ups backup for solar domesic hot water circulation pump

2 Posts
Feb 14, 2011 12:44 pm
ups backup for solar domesic hot water circulation pump

I have a solar domestic hot water system that works great. One problem, In the event of a power outage my 115 volt gruntfos circurlating pump will not run,  causing an overheating situation. The pump draws only .57 amp and 65 watts.  Does anyone know of a affordable battery backup system that is an automatic switch over in the event of a outage.   Thanks Pat
 
99 Posts
Feb 14, 2011 01:27 pm
Re: ups backup for solar domesic hot water circulation pump

Have you considered using a PV-powered DC pump?  With a small PV panel, the pump will circulate whenever the sun comes out.
 
99 Posts
Feb 14, 2011 01:37 pm
Re: ups backup for solar domesic hot water circulation pump

Otherwise, you can probably source the individual components and put it together yourself.  You'll need a 100-200AH marine deep-cycle battery (depending on how long you want to provide for a power outage), a 10A 12V battery charger, and a 100-200W inverter (check your pump docs to see what kind of surge to expect and ensure the inverter can handle it).  For this size, the components should be relatively cheap.  Under $500 total.  Just connect your pump to the inverter.  Don't worry about switching between circuits.
 
2 Posts
Feb 14, 2011 02:09 pm
Re: ups backup for solar domesic hot water circulation pump

Thanks, I am not understanding, " dont worry about switching between circuits".  Won't that be a problem when the grid power comes back on?       Pat
 
462 Posts
Feb 14, 2011 02:25 pm
Re: ups backup for solar domesic hot water circulation pump

...or you can purchase a small inverter here at AltE for around 100+ bucks (Go power 1000 Watt or similar). Then you can just plug the differential controller into that. Any deep cycle battery, or 12 volt battery should work. Consideration of how long you need power for should be a thought, as Thomas A. suggested, if indeed power is lost for a long time. Otherwise, the battery can be recharged using a regular battery charger when AC power is restored or use a PV panel and cheap charge controller for year round charging and operation of your HW system and emergency lighting. You may even have enough power from the inverter to operate your boiler for home heating during power outages.
 
26 Posts
Feb 14, 2011 07:22 pm
Re: ups backup for solar domesic hot water circulation pump

Thanks, I am not understanding, " dont worry about switching between circuits".  Won't that be a problem when the grid power comes back on?

Nope.  The load is always plugged into the inverter and the battery is continuously replenished by the charger while power is available.  When power goes out, the battery starts being drained.  When it comes back, the charger charges it back up again.  65W @ 12VDC is roughly 5.5A (rounding up slightly), so a 10A charger will allow you to run your pump and still charge the battery with 4.5A at the same time.  It's true that this is a little less efficient than switching between grid power and backup power, but you'll only lose about 20% in the process (assuming charger and inverter are each 90% efficient), i.e your 65W pump is now effectively 78W, but the benefit is immediate failover without any fragile electronics (which would also suck some amount of power).  And that 13W difference (the amount of a single CFL lightbulb) while the pump is running is insignificant if you're on grid power.

The alternative is a product by APC, Tripp Lite, et al., for twice or more the cost.  A 100Ah battery would run your pump for 9 hours until it is 50% discharged.  You can get a Trojan AGM (sealed) 100Ah battery for $200.  The charger should be another $100-$150.  And the inverter under $100.  So no more than $450 total.  For a commercial UPS solution, you're looking at a minimum of $1000, or perhaps much more for 9 hours of backup power.  Most computer backup systems provide no more than a few minutes of power.  Also, they're still going to be only 90-95% efficient max.

You could also eliminate the inverter inefficiency by changing your pump to a DC model that runs directly off the battery.  And you could eliminate the charger and the battery itself by converting to a PV-driven pump, as I originally suggested.  Since your solar thermal system can only overheat when the sun is shining, a pump that runs only when the sun is shining is ideal.
 

Disclaimer and Disclosure

The Alternative Energy Store, Inc reserves the right, within its sole discretion, to refuse or delete any posting or portion thereof, or terminate or block the access to this forum.

The opinions and statements posted on this forum are the opinions and statements of the person posting same, and do not constitute the opinion or act of the Alternative Energy Store, Inc (AltE). The Alternative Energy Store, Inc does not endorse or subscribe to any particular posting. No posting shall be construed as the act or opinion of the Alternative Energy Store, Inc.

Click here for BBB Business Review

McAfee SECURE sites help keep you safe from identity theft, credit card fraud, spyware, spam, viruses and online scams
Desktop Website | Mobile Website

Share

Click on an icon to share! If you don't see the method you want, hover over the orange "+".

Feedback

What can we do to help you?

Please enter a summary
Sorry, the copyright must be in the template.
Please notify this forum's administrator that this site is using an ILLEGAL copy of SMF!
Copyright removed!!