# Electrical Engineers!..Check My Work?



## doc- (Jun 26, 2015)

I heat with a wood-burning/gassification furnace/boiler system. It employs a small computer to regulate things (minimal draw on current) a small ventilation fan (?draw; intermittent use-- 6 hrs/d) and two water pumps-- one to circulate heated water to the reservoir tank and one for general circulation thru the house-- those two are each 1/6th HP (~125W)-- They each are actually running about 6 hrs /day....I figure I need ~ 125W x 2 x 6hr = 1500W per day + whatever the fan takes....

Worried about the grid going down long term, I'd like to install an urelaiable power source. ( I can use a gas powered generator for short term outages, but that won't work for long term or if gasoline is unavailable.)...Here in WI, we rarely see the sun from Oct to April, so PV is out...That leaves Wind...According to the NWS, around here we average wind speeds of 17mph thru the winter.

A small wind turbine-- rated 400W at wind speed ~ 30mph can be had a cheaply as $110 (I wonder how much on-going bubble gum expense it takes to keep it held together?) and prices can get up to $600 for 400W units (are they better or just more expensive?)....I understand that Power generation increases/falls off with each doubling of wind speed by a factor of 8, so that 400W unit would only produce 50W @ wind speed of 15mph....50W x 24 hr = 1200W/d.

Two questions-- are my figures above so far correct?...and could two of these small units be put to work in tandem to generate 2400W/d and then use, say 4 standard car batteries (each 12V & 50 amp = 600W) to hold 2400W?

I figure a set-up like this would only cost <$1000-- pretty cheap way to ensure my heating.


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## JRHill02 (Jun 20, 2020)

I don't use wind but know from the experiences of others over the years that inexpensive wind turbines are quite prone to failure before they pay for themselves. I am sure someone is going to come back and say they have had wonderful production - great.

Did you ever make any progress with this project?

BTW, as an alternative to wind I recently found out that you can order a 100 watt solar panel and controller from Home Depot for <$90 and they are polymorphic panels, not the mono panels like in the Harbor Freight kits that are inefficient and degrade quickly (over years). They also have some higher wattage options and attractive price/watt for a kit.


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## furnacefighter15 (8 mo ago)

The battery and inverter outputs need to be sufficiently sized to handle peak demand loads.

On a pump, thats inrush current.

125 watts sounds low for 1/6 HP

I looked up a Bell Gosset pump with 1/6 HP motor its more like 1.9 amp 

Which is more like 220 rated watts.

Your operating point will likely be lower then then that. But probably not 125 watts.

But the bigger issue is in order to get the motor running, the locked rotor inrush current is typically 6 times the rated running current few about 3 seconds.

So that 220 watts becomes 1320 watts. 

So I would want the batteries and the inverter surge capacity at least twice that for reliability.

You can limit your total capacity requirement by starting 1 motor at a time.

If your boiler has an AC motor, same rule applies.

Personally I would look into gravity hot water heating to eliminate your pump requirements altogether.


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## doc- (Jun 26, 2015)

The two motors work independently, each controlled by thermostats. Over-riding control of the furnace circulartor is not feasable. I do use a timer to contol the general circulator pump because floor temp goes down too low before air temp falls enough to trip thermostat.

Cost of gravity fed circulation would be prohibitive, even if control mechanism were easy to devise-- 300 gal water reservoir and a one story house. (How do you power pump to get return water back to the elevated reservoir? Larger pump than one needed for level circulation. Doesn't make sense.)

1/6th HP = 123 W Online Conversion - Energy Conversion A = V/W = 110/123 = 0.9amp.... W = V/A= 12/0,9 = 13.3....13.3 x 6 = 80 W. ...Car batteries have "cold cranking amps" in the hundreds....These pumps are only the size of my fist.

Solar not feasable in my location-- Winter has <3 hrs per day of "sun"- which itself is a euphamism in this usually 100% over-cast sky. I could cover 10 or 20 ac with solar cells to compensate just to run my little pumps 6 hrs a day. Won't work.

I realize the little wind turbines may have quality issues. The cheapest ones are ~ $120. The expensive ones are $1500....I can't see the bearings (the only part that wears) being $1380 "better" than the cheapies...I bet there's no difference at all in the turbine you get, except the price.

