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Simplifed(?) drainback Solar Thermal (for small) Hot tub heating

NIMAN
NIMAN Member Posts: 2

Based on this comment on closed thread:

https://forum.heatinghelp.com/discussion/comment/1061692/#Comment_1061692

But you also need a way for the supply to the collectors to drain. A small tube run between supply and return will allow the supply to the collectors to drain back, once the pump is off.

I prefer not to use air vents or vacuum breakers as neither holds up well to the harsh conditions found on collectors.

I was wondering if my attached image configuration is something similar to what Larry Weingarten might (/ does) have had in mind - i'd like to forget about Glycol and a heat exchanger in my, planned. modest hot tub.

Could that work? how small could/should the "small" tube between supply/return be?

Comments

  • hot_rod
    hot_rod Member Posts: 23,367

    I've never piped that air break in any of the drainbacks I have done. I have two pressurized DB systems on my shop and home now, one with a 27' long collector, they drain fine.

    The red pipe above the tub, in your drawing will allow air into the piping

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • NIMAN
    NIMAN Member Posts: 2

    Hi Bob.

    I see you were involved in that 2007 thread - perserverance & congratulations 🤗

    I now guess an "easy" Drainback type setup for open hot tub scenario could be unreasonable.

    Good to hear that long collector system works fine … the little i've read about Solar Thermal makes me think DB is, relatively, under-appreciated.

    Anyway, thanks for your comment.

  • Larry Weingarten
    Larry Weingarten Member Posts: 3,588

    Hi, If the red pipe ends underwater, I'm not sure how air could get back into the system, allowing the collectors to drain. Drilling a small hole in the pipe above water level, can fix this and not have any of the longevity problems vents and vacuum breakers have. 👍️

    Yours, Larry