Geothermal Hydronic Desuperheater pump fried
System is seven year old Enertech. Started getting high head pressure lockout. HVAC company scratched their heads as to the cause, plumber declined to even come out, so I took off the panels to see if there was anything obvious.
Desuperheater recirculating pump looks corroded at a minimum, likely fried. Other evidence of overheating in the compartment as well.
There simply aren’t qualified professionals in the area to service these units, so I am leaning towards hiring a HVAC company to replace the pump. However, I fear that the pump’s failure is merely a symptom of some other issue that will go uncorrected, and I really don’t want to cut corners.
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Replies
That sort of corrosion on the outside of the pump is a symptom of water leaking onto it. Those Grundfos are normally very reliable, they can last decades. If they fail, most commonly it's because there's air in the water. They can also get jammed by debris in the water.
I would be looking for leaks.
Thanks for confirming my suspicions. I’ll get someone out here to replace the pump and flush the system!
As I recall the location cover in “corrosion” is a solid cast iron surface without much of anything to leak except the pipe joint.
What you are seeing looks more like a slow leak of water that was evaporated by the heat leaving the mineral from the water behind.
I doubt the pump is bad simply because it has some mineral deposits on the outside.
Consider finding a different HVAC company clearly the one you have seem to be in over their head.
Note I think you should reframe from diagnosing the fault and condemning parts as bad. Consider describing what symptoms have observed and allow your technician to make the diagnosis.
I thought the use of the desuperheater was optimal and its failure should not set a code.
Is your system an open or closed loop?
High head pressure would indicate poor heat transfer from the refrigerant.
Consider posting on the GeoExcange forum.
https://forum.geoexchange.org/
Walta
Desuperheater pumps on many systems are directly exposed to potable water (e.g. the supply and return for the loop is a DHW “pre-heat” tank with no internal heat exchanger). If this is true for your system, any replacement pump must be compatible with water with a high amount of dissolved oxygen. So it has to be brass or stainless, not cast iron.
Appreciated! That sounds exactly like my setup - water heater supplies Geo unit, which supplies storage tank, which supplies floor manifold. There is an expansion tank in the mix as well.
As such, all the piping is copper and there are numerous brass fittings. The housing on all pumps appears to be cast iron! The only pump showing insult is the one inside the compartment, though, and it is alone in the amount on insult (slight copper oxidation a couple of places, primarily on the oil separator fittings).
That circulator is brass.
Thanks, Paul.
If they bend up replacing the pump, I will disassemble it out of curiosity!!
Thanks, Walta!
It was I who presumed the pump is faulty, based only on the presentation of the cover and joints.
Some of the pipe wrap in the compartment melted enough to fall off the copper, so my presumption is that there is inadequate cooling that is triggering the high head pressure lockout. Whether that is due to pump failure, dirt (closed system so very unlikely), or air in the system (never heard any knocking) remains to be seen.
I can only hope the company coming out in the morning is knowledgeable. I admittedly am not!!