March pumps vs. battery voltage [RE-wrenches]

Windy Dankoff, Dankoff Solar windy at dankoffsolar.com
Thu Feb 12 09:12:41 PST 2004


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Wrenches,

RE: previous thread   Voltage limiting w/ C40 [RE-wrenches]

I asked our local off-grid hydronic/DC guru Bristol Stickney about 
his experience. He says:

>I have never experienced this problem with any of the March pumps I have
>installed. Some of the other email suggests that this may be a 
>problem specific to the
>High Speed (HS) models.  I don't use many of these, so don't have a large
>sample to talk about. But the few I have installed never had this problem.
>All I can say is, to my knowledge, it never happened to me.  -- Bristol


All manufactured products vary within (or sometimes beyond) 
tolerances. It's quite possible that the HS pumps that were 
decoupling had slightly weak magnets, and/or slightly extra rotor 
friction, and/or were in a very low-friction fluid loop that tends to 
add to the motor's torque load as the flow increases. -- These 
factors I explained previously.

So this whole topic may be moot. It might be best to install the 
pumps straight, and jack up the voltage to max-ever-expected and see 
what happens. Remember, de-coupling in no way harms the pump or motor.

One thing I hate to see is a simple DC load get fed through an 
unnecessary electronic converter just to solve a dubious problem -- 
or through some otherwise non-associated device (inverter relay) that 
make the system complex and hard to decifer for a heating technician.

Windy

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