the mold by installing "coldish" climate 3 ton air to water split heat pumps (outdoor compressor units with antifreeze heat transfer fluid). The most challenging aspect of our design was the down- sizing of the DHW distribution piping. This critical element was needed to reduce standby energy losses, speed up hot water delivery and save money on piping, insulation, fittings and labor. Doing so comes with a price, however. Smaller pipes increase pressure losses and low pressure can jeopar- dize renter satisfaction - especially important for showering. We knew that the cold water pressures in the town were not high - roughly 50+- psi at the riser. Did I mention that a good shower is the kingpost of any hot water system? So, to make sure the smaller pipes would really work in these buildings, we confirmed our pressure loss estimates for the trunk/trunkette segments as soon as the pipes were hung on the ceiling of the second floor corridor. Check! We set up a testing rig for 10-40 foot segments of 3/8" PEX home run lengths (plus the manifold and reducer couplings). The test- ing determined pressure losses and delivery times at various flow rates through 3 gpm. For flows up to 2 gpm, the losses were not insignificant but acceptable for good showerhead sprays. Check! But, we forgot to test the shower valve/ cartridge combo plus the twigs. As soon as the construction debris was out of the tubs a few days before move in day, the plumber tried the design was from his previous years' of experience with trunks and branches but with the GC's support, a very good approximation of our design got installed - 1 " PEX feed line to 1" and " PEX east and west 'trunkettes,' (exten- sions from the larger trunk line feeds). We finished off the system with 3/8" PEX home run lines to every fixture group (shower, washing machine, lavatory sink and kitchen sink/ dishwasher.) We also installed in each building a 14-panel rooftop SHW system feeding a 1,200 gallon R-35 insulated solar tank with dual electric hot water back up tanks. We
Solara Phase 1 buildings on a snowy New York day. Note that the thermal panels have already shed their snow on a grey day.
Netzero
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