On demand and storage tank pump problems
Last Post 05 Mar 2015 07:50 PM by jonr. 2 Replies.
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hayseedUser is Offline
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14 Feb 2015 10:59 PM
Hello everyone I am new here and a do it yourselfer. My dillema is pump problems in a loop from the Noritz tankless 195,000 btu which has fed my house slab and large garage.................. The noritz will make 3 us gallons/minute all day into a bucket but when I run a closed loop from heater to tank and back I appear to only flow about 1 1/4 gallons. I am running what I consider a huge pump( grundfos ups 26-99 fc ) and would like to use the output from the noritz and use the tank as heat storage.............Then draw down the temp 10 or 15 degrees and then have the noritz kick in. .............................................................................................. Can someone advise as to what type of head preassure is created when when going against the check valve ( city preassure is about 60 lbs ).............................................................................................. When I fudge the check valve open I seem to achieve a much better flow in the loop but can not leave the check valve open as it creates cold water in the domestic supply to the house.................................... ( is there a different style of pump that can be used to create more pressure? ) ................................................................................................ I decided to add a 60 storage tank with 2- 40 foot 1 1/4 dia coils, the coils are to feed the house and garage slab individually, as I am running friendly anti freeze in the garage as I shut it down when I am away for several months in the winter ( infrared tube takes over ) but there is potential for freezing, (up till now I blew out the lines with compressed air.) the system is 7 years old and previously did not have the tank. ................................................... Also I want to keep the tank water fresh so I would like to use the water on the domestic side as much as possible

Attachment: tank_and_tankless.jpg

ronmarUser is Offline
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04 Mar 2015 09:26 AM
The grundfos is not a positive displacement pump, and your checkvalve is on the suction side of the circuit. Any pressure differential it may be building could be absorbed by the exp tank. Relocate the circ pump to the blue line in the drawing just upstream of the check valve. That should improve flow thru the circuit as teh pump output force would be directly applied to the check valve. You could also possibly use a solenoide actuated valve in place of the check valve. Wire it so the valve only opens when the pump is on. That would probably give you the best flow...


jonrUser is Offline
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05 Mar 2015 07:50 PM
A swing check valve will have low resistance.


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