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RE Re: heating cables & pump heat effects

James Purchase had written:
"- I was using an Eheim pump capable of
1200 L/hr and I measured the flow thru the manifold - I lost 90% of the
rated flow to friction and back pressure. That energy had to go
my guess is that it became heat."

For what it's worth, this prompted a query to Eheim, who said in reply

a 7 watt pump on a 30 gallon tank will increase the temperature by 1
degree C or 1.8 degrees F--other things being held constant.  Thus, a
2213, which consumes 8 watts  will increase a thirty gallon tank by a
little more than 1 degree C.  A 25 watt pump/filter will increase the
temperature by an additinal 4.37 F.  A model 1250, at 28 watts, will
raise the 30 gal. tank an additional 5.1 degrees F above the temp with
a 2213.

I presume that Eheim is assuming the rate of heat loss from the tank is
remaining virtually unchanged and is stable without any pump running at
all.  In winter months with ambient temperatures of about 68 degrees F,
those low amounts of added heat would probably be lost as fast as they
entered the system.

In a 130 gallon tank such as you used, the figures would scale down to 
less than one fourth the above--assuming that the rate of heat loss
from the tank was the same for a 130 gal. and a 30 gal.  (Actually, the
larger tanks tend to conserve heat better due to thick glass and a
higher ratio of mass to surface area.)

Scott H.

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