Will Iron in Well Water clog Geo Heat Pump Heat Exchanger in an Open System?

It's looking like my existing domestic water well is a good candidate for use in an open Standing Water Column arrangement.  The one remaining question is water quality.  There is enough iron in the well water that we needed to add a back flushing filter system for the domestic water to remove it - However, I don't think it's practical to run all water through the filter, it's not designed for that amount of use.

Have other people been able to use water with iron in an open system?  Are you able to clean the heat exchanger when needed?  Is there a more cleanable heat exchanger in certain brands of heat pumps?

For reference, the untreated water looks like this:

pH = 6.91

The below is my failed attempt to past a table from a Waterfurnace install manual. Where you see two values they are for copper and cupronickel heat exchangers. If your iron is same as WF's iron oxide, then it looks like your water isn't suitable. Your solids are high as well. In theory, heat exchangers can be cleaned by isolation and flushing. I plumbed mine with isolation valves and flush valves on tee fittings below the isolation valves so as to be able to pump a cleaning solution through the heat exchanger. I doubt that there are differences in heat exchanger cleanability.

Sorry the below isn't more readable

Water Quality
In ground water situations where scaling could be heavy or where biological growth such as iron bacteria will be present,
a closed loop system is recommended. The heat exchanger coils in ground water systems may, over a period of time,
lose heat exchange capabilities due to a buildup of mineral deposits inside. These can be cleaned, but only by a qualifi ed
service mechanic, as special solutions and pumping equipment are required. Desuperheater coils can likewise become
scaled and possibly plugged. In areas with extremely hard water, the owner should be informed that the heat exchanger
may require occasional fl ushing.
Units with cupronickel heat exchangers are recommended for open loop applications due to the increased resistance to
build-up and corrosion, along with reduced wear caused by acid cleaning.
Iron, Fe2+ (Ferrous)
Bacterial Iron Potential
Material Copper 90/10 Cupro-Nickel
pH Acidity/Alkalinity 7- 9 5 - 9
Scaling Calcium and Magnesium Carbonate (Total Hardness) less than 350 ppm (Total Hardness) less than 350 ppm
Hydrogen Sulfide
Less than .5 ppm
(rotten egg smell appears at 0.5 PPM)
10 - 50 ppm
Sulfates Less than 125 ppm Less than 125 ppm
Chlorine Less than .5 ppm Less than .5 ppm
Chlorides Less than 20 ppm Less than125 ppm
Carbon Dioxide Less than 50 ppm 10 - 50 ppm
Ammonia Less than 2 ppm Less than 2 ppm
Ammonia Chloride Less than .5 ppm Less than .5 ppm
Ammonia Nitrate Less than .5 ppm Less than .5 ppm
Ammonia Hydroxide Less than .5 ppm Less than .5 ppm
Ammonia Sulfate Less than .5 ppm Less than .5 ppm
Total Dissolved Solids (TDS) Less than 1000 ppm 1000-1500 ppm
None None
Iron Oxide
Less than 1 ppm. Above this level
deposition will occur.
Less than 1 ppm. Above this level
deposition will occur.
Suspended Solids
Less than 10 ppm and filtered for max
of 600 micron size
Less than 10 ppm and filtered for max
of 600 micron size
Threshold Velocity (Fresh Water) 5-8 ft/sec 8-12 ft/sec
Corrosion
Iron Fouling
(Biological Growth)
Erosion
Note: Grains = PPM divided by 17 • mg/l is equivalent to PPM

If you are using an open system with water with high mineral content, you will likely experience fouling or scaling problems.  Plate and frame heat exchangers are made to be disassembled and cleaned and are suitable for well water.  We use them commercially, but I do not know how small they are made.  Shell and tube type heat exchangers are difficult to clean.

Bruce

It's not only the heat exchanger that will need to be cleaned, but the solenoid valves may gum up, too. There is a local in my area with an open loop system with higher iron content. He has to replace solenoid valves every other year, along with periodically changing other parts that corrode from his water. It's a maintenance headache.

Shell and tube exchangers can be cleaned by removing the end cap and bore brushing the individual tubes. That's not particularly relevant since resi geo units use coaxial tube-in-tube heat exchangers, The only way to clean those, to my knowledge, is via flushing.

thanks Engineer for sending those specs.  It does look like the built in heat exchanger will probably get clogged and I know it will be a pain to clean it, which will probably be less than 100% effective anyway.

So, yet another level of heat exchange might be the way to go - plate and frame as Bruce says.  I know these are available in smaller sizes, and you can go with less plates.  I've seen them on eBay...

Another problem solved!  thanks for your ideas.

Then I've learned something - I had no idea plate and frame heat exchangers are being used on residential-sized equipment. I've seen great honking dumpster-sized examples mated to 1000 ton chillers, but nothing itty-bitty.

I don't know if they're being used much by 'normal' people, but I have seen ones smaller than you would see isolating a free cooling loop on a chw system for example.  Buying one new would be painful but probably do-able on eBay from what I've seen in the past.  Filing this info away....

EarthLinked in their water heating units uses a plate heat exchanger for 2-6 tons. Don't know what brand it is, though.

Hi Clark,

Yes, I think that is going to be a brazed plate heat exchanger which are very nice, but with junky water they are hard to clean.  You can't take them apart, only try to purge them and run acid through them.  The nice thing about the plate and frame is you can dissasemble it when it gets bad enough and clean it up.  (not something you want to do every day!)