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to pandora
Re: Anyone have a suggestion for standby whole home generator?said by pandora:We will have 2 4 ton heat pumps running 4 A/C zones.
The electrician has suggested a 20K unit, guess I could ask him for more information about why he made this suggestion.
I remember from a different thread now... a 4-ton unit will suck some 3000-4000W depending on temperature. Problem is that you'll have strips for backup heat IIRC and at 10000W each you may be already over the power of the generator. In all honesty I'd use the propane for backup heat and then a 10kW generator will do. Or if you *really need* to run both units in summer for AC then the 20kW will insure that both can run. |
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 IowaCowboyLost in the Supermarket
Premium Member
join:2010-10-16
Springfield, MA ·Comcast XFINITY
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to Jack_in_VA
said by Jack_in_VA:My august usage was 830 kWh. Not bad for around 1500 sq/ft at 75 deg F.
My usage was 836 kWh last month for a 936 sq ft house. Average temp was 73. One of the problems I have is my bedroom is on the east side of the building (takes the morning sun) and the duplex has wood siding that is stained a dark color along with a black roof (absorbs the heat) so I am running the bedroom A/C constantly (even when it is mild). The gadgets I have in the bedroom (cable modem, computer, DVR, HDTV, and a printer) also generate heat. If I bought this building, I would get a lighter color roof and either paint the siding white or put on new vinyl siding that is a lighter color to reflect the heat. |
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pandora
Premium Member
join:2001-06-01
Outland |
pandora to mix
Premium Member
2012-Sep-21 10:29 pm
to mix
said by mix:How big of a battery bank could you build to power your computer equipment for the price you are paying for a generator, propane tank and accessories?
I have absolutely no idea. I have no idea how it'd be connected, what sort of inverter would be needed to manage 20KW, or how long batteries would last or how to maintain them. I suspect there could be hazardous material issues as well. If battery banks worked on residences, we'd be seeing them sold by the box stores, not stand by whole home generators imo. |
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| pandora |
to Jack_in_VA
said by Jack_in_VA:Let's calculate this:
3 gal/hr x 24 hours = 72 gal x $4.00/gal = $288/day
$288/day x 30 days = $8640
You know Mr. Matt I'm not sure I could stand much of that financially.
Our longest power failure lasted 7 days. Our cost of propane in small quantities is about $2.99. Larger quantities and owning your own tank lower the cost substantially. Consider $3 per gallon times 3 gallons per hour times 24 hours per day, $216 per day? Times 7, $1512. I'd pay that than have my family freeze. It depends on what you value and how much you can afford. According to Lowes, fuel consumption at full load is 3 gallons per hour. - » www.lowes.com/pd_36_0__? ··· =3231536 at half load Generac literature indicate use of slightly more than 50% of full load - » www.google.com/url?sa=t& ··· 3ss3r_OgIf my consumption doubles to 5000 kwh per month (which it won't, better efficiency heat pumps, better insulation, residing with R9.6 sheathing is being installed. I get an average of about 6.4 KWh per hour (averaging out over my monthly usage, assuming almost double use). The load would average less than half on the unit on average. Which likely indicates something under $500 per week assuming there is a decent discount for providing my own propane. $500 is less than the cost of groceries lost in the last long outage (we have 2 large freezers, and a large fridge with freezer). It all depends on what we value and can afford. |
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 nunyaLXI 483
MVM
join:2000-12-23
O Fallon, MO
1 recommendation |
to pandora
Also remember that generators do come with an "off" switch. You don't have to run the thing 24/7 unless you feel like it. During the day, it may not even be necessary.
If computer / network equipment is an issue, a good UPS can allow you some downtime for the generator (maintenance). Since I've consolidated to virtual servers and low power PC appliances, my Minuteman can keep everything up nearly 2 hours. Granted, it is more of a commercial type unit.
Around here, we are looking at $2.10-2.20 / gal of delivered propane. |
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pandora
Premium Member
join:2001-06-01
Outland |
to IowaCowboy
said by IowaCowboy: I don't know what part of the country you live in but if you lived in the Northeast (New England states/New York), your electric bills would be through the roof. I live in Massachusetts and I pay twice as much per month for my side of the duplex than my former neighbor pays for a single family home in Iowa. Connecticut has even worse electric rates than we do in Massachusetts, and Maine is more reasonable. Of course I've changed almost every light with CFL/LED light bulbs (the only place I don't use CFL light bulbs is the full bath because the steam from the shower murders CFL bulbs so I use traditional incandescent light bulbs there) and my electric bills are still high.
