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Water Furnace pump failures

Both pumps on my Water Furnace flow center keep failing.  In the past 10 years, they both have been replaced two or three times.

Now the compressor has failed and one of the pumps is drawing very high amperage.

Has anyone come across similar problems?


  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840
    When will they ever learn....

    You have non oxygen barrier tube in your loop field. You have ferrous components (pumps) moving that fluid. Rust NEVER sleeps, and oxygen ALWAYS seeks equalibrium.

    The bearings in your pump are water lubricated. The water carries ferrous oxides (rust) and the bearings lock up.

    Alcohol is NOT a good water treatment to avoid oxidation. I'm not even sure if there IS a good, suitable, compatible water conditioner for a GSHP cocktail. If anyone knows, it would be Dwight Hedgpeth of Rhomar Water.

    GSHP's were developed by a bunch of farmers out in Oklahoma who have just enough knowledge about hydronics to get themselves into trouble. They refuse to recognize the basic tendencies of water to expand and contract (no expansion tank on their loop fields) and refuse to accept that oxygen can and will penetrate the walls of PE tubing and cause havoc with ferrous components. In order to keep costs low, they refuse to go to an oxygen barrier type of tube. They at least need to start using non ferrous components on the loop side of the system. When asked about the pump failures, they will tell you it is the nature of the beast. It may be the nature of THEIR beast, but not a properly designed beast.

    They also have not changed the compressor technology since forever. Bang Bang compressors in a variable load world = early compressor failure.

    Over half the compressors I had in the field failed within the warranty period. I was told by the rep, that due to the fact that we were using it for preheating DHW, that we were working it too hard, and running it at too high of a temperature. Oh really? If your equipment can't be operated at 140 degrees F, then maybe you shouldn't show performance charts with output temperatures at 140 degrees F, and maybe you should put an internal high limit on YOUR equipment.

    Until which time someone comes out with GSHP with a variable speed, soft start compressor, I have taken myself out of the GSHP market. I don't need the headaches and heart aches of trying to explain to the consumer why it is that an appliance that is supposed to last as long as a freezer or refrigerator is dying such a fast death. They also need to offer them with stainless steel pumps.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Branded
    Branded Member Posts: 9
    Water Furnace pump failures

    Thanks Mark,

    I appreciate the reply.
  • ddlong1286@yahoo.com
    [email protected] Member Posts: 139


    Is that why, when I went thru WaterFurnace training, I was taught to "goose" the loop? They explained that the pipe would contract and expand going from cooling to heating and that we would need to add pressure to the system to keep the pressure up above the minimum needed(above 10 lbs?)to lubricate the pumps.

    Where you seeing the comp. failures with all style and brand of compressors? Scroll, two stage etc. What if they had accumulators? Did that make a difference?

    I worked on one brand that stated they did not need a main loop pump for large commercial systems, just the pump at the unit was all that was needed. Were they being accurate?

    I think Copeland is coming out with a variable speed scroll, would that get you back with GSHP?

    Enjoy your post's, always educational and sometimes entertaining

    Don in MO
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840
    Not sure Don...

    Has been a long while ago. I think they were single state recips and rotarys.

    And yes, If someone comes out with a variable speed compressor, I would be willing to jump back in, but I will do stupid things, like incorporating air removal and expansion tanks into the loop piping :-)

    As for only needing individual pump and not a loop pump, I guess one could design a system that way. Parallel pumps to a single loop field.

    As for brands of compressors, I haven't the faintest because I wasn't properly licensed to work on the refrigerant side of the system.

    Hopefully, the next time I do install a GSHP, the manufacturer will have included their own internal high limit temperature control instead of just depending on a high head pressure cut out on the refrigerant side.

    Thanks for reading, learning and laughing along.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Geosman
    Geosman Member Posts: 23
    Explanation for pump failures

    Geothermal loop pump failure is not specific to a single manufacturer and exists industry wide. As a Geothermal Systems Contractor that services over 9,000 systems from over 43 different manufactures; I can say this issue is industry wide and it has an explanation and a solution to prevent repeat failures. First, I can't remember the last time I met a heating or plumbing contractor who had a water chemistry background and could identify the reason for repeat pump failures. If the problem occurs in the first few years it's considered a "Warranty Issue" but once out of warranty it turns into a "sorry, but S_ _t Happens" issue. When it comes to loop antifreeze solutions, the vast majority of us simply follow the suggestions we see in the installation manuals while others simply ignore the manuals and do as they please. Unfortunately both practices seem to lead to a toxic cocktail for geothermal loops. To this comment I must digress with a discussion......

    The good folks at IGSHPA AHRI and a host of manufacturers are all focused on providing the best possible system efficiency at low temperature loop conditions. The glycols, both the toxic Ethylene Glycol and the non-toxic food grade Propylene Glycol increase in viscosity with concentration and reduced temperature. Consequently, in order to attain turbulent flow at low loop temperatures they require more pumping head to overcome the increased viscosity. If loop designs are meant to remain at or above the freezing point, the glycol concentration need not be more than 20% and the viscosity penalty is hardly noticeable. However, if a loop is designed for a minimum length or needs to operate in the mid 20's a heavier concentration is needed and viscosity and heat transfer efficiency becomes more significant. This brings us to the use of alcohol solutions as a low viscosity antifreeze for testing geothermal equipment. Methanol (racing alcohol) is easily obtained whereas ethanol (corn alcohol) is highly regulated by ATF. In the early development of geothermal closed loop technology, methanol mixed with water to a concentration of 15 to 20% was an industry accepted low viscosity antifreeze.

