Author Topic: Descaling Ground Source System?  (Read 3688 times)

Bob W

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Descaling Ground Source System?
« on: May 13, 2015, 02:08:45 PM »
My hot water heater was 1.5 feet deep with lime deposits prompting me to start using my water softener. 

Plumber says he is concerned about the Geo thermal system.   

I do a little research and am unclear.    My system is a pump and dump -- water pumps from well and runs through system and out back.    It is very efficient it appears costing about $70 a month to heat and cool a 3000 sq foot home per month.

Anyone know about this or is it worth attempting to descale or is it more likely to cause problems? 

alberteh

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Re: Descaling Ground Source System?
« Reply #1 on: May 13, 2015, 04:20:12 PM »
get the water tested. If your water heater and the heat pump both get water from the same source then it is likely scaling (you have a temp. differential that causes things to precipitate out). I'm not that well read on geothermal but aren't the lines pretty darned big (2" or so?) if so then it is unlikely to cause problems in the line but may be a concern in the heat pump unit itself.

zataks

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Re: Descaling Ground Source System?
« Reply #2 on: May 13, 2015, 04:36:23 PM »
1.5 FEET deep in scale?  You're losing a good amount of volume and likely efficiency.

I'd remove it.  If it accumulated over 20 years, I wouldn't worry too much about it.  If it's a shorter time frame, you might consider cleaning it every year to every 2-3 years just as a precaution and to keep things running well. 

Not sure what the flow path to the Geothermal is but it sounds like it's worth looking into to me.  Preventative maintenance is typically cheaper than corrective.

Rural

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Re: Descaling Ground Source System?
« Reply #3 on: May 13, 2015, 04:44:52 PM »
My parents' geothermal heat and cooling system is decidedly not from the same source as their potable water. Are you on a well for drinking water? Even so, usually it isn't the same well (my parents are on a spring for geothermal and county water for potable).

QajakBoy

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Re: Descaling Ground Source System?
« Reply #4 on: May 13, 2015, 05:59:55 PM »
Wow, your well water is very hard, but not unusual for much of Missouri. 
However, it most likely won't make sense to soften the water going to your open loop ground source heat pump, since it is probably such a large amount of water that the system uses.   Fortunately the temperature difference of the water going through your heat pump is not as great as that in a hot water heater, so the water to your heat pump has less potential for scaling up your heat exchanger.  Also, the water in the heat exchanger is constantly moving which helps. 
But, even a small amount of scale could build up over time, hard to tell from here.  In the off season, might want to take the system down and see how bad it looks. 

Bob W

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Re: Descaling Ground Source System?
« Reply #5 on: May 14, 2015, 08:17:15 AM »
The geothermal uses the same well water as the water heater.   The water heater is old and never been cleaned.  We don't use the water softener as hard water stains have not been an issue.

The well runs off a variable speed (2 year old) very fancy pump.     

I guestimate that when the geo is running that it is pumping approximately 3 - 4 gallons of water out.  Although,  I have never time measured it at the dump site. 

(if you're in a dry area please don't panic about our 3,600 gallons per day of water usage.  In our area we have karst topography and lots of rains.  We also live near a very large lake and I'm guessing that my well draws water from below the lake level.   It rains a lot around here)

I did run across some charts that showed 20-30 percent efficiency drops with scaling.   I'm not too concerned about that as the system is really pretty damn efficient already.   It is perhaps the most efficient type of heat pump available.   In the winter for an all electric 3000 sq ft house and 25 degrees average temperature our top bill was about $200.   Of that I guestimate 40 for hot water,  20 for BS utility company charges and 40 for misc.   So maybe $100 for heat.   In the summer the system circulates through the hot water heat to essentially provide hot water.     

The well water temperature is approximately 53 degrees. 

There is no electric resistance heat at the coils. 

My main concern is if the build up will ever get to the point that the system will go belly up?

zataks

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Re: Descaling Ground Source System?
« Reply #6 on: May 14, 2015, 10:57:52 AM »
My main concern is if the build up will ever get to the point that the system will go belly up?

Yes.  Eventually it could.  Time frame is hard to say and depends on many variables.  Sounds like your water heater will be the first to go, though.

Faraday

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Re: Descaling Ground Source System?
« Reply #7 on: May 14, 2015, 12:10:23 PM »
Bob, I drain my water heater annually and get about 1 or 1.5 cups-worth of precipitated scale and minerals.

I suggest you set a time to drain the water heater again and see what you get out of it. If you are fairly sure you completely drained it last time of all scale, then you've got a set point so you can gauge how fast the minerals are building up.

