New DSH install - pump not moving heated water

Greetings,
I've had a Enertech geothermal install just under a year now. In early July, I completed the move of my solar hot water system to the center of my basement where my geothermal installation sits and also hooked up the DSH to a non-powered 30 gallon Utica Boiler tank left over from my previous oil fired boiler setup. The Utica tank is setup as a preheat tank for my solar powered hot water tank. I live in an area that needs little air conditioning (we had a total of 6 AC days this summer and it was one of the hottest summers on record...otherwise my HP has been off since early May) so I'd prefer not to invest in a new 50-80 hot water tank until I new how much benefit I will get out of the DSH. I followed Enterch's piping instructions and have connected the DSH Output to the drain of the Utica tank and connected the DSH Input to the fitting on the Utica tank that previously had the hot water temperature sensor for the boiler. I have added isolation and drain valves in the lines between the DSH and the Utica boiler so that I can drain either the Utica tank or the DSH loop without having to drain both. This has allowed me to easily purge all the air out of the DSH loop (I ran about 20 gallons through the 1/2" plumbing with the DSH return line drain valve wide open). When I connect the DSH pump motor spade connector to the HP wiring junction block I see a small spark which indicates to me the two temperature sensor contacts are closed and the pump is seeing voltage and drawing current. No hot water moves, however, unless I open the DSH return line drain valve....so I know there is hot water in the DSH but it isn't circulating. I've read on this forum that there needs to be about a 2lb pressure differential for the DSH pump to work....but I haven't figure out how to insure that is the case on my system. Thoughts and suggestions appreciated.

Tim

(I spoke with a rep from the company that installed my system back in July and they told me they would be by to look at my DSH install the next time a service person came to my area. Failed attempts to reach my installer prompted me to call an acquaintance that has system installed by the same compay...it seems the company no longer exists. My friend has the same HP and said that their DSH produces hot water year round...if so, I would have no problem replacing the 30 gallon Utica tank with a 50-80 gallon non-powered tank...but I would really like to see the DSH work before investing more $$ in the system)

 

There is usually a little sticker on the DSH circulation pump which says "burp me". Most common reason is that the pump is air locked.

 

Docjenser - No sticker on the pump but the instructions do refer to loosening the screw at the center of the pump housing to purge the air.. The first two times I turned the screw counterclockwise, I got water that clearly had air mixed with it (milky)...every subsequent time I've only got clear water. I ran the 20 gallons or so of water through the pipes after I got clear water from bleeding the pump. If there is something else I should be doing in terms of bleeding the pump, please advise.
Thanks
Tim

 

Maybe a dip switch

My GHP came shipped with a dip switch setting which had the DSH pump in the off position. Had to throw the dip switch. If not done, check owners manual for which switch position should be...

The fact that you saw a spark when you connected spade suggests you did not pull the breaker for the unit. Bad practice. Not sure if that would indicate 240V required for the pump, maybe the line has voltage, but not signal for on if dip switch is incorrect setting. Post your unit model number and folks who know more than me can tell you which switch and what position it should be.

 

mtrentw
I have read other posts on this site which make mention of dip switch settings for some HP brands. When I spoke with my company techie in early July asking permission to energize the DSH, I asked him specifically if there was a dip switch on my HP for the DSH. His answer was no...simply connect the wires of the DSH to the terminal block. The terminal block appears to be for the DSH only and is protected by two 7 amp circuit breakers. Although the wires are red and black he said it didnt' matter which wire I connected to which terminal since it was AC, however, for the sake of conformity I have connected the black wire from the DSH to the terminal block black wire and the red wire from the pump to the red wire on the terminal block. Also, his instructions to me were to make sure the piping was full of water and purged of air as much as possible before connecting the DSH wires to the terminal blocks. I've been through the piping and pump purge routines several times trying to insure there is no air in the system. When no hot water seemed to move through the piping, I decided to connect the DSH pump manually while the HP was running to see if I could feel a change in the pump vibration indicating the pump motor had started spinning as there was no other way for me to confirm the pump was turning. It was during that proceedure that I noticed a slight spark indicating to me the electrical circuit was complete.