Connecticut Light and Power (and I suspect it's mirror image on the other side of the state) has created a virtually incomprehensible billing system. We do get to pick our electric provider, but CL&P charges for transmission through it's wires. The charges for CL&P are higher than the electric rates. The "generation rate" I pay is about 7.2 cents per KWh. However, transmission, and various taxes and mystery fees raise that to nearly 20 cents per KWh. As I just lowered my rate to 7.2 cents from 8.0, I won't be able to compute the new rate until a bill comes. However it'll be in the range of 18 to 20 cents per KWh. Connecticut is very NIMBY. Some of our richer towns, refused to have new overhead lines installed (an eyesore) the cost of burying the lines is many times higher than running them overhead. We are assessed a monthly cost for the burying of cables, the nearest of which is about 25 miles from my home, and none of the buried cables provide power to my town or any town near me. We also have some sort of federal punishment fee added to our bills due to failure to generate locally. I believe this is about 8% of the transmission bill. Nobody will permit any new electrical generation in any town. The last effort I recall was in New Milford, it was to be a natural gas plant with oil as a backup in the event of loss of natural gas. Turns out the location (on top of a hill) was bad, because the slightly higher CO2 could run down into a nearby river and deprive the poor fish of air. To the best of my recollection no science was ever presented to prove that true, but it is the sort of nonsense that happens here all the time. Everyone wants great infrastructure, but nobody wants it near their home. |
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to nunya
said by nunya:Also remember that generators do come with an "off" switch. I'm planning a whole house unit with a MANUAL transfer switch so that I can, on a power failure, set breakers where I want them (so some can be OFF of course), before switching-on the generator. If I have a 200 amp service, and have had that 200amp breaker TRIP, what is the likely kW I'd have been drawing when that happened? Obviously I have a mix of 240 and 120 loads so is the answer simply "somewhere between 24kW and 48kW (200 x 120 vs 200 x 240)? |
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southla to pandora
Anon
2012-Sep-22 10:54 am
to pandora
I have been researching to make the same decision. I currently have a portable with manual transfer switch that works well (60 hours in 6 years, been lucky), but chasing gas is more than I want to deal with as I get older (propane is not allowed). I assumed that I would go with Generac since that is largely what I see, however after deciding on a dealer that I am comfortable with, they recommended and I ended up deciding on a GE (Briggs and Stratton) 20KW air cooled. The warranty is 5 years (or 1800 hours) parts and labor as opposed to 3, and the unit is better engineered (from a mechanical / maintenance point of view) than the equivalent Generac in my opinion. I have other equipment with the Vanguard engine have never had a problem. I just pulled the trigger and the unit is not yet installed, so I can't comment on operation.
I will have it installed where I can still use my manual / portable as a backup in case a live oak takes out the natural gas line.
I did note some issues in reviews, but largely they were due to not being able to get service (big box purchases), using a a dependable dealer should eliminate that. In the recent storm, several friends and acquaintances had Generacs that didn't work and had the same issue, couldn't get service.
