Constant Flow

Paul Rohrs_2

I have been impressed by Oventrop and their Unibox Plus control and TRV. I am thinking about using them on a Constant Flow - Outdoor reset system for a 30,000 sqft addition on a Nursing Home that is requesting individual room control for infloor heating. (Seems ideally suited)

I am pursuing the layout on a primary (boiler loop) secondary (system loop) and am wondering about the pex layout. Each room will be a separate circuit,(off of a central trunk line) but according to Oventrops layout, I should be direct return. To give my adequate flow thru each room, I would think reverse return would be a better solution, but for constant flow, I need a complete secondary loop with perhaps a pressure bypass differential to give me enough head to allow TRV's to have flow thru them. Am I overthinking this? I have attached their (lengthy) PDF file. This is my first go around with TRV's and just want to be certain about design before I consider going back to my tried and true zoning by circulator. Budget is an issue in this job and it just seems less controls,less circulators and constant flow with outdoor reset will be the best of all worlds. I know Mark Eatherton had talked about this system for his residential dream system and agree this might just be "the ticket".

PR

Alan(CaliforniaRadiant)Forbes

I made the same mistake

That is, I installed a system with TRV's on all the radiators and piped it reverse return and later realized that TRV's will balance the system by themselves.

I could have saved a lot of money by piping direct return.

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Paul Rohrs

Flow

Was it as simple as running a primary header for supply-return? I am just worried about enough flow on the farthest zone.

PR

Dan Peel

design

Design for adequate flow at design load. Every trv open and differential pressure bypass sized to accomodate. Remember you can go to multiple manifolds/circs/DP bypasses to simplify the local flow volumes. Home run, direct return and constant flow with reset all work. The TRV's then only balance the system. Dan

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