In addition to the pump air bleeding I mentioned in my last post, I have also closed the gate valves on the DSH input and output pipes, removed the the bleed screw cap completely and used a screw driver to manually but slowly turn the pump motor shaft clockwise several revolutions looking for any binds or resistance to turning....all seem s to be fine. I have then reinstalled the cap screw tightly, opened both valves and then bled the pump one more time to try to insure there is no trapped air in the pump itself.

As requested the model number of my HP is GWT058A11AAACSS,

Thanks for your interest and suggestions....

Tim

 

Just follow the checklist. Is the pump spinning yes/no? If no, is there power at the pump? If no, is there power at the relay and at the terminal? Is it an old tank with debris in there which no plugs up the pump? Just follow the steps.

 

Some tanks are equipped with back flow preventers on the cold water inlet.It would need to be removed.

How do you know the water isn't moving?

 

jrh,
The cold water inlet on this tank has always been at the bottom where the drain is also located. Currently the tank is in series with my solar tank and I have no problem getting hot water to my faucets. The tank is an indirect heated tank..ie there is an internal coil through which the oil fired boiler hot water circulated to heat the tank. The indirect coil is not plumbed/used in the current configuration The hot water outlet to my faucets is at the top of tank.

I know the water isn't circulating because I never get anything but room temperature readings from my thermometer probes on both the DSH input and outlet. The only time I have seen anything but room tempertature readings was when I opened the bleeder valve on the DSH output just before it enters the storage tank....then I saw temps approaching 103F.

Tim

 

But now you have added a tee right?
And now you are pulling water through a port that typically only has water pushed through it.

 

jrh,
Both the domestic cold water and the DSH output join at a T...the other end of the T is connected to the fitting at the bottom of the storage tank...ie the domestic cold water and DSH output both flow the same direction into the bottom of the tank. When the tank was installed on the oil boiler, the domestic cold water entered the tank at the same spot..only difference was there was no DSH output present at the same point. Currently, the domestic cold water passes through the DSH storage tank before reaching the input of the solar tank.

I'll attempt to upload a picture here in hopes it clears things up. The two insulated pipes at the bottom are the 1/2" copper lines that go to the DSH which sits to the right (out of view). The line in front connected to the silver flex hose (blue arrow) goes to the DSH input and the line to the rear comes from the DSH output and goes to the bottom port on the tank (red arrow). Also visible are the domestic cold in and the storage tank output which feeds my solar tank (partially visible to the right). Ther are no ports on the top of the tank..what you see in the picture is a fitting and roll of pipe tape that just happen to be sitting on the tank when I took the picture.

FYI...I originally had the DSH Input connected to the valve below the T where the hot water exits the storage tank...I wasn't getting any different results there. Since we typically use less than 30 gallons of hot water a day, I moved the connection to where it is in the picture in hopes of the DSH seeing the coolest supply of water.

Tim

 

DSH does appear to be working after all.

I was explaining to my wife the issue of the DSH and was showing her the DSH IN and DSH OUT on the HP. I touched the DSH IN and it was warm but the DSH OUT was cool. I was a bit perplexed as I would have expected just the opposite. I decided to reconnect the DSH pump motor to AC power and a few minutes later the HP came on. I then touched the DSH IN and DSH OUT again and the DSH IN was warm but the DSH OUT was warmer. I fired up my monitoring system and sure enough the DSH IN was sitting at 78F and the DSH OUT was 88F...the room and tank water temperature were both 50F...so it appears the DSH is working. I guess now I don't understand why saw 50F on both the DSH IN and DSH OUT when the HP was running in the cooling cycle. I'm glad it seems to be working at least but I'm confused why I didn't see these same temps during the cooling cycle which I understand should produce more hot water than the heating cycle.

Where am I going wrong here?

