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Thread: Winterizing Solar Heating

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    Winterizing Solar Heating

    A pool contractor told me that I need to install a drain spigot on either the fill or return pipes for my roof-mounted solar collector to prevent the water from freezing and damaging the collector. Is this true? It's my understanding that water is only in the collector when heating is needed (solar valve open and pump running), and drains by gravity at other times.

    He said this is needed since there is a check valve on the solar return pipe. But isn't that normal? This check valve/solar return is between the solar inlet/bypass valve and the gas heater. That seems appropriate to keep the solar from filling (backwards) when the valve is set to bypass solar.

    There is another check valve on the other side of the solar inlet/bypass valve where water comes in from the pool, but I'd think the solar collector would drain towards the gas heater and on to the spa/pool, not backwards.

    Note, this is for an area of Southern California that does very rarely get below freezing in the winter, but only for brief periods during the night. So I don't think I need to be concerned about water in the pipes below ground.

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    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Tucson, AZ

    Re: Winterizing Solar Heating

    Welcome to TFP!!!

    Ideally it will drain itself automatically if the installation was done correctly.

    My first house had the panels on the opposite side of the roof from the equipment (the pipe went up and over). So they did not fully drain and they installed a hose bib on the bottom of the panel array that I would open in the winter to ensure they were drained.

    My current house I installed the panels in such a way that they should fully drain. But, I added another hose bib at the low point of the panels. Just opened it up this past weekend and barely got a trickle of water out ... so mine appear to be draining pretty well.

    We too rarely get below freezing, so this draining is really likely more for piece of mind.

    BTW, I edited your post to remove the link which was not providing any additional information (and sort of violates the forum rules) ... well I was going to, but looks someone already did
    Jason, TFP Moderator
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    Isaac-1's Avatar
    Join Date
    May 2010
    SW Louisiana

    Re: Winterizing Solar Heating

    Like Jason says a lot of this has to do with correct installation so the panels drain, but it also depends on the type of panels you have installed, as some have small enough tubes that water can get trapped and not fully drain, or your check valve may be of a model that requires too much pressure to open under gravity alone. This gets back to correct installation. In general with check valves they are either of the swing variety that have the lowest effort to open, but usually have to be installed in certain orientations only, or they are spring variety which which typically require between 1/2 pound to 2 pounds of effort to open. The one on my solar heater is a 1/2 pound spring valve which installed at near ground level will easily open under the weight of the water column, and the flowing water has enough force to fully drain the pipe before the spring closes it. If you have one with a 2 pound or higher spring this may not be the case. I live in a climate that may be a little colder than yours in the winter (we have experienced 5 or 6 nights below freezing so far this year with the coldest night this year getting down to 27 degrees this has been a particularly cold year as half the time we do not get our first freeze until after new years, perhaps once every 4 or 5 years we will stay below freezing for over 24 hours or have lows in the teens. This is my first winter with my newly installed upgraded solar heater, and I have been relying on the "freeze protection" feature on the solar controller which turns on the pump and flow to the panels when it senses temperatures below 35 degrees F to prevent the panels from freezing, not just the gravity drain with the check valve. Sort of a belt and suspenders approach.

    Indoor 20x40 35,000 gallon vinyl pool with 1.5 HP 2 speed Jandy FloPro pump, Hayward EC75 Perflex DE filter, 11 4x12 Techno-Solis solar panels w/ Aquasolar controller, Aquabot Turbo T Robot Cleaner. Also LMI metering chlorine dispenser pump and HotSpring Jetsetter
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    Mark R's Avatar
    Join Date
    Nov 2013
    Desert Southwest, USA

    Re: Winterizing Solar Heating

    I just drained mine with the installed pipe drain spigot the contractor installed. It's getting down to 25 the next 2 or 3 days. Panels are on the east side of my roof and both pipes run up the east side of the house and I usually open it up every week or so during the day to double check. Heliocol did the instal and did a fine job. Equipment and under ground plumbing are both east side of the back yard. Plumbing is buried about 8 inches under paver stone. I had the heater on for 7 hours today, hopefully that will keep the water at a higher temp until I get back Sunday, I now run the pumping system from about 1am until 6am until this weather warms to normal. Probably just wasted a bunch of therms though.

    Better safe then have a freeze break the tubes
    12k gal Gunite/Hayward filter C5520BH with quad 33 inch filters. 2.5 hp motor. Pool is on south side, so full sun light. Spill over spa.
    Laar's heater LT250-Low NOx Gas Fired for pool/spa 250,000 BTU. Roof mount 6 panel solar system installed east/south. TF-100 test kit. May-September 100+ degrees out side.

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