Dave_eng
After reading reports of overheating and exploding batteries, I decided to move my battery outside the generator enclosure and put it in a marine battery box.
My battery, supplied by my Generac dealer when I bought the unit, is a sealed Delco and impossible to check fluid levels. The Generator display panel shows the battery voltage at 13.2 which seems OK. Is there anything else I should be checking? Can I rely on the generator panel for a voltage reading?
Dave p



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Skip Douglas SkipD
I would suggest that you invest in a decent quality multimeter to read the voltage from your battery. You can also use it for other electrical tests, of course.

Is your propane cylinder large enough? You may want to do some serious research with this [URL="http://www.guardiangenerators.com/PublicPDFs/0172610SBY.pdf"]Generac Generator Sizing Guide[/URL]. Page 9 is where you need to concentrate for this.
Skip Douglas
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d11gnccer
The size of the propane tank caught my eye too.
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Dave_eng
Tank is biggest vertical I could get. It is 30" in dia, approx 40" high. 450 litres. According to the Generac dealer's comment, his customers are using smaller tanks successfully. I welcome further comments if you think dealer was wrong and I need a second tank.
I have an expensive multimeter which will also measure frequency but since I have a problem walking after a spinal injury was reluctant to go and get it in my shop which is some distance from my home. I hate hauling tools back and forth as I have to use two hiking poles to walk and carrying tools is a big problem for me.

Dave p
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Skip Douglas SkipD
Dave_eng;11597 wrote:
Tank is biggest vertical I could get. It is 30" in dia, approx 40" high. 450 litres. According to the Generac dealer's comment, his customers are using smaller tanks successfully. I welcome further comments if you think dealer was wrong and I need a second tank.
I have an expensive multimeter which will also measure frequency but since I have a problem walking after a spinal injury was reluctant to go and get it in my shop which is some distance from my home. I hate hauling tools back and forth as I have to use two hiking poles to walk and carrying tools is a big problem for me.

Dave p
Dave - please read the charts on page 9 of the document I linked for you above.

You need to consider the draw of your generator on the fuel source (up to 294,000 BTU/hour for a 20kW) and the possible ambient temperature in the winter. Considering that you're further north than I am, I think you'll need at least a 500 [U]gallon[/U] (~1900 liters) tank to be able to convert the liquid to gas at the rate you'd need it for a power outage in the cold of winter. Surface area of liquid in the tank is what's critically important here. You'll probably wind up with a horizontal tank.

Your generator can draw about 2.8 Gallons (11 liters) [U]per hour[/U].
Skip Douglas
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Canada_Guy
What area of Canada are you in Dave? I'm in the banana belt of southern Vancouver Island (similar weather and temperatures as Seattle).

On my 14kW unit, I run a bank of 4, 100lb tanks. Only 2 are on at any one time. I did my break-in running 25, 50, 75 then 100% load, each for 2-hours. At that time, the 2 tanks that I was running on were only about 25% full. Outside temp was about 50 degrees F (10C). There was some icing around the bottom of the tank, but the generator didn't skip a beat and supplied full power.

The charts show that there shouldn't be sufficient vaporization on tank this size, at that load and temperature.

I'm not saying to ignore the charts, but I think they are worst case and many generators average output is far less than rated output (mine typically runs about 2 KW except when my water pump hot water tank cycles).
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Skip Douglas SkipD
Canada_Guy;11599 wrote:
Outside temp was about 50 degrees F (10C). There was some icing around the bottom of the tank, but the generator didn't skip a beat and supplied full power.
Have you run your generator at sub-zero (Fahrenheit) temperatures?
Skip Douglas
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Canada_Guy
SkipD;11600 wrote:
Have you run your generator at sub-zero (Fahrenheit) temperatures?


Fair question, no I haven't. The spec. for my generator shows around 220,000 BTU/hr at full load, where my 2, 100 lb tanks at 20% full and 50F show about 150,000 BTU/hr total vaporization between them.

