Setting up a Generator

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Our cabin recently was subjected to multiple days of no electricity during to a bad storm taking out trees and power lines I would like to set up a generator to run the following 1) well water pump 3/4 hp (120v) 2) refrigerator (120v) 3) freezer (120v) 4) hot water heater (240v) 5) stove (240v)
I would like to set it up so that is one appliance is drawing power, everything else waits. It would also be nice to set up the chain in the order listed above
It should also be noted that: a) the stove is optional since there is a great fire pit where food can be cooked and hot water heated in large enough quantities for hand and dishwashing and sponge baths. b) the hot water heater is big enough to hold enough water from one heating cycle for all daily hand and dishwashing needs + couple of showers. Which means that unless there are more than 2 people using the cabin, it would only need to run once - possibly in the morning to start the day c) the freezer only needs to run once every 2 days d) the refrigerator only needs to run once a day if access is controlled, otherwise twice a day will keep it cold enough e) the well water pump only needs to run if water pressure has dropped low enough to trigger it.
I already have an electric start generator to run everything at the same time. But I would prefer not to load it to the gills at the same time,
So I'm looking at 1) a box that will make sure that when the generator is going, it will sequentially feed the 5 devices and then shut off by itself when there is no demand... 2) If the generator is going, then IF a higher priority device wants power it can bump of a lower priority one. After which the bumped device gets serviced.
Any help and suggestions are appreciated
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I think you're making a simple problem into a very complicated one. The "box" you're seeking would need current/sensing, relays on the various loads and a microprocessor to enforce your rules. I know of no commercially available product, but if it was availbable, I suspect no one would pay the price for it for the above application.
You say the generator you have could run everything on the list, but you don't want to fully load it. So, take the stove which is a huge load out of the equation, since you say it's optional. Now you can run everything else at far less than the generator capacity. Or you can just work the breakers manually on the loads like the rest of the world does.
Or are you a troll?
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On 7/13/2011 3:54 PM, snipped-for-privacy@optonline.net wrote:

It's pretty simple. If he already has a generator that can handle the entire load, but doesn't want to "load it to the gills at the same time", just turn something off. The generator is only going to work as hard as it has to, to keep up with the load. This is why the generator specs tell how much fuel consumption @ full load, half load, etc.
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Yeah, and the easy way to do this is to not cook after a shower. The OP already has direct control of the biggest item which is the stove. The rest seems pretty automatic already. He has indirect control of the water pump, and indirect control over the fridge and freezer (don't open the door).
The OP can just turn off any of these at the panel.
You can install relays to do this automatically, but it would cost you.
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On 7/13/2011 3:24 PM, D.A. Tsenuf wrote:

