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Cost of operating well

Posted by marknmt (My Page) on
Thu, Feb 1, 07 at 18:30

Here's a question I've tried to get answered for a while and haven't found it yet, so please bear with me.

We run a new well pump to supply water for a new open loop ground source heat pump and have been experiencing higher than expected electricity bills. We don't know whether the well pump or the heat pump is the culprit, so we don't know on whom to lean. We're getting the heat pump installer out here Monday or Tuesday to check the installation, and we want to be able to clearly delineate the cost of the well in order to say how much the heat pump is costing to run, or vice versa.

We measured the draw on the well- when it's running it pulls just over 7 amps on each of the two legs. Currently (it's in the teens and twenties here lately) it's running about 2/3 of the time, or 16 hours per day. It runs the entire time that the heat pump runs (as it should.)

We're paying .0899/KWH.

Can anybody help here? FWIW, the static level of the well is 50 feet below the discharge level of the heat pump, if that matters. The well pump is a 3/4 HP Goulds single phase. Wiring is brand new too, inspected and everything!

Thanks VERY much for any thoughts.

M


Follow-Up Postings:

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RE: Cost of operating well

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7 amps . . 120VAC . . 16 hrs / day. 7 x 120 = 840 watts or 0.84 kW. Multiply by 16 hours => that works out to about 13.4 kWh / day. At 9 cents per kWh; about $1.20 a day to run the pump. You don't say what your total monthly usage is; but I'll bet that the water pump is a relatively small amount compared to running the heat pump itself ( compressor etc ).

I run my entire house on ~ 10 kWh / day in the winter; less in the summer . .

Bob


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RE: Cost of operating well

Bob, thanks- I should have specified it's a 240 v pump. So that would be 1.68 kwh?, thus $2.40/day, or about $72.00/month?

That would leave our heat pump costing about $80/month, which is pretty close to $2.61/day, which does tally with the meter that's on the heat pump. So apparently the heat pump is costing more than well pump. (This matters because the heat pump guy is trying to say the well pump is drawing too much current. We suspect that the heat pump is using much more than expected, which would indicate an internal problem in the heat pump- but we don't want to press the issue if we're wrong.)

Our total useage for the month was 2039 kwh, or $183.24, of which in a typical month about $28.00 (311 kwh)would go to our other household uses. (There's also 35 bucks going through our gas water heater every month until we get the desuperheater connected!) The reading on the heat pump meeter is uncertain because the decimal point is not clear ... Yeah, I don't like it either! The heat pump installer includes the meter in the installation, says we're only using "X" per day, but I say we must be using "10X" per day and he says "nah, there's something wrong with your well pump or maybe your refrigerator's going bad". And I'm saying "well, show me". If the meter is being read wrong by either of us it makes a difference of ten fold.

Don't misunderstand me; I like the system. But it's costing us quite a bit more than we had been led to believe, and if it can be worked on to improve the results than we can't afford to ignore that. If it can't be improved we need to know that and move on. If nothing else he needs to know if his meters are being read wrong!

Thanks for your time and your help. I appreciate it very much and i'll be grateful if you, or anyone, have anything further to suggest.

Thanks again,

Mark


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RE: Cost of operating well

Hi Mark,

Take a look at the link below. These pumps are probably the best in the industry and are considered by many as the Gold Standard for GSHPs. Study the data. If need be, contact the company telling them your considering swapping out your Goulds pump for one of theirs. First verify your requirements from your GSHPs installation manual and ask which model they recommend and how much power (or current) it consumes. This may provide some useful information.

Good luck; keep us posted.

SR

Heres another useful link: http://www.gothotwater.com/D'MAND/components.asp

Look at the Taco Model 0011 specs!!!

Here is a link that might be useful: Grundfos Pumps


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RE: Cost of operating well

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Yup . . about $ 2.40 / day if 230 VAC pump.

Sounds like you're discharging water back into the well ? . . . a dedicated well just for the heat pump ? . . if so, I'd be concerned that you're not getting enough thermal exchange in the well. If you're cooling the whole well down, it may not be able to pick up enough heat from the surrounding ground. A standard well casing doesn't hold many gallons . . . That would certainly say that the heat pump needs to run longer . . . which in turn says your well pump needs to run longer. Who did the system design ? . . . the ground source heat pumps I've seen pull from a well and then discharge elsewhere => that's how you pull heat from the ground; by constantly pulling in fresh water. If you just dump it back into the well; you're simply cooling it and it's surroundings down => everything will need to run longer to generate sufficient heat. Can you read the intake temp of water coming from the well ? . . I'm no HVAC guy but this might give you a good indication if things are working right / designed right . . . . . around here; ground water is ~ 60 year round . . .