So what I'm saying is, come up with a way to measure the rate of accumulation, then decide whether to act or not.

Rural

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Re: Descaling Ground Source System?
« Reply #8 on: May 14, 2015, 05:22:27 PM »
Bob, my folks are on karst, too- water straight out of limestone. I can ask if they've ever had a problem with scaling if you like. I know they've been through several pumps (system is near 50 years old), but I think debris from the spring has been the issue...plus one washed away in a flood, pre-pump house.

Just realized: are you only using your system for hot water, not for heating and cooling the house?
« Last Edit: May 14, 2015, 05:24:57 PM by Rural »

Glenstache

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Re: Descaling Ground Source System?
« Reply #9 on: May 17, 2015, 02:40:21 PM »
Bob, there are two parallel issues going on here: 1) your now-dead water heater and 2) your ground sourced heat pump system that uses groundwater as your thermal sink for the heat exchanger. The ground source heat pump potential for scaling will depend somewhat on how the system is configured (two wells for an open loop, water exchange back into the same well, water discharge to some other place?). Regardless, of the configuration the two potential issues are scaling your lines and clogging your well screen and/or sandpack. The pipes you should be able to assess by popping them open at a joint or two and looking. Pretty straightforward. The well can be trickier in all regards and the issues there could not be visible in the above ground piping. Depending on the well construction and appurtances, you may be able to use measurements of drawdown relative to flow rate (Specific Yield) to track well efficiency through time, of you can rent a video camera. Should you have clogging in the well screen, well rehab amounts to pulling pump and using mechanical and/or chemical approaches to break up the scale or bacterial fouling, neither of which is a sure fix. If you are indeed in a karst area and your well just stubs into an underground cave somewhere, the well efficiency isn't like to be an issue, but there could be other things to keep you up at night... like sinkholes.

zataks

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Re: Descaling Ground Source System?
« Reply #10 on: May 17, 2015, 03:53:10 PM »
Bob, there are two parallel issues going on here: 1) your now-dead water heater and 2) your ground sourced heat pump system that uses groundwater as your thermal sink for the heat exchanger. The ground source heat pump potential for scaling will depend somewhat on how the system is configured (two wells for an open loop, water exchange back into the same well, water discharge to some other place?). Regardless, of the configuration the two potential issues are scaling your lines and clogging your well screen and/or sandpack. The pipes you should be able to assess by popping them open at a joint or two and looking. Pretty straightforward. The well can be trickier in all regards and the issues there could not be visible in the above ground piping. Depending on the well construction and appurtances, you may be able to use measurements of drawdown relative to flow rate (Specific Yield) to track well efficiency through time, of you can rent a video camera. Should you have clogging in the well screen, well rehab amounts to pulling pump and using mechanical and/or chemical approaches to break up the scale or bacterial fouling, neither of which is a sure fix. If you are indeed in a karst area and your well just stubs into an underground cave somewhere, the well efficiency isn't like to be an issue, but there could be other things to keep you up at night... like sinkholes.

Or an electric tape/sounder. Or a string with a weight and a tape measure. :-p

Glenstache

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Re: Descaling Ground Source System?
« Reply #11 on: May 17, 2015, 04:11:21 PM »
Bob, there are two parallel issues going on here: 1) your now-dead water heater and 2) your ground sourced heat pump system that uses groundwater as your thermal sink for the heat exchanger. The ground source heat pump potential for scaling will depend somewhat on how the system is configured (two wells for an open loop, water exchange back into the same well, water discharge to some other place?). Regardless, of the configuration the two potential issues are scaling your lines and clogging your well screen and/or sandpack. The pipes you should be able to assess by popping them open at a joint or two and looking. Pretty straightforward. The well can be trickier in all regards and the issues there could not be visible in the above ground piping. Depending on the well construction and appurtances, you may be able to use measurements of drawdown relative to flow rate (Specific Yield) to track well efficiency through time, of you can rent a video camera. Should you have clogging in the well screen, well rehab amounts to pulling pump and using mechanical and/or chemical approaches to break up the scale or bacterial fouling, neither of which is a sure fix. If you are indeed in a karst area and your well just stubs into an underground cave somewhere, the well efficiency isn't like to be an issue, but there could be other things to keep you up at night... like sinkholes.

Or an electric tape/sounder. Or a string with a weight and a tape measure. :-p

Sorry, that was unclear. Yes, a sounder to measure water level, or a video camera to take a look and see if there is visual evidence of scaling. Water levels with a video camera would not make sense at all. Note that unless you have measurements of specific yield at the outset, measurements now won't let you know if you have well efficiency issues in and of themselves, but will help in the future.