Like I told my wife, it's a Ford / Chevy decision, but my comfort level was higher in the end on the GE. |
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to IowaCowboy
said by IowaCowboy:said by pandora:Our last electric bill for the older (smaller home, 3,200 sq ft) was about 2600 KWH over 28 days. 93 KWH per day, 3.8 KW per hour if all use was average. I don't know what part of the country you live in but if you lived in the Northeast (New England states/New York), your electric bills would be through the roof. I live in Massachusetts and I pay twice as much per month for my side of the duplex than my former neighbor pays for a single family home in Iowa. Connecticut has even worse electric rates than we do in Massachusetts, and Maine is more reasonable. Of course I've changed almost every light with CFL/LED light bulbs (the only place I don't use CFL light bulbs is the full bath because the steam from the shower murders CFL bulbs so I use traditional incandescent light bulbs there) and my electric bills are still high. 5000 square feet is going to cost a lot to heat/cool. We have 2700 here and our electric bill averages around $150 in the summer. I don't do any budget billing nonsense because I like having a lower bill in the winter (we use wood and propane) and like to see what effect rate hikes have. |
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IowaCowboyLost in the Supermarket
Premium Member
join:2010-10-16
Springfield, MA ·Comcast XFINITY
1 edit |
said by fifty nine:said by IowaCowboy:said by pandora:Our last electric bill for the older (smaller home, 3,200 sq ft) was about 2600 KWH over 28 days. 93 KWH per day, 3.8 KW per hour if all use was average. I don't know what part of the country you live in but if you lived in the Northeast (New England states/New York), your electric bills would be through the roof. I live in Massachusetts and I pay twice as much per month for my side of the duplex than my former neighbor pays for a single family home in Iowa. Connecticut has even worse electric rates than we do in Massachusetts, and Maine is more reasonable. Of course I've changed almost every light with CFL/LED light bulbs (the only place I don't use CFL light bulbs is the full bath because the steam from the shower murders CFL bulbs so I use traditional incandescent light bulbs there) and my electric bills are still high. 5000 square feet is going to cost a lot to heat/cool. We have 2700 here and our electric bill averages around $150 in the summer. I don't do any budget billing nonsense because I like having a lower bill in the winter (we use wood and propane) and like to see what effect rate hikes have. For our 936 sq ft unit, the electric bill in the summer (running two room air conditioner units) is about $90 per month. In the winter, it usually goes over $200 per month and has been as high as $350 one month in January of 2004. There is a built in air conditioner (through the wall unit) provided by the landlord but the unit is so old (dates back to 1988, when the building was built) that we use a portable air conditioner in the living room (that is so much cheaper to run). In the bedroom, I have a window unit. As for the discussion on generators, I bought a generator during the October snowstorm and I did not have to use it as power was restored a few hours later after being out three days. I am in the process of installing a manual transfer switch in the main panel. I have the switch installed and I just need to wire the inlet box. I am powering essential circuits (downstairs heat, lights, fridge). Sure beats using a so-called "suicide cord" to backfeed a generator into the house (as those will burn the house down, fry the appliances/gadgets in the neighbor's unit, or fry a utility worker). I make an effort to do things properly and in a workman like manner. I have some holes leftover from a Sattellite tv antenna that I no longer use to run the inlet box but I might drill in the front of the house and use PVC conduit to run the power inlet box. The tv holes are in the back of the house and I want to put the inlet box in front to save wire as 10/3 is very expensive. As for installing a generator transfer switch in a rental, I have a medical condition that may be life threatening in an outage. I am going to plug the medical equipment into a UPS that will give me time to switch the power over to the portable genset. I also have the a medical alert on file with the poco so they will notify me by phone if outages may be possible. We have rarely had outages up until last year when it went out twice (once lasting three days in October), and with my worsening health, we got the portable genset. It seems that the weather here is getting more extreme. We had really bad weather last year, the Jun 1st tornado (not a common sight here), Irene, and the October snowstorm. We've lived at our house for ten years and don't plan on moving anytime soon. |
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to southla
Consider that the oil change interval on the GE/Briggs and Stratton is 100 Hours or One Year while the oil change interval on the Generac is 200 Hours or Two Years. In the case of a long term power outage the GE/Briggs and Stratton would require an oil change every Four Days while the Generac would require an oil change every Eight Days.
The GE/Briggs and Stratton with the Symphony II Transfer Switch has 8 load management priorities with the control signal transferred via RF over each controlled circuit to the load management relay, while the Generac only has 4 priorities and requires a hard wired connection between the transfer switch and each managed appliance or relay. |
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| Mr Matt |
to tomupnorth
Your main breaker can trip if the loading on the legs of your 120 Volt circuits are severely unbalanced even if the total load does not exceed 200 Amps. If one leg is carrying over 200 Amps breaker trips. Check with clamp on amp meter. If you add a generator be aware that most generators cannot accept an unbalance of greater than 50% between each 120 Volt Leg. |
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ncbill
Premium Member
join:2007-01-23
Winston Salem, NC |
to pandora
Given your cold climate why didn't you spec at least one heat pump with a propane-fired furnace as backup? If you can still change this, do so. It makes no sense to run a generator to operate an electric heat pump - you'll drain even a 500 gallon tank in short order. said by pandora:Our longest power failure lasted 7 days. Our cost of propane in small quantities is about $2.99. Larger quantities and owning your own tank lower the cost substantially.
