I recently had a Bosch 3-ton Open Loop (Pump and Dump) 2-stage Geothermal Heat Pump installed. My HVAC installer did not initially set up the water lines correctly (see attached photo). He did not put any valves at all on the discharge line, even though a Taco Zone Control valve came with the unit. Obviously I then had a problem with water hammer. I contacted my well driller who has extensive experience in geo water line configuration and together we (believe) configured the lines correctly (see attached photo). The original configuration had a Honeywell DS06-101-LF pressure regulating valve and an adjustable flow regulator on the inlet line. Within a few days the unit froze up and my HVAC guy thought the flow control valve was malfunctioning and replaced it with a manual ball valve. Still had the same problem. When my well driller and I got together we removed the Honeywell valve and found that it was clogged up with sand. We then proceeded to re-configure the lines. Inlet: spin down filter > ball control valve Discharge: Taco slow opening zone control valve > flow regulator. (The Honeywell valve was removed.) We then experienced water hammer on the inlet line and installed a bladder tank as you can see in the photo. This helped but still experience a softer hammer. The Taco valve seems to be working properly, but there is now an issue with the discharge line being very noisy with the gurgling sound of water rushing though (but no more loud hammer). The 1" discharge line goes up then across the basement ceiling and connects with an elbow at a sidewall to a 1-1/4" line that drops down 6 feet and goes out underground to my pond. (Could the difference in line sizes cause the problem?) I think the issue with the inlet line still slightly hammering can be solved with tweeking the bladder tank. The more pressing issue is to try and solve the discharge line noise. Of note the unit requires 6 gpm minimum, but we have the all the valves wide open because this seems to give the best heat/fan performance (probably running 15 gpm). When we throttle back the gpm flow that seems to increase the discharge line flow noise. Both water line's entrance/exit points are located directly under my bedroom....so my sleep gets interrupted.
To reduce inlet water hammer, reconfigure your bladder tank and T so that the bladder tank is directly in-line with the supply line and so the line to the heat pump inlet taps off the leg of the T. In your current configuration, the surge of water from your pump goes right past the bladder tank and hits that hard 90 degree fitting right at the inlet to the heat exchanger. The bladder tank doesn't see the initial pressure surge until the pressure wave is reflected back from the 90 degree fitting. Putting the bladder tank directly in-line with the supply line will let the rubber bladder in the tank absorb the initial pressure surge. Also, what is the air pressure in the bladder? It is typically set ~2 PSI below pump turn on pressure, but in this case with no pressure switch or tank, I would say you want it set very low, say 5 psi or less, to provide maximum pressure surge absorption. What HP is your water pump and where is it located? Is the pump dedicated to the heat pump? From a previous post, that appears to be the case and your pump is a submersible. If so, it sounds like you have way more pump than you need if you are pushing 15 GPM and only need ~6 GPM. Is it too late to switch to a lower HP pump? You are going to waste a lot of energy with that oversized pump. Depending on how high you have to lift the water (distance from top of water level in well, not the pump depth, to highest point in the discharge line), you might be able to get by with a 1/3 or 1/2 HP submersible pump. If you are stuck with the pump you have, you might put a restriction in the line at the pump discharge to limit flow and resulting downstream water hammer and noise generating turbulence. This would move some or all of the flow noise to the restriction, so if it could be placed outside the home would be best. If your line is underground from the well to the house, you might install a valve box to provide access. If you have a 3/4" or 1" supply line from the water pump to the heat pump, you might install a ~2' section of 1/2" pipe near the pump discharge to limit flow. Better yet, put a loop of 1/2" pipe to further absorb the surge from the water pump kicking on. If you have PVC pipe from the pump to the unit, you could install adapters with barb fittings to install either 1/2" rubber or flexible black HDPE pipe in the line.
When I check the pressure with a pressure gauge on the HP inlet valve it reads 50psi at well pump start up, then reduces down to about 12psi when HP is running (after the slow start Taco valve kicks in). The inlet line hammer was originally very loud but has been significantly reduced with the bladder. I believe we have the bladder set at 15psi. I think we should try tweeking it's pressure and see if we can get the hammer even lower. If I understand your response you think we should mount the bladder right where the 90deg inlet is at the HP? We installed a 1.5hp Goulds 25gpm submersible well pump because it is located downhill next to my pond. The pump is set at 160ft and it is a 300ft run uphill to the house at about a 30ft rise in elevation. I have to say we were surprised when we checked the line before drilling it through the basement wall and it had 40psi and 15gpm. We did install a hydrant adjacent to the well at the pond to provide supplemental water to the pond to keep it full only periodically as needed, but we don't believe we can run the hydrant and the HP at the same time. The well pump supply and discharge lines are both 1-1/4" where they enter the basement wall and rise to the ceiling where they then connect with elbows to 1" lines going 50ft to the HP. (Note: I originally bought a 1hp Goulds 25gpm pump to install at the pond to only supplement the pond water level. However, my driller told me I could use the well he was drilling to convert my HVAC to geothermal which I decided to do, but he said I would have to upgrade to a 1.5hp pump.) I will print out your response and show it to my driller. On another matter, I still have this issue with the very loud water rushing/gurgling noise on the discharge line at startup, along with a little less loud noise when running, and then a louder noise when it shuts down. I'm assuming there is air in the line since it discharges to daylight at the pond. Do you have any recommendation on how to solve this discharge noise problem that keeps me awake? Thanks !!