Maybe there is a lot more room for error above freezing, but from the charts, it seems that there is no way my tanks should provide sufficient vapor, but they do.
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phabib
My propane supplier told me that as a rule of thumb you wanted to have 100 gallons of tank for each 100k BTU/h of draw. I wound up with a 500 gallon horizontal tank to ensure that my boilers and generator can both have all the gas they can burn.
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Dave_eng
I live in Ontario near the Quebec and New York State border. It gets quite cold. I know enough to keep the snow away from the propane tank so it can absorb energy from the outside air. My home is heated with an air source heat pump which switches to straight resistance duct heating when it gets very cold. I do not try to run the heat pump or duct heater on the generator. I installed a 38,000 btu gas stove to do most of the heating during power outages and have a few 1,500 watt baseboard heaters in critical areas. Most of the time my generator is not even close to being loaded to 20 KW. The gas stove also draws from the same tank but on a different regulator. I bought a larger generator than I could have nursed by with because I was tired of doing load management when living on my 3,500 watt honda. If the well pump and electric hot water tank want to be on at the same time, fridge, freezer and all lights are on, the the generator just shrugs it off. Periods of heavy load are infrequent and short. I bought my propane tank as I did not want an on going expense by renting it. Having a second tank sitting full of propane represents a lot of money to me now that I am injured and no longer working. However, if the wise members feel I am pushing my luck, I will buy another tank as the last thing I want is emergency equipment which gives up when needed most.

Dave p
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johnc
Don't know much about propane usage. What if you were to shut off your utility electric on a cold day, operate everything in the house as normal for a specified time period. Is there a way to determine the usage? Sometimes charts work fine but actual results may vary. Could be a good starting place?
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HKFever
Dave_eng;11604 wrote:
I live in Ontario near the Quebec and New York State border. It gets quite cold. I know enough to keep the snow away from the propane tank so it can absorb energy from the outside air. [B]My home is heated with an air source heat pump which switches to straight resistance duct heating when it gets very cold.[/B] I do not try to run the heat pump or duct heater on the generator. I installed a 38,000 btu gas stove to do most of the heating during power outages and have a few 1,500 watt baseboard heaters in critical areas. Most of the time my generator is not even close to being loaded to 20 KW. The gas stove also draws from the same tank but on a different regulator. I bought a larger generator than I could have nursed by with because I was tired of doing load management when living on my 3,500 watt honda. If the well pump and electric hot water tank want to be on at the same time, fridge, freezer and all lights are on, the the generator just shrugs it off. Periods of heavy load are infrequent and short. I bought my propane tank as I did not want an on going expense by renting it. Having a second tank sitting full of propane represents a lot of money to me now that I am injured and no longer working. However, if the wise members feel I am pushing my luck, I will buy another tank as the last thing I want is emergency equipment which gives up when needed most.

Dave p

A heat pump in your climate is pushing it with electric resistance second stage heat. I would have gone "Dual-Fuel", meaning a heat pump with a gas furnace backup instead of electric heat. Set the change-over from heat pump to gas furnace at 35F and no more defrost cycle. If you want to run your heat pump to a lower ambient you will need a "Bonnet Sensor" (or control) to shut down the gas furnace when the heat pump calls for second stage or goes into defrost. Also you will have sufficient heat with very little electrical usage when the heating requirements are at their greatest.
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Dave_eng
The heat pump itself is two stage and the resistance heating is an additional two stages. We live in an area with cheap electricity and no time of use rates. Electricity per BTU is cheaper than propane without even considering the Heat Pump's coefficient of performance being greater than 1:1. It is a rural area with no natural gas.

The heat pump will run to -10F although I have set it to switch to resistance heating only at 0F to reduce the wear and tear a little. It has a 10 year no cost for parts and labor warranty.

The defrost is demand based and not time based so the loses when defrosting are not excessive.

I understand your point but the situation is totally dependent on the cost and metering of electricity. I think the energy situation is much different in most areas of the USA and Canada than where I live.

Any comments on my tank requirements?

Dave p
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genme
Dave_eng;11604 wrote:
...keep the snow away from the propane tank so it can absorb energy from the outside air
...and the sun too. Thanks for the good tip. :)
Model 5875, Nexus controller, 999cc Engine, 20kW LP, 2011
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HKFever
Dave_eng;11615 wrote:
The heat pump itself is two stage and the resistance heating is an additional two stages. We live in an area with cheap electricity and no time of use rates. Electricity per BTU is cheaper than propane without even considering the Heat Pump's coefficient of performance being greater than 1:1. It is a rural area with no natural gas.