I can afford to blow $120 on a proof of concept experiment.


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## furnacefighter15 (8 mo ago)

This is where the 1.9 amps came from.









102210 - Bell & Gossett 102210 - 1/6 HP, HV NFI Circulator Pump


Bell & Gossett 102210 - 1/6 HP, HV NFI Circulator Pump - <b>Overview</b><br><br>The Series 100 is a leader in applications such as hydronic heating and domestic hot water circulation, with over 10 million units installed. Series 100's three-piece, oil lubricated design provides for easy field...




www.supplyhouse.com





I do boiler work and HVAC for a living as a pipe fitter, so thats why the watts sounded low to me from the jump for 1/6 HP

You have the pumps. Just go look at the rating label. Thats what you will have to base your calculations from.

If your just looking to have heat for during a power loss, you can use batteries alone for that, no need for a turbine.

Let the grid charge the batteries.

If you are looking to power your needs indefinitely, then you will need to size the turbine for nearly peak running load as-well.

Manual operation of pumps would be: 

Power goes out- you shut down all the devices, transfer over to your batteries, manually turn on each item one by one. If your not willing to do that, then you will not only need bigger batteries and inverters, you will also need an automated power transfer switch.

Gravity heating uses thermal buoyancy to drive the heat up, and gravity to bring it back to the boiler.

Boiler needs to have some mass, like cast iron to handle low flow rates. 

The way it works is the heat source is at the bottom of the system, all the heat emitters (radiators or baseboard, etc…) would be above that. Add heat to the boiler, the water will begin to churn, the higher energy water in the boiler will naturally rise, the cooler water away from the boiler will naturally fall to take its place, once it gets going the flow can be nearly as much as with a pump.

In fact, its such a natural phenomenon that we often have to add means to prevent it from happening on modern systems.

No large elevated tanks required. That would be for shower water.

And speaking of, a well pump is a significant load too, assuming you dont have city water.

This is from a quick search of : “Gravity boiler heat system”









WHAT IS A GRAVITY HEATING SYSTEM? - Gravity Convection Heating Revisited - Boilers On Demand


What is a Gravity Heating System? A century ago all water-based hydronic heating (hot water and steam) employed the natural gravity convection attributes of heated water and water vapor (steam) to distribute energy. NO DISTRIBUTION ENERGY WAS REQUIRED! They were effectively single-zone systems...



www.boilersondemand.com





The first picture is the general layout, then next is some sales pitch thing - feel free to ignore the sales pitch.


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## JRHill02 (Jun 20, 2020)

doc- said:


> Solar not feasable in my location-- Winter has <3 hrs per day of "sun"- which itself is a euphamism in this usually 100% over-cast sky. I could cover 10 or 20 ac with solar cells to compensate just to run my little pumps 6 hrs a day. Won't work.


I understand the above. We are in the rain shadow of the Cascades and for 9 months of a normal year get by with almost 100% solar. For the other 3 months up to the solstice and afterward not only are we impacted by clouds and snow but also the sun gets below the tree tops at the top of the canyon. So the generator spins a lot during those times to charge batteries

The solar I mentioned was only to point out how inexpensive it has gotten. Of course you need to size the system for the needed work to be done.


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## doc- (Jun 26, 2015)

furnacefighter15 said:


> This is where the 1.9 amps came from.
> 
> 
> 
> ...


Thanks for the references....apparently a well disguised bit of advertizing hocus-pocus. A heat siphon works using the bouancy principle to propel water against gravity. That works for small systems, but a large house system has 100 gal at a time to move and requires an externally powered pump-- called the dT ECM Circulator in that article.

We won't bother discussing the costs of converting the plumbing...

...and I'm planning for the complete loss of grid power. As I originally said, I could just use an ICE powered generator for short term grid outages, as long as fuel were available....Batteries charged by the grid would only work for one discharge period. (5 full batteries would only last one day.)


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## doc- (Jun 26, 2015)

this is my pump-- they don't seem to give the electrical specs UPS2


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## furnacefighter15 (8 mo ago)

1/6 hp grundfos, Id guess its this one:



https://s3.amazonaws.com/s3.supplyhouse.com/manuals/1297872762860/47830_PROD_FILE.pdf



197 watts peak

If your actually interested in gravity heating, here is a much better resource. In fact this is a great resource for all things boiler, also a very good forum on the site.