Open loop water noise is a common issue. Any component in the system that creates more than a 8 psi pressure drop can create water noise. In your system with 50psi inlet and 0psi (to atmosphere) outlet has greatest potential to make noise. It can be greatly reduced with appropriate pressure settings, pipe sizing and flow rate. At this point, instead of starting from scratch, try installing a valve outside on the outlet to pond and throttle down until you have the proper flow through the heat pump. This will will force the greatest pressure drop (noise) in the system outside.
I'd like give you some background and additional info on this project you may find interesting (if not sad). I do wish hindsight was 20/20. Last year I had a 3/4 acre 20ft deep pond installed at a location 300ft downhill from my house. It was filling very slowly and in late summer would lose over 2ft of water level due to evaporation. I decided this fall to go ahead and install a well at the location, along with a 230v pond aerator/compressor system. So I ran UG wire to a subpanel with circuit breakers for the well and aerator and had the well dug. I had originally purchased a 1hp 25gpm pump, but soon after drilling began my driller happened to mention that I could use this well for geothermal if I wanted to. I had plans to replace my existing electric furnace anyway, so I decided to go in that direction and contacted my HVAC guy to do the install. My driller felt that I needed to upgrade to a 1.5hp pump, which I did. I have an existing 1hp well in my front yard that supplies water to the house. I was never happy with it's pressure, although it is on a 30-50 pressure switch. I've not tried to measure its gpm, I only know the original driller bailed it at 12gpm. I thought separate wells for the pond and the house was acceptable at the time. I was going to have the geo installed in an unfinished basement room directly below the location of the electric furnace on the main floor, which is a central location for the ductwork. However I have an equipment room in the basement that has a floor drain so I decided to install it there, and the electric panel is nearby (see attached photo). This room is where the other well enters and the pressure tank is located. Had I known back then what I know now I would have done things totally different. I would not have drilled the new well and only had a ditch dug to the pond for the discharge line (and electric line for my aerator). I would have upgraded the existing well capability, plumbed it to the geo and domestic via the pressure tank, and installed a bypass where I could run more/continuous water down the discharge line to supplement the pond (turning other components off temporarily if needed). I certainly would also have not installed the discharge line directly under my master bedroom. So, regarding the problems I'm having, I'm guessing adjusting the flow rate down on the inlet ball valve and on the discharge flow control valve will not solve the issues. Also of note regarding your proposed steps, the water lines are buried 6ft underground. - Since the most noise on the discharge line seems to be coming at the point where the 1" line elbows at the ceiling and connects to the 1-1/4" line running down the sidewall, he thinks extending the 1" down the 6ft and connecting it where the 1-1/4" line exits the wall might be quieter. - He also previously discussed installing a 1" 10gpm static flow valve somewhere in the system (see attached photo). Do you think this would help, and if so where to install it...maybe at that point where the 1" line will connect to the 1-1/4" discharge, 6ft down from the ceiling? Since the geo is located in the equipment room, other considerations might deal with reconfiguring the wells and water lines. - Connect the pond well pump inlet line to the existing pressure tank switch (no more hammer), then plumb over to the geo. This would run both wells at the same time when water is called for. Or install two separate pressure switches with different settings for the geo and domestic - Maybe switch the order and connect the 1.5hp well to domestic/pressure tank, and the existing 1hp well direct to the geo. - I still have the brand new 1hp pump and could consider replacing the 1.5hp, and maybe replace the 1hp domestic with it, leaving the existing configurations as is. - Would re-installing that Honeywell pressure regulating valve somewhere help out? - Also, I thought my HVAC guy had once mentioned he could install a pump on the discharge line. I wish I could say this has been fun. Thanks !!
When you upgraded your pond pump from 1hp to 1.5 hp what is the gpm rating for that 1.5hp pump? Geothermal needs flow, not pressure. A pressure reducing valve on the inlet side taking 40 psi down to 10 or 15 psi prior to entering the unit would make a huge difference imho. 50 psi to atmosphere is a pressure drop night mare as already mentioned. Eric