The heat pump will run to -10F although I have set it to switch to resistance heating only at 0F to reduce the wear and tear a little. It has a 10 year no cost for parts and labor warranty.

The defrost is demand based and not time based so the loses when defrosting are not excessive.

I understand your point but the situation is totally dependent on the cost and metering of electricity. I think the energy situation is much different in most areas of the USA and Canada than where I live.

Any comments on my tank requirements?

Dave p


So you have a two-stage heat pump? What is the "balance point" of your home? Most houses have a balance point of approx. 30F so although yours might run to 0F at what temp does it start calling for your backup heat? And yes, very cheap electric must be real nice. :)
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Dave_eng
Balance point is 0F. Unit is set up so that when heat pump cannot handle the heating load it switches to resistance only. The heat pump and resistance duct heaters never are on at the same time.

Heat pump has a special setting for very cold weather wherein both stages start at the same time to keep the temp of the air being discharged into the home warm.

Dave p
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HKFever
Do you mind me asking which brand and model number of your outdoor unit?
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genme
Dave_eng;11624 wrote:
Heat pump has a special setting for very cold weather wherein both stages start at the same time to keep the temp of the air being discharged into the home warm.
When you say "special setting", do you mean the higher compressor stage, or resistance heat during the defrost cycle, or something else?

The units I'm familiar with are called "2-stage", but in reality 1st stage is the compressor running at roughly 2/3 capacity, and 2nd stage is full (100%) capacity (a Copeland Scroll compressor.) What I am describing is not really 2 compressor stages that run at the same time. But, I have no idea what you have.
Model 5875, Nexus controller, 999cc Engine, 20kW LP, 2011
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HKFever
genme;11627 wrote:
When you say "special setting", do you mean the higher compressor stage, or resistance heat during the defrost cycle, or something else?

The units I'm familiar with are called "2-stage", but in reality 1st stage is the compressor running at roughly 2/3 capacity, and 2nd stage is full (100%) capacity (a Copeland Scroll compressor.) What I am describing is not really 2 compressor stages that run at the same time. But, I have no idea what you have.


It sounds like he has a two compressor setup (Y1/Y2). Some control boards have a jumper setting to allow for both compressors to run in low ambient to pull as much heat as possible from the air and can run the indoor at a lower CFM to raise the discharge air temperature. You are describing Copeland's "Unloading" scroll which is 67% unloaded with a reduced indoor CFM and then 100% fully loaded at full indoor CFM.
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genme
With geothermal heat pumps, the two separate compressor design was not very reliable (per geothermal forums.) I imagine a true 2 compressor air source heat pump would fare worse (due to being outdoors). But I digress.
Model 5875, Nexus controller, 999cc Engine, 20kW LP, 2011
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Dave_eng
Guys
This thread has digressed greatly from my original question on the accuracy of the control panel reading of battery voltage. I appreciate the comments on the size of my propane tank and welcome any constructive comments on my current setup. As for my heat pump, we can debate the relative pluses and minuses of them but the simple reality is I bought it, it is in place and has been running well for three years saving me significant $. If you need details about my heat pump for some legitimate purpose I will gladly provide as much detail as I can.

[email]david.petepiece@sympatico.ca[/email]

As a closing comment on the this thread about heat pumps, I spent 30+ years as a mechanical engineer managing 130 facilities. I have a lot to learn from those who work in the trade but I too did a lot of hands on stuff having my own shop with my my own vacuum pump, electronic leak detector, electronic vacuum guage, refrigeration guages, etc. My decisions surrounding the specification and installation of the heat pump were done with a lot of thought to local energy costs, the stability of rates and if I get sicker, what my wife can easily have looked after.

I hope the last paragraph does not sound like a grumpy old man as the last thing I want to do is disrespect forum members.

Dave p
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HKFever
Dave,
Sorry I took your thread off track, I deleted my replies.
John
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Dave_eng
I checked the battery voltage today with my multi meter. 13.33 volts while the display panel said 13.2.

Dave p
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