How Gravity Hot-Water Heating Systems Work


In this video, Dan Holohan teaches us about gravity hot-water heating systems. Classic gravity heating is both the simplest and the most complicated system of all. It’s simple because it has few moving parts.



heatinghelp.com





May not be all that practical to do in a hurry, but would be possible, and sustainable in the long term.

May be much simpler then you realize.

I run into all the time at work, spaces overheating because of gravity flow on zoning systems. 

Really depends how your pumps and piping are configured. 

The grundfos pumps often have an internal spring loaded check valve to prevent gravity recirculating of water.

A simple way to find out if in a pinch you can getaway without would be to install a spool pipe inplace of the pump, activate the boiler and see if you get heat where you need it. - only try it if the boiler you have has a good amount of thermal mass - IE cast iron. 

As far as powering what you got.

200 watts running load per hour, and 1200 starting watts per pump would be a safe assumption of requirements.


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## backwoodsman7 (Mar 22, 2007)

doc- said:


> 1/6th HP = 123 W Online Conversion - Energy Conversion A = V/W = 110/123 = 0.9amp.... W = V/A= 12/0,9 = 13.3....13.3 x 6 = 80 W.


123w is close enough for 1/6hp running watts, but you have your first formula backwards. And it's only 110v when the circuit is overloaded, but maybe good to use that for calculations to provide a bit of a margin. So that gives 1.12A running current. 197w peak is 1.79A at 110v; that's the current you need to plan for.

Not at all sure what you did with the rest of those calculations, but 80w at the end when you had 123w at the beginning tells you you need to take a real close look at your figures before you start buying or building anything.


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## doc- (Jun 26, 2015)

furnacefighter15 said:


> 1/6 hp grundfos, Id guess its this one:
> 
> 
> 
> ...


Thanks for the ref...I couldn't it find it again.

For ther gravity system..am I right that it still requires an electric pump? If so, it doesn't solve any problems.



backwoodsman7 said:


> 123w is close enough for 1/6hp running watts, but you have your first formula backwards. And it's only 110v when the circuit is overloaded, but maybe good to use that for calculations to provide a bit of a margin. So that gives 1.12A running current. 197w peak is 1.79A at 110v; that's the current you need to plan for.
> 
> Not at all sure what you did with the rest of those calculations, but 80w at the end when you had 123w at the beginning tells you you need to take a real close look at your figures before you start buying or building anything.


Thanks for pointing out my error with the formula.

The pumps run for ~15 min each hour x 24 hrs, so ~2A x 6hr = 12 amp-hr x2 pumps per day = 24 A-hr of juice required each day....a car battery holds ~50 amps...One should do it?

Re; 123 w VS 80-- The 80 was derived (using the wrong formula) based on a 12 V battery. It should be W/V = A .....if we know the pump draws 123W and the battery is 12V, then 123/12 = 10A; for 200W max draw, then 200/12 = 17A...The surge needed 4x each hour as the pumps start up is only for a second or two, so minimal extra draw from the bettery supply, but can a car battery with 600-1000 CCA supply it?


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## doc- (Jun 26, 2015)

edit not working ^^^ There's still a discrepancy-- If the 2A/pump number is right, then daily use is 24 A-hr, but if the 10A number is right, then it's 120Amp-hr....Where's the mistake?


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## furnacefighter15 (8 mo ago)

A true gravity heating system uses no pumps.

Prior to advent and proliferation of electricity, boiler systems were either steam, or hot water.

Hot water got real traction because for a period of time, there was a 50/50 shot that steam boiler would explode (typically from dry firing, being superheated cause the coal was still burning, then water would suddenly be introduced - expand at a rate of 1200 to 1 and kablamo)

Like I said before, you system may work without the pumps at all, but it also may not.


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## furnacefighter15 (8 mo ago)

doc- said:


> edit not working ^^^ There's still a discrepancy-- If the 2A/pump number is right, then daily use is 24 A-hr, but if the 10A number is right, then it's 120Amp-hr....Where's the mistake?


Find total daily watt hours

Divide by source voltage. That tells you amp hours


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