Is there any particular reason why it needs to be so complicated and automagic? If the generator you have can handle all of the load and if the loads have the duty cycle you described the generator will almost never need to run at full load (and if it does so what?). If it does and the generator labors why can't you simply turn off the range or water heater for a while?
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I imagine the water is the biggest load. Maybe at least 5 kw. The stove depending on the elements will be less.. Each device would have to have a relay of required rating. Put the heater priority first. This could be a timer, 2 hours before sunrise, 2 hours before dinner.
You would need a computer or processor to do the rest. Shutting the fridges off during defrost is hazardous, especially during usage. Stupid units don't have adjustable setponts, user specified with control panel, but a smart controller may loose programming with power off. A lot of problems.. During power outage, manual may be the way to go.
Greg
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Some years back we were having a problem with oil flow when both the oil-fired water heater and oil-fired boiler were on at the same time. We put a relay on the water heater circuit so that if the furnace was on, the water heater would not run. I suppose that with five appliances you could hook up a series of five relays in a way to give a sequence of priorities. There's probably a micro-chip device that can be programmed to do the same thing, although I've never heard of one.
Paul
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It's pretty straight forward to put a lockout relay on two devices hat already are controlled by low voltage circuits. What he wants is a couple orders more complicated.
If ou really have a generator capable of running everything then you have a pretty large generator. Stoves and electric hw heaters draw a lot. So you don't really need to worry about it.
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Microprocessor controllers are available for everything from elevators to traffic signals to industrial washing machines...
Rigging one up to do what the OP wants would cost a lot of money, require that every load is controlled via a relay panel and would have to have sensors which could interface the generator to the controller so it can know when to shed load to wind down when it is about to fail...
As another reply said here, this is orders of magnitude more complex than a few relays being interlocked via auxiliary control contacts...
~~ Evan
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My suggestion is to use some self control instead of sequencing, prioritizing, and adding a lot of controls and relays. Don't use a lot of hot water until the cooking is done. Let the freezer and fridge draw the few amps they need as called for.
Price this setup first, Then look at how often it is really needed. They with the money you'd spend on the control panel, buy a bottle of really good bourbon, a couple of steaks, and relax with them. I bought another bottle of Maker's Mark 46. That and a couple of rib-eyes makes more sense that the once in dozen years power/generator problem.
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Heating anything with resistive electric heat is an offense against the laws of natures God. Since you didn't mention space heating I'll assume that it is not electric. That raises the question of what it is fueled by. If you want to put your home on an electricity diet then put in an propane fueled hot water heater, a propane fueled stove. You then have a propane adapter fitted to your generator so that you no longer have to handle gasoline unless you run out of propane. That would leave only the well pump, refrigerator, and freezer to be powered by the generator. You will have reduced the load on the generator considerably and made the generator much easier to run.
If you really want to implement a priority sequential operating scheme then you will need four relays with normally closed auxiliary contacts. The control voltage for all of the relays comes through each auxiliary contact in turn. As long as the the relays upstream of the load in question are open then their auxiliary contact will be closed and control current will be available to the relays down line from each relays auxiliary contact. If the water pumps relay is pulled in then the remaining loads will not have control current and they will remain off. Once the water pressure reaches cut out then that relay would relax thus closing it's auxiliary contact and permitting the refrigerator to run. When both the water pump and the refrigerator have reached their set points the control power would reach the freezer's relay allowing the freezer to run until it is cold enough and control current would then be passed along to the hot water heater. When the hot water heater reaches it's upper limit then it's relay would relax thus closing it's auxiliary contact and permitting the stove to get power. If any higher priority load comes on it opens the control power circuit to the lower priority loads and they drop out until control power is again available because the relays for the higher priority load is now open thus closing it's auxiliary contact and passing control current along the chain to the lower priority load. This scheme has the virtue of electrical simplicity but it does mean that you will have to be careful in what load you are using so as not to start a higher priority load when what you really want to run at that moment is a lower priority load. Manually opening and closing switch rated breakers is a much cheaper and somewhat more flexible way to accomplish this but if you have to have automatic load selection then that is the simplest means I know to accomplish that. -- Tom Horne
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On Thu, 14 Jul 2011 13:00:02 -0700 (PDT), Tom Horne

I think you left out some CTs. I would have to see it on paper to be able to follow your suggestion. If you get bored, I would like to see a rough sketch of what you come up with. This doesn't seem to be as "simple" as you suggest, but I could be wrong.

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On Wed, 13 Jul 2011 14:24:20 -0500, "D.A. Tsenuf"