Bob


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RE: Cost of operating well

Thanks to you all for the input.

I have something of an update. The tech came out and checked the well and heat pump and found both working as they should, but was surprised at the high heat level in our registers. He finally decided that our vents were not large enough for the system and were in effect holding the heat in the heatpump (i.e., the airflow is not sufficient. You have to remember this is a retrofit in a 100 year old house.) He recommends, and I think he is right, that we find a way to get more vents working. Another part of the problem is that the vents are located in the center of the house, and the cold air returns are at the perimeters. So the outside walls never really warm up (and remember they are stucco exterior over tile block with plaster interior). The thermostat is centrally located, senses correct temperature in the center of the house, and shuts down the system. But those outside walls are still cold, and in a few minutes the chill reaches the thermostat and on comes the system again. In fact, it runs about 2/3 of the time in colder conditions. It appears the heat pump is probably responsibly for about 60 percent of the electrical draw and the well pump the remainder.

The tech set the fan to run longer and turned the heat up a couple of degrees, and that appears to be helping; the run-time is comparable (about 14 on, 7 off) and the comfort level is higher, so he's accomplished something, it appears. I'm supposed to hear from another of the company Monday about the vent question.

We don't discharge the water into the well casing; we have a "dry well" (just a small sump) that receives the discharge. We sit over an acquifer that exchanges completely every day and pump from 80 feet (58' static level) and our water temperature is about 48 F. The water we discharge has a long was to go to reach the well pocket, so that doesn't seem to be a problem.

The well serves the irrigation system as well as the heat pump.We may yet use well water for part of our household use, might save $10/month to do so. But we're still on city water, the minimum charge for which is about $15.00/month.

I think too that we could save an addition $20 or thereabouts once we get the desuperheater hooked up, since we're paying $36ish for our only gas appliance, our water heater. At least if we do that it'll be perfectly clear where the money's going!

Thanks again to you all for your help. Stay tuned ...

:-)M


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RE: Cost of operating well

Mark:

Im just curious. Whats the temperature at the plenum and at the furthest register? Does your fan run 24/7 (single speed or 2 speed)? What kind of filter are you using?

Your well pump still sounds awfully big; is one that big really necessary?
How many CFM was your old system vs. new system?

SR


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RE: Cost of operating well

Hi SR.

I don't know about the plenum temperature and I don't want to open the cabinet to take it. I was told the heat pump's output seemed to be on the high side, which the tech attributed to the heat not being able to get out of the heat pump efficiently. I took a few temperatures at the registers and got ranges from 96 F to 101 F.

The temp's pretty good: EPA certified, licensed electrician and plumber, California qualified on everything too. Answers my questions in a straightforward, honest way. Didn't try to pretend the system was everything we should expect it to be, but did steer us to a number of things we should have done better (cold air infiltration, insulation, of course). Plus, we both like him, and he's made an effort to get to us right away.

The filter is the one included with the machine. I think it's the "Nothing Special" option. It's two months old.

The fan is a two speed fan. It's NOT running all the time- I thought the tech had set it to run constantly but I was wrong.

The well pump sizing is a question for me. It may well be too large for the application, but it also serves as our irrigation pump. (I think it may be too large for that too, but I don't know; it sure doesn't have any trouble covering the area!)

It's worth remembering that our duct work was set up for a truly ancient system. Our cold air returns are at the far corners of the house (our bathroom has none at all) and the hot air vents are all pretty centrally located. I'm sure it was better than a Franklin or parlour stove or one of those gas space heaters I grew up with, but it still wants to keep the heat too close to the center of the house. We may find ways to improve that, and that may help. We'll see.

I don't know the CFM figures for either system. The old system blasted out air pretty hard, the new system is much gentler (and more pleasant). The house was either too hot or two cold, seemed like the comfortable middle range just went by the wayside.

Thanks for your interest. Stay tuned ...