    (Due to the toxicity of methanol, some communities, health departments and EPA offices forbid its use and specify that a non-toxic antifreeze be used for closed loop geothermal installations). ( The latter restriction has lead to the development of Ethanol based "inhibited" heat transfer solutions that are non-toxic, low viscosity and do not require ATF regulation for their distribution.)

    This brings me to the issue of corrosion and failure of loop pumps. The term "inhibited" means that the antifreeze contains corrosion inhibitors to protect metals within the system.

    Methanol by its nature is pure and does not contain corrosion inhibitors. Those of us old enough to remember Sohio gasoline with Ice Guard may also recall the need to replace leaky gas tanks, fuel lines fuel pumps and carburetors due to corrosion caused by the methanol additive in the gasoline. For the same reason today we find pit crews for top fuel dragsters and funny cars need to replace their "fuel cell" gas tanks on a regular basis or risk a methanol fire. This brings me to the issue of methanol as a geothermal loop antifreeze. When mixed with mineralized water from city or well water, or for that matter, heaven forbid, high sodium water from a water softener, the methanol solution becomes a corrosive cocktail that acts upon the least noble metal in the Galvanic Series. Steel and Cast Iron that comprise the loop pump bodies of most conventional geothermal loop flow centers are very low on the galvanic series and become the "sacrificial anode" for the entire installation. Copper, Cupro-nickle, brass and stainless are much higher on the Galvanic Series and are not affected.

    When faced with pump failures due to corrosion, the best means to avoid a repeat failure is to replace with a bronze or stainless body pump. For new installations it is best to use a distilled or de-ionized water system flush as the initial flush and follow up with an inhibited ethyl alcohol or propylene glycol antifreeze. Flush solutions must be clean and bacteria free. Well water or non-treated water with mineral content should never be used for mixing with an antifreeze solution. The mineral content in these waters will "complex" with the inhibitors in the antifreeze causing them to precipitate as a white sludge and render the inhibitors useless. If the make up water contains bacteria, as is likely with non-chlorinated supplies, the bacteria will create slime in glycols and eventually cause the glycol to breakdown as a vinegar-like solution that smells more like silage than glycol.

    For a great "read" on this topic I might suggest the following link to an article in the HARDI Journal.....

  • Jack
    Jack Member Posts: 1,046
    I just don't get it!

    I was installing them back in the late 70's where we used a glazed solar system to heat a covered pool, which provided the drive. Could not keep the equipment together. Gave up then. When I look at the output numbers from the mini-split heat pumps I cannot see spending the money on a gshp. To much to go wrong vs, simple install, net to the space, great zoning and much lower cost. As well the leaders in all the technology you say you are looking for. As far as I am concerned they are selling the tax credits.

    I heard from one of the manuf of gshp this week and he said there is a big announcement coming on them this week. Wouldn't elaborate. Guess we will see.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840
    Let me guess Jack...

    A VARIABLE speed compressor!! No more need for a buffer tank.

    Guess we'll have to wait and see. I agree with you. I think that ASHP's are taking a large market share away from the GSHP market, and they realize they'd better do something to stop the bleeding, or else...

    Time will tell. Let us know when you hear what you hear.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • zacmobile
    zacmobile Member Posts: 211
    wrong tree

    I have encountered this problem many times before, it isn't so much the water chemistry it's the complete lack of any kind of expansion/contraction allowances in the ground loop piping that is industry standard. Take an undersized slinky loop and run it hard all winter, not only do you freeze the ground but all that plastic pipe contracts and the pressure goes through the roof. Summers here, the loop runs hot, the pipe expands, pressure drops into the negative, pumps cavitate & die.

    There are non pressurized flow centres on the market that alleviate this problem and I have used them, but all you need is an expansion tank on the loop piping & problem solved. I don't know why the geo industry doesn't get that you can't have a closed loop with a wide variance in temperatures & pressures & not expect to have problems because of it. I have been told by someone in the industry that that was what the rubber hose kit was for. Give me a break!
  • CGUstudent
    CGUstudent Member Posts: 1
    pump failure

    I have read about the freezing temperture causing problems, however what about in Florida?  Yes, there has been a few days off just below freezing temps but not for more than two or three days.  2 pump replacements and technicans still don't know what is causing it.  HELP!
  • zacmobile
    zacmobile Member Posts: 211

    Add an expansion tank, pressure gauge and an air separator if they are not already present, the air separator is recommended but can be omitted if the system is purged really well. In addition get the water analysed by a heating speciality lab and treat as necessary. By far the most likely reason pumps caff out is because of cavitation due to loss of pressure. If you have an expansion apparatus in the system it will alleviate that.
  • Housedoc
    Housedoc Member Posts: 66
    Expansion tank

    I'm not getting the relationship between the corrosion and the expansion tank. I can see that expansion of the piping would move dirt away. Then contraction might allow a small air space that inhibits heat transfer. But I ain't getting why an expansion tank would inhibit corrosion. Can someone school me please?

    One more question. What is the ideal pressure for ground loops? I have seen 10 to 50 psi. Is there a scientific answer?
  • zacmobile
    zacmobile Member Posts: 211

    An expansion tank won't prevent corrosion, like I mentioned, if there is corrosion present in the system you would have to get the water analysed & take action based on the results. ie: adding a corrosion inhibitor chemical like furnox or the like. (make sure whatever you put in the system is compatible with the current fluid such as methyl hydrate which is common in geo ground loops)

    I usually set my ground loops at 45 PSI or so, it would work fine at any pressure as long as the suction side of the pump doesn't dip at or below zero, that's when cavitation happens. However, since it is a completely closed loop with no make-up I like to set them where I do to add a pressure "buffer" in case pressure is lost over time it can be topped up at the next service interval.
This discussion has been closed.