Heating system power backup

Old 01-12-23, 12:12 PM
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Question Heating system power backup

I am trying to set up a battery-based backup for my hot water heating system. A lithium battery power station will supply the power via a transfer switch, providing a few hundred mAmps AC for the gas control valve and thermostat transformer. The problem is the B&G series 100 circulator pump (#106189). When the pump is running it draws 1.75 amps, but I don't know how much the pump draws in order to start--I understand it could be more than 5 times the running current. Can anyone tell me how much this pump draws to start so I can size the power station accordingly?
Old 01-12-23, 05:16 PM
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What is the output rating of the lithium "power station"? If you want to run the circulator pump, you will probably need a lead-acid storage battery feeding a DC-AC inverter.
Old 01-12-23, 05:32 PM
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Welcome to the forums.

I was trying to calculate and I came up with 4.4 A
I found a motor close to it in the chart and it say 5.1A.
Old 01-12-23, 05:51 PM
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mif2000: The electric load and cost of a battery backup will be far lower, if first replacing power hungry, stone age B&G Series 100 with modern Grundfos Alpha2 circulator with high efficiency ECM motor.

A general rule is while starting AC motor use 3 to 4 times running Amps!!!

Alpha2 set up with 12O volts always on (.65 A max) senses load change and ramps up to maintain pressure flow as various zone valves open and close. Has live digital displays of actual GPM flow and electric watts. Also eliminates need for zone controller.


A new B&G Series 100 costing $515 + is more than a Alpha2 $231, with same capacity and many great cost saving features. Replacing original 30 year old technology part is often far more expensive than modern technology improved units with many benefits. .https://www.google.com/search?client...UTF-8&oe=UTF-8

Last edited by doughess; 01-12-23 at 08:21 PM.
Old 01-13-23, 07:44 PM
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I would agree with DH about changing the circulator to a variable speed ECM circulator, much less draw on batteries. Just beware the B&G could move much water than the wet rotor circulators dependent on the system. Make sure you size the circulator to your system.
Old 01-13-23, 09:17 PM
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The B&G 100 is over capacity for most typical homes. Because it fixed speed is constant waste of electricity.

The lower capacity Taco 007 has far even less GPM and is widely used for typical homes.

Alpha2 sense system load, automatically adjusting GPM to actual need, optimizes performance and lower electric costs. The “auto sense control” ends sizing problems when selecting fixed GPM and selected speed pumps.

DH home has very demanding system with 200 feet, 1” copper, feeding 12 elements with mono-flow tees thru 6 zone valves . Original B&G 100 failed and was replaced with Alpha2

DH is paranoid about failure on cold, winter, snowbound night, keep a spares of everything, including Alpha2. If burner control locks, out sounds battery powered alarm. Better than waking up to cold house.

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