Consider $3 per gallon times 3 gallons per hour times 24 hours per day, $216 per day? Times 7, $1512.
I'd pay that than have my family freeze. It depends on what you value and how much you can afford...
$500 is less than the cost of groceries lost in the last long outage (we have 2 large freezers, and a large fridge with freezer).
It all depends on what we value and can afford.
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Southla to Mr Matt
Anon
2012-Sep-23 7:15 am
to Mr Matt
I am aware of both. The oil change interval of my current set up is 50 hours, and that has not been an issue. Moreover, the 200 hour interval is equivalent to 10,000 miles on my car, and even using synthetic, I go a max of 5,000. I would never go that long.
We don't plan to use any load management relays. My typical non AC load is 2.5 to 5 KW and we calculate the AC will start OK. If we are wrong, we can add one. The AC will be within 10 feet of the controller. |
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disconnected to Jack_in_VA
Anon
2012-Sep-23 7:19 am
to Jack_in_VA
said by Jack_in_VA:I thought the 12 gallons my Honda was sucking up in 16 hours was bad. That would be $48/day at todays prices.
Gee, and I thought 6-1/2 gallons for 16 hours of operation was a lot. My Generac 7000EXL used $240 in gasoline during the October snow storm (7 days without power) and I was filling up the 7 gallon tank once per day. I used a total of 42 gallons that week. Granted, I run the genny on synthetic motor oil, which seems to make a substantial difference when the load is generally light. If all you are running continuously is computers and a few lights, then much of the load is internal friction, so I discovered. Reducing that friction really helped. My other secret was adding an ounce of acetone to the fuel. That stopped the after running and backfire after shutting down problem that these small engines are notorious for. |
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pandora
Premium Member
join:2001-06-01
Outland |
to ncbill
said by ncbill:Given your cold climate why didn't you spec at least one heat pump with a propane-fired furnace as backup?
The cost of adding a propane fired furnace would likely be higher than the $129 cost of the electric resistance auxiliary heat panel for the air handler. |
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HarryH3
Premium Member
join:2005-02-21 |
HarryH3
Premium Member
2012-Sep-23 1:48 pm
said by pandora:said by ncbill:Given your cold climate why didn't you spec at least one heat pump with a propane-fired furnace as backup?
The cost of adding a propane fired furnace would likely be higher than the $129 cost of the electric resistance auxiliary heat panel for the air handler. I believe that the point that was being made is that it takes far less generator to power the propane furnace than it does to power electric strips.  |
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to pandora
i think the whole point harry's making is it will take 3 times the propane to make electricity to convert back to heat .. than to just use propane to heat .. so the propane will last longer |
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ncbill
Premium Member
join:2007-01-23
Winston Salem, NC |
to HarryH3
Yeah, you could probably run the thermostat/blower fan for a propane furnace off a 2-cycle $99 HF genny. As other posters have pointed out, a 20kW genny is not going to run both aux heat panels. Even a 80% efficient furnace beats running a generator to operate a heat pump. I'm betting if one can afford to nearly double the sqft of their house they can also afford to add a propane furnace to at least one of the heat pumps. In case of a long power failure there will be much more run-time using the propane for the furnace rather than the generator. said by HarryH3:said by pandora:said by ncbill:Given your cold climate why didn't you spec at least one heat pump with a propane-fired furnace as backup?
The cost of adding a propane fired furnace would likely be higher than the $129 cost of the electric resistance auxiliary heat panel for the air handler. I believe that the point that was being made is that it takes far less generator to power the propane furnace than it does to power electric strips. |
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pandora
Premium Member
join:2001-06-01
Outland |
to HarryH3
said by HarryH3:I believe that the point that was being made is that it takes far less generator to power the propane furnace than it does to power electric strips.
