tLmIULgdby Admin
27
Feb 2014


Message:

I'm considering a Solar Hot tab configuration using a cedar hot tub (300 gals). I have a few questions.

First off I live in the San Francisco bay area, we get a good deal of sunshine, even in the winter, frost here is really rare maybe 1 or 2 days a year when the temperature gets close to freezing for a few hours over night.

I think I can used an open loop system and drain it on the few frost likely days. Here are the questions:

  • How many collectors will I need ? And how much do the weigh when full of water ?
  • Do I need additional filtering ?
  • What happens if the system gets too hot ? And can I have the system empty of water, or will it overheat ?

The system will only heat the tub, while I would like to use it for domestic hot water, all your tanks are too big, I have a very limited installation space for my hot water tank.

Thanks

Mark

Dated on : 13-12-2011
 

 

Replies :

 
Mark, we do have a design for the application you are referring to.  Basically by using 2 x TZ58 1800 30R collectors mounted above the hot tub in an open loop configuration, you can control the heating of your hot tub.  If the hot tub reaches its set temperature then the solar loop circulation pump will stop there by draining any water in the collectors back to the hot tub.  If the tub temp drops below the set temperature and the collectors are hot enough to provide positive gain then the pump will turn on until either the tub has reached the set temperature or the collectors temperature is less than the hot tub temperature. 


This system obviously only works during the day so at night the tub will drop in temperature somewhat.


Dan

Post By : Dan Jung Dated On : 29-07-2011


 

 


 Replies:

 Hi Dan,


So there is no danger of the collector overheating without any water in it ?

Would this also work using a heat exchanger, the collector loop

would have anti-freeze in.

Again could this overheat ?



Thanks


Mark


Post By : Mark Fenwick Dated On : 29-07-2011


 

 

Replies:


Mark, if you are using a heat exchanger and glycol this would then be a closed loop.  Over heating then becomes a problem and you would need an expansion tank.  The way I describe it using only water would be the best method as overheating with water is not an issue.

Dan

Post By : Dan Jung Dated On : 02-08-2011

 

 

Replies:


Hi Dan,



Going back to the open system again, how much lift can the solar

dc-5 pump provide ? The collectors would be on the roof (single

story) of the house, the tub base would be 3 feet below the ground.


Thanks


Mark


Post By : Mark Fenwick Dated On : 02-08-2011
 

 

 

 

Replies:


Mark if you click on the spec here you can see the pump curve.  https://www.solartubs.com/ebayphotos/1254857048Laing-DC-5.pdf

Dan

 

Post By : Dan Jung Dated On : 03-08-2011

 

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