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Reducing SWT for existing hydronic systems

hot_rodhot_rod Member Posts: 13,204
A teaser slide from next weeks Coffee with Caleffi webinar, Heat Transfer in Hydronic Systems. John Siegenthaler will be the presenter with some new and helpful formulas.

A common question that comes up regarding SWT after building upgrades or added or upsized heat emitters, how to calculate new SWT.

This could also apply to systems that were over radiated from the beginning. The info from this number crunching exercise could also help determine if a mod con would be a consideration, to replace a non con. Keep in mind these are design day calculations. In many areas a small % of the year is at design conditions.

You can get weather data at the NOAA site to calculate % of HDD and determine what % of the year is at what load condition. A good read on how to use HDD here

Thanks to Vaughan Woodruff for the links presented in his Home Power magazine July/Aug 2018 article "PV and MSHP" A case study on a Maine home heated with a mini split, with a PV array.

We will also cover the calculations to show how much additional fin tube would be needed to reduce SWT
Bob "hot rod" Rohr
trainer for Caleffi NA
The magic is in hydronics, and hydronics is in me


  • GordyGordy Member Posts: 9,523
    Will be an interesting one. Yes much talked about here.

    Still comes down to do diligence in doing a heatloss, and an emitter survey. Never know what the other owners did.
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