The likelihood the strips will be used for any length of time is near zero. |
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| pandora |
to pferrie3
said by pferrie3:i think the whole point harry's making is it will take 3 times the propane to make electricity to convert back to heat .. than to just use propane to heat .. so the propane will last longer
I haven't performed a full calculate the conversion rate between 18 SEER heat pumps, propane used to make electricity and direct propane per BTU. The unit specification is here - » www.goodmanmfg.com/Porta ··· ZC18.pdf you'll want to look at the 4 ton unit. At 95F degrees outside, to produce 70F degrees inside at high airflow it looks like 1.67 KW per unit, or slightly over 3 KW for 2 units. At -10F outside to produce 70F indoors seems to require 2.66KW per unit, or about a bit over 5 KW. If it goes below -10F, I guess the 20 KW heater elements will try to fire and be shut down. In Connecticut, according to » www.weather.com/weather/ ··· ph/06813 once in history we had a -18F day. All other months have a maximum of -10F or less. So unless it's a power failure on an unusually cold winter day, the heat pumps should work fine of 5 KW at -10F. The average low is +19F in January, which is well within the tolerance of the units. The spec for the house is 77F in winter with the heat pumps down to 0F, and 68F in summer up to 110F. The units were sized with a heat loss computation using the blueprints we are building to. Installation of a propane heat element, would likely be expensive and only cover the outlying situation when we have temperatures below -10F. |
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to Mr Matt
said by Mr Matt:Your main breaker can trip if the loading on the legs of your 120 Volt circuits are severely unbalanced even if the total load does not exceed 200 Amps. If one leg is carrying over 200 Amps breaker trips. Check with clamp on amp meter. If you add a generator be aware that most generators cannot accept an unbalance of greater than 50% between each 120 Volt Leg. I did not know this, and it does certainly complicate my idea that on a power failure I would first set a number of breakers to OFF before firing-up the Generator and throwing a transfer switch. Thanks for the info. FWIW I don't think our 200A breaker tripping was due to imbalance, but rather: it was very, very cold, multiple blowers with heat strips were On, pool pumps were Running as they do below 35F, and probably the wife was doing laundry (Electric Water Heaters) and all these are 240VAC. Too many loads on at once. With a whole house genset I'd still on a power failure want to force some number of these Off, e.g. nonessentials like the water heaters... |
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HarryH3
Premium Member
join:2005-02-21 |
to pandora
said by pandora:said by HarryH3:I believe that the point that was being made is that it takes far less generator to power the propane furnace than it does to power electric strips.
The likelihood the strips will be used for any length of time is near zero. Did you not see that this thread is about a GENERATOR? Why burn a huge amount of propane, to generate electricity, to run a heat pump compressor (or heat strips) that finally heats the house? The OP can buy a MUCH smaller generator if he just burns the propane directly in a furnace.  |
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pandora
Premium Member
join:2001-06-01
Outland |
pandora
Premium Member
2012-Sep-23 4:44 pm
said by HarryH3:said by pandora:The likelihood the strips will be used for any length of time is near zero.
Did you not see that this thread is about a GENERATOR? Why burn a huge amount of propane, to generate electricity, to run a heat pump compressor (or heat strips) that finally heats the house? The OP can buy a MUCH smaller generator if he just burns the propane directly in a furnace. Heat pumps heat AND cool a home. Propane furnaces, not so hot for cooling. The use of the 2 heat pumps is about 5-6 KW, not certain what the air handlers use, but likely less than another 1-2KW. An entirely separate propane heating system, for times when the power would be off, really isn't cost effective. The BTU output of each unit is 47,000 BTU/hour, around 90,000 BTU. Over here » www.ask.com/answers/1426 ··· n-of-lpg it says an 80,000 BTU/hour propane heater would consume about 3.2 gallons per hour. My generator would consume a bit more, but not need a separate flue, need carbon monoxide detectors, or blowers, and the only use for the propane heater would be when there was no power (about 3 days per year averaged out over the past 10). The cost of a flue, propane furnace, hookup to 2 air handlers, carbon monoxide detection, and maintenance would surely exceed any savings for a few days of power outage. |
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nunyaLXI 483
MVM
join:2000-12-23
O Fallon, MO ·Charter
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nunya
MVM
2012-Sep-23 6:26 pm
The cost of a flue, propane furnace, hookup to 2 air handlers, carbon monoxide detection, and maintenance would surely exceed any savings for a few days of power outage.
