Inverter Requirement to Run AHS S130 Coal Gun From Batteries

I'm considering installing a battery back-up with inverter to power my AHS Coal Gun in the event of a power outage situation. What is the maximum wattage (or amperage) of brief surge I might encounter if the unit fires with both the 1/2 HP fan motor and the 1/20 HP (I believe) ashing motor initiating simultaneously?

The unit I purchase would (in addition to the above) also need the additional capacity to open and close my 4 Taco zone valves, power my Taco 4 zone valve control module, and power my Taco 1/20 HP circulator. These items would be powered off of one receptacle from the inverter and the boiler would be powered from another receptacle on the inverter (but either way they are all pulling current off of the same inverter at the same time).

Will a 2000 Watt rated pure sine wave inverter with momentary (1/2 to at most 1 second) 4,000 Watt surge capacity be sufficient? Or would something more along the lines of a 3000 Watt pure sine wave inverter with 6,000 watt momentary surge capacity be needed?

If 1/2 HP is about 372 Watts, and the fan motor is about 70% efficient, then it should be drawing roughly a steady 531 Watts when running. Should I consider a factor of up to 5X for the start-up surge?

5 x 531 Watts = 2,655 Watts at the peak of the start-up surge

Does this sound like its in the ballpark, or would this only be valid for a motor like mine starting up with no load on it, and would my brief surge potentially be higher than this due to the load?

Or might the surge factor be more along the line of 3X, in which case the maximum brief surge would be only about 1,600 Watts?

I have the boiler on a standard 120VAC line with 15 amp breaker, and in three years it has never once tripped the breaker, but should I assume that typical residential use breakers are slow enough to permit a brief surge of greater than 15 amps (1,800 watts)?

Seeing 20 times, but in reality I don't think it is that much. 1.6 times the Locked rotor current of the motor. Rig up a test fixture and see what fuses blow, fast or slo blow.

https://en.wikipedia.org/wiki/Inrush_current

http://www.cooperindustries.com/content/dam/publi ... rrents.pdf

Wow! 20X would be approaching 11,000 Watts for my 1/2 HP motor.

I just found this link with typical surges of all sorts of things and it says a typical A.C. motor of 1/2 HP has a surge of about 3X.

http://www.generatorsales.com/wattage-calculator.asp

It shows a 1/2HP furnace fan which draws 875 continuous Watts surging to 2,300 Watts. Further down it shows a 1/2HP motor which draws 650 continuous Watts surging to 1,800 Watts.

I'm now thinking that an inverter with 3,000 Watts of honest surge coverage might even suffice. There are 1,500 Watt continuous inverters making the claim of handling 3,000 Watts of brief surge. The trick may be in finding one that is honest about both its continuous output and its surge capability.

I'm confused...batteries being used or not?

McGiever wrote:I'm confused...batteries being used or not?

Not yet. Need to size the inverter to handle continuous demand and surge demand first. Then consider the batteries second.

After a few years of operation, I've noticed that my home (which can get by on about 480 KWH of electricity per month on average during the warm months when we're not running any air conditioning and the boiler is only being called upon to provide DHW) requires 540 KWH per month for the months of December, January, and February. From this I can tentatively conclude that the boiler draws on average roughly 60 KWH per month (540 - 480 = 60) to heat our home. That averages out ~2 KWH per day, or ~2,000 Watts per day to run the AHS Coal Gun boiler when the T-Stats are calling.

When we hit -17 degrees for one single day I guesstimated that the boiler ran 1/3 of the time to perhaps 1/2 of the time on that day. If the fan and ashing motors draw a combined 800 Watts per hour, then for every 1/3 of an hour to 1/2 of an hour they were pulling on average 267 Watts per hour to 400 Watts per hour. Over 24 hours that comes to about 6,400 Watts to 9,600 Watts consumed by the boiler for the coldest day of the year. Somewhere between 6.4 KWH and 9.6 KWH of electricity are needed to keep the boiler running (and ditto the zone valves functioning, and the circulator cranking) and the home warm when it hits a low of -17 outside.

So what kind of battery bank is needed to meet that demand?

Sounds like my thought processes of a few years ago. How many KWH are you going to keep in reserve. So a backup for 1 hour, 1 day , 1 week it gets horrendous. Remember to factor in battery regeneration and many other things. I decided it was not worth it and hence my push to run the house without power. Who wants to buy my Lister 6/1s.. Candles and a baseburner and if absolutely necessary a Victrola.

Rob R. wrote:So what kind of battery bank is needed to meet that demand?

A battery bank that is huge! Assuming that as a rule you only ever want to discharge a deep cycle battery bank to 50% of full charge, and using a midrange one day demand for the coldest day of the year of 8,000 Watts required (8 KWH), and assuming a 24V inverter I get:

8,000 Watts / 0.5 (for 50% discharge) = 16,000 Watts worth of batteries

16,000 Watts / 24 Volts = 667 amps worth of batteries. Multiply times 1.1 for the typical 90% inverter efficiency and you get 734 amps.

3 parallel wired banks of 245 amp rated 6 volt deep cycle batteries, each bank leg with 4 batteries (since 6V x 4 = 24V) would do it. The 3 banks in parallel would deliver the required 734 amps (3 x 245 = 735 amps). 12 batteries total. For average winter days this should provide up to 4 full days of boiler operation on batteries alone, but on the coldest single day in the past 10 years it would only (perhaps) provide 1 full day of heat.

The first battery seen on this website would come close. http://www.altestore.com/store/Deep-Cycle-Batteri ... Acid/c435/
12 x $200 = $2,400 for the batteries.

coalnewbie wrote:Sounds like my thought processes of a few years ago. How many KWH are you going to keep in reserve. So a backup for 1 hour, 1 day , 1 week it gets horrendous. Remember to factor in battery regeneration and many other things. I decided it was not worth it and hence my push to run the house without power. Who wants to buy my Lister 6/1s.. Candles and a baseburner and if absolutely necessary a Victrola.

That's why plan A is a hand fired stove. if it takes that much battery power just to keep the boiler running, imagine what it would take to run the whole house on batteries.

That's why plan A is a hand fired stove.

Smart man. Or go to Lowes or HD and sign up for the solar program. That way when the power goes down in January in a snowstorm you would only need 5 cubic miles of PV panels to run your boiler. Of course unless you use superconducting wires, the line losses might mean you could never get enough power to the boiler. Chit another bunch of stupid liberal ideas down the c rapper.

I just looked up a 2000 watt Honda generator. It would run over 2 weeks straight on a 55 gallon drum of gasoline.

I just looked up a 2000 watt Honda generator. It would run over 2 weeks straight on a 55 gallon drum of gasoline.

So you would have to have 55 galls on hand when the SHTF. You can't store 55 galls as it will degenerate. Stock rotation would be theoretically possible but troublesome. If you have contacts perhaps the local airport might help out with ethanol free gas even though it is illegal. How much gas will your insurance company allow you to store. Are you sure you don't want a hand fed and be done with it.

Not getting into this thread, but see this, hope it may help if you go this way, and for what its worth.....

http://www.smartgauge.co.uk/batt_con.html

Get a whole house propane generator and this will solve your issues:-) A easy fix! No worries about the sine wave issues too.