[RE-wrenches] tankless hot water and pumping question

Allan Sindelar allan at positiveenergysolar.com
Thu Nov 13 18:53:38 PST 2008


Todd,
They have an integral pressure switch. It's adjustable via a single screw,
but the spread (between cut-in and cut-out) is not.
 
Re Bob's recommendation: my opinion is a bit different. Run a pressure tank,
but I don't see the need for a big one. The pump is cheap and forgiving -
put any tank on it, even a two gallon surge tank. Sure, it'll cycle on and
off, but it's made to do that, as it's an RV pump, basically.
 
The 3.3 gpm is peak, and goes down as pressure rises. Make sure it works
with your choice of tankless heater. I don't know the answer to that.
Certainly a large pressure tank(s) will allow you to exceed the pump's flow
rate until the PT reaches cut-in.
Allan
 
-----Original Message-----
From: Todd Cory [mailto:toddcory at finestplanet.com] 
Sent: Thursday, November 13, 2008 7:24 PM
To: allan at positiveenergysolar.com; RE-wrenches
Subject: Re: [RE-wrenches] tankless hot water and pumping question


Thanks for the recommendation. Does this unit need an external pressure
switch or is that integral? Does these work w/o an expansion tank or will
they cycle on/off excessively set up in a direct pumping situation?

Todd

Allan Sindelar wrote: 

Todd,
The Shurflo 2088-24 (model 2088-474-144) is a reliable and cheap surface
pump; tolerates sediment, field rebuildable (until the motor brushes
eventually wear out, but in this app that could be many years) and retails
aroud $125. About 2 gpm at pressure. Not freeze-tolerant.
Allan


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