I hear there may be a few NASA engineers in need of work shortly.
If you have the budget I'm sure you can find someone to design the system, write the software,find the parts, assemble the parts, and install.
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It could be done with a computer controlling it or it could be done electomechanically with a set of relays. Either way you will need to build it. There is a small control processor that a lot of people like to play around with if you want to take that path I believe you can get some kits for it. Either solution will require you to get some rather large contactors or some pretty big thyristors for most of your loads. I think you will find it rather frustratng to have your stove repeatedly turned off as you are trying to cook because other things needed to come on. I would expect you to have a few hundred hours as well as several hundred dollars into this before you are done.
That sound like it's worth it to you? Cause I think the opinion in the group is that it's not worth it. But perhaps you view this as a challenge and want to do it for the experience?
Everyone I know with a large generator just moderates their behavior to manage the load. The minor difference in wear to your generator from it occasionally working at a higher load is not going to be noticable.
You never clarified what specific generator you have?
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# # It could be done with a computer controlling it or it could be done # electomechanically with a set of relays. Either way you will need to # build it.
Not a problem Have experience putting together computer controlled devices
# There is a small control processor that a lot of people l# ike to play around with if you want to take that path I believe you # can get some kits for it. Either solution will require you to get # some rather large contactors or some pretty big thyristors for most of # your loads.
Thank you for point out major parts needed
# I think you will find it rather frustratng to have your # stove repeatedly turned off as you are trying to cook because other # things needed to come on.
As pointed out in the original post, the stove is really a minor issue for 2 reasons 1) Minimal use in the summer to keep cabin cool 2) Fire pit set up to cook, and even bake most about anything Stove to be set up for use as an (low-priority) alternate.
# I would expect you to have a few hundred # hours as well as several hundred dollars into this before you are # done.
# That sound like it's worth it to you? Cause I think the opinion in # the group is that it's not worth it. But perhaps you view this as a # challenge and want to do it for the experience? #
That's OK Some of my "hare-brained" schemes turned into money-makers over the last 40+ years... Paid for all the others that were economic or technical duds.
Also trying to avoid re-inventing the wheel is such a produc is already on the market.
# # Everyone I know with a large generator just moderates their behavior # to manage the load. The minor difference in wear to your generator # from it occasionally working at a higher load is not going to be # noticable. # # You never clarified what specific generator you have?
14Kw Generac, that I got in lieu of cash payment. The cabin, which was built as all electric, will serve as a test bed. And although the idea of converting to propane is a good one, it's only going to happen as fridge, stove fail and need to be replaced.
Ultimately would like to move it to city house and then run it off the natural gas line, as a SHTF backup The thing about natural gas is that it rarely stops flowing when the power goes out, and can be backed up with propane if needed.
But I don't want a generator that is running 24/7 I would like to have one that is set up to start when demand occurs, service the demand, reset all the systems that need re-setting (load up water pressure, heat up hot water tank, chill down freezer/fridge) and then shut down and wait for next demand point.
One comment from an OP raised the issue that I do NOT need a linear decision tree for usage. In effect if the stove is in use, the only other critical system is water pump. So it would be interesting to have hot water tank go on ONLY after water pump stops but not when pump or fridge/freezer is running.
And I definitely was thinking of running a processor to control the logic and servicing the systems Could even be run off the 12V battery for starting the generator. Could even have a trigger to start the generator if the battery falls below a certain level of charge.
I think the problem can be solved What I would like to figure out is: 1) What are the possible solutions 2) What do I need to implement possible solutions 3) What are the final costs involved in such implementation
Ultimately I think my "solution" could be an "intelligent" transfer switch, that not only separates the circuitry from the (utility) supply line, but also allows for more efficient use of a smaller generator that does NOT require a lot of manual control to operate.
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You do realize that fuel consumption is greatly influenced by the load don't you? For example, I doubt that you will save by running two 2Kw loads for two hours, as opposed to running one 4Kw load for one hour. In fact, I would not be surprised to find you'd use MORE fuel. And certainly the generator is going to have twice the number of hours and revolutions on it because it's spinning at exactly the same speed for twice as long. This sounds like assuming you would save on gas by making two trips of 100 miles at 30mph instead of one trip at 60mph.
Usually switching in and out loads is done to reduce the size/cost of the generator needed. But you've said the generator you have is capable of handling the entire load. Given the loads, this generator must be larger than the typical backup home generator. What is it's capacity?

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On 7/15/2011 8:29 AM, snipped-for-privacy@optonline.net wrote:

Which "typical" do you mean? With the phenomena of McMansions and everyone needing to drive trucks for personal transportation other things have scaled up. It isn't at all unusual to have 50 kw gensets installed for homes to make sure the hot tub and other essentials can be operated in emergency conditions.

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D.A. Tsenuf wrote:

Ah, well, in that case look up "Shabbos goy."
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Funny how so many responders can't address the question and instead respond in other ways... Just goes to show the rule that 90% of the universe is "chaff" and it most of life is about separating the wheat from the chaff...
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In this case it's more of a question of making sure you understand what you are getting into. It wasn't clear that you did. It's still not completely clear. You do wish to build this?
If so narrow it down a bit. There are a lot of answers to your general question of doing this. How do you wish to proceed? What mix of digital verses electromechanical infrastructure do you want to build for this? Do you wish to completely roll your own or is money no object and assembling this from commercially available stuff an option. The $10k another poster joked about is not totally outlandish if you wish to buy a complete or near complete solution.
It's not a task that is beyond some of the members of this group but even laying out a solution would probably require more time than anyone is going to provide for free. Best you should expect from here is some general suggestions on where to start looking. But there are a number of direction you could head and we'd need to get an idea of which way you want to go first.
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