You may be surprised. That's why I advised you to at least "look into" using propane furnaces rather than electric resistance furnaces as backups to the heatpumps.
The operational limits of air source heatpumps tend to be greatly exaggerated (especially by their fanboi's on this site). While they are great if you live in a milder winter climate, they lose efficiency fast the colder it gets. Trust me, it will be well above -10 when the air source heatpumps will not be able to keep up with your heating demands by themselves.
You should consider the cost of propane / btu vs. electric / btu only so far as the "auxiliary" heat is concerned (resistance heating).
Naturally, a power failure is most likely to occur during extremely inclement weather (coldest or hottest).
Unfortunately, the price of propane isn't nearly as stable as electric rates, but both are subject to fluctuation.
This "dual hybrid" scenario actually makes a lot of sense when a generator is thrown into the mix.
The potential for savings isn't going to be just "generator" time, but any time in the colder months when the auxiliary heat must fire up to keep your house comfortable. This is going to happen a lot more than you might expect. |
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The main problem I have with propane is the propane mafia. If you're going all in with propane and lease your tank be prepared to call your propane company every season and haggle.
Otherwise be prepared to pay megabucks to install your own tank. |
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said by fifty nine:Otherwise be prepared to pay megabucks to install your own tank.
Megabucks? Hardly. I paid $1800 for the underground tank and $400 for installation. That's hardly megabucks compared to what I've saved vs a leased tank in 3 heating seasons. |
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 herdfan
Premium Member
join:2003-01-25
Hurricane, WV |
to Mr Matt
said by Mr Matt:Consider that the oil change interval on the GE/Briggs and Stratton is 100 Hours or One Year while the oil change interval on the Generac is 200 Hours or Two Years. ..... while the Generac would require an oil change every Eight Days. Since I immediately fired my Generac up as we were in the middle of a power outage, I changed the oil after about 16 hours which was more than the 8 it recommended. But the change took me about 10 minutes and I was back up and running. It has a nice oil drain hose. No mess at all. |
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| herdfan |
to pandora
said by pandora:Heat pumps heat AND cool a home. Propane furnaces, not so hot for cooling. The use of the 2 heat pumps is about 5-6 KW, not certain what the air handlers use, but likely less than another 1-2KW.
An entirely separate propane heating system, for times when the power would be off, really isn't cost effective. The BTU output of each unit is 47,000 BTU/hour, around 90,000 BTU.
The cost of a flue, propane furnace, hookup to 2 air handlers,
I have 2 heat pumps. One has heat strips for Emergency or Aux. heat. The other has a NG furnace. The HP works as a HP until the outside temps drops into the 40's, then the Emer/Aux. heats kicks in. But I rarely use the electric heat strips as the NG furnace in the basement puts out enough heat to keep the whole house warm. As for the cost of the flue, the new efficient models use Schedule 40 PVC with a blower. Not much expense at all. Plus, and I am sure I will get arguments here, but propane and gas heat feel warmer than electric. Maybe it is because it is more humid heat and feels warmer, I don't know. But it does to me. |
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to pandora
Pandora, I was not able to find a comment in this thread regarding how various heat pumps operate while in the defrost mode. In my case when each heat pump goes into the defrost mode the compressor and heat strip operate together. My condensers and air handler fans draws a total of 41 and 45 Amps respectively at 240 Volts when in the defrost mode. The heat strip in each system is rated at 4.8 KW or 20 Amps at 240 Volts. A generator powering my 30,000 BTU heat pump in the defrost mode would have to supply 41 Amps or 9840 Watts and my 42,000 heat pump 45 Amps or 10,800 Watts. That total requirement would exceed the capacity of a 20,000 Watt generator which is why a load management system is required to use a 20,000 generator in my home. That is probably why one Generac dealer recommended a 36Kw generator for my home if I stayed all electric.
I agree with nunya that if you can use propane rather than electric heat strips for back up heat you can use a smaller generator and in my opinion your system will probably provide better quality heat. The key facts that one has to review is the total capital investment in you appliances for an all electric solution and the total capital investment for a propane/electric solution, along with the yearly operating cost and how long you plan to remain in this house. If the difference in cost is significant, I would also consider the convenience factor for the two different systems, to determine if the more expensive solution is better. |
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