Tim

 

Heating cycle produces more DSH than cooling cycle, depending on your loop temperature. Where are you located?

 

Docjenser,
I'm located in South Central NY...about 20 miles north of the NY/PA Border, about 20 miles South of Cortland and just a couple miles West of I-81. FYI In late July when I asked the service tech about the DSH OUT temps I should expect, he indicated I should see temps in the high 80's to mid 90's...about what I'm seeing now during the heating cycle. Maybe my expectations are off but clearly I wasn't seeing any difference between DSH IN & DSH OUT and the ambient cold water in and basement temps....all about 50F. My temp probes were installed then and remain installed without any modification...so nothing has changed in my geo environment other than switching from cool cycle to heat cycle.
Thanks,
Tim

 

DSH temps depend on water usage, but mainly on run time and source temperatures. You are heating dominated and you do not have much runtime if your unit is sized for heating.


During the A/C season, due to cold grounds (65F max) and cycling in 1st stage I usually see temps around 90-100F in the buffer tank.
Now the heating just started, and again the unit is cycling in 1st stage, resulting in about 90F buffer tank temp, but will increase steadily. You will see much hotter water pretty soon.

Check out some monitoring and look at the buffer tank temp and DSH in and out temps.
Temperature and Energy logging by: Web Energy Logger

Here are more
Buffalo GeoThermal Heating

 

Dojenser,
The water in the preheat tank is getting warmer even though the HP has only cycled a couple of times. I guess I'll just be happy that it appears to be working now.
Thanks much,
Tim

 

Some systems detect when conditions are not favorable for hot water generation and stop the DSH pump from operating. Cooling mode with low loop temperatures can produce unfavorable DSH conditions - the possibility of tepid refrigerant transferring heat OUT OF rather than into a tank of water.

 

Curt,
I guess I'm somewhat confused by two things:
1) the sales person's explanation of how the DSH in my HP was going to work vs how it actually works. I was originally told that in the heating mode the DSH would transfer any "residual heat" left in the HP at the end of a cycle to the preheat tank and, in cooling mode it would scavenge the heat from the house and transfer it directly to the preheat tank rather than sending the heat out to the loop. It is evident the DSH runs concurrently with the HP not sequentially after the HP stops. In cooling mode, I was and I am expecting the DSH should be running any time the HP runs once there is sufficient heat for the temperature switch to close.
2) Subsequently I have learned the DSH has two temperature switches that determine if the DSH pump runs. Since in cooling mode I was seeing a slight spark when I connect the DSH pump leads to the terminal block, I thought that was telling me the electrical connection to the DSH pump motor was energized and the pump motor should be turning and pumping. I see the same spark when I connect the DSH pump motor leads during the heating mode...the only difference is I'm seeing hot water going to my preheat tank in heating mode. Although I've done nothing with regardst to the DSH since I gave up trying to get it to work in cooling mode, at this point, I'm content that it is working in heat mode. I'll wait til next summer to see what happens in cooling mode then.

 

the guy was obviously misinformed.

The DSH takes heat from the refrigerant first in the heating cycle not last.

 

Here are two diagrams showing the refrigerant flow in a heat pump in cooling and heating modes.

 

Good diagrams from Dewayne

The thing to understand is that refrigerant enters the compressor as a somewhat superheated vapor, regardless of whether in heating or cooling mode.

After the refrigerant passes over the compressor's hard working motor windings and other moving parts it picks up substantial additional superheat.

Upon being compressed, the refrigerant's temperature is substantially increased, and the superheat is added, carried along for the ride.

All that superheat and heat of compression results in the compressor's discharge being quite hot, well above the temperature of a typical domestic water heater. That means that heat energy in the superheated hot gas discharge from the compressor is ripe for harvesting to preheat domestic hot water.

Under certain circumstances the compressor discharge won't be warm enough for effective addition to domestic water. It is then that the desuperheater water pump is stopped.

I very much doubt your salesperson is adequately aware of these facts.