:-)M


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RE: Cost of operating well

I submitted this elsewhere and wanted to get it out here too. Grateful for any comments, input, advice, or sympathy :-)

Today our HVAC contractor sent out their duct/sheet metal person, and he looked long and hard at our ductwork, pointed out what could be done, and then suggested it might not be worth doing. Candid, straightforward, honest, experienced. Also gentle in his manner and a fine listener. I liked this guy and his approach. But essentially said our ductwork isn't that bad, any improvements would be fairly marginal.

And now I am left with the conclusion that (contrary to my initial feeling) the heat pump is pretty well doing what it should be, and is sized well for our house, our ducting is OK enough, the contractor treated me mostly fairly (I qualify that because he is terrible at communicating and also sold me something he told me not to buy and then charged me for it when he said he wouldn't!) and I should be happy with it-

But: the well pump is costing too much to run. Sized at 3/4 horse when this part of the job could be done with much less, it's great for the sprinkler system (which we run a few hours per week all summer) but, as said, is way overkill for the heatpump (which we run several hours per day all winter).

The solution, low tech and not too expensive, is probably some kind of local passive storage system that the pump can fill at its rate and that the heat pump can draw on at its rate.

I'm guessing a 50% reduction in the run time of the well pump. Just how much of the total cost of running the system is the well and how much the heat pump I'm still uncertain, but it might be 50% -or even more- of the total. So that 50% reduction in well time would be worthwhile. I need to ask a question about how to read an Itron watthour meter Type C1S, but I guess I should do it in another thread. It's a digital meter - I just don't know where to put the decimal!

Best,

Mark


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RE: Cost of operating well

Hi Mark,

Personally, I would have completely separate systems. Are you really saving any money using your well for irrigation as opposed to municipal water, if you have any? If you continue using the well for irrigation, you can use that 3/4hp beast for a few hours a week during the summer if its worth it!

If your HP is a Tranquility 27, 3-ton unit, its not pushing that much air (1080 1250 CFM) so Im not surprised your ducts are OK.

Regarding your Itron C1S meter, read your owners manual; what can be simpler? I would imagine if the display has no decimal point then there is no decimal.

SR


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RE: Cost of operating well

Hi SR, and thanks for your reply. Sorry I couldn't respond yesterday.

As for separate systems, I'm afraid the cost would be prohibitive. It cost about $4400 to drill the welll we have and equip the system. Drilling another, trenching again, new circuits, wouldn't be much cheaper. (Just the cost of drilling was $2400.)

This project penciled out because we looked to save several hundred/year on irrigation, and that has worked. May be the saving grace, in fact. We had also hoped to save several hundred on heating, and we will save some. So the system, which we love, will pay for itself in time (probably about 12 years instead of the 8 we had hoped for) but there may well be ways to improve it.

I wish I had a manual for the Itron, but I don't. My contractor told me it should be read as if it has a decimal but it does not show one- like you, I would imagine if the display has no decimal point then there is no decimal.

Thanks again for all your help. I'll let you know how things work out.

M


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RE: Cost of operating well

Re: marknmt

Is it at all possible to have 2 different pumps/systems for the same well?

As for the Itron, see if you can find an owners manual on-line. Another alternative would be if you have, or can borrow, a clamp-on ammeter or a DVM with a clamp-on ammeter attachment, such as a Fluke, just for say, a 48- hour period. This would provide a very close comparison for you to determine where (if) the decimal should go.

A word of caution DO NOT go this route unless you are experienced and comfortable around high voltage/high current you could get electrocuted!

SR


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RE: Cost of operating well

>>A word of caution DO NOT go this route unless you are experienced and comfortable around high voltage/high current you could get electrocuted!<<

:-) Thanks. I'll be careful. I'm skittish about electricity, and you can trust that I'll take care. I do have an experienced, licensed electrician I can call on who'll keep me out of trouble.

I'm cogitating on whether it would be possible to drop a second, say, 1/3 hp pump on top of the 3/4 hp. Obviously there isn't room for the drop tube to pass the lower pump, but if the big pump is far enough below the static level the little pump should have enough to draw from. I'll ask my driller.

Best, and thanks again,

M

(In all likelihood I'm going to end up using the big pump to fill a 100+ gallon tank in the basement, which will feed the heat pump. We'll see).


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