Ok, GeoMax operating.

My ground loop delta measured at the manifold with probe thermometers is 7 F. 67 EWT, 74 LWT.

probe thermometers on the DSH lines by the GeoMax read: Cold/DSH IN: 109 F Hot/DSH OUT: 87 F

But at the far end of the DSH pex lines that connect to the water heater tank, I could not tell any difference between the Hot and Cold pex lines. I would assume that means the pump was *not* circulating the water through the DSH. I can't imagine 30 degrees of heat would be lost over 25 feet of pex tubing.

The more I check the system, the more I don't think my DSH is working at all. We've used a little hot water today, the GeoMax has been running off and on all day very regularly, but the AirTap is still coming on (thermo on AirTap set to 115) to heat the water! When I turned the AirTap down, the whole system failed to produce satisfactory hot water. I don't think the DSH ever comes on, or if it does, it's extremely minimal.

Since I'm not home much, it difficult to monitor the DSH circulation pump all day.  Without buying an entire WELserver, could I make do with a single current-detecting switch for $23?
I'm guessing the current-detecting switch slips over one of the a/c wires to the DSH pump and when the wire "goes live", the switch closes?  I could hook up a battery and LED to the switch, right? and the LED would light when current flows.  I could then aim a usb camera at the LED, then record the entire day on video on the laptop, then playback to see if/when/how long the DSH came on for?

Posted By stuart.wyss on 29 Aug 2010 07:29 PM
The more I check the system, the more I don't think my DSH is working at all.

I think you might be right

me too - the in/out temps may be explained by very low flows resulting from natural convection

Borrow a clamp amp meter to determine DSH pump current, though it is quite low, 1/2 amp or less. Pump itself gets quite hot if it has been on awhile.

Feel refrigerant line temps in and out of DSH after compressor has been running for awhile, say 10 minutes - if operating there should be a substantial drop in refrigerant line temp

Posted By geodean on 29 Aug 2010 10:44 PM

Posted By stuart.wyss on 29 Aug 2010 07:29 PM
The more I check the system, the more I don't think my DSH is working at all.

I think you might be right

This has been discussed in detail. Probably your EWT is too low to have the compressor discharge temp above 125 degrees. Thus your DSH pump does not turn on. All the R-410a units from Heatcontroller have those "symptoms". http://www.greenbuildingtalk.com/Forums/tabid/53/aff/13/aft/77450/afv/topic/afpgj/3/Default.aspx

I have been reading all those posts. My annoyance is this: How would I ever get the DSH to actually run? I mean, I can't raise my EWT, and a low EWT is good, isn't it? Doesn't it mean my loops are doing really well? A delta of 7 in the loops seems great, too.

Plus, in cooling mode, wouldn't the most logical place to dump heat from the house be the DSH, regardless of the EWT? I can't believe that the house isn't supplying enough "waste" heat that the DSH can't make use of it. It seems completely illogical to me.

I can see during the winter that the DSH might not come on if the loops aren't providing enough heat for everything, but in summer, it seems to be a complete waste of heat to not put it in the DSH. 

The first step may be to verify the DSH is working properly.

I wonder if putting the system in heating mode for testing purposes would be helpful? The manual that I downloaded lists that SW10 can be used for 5 minutes for testing or purging of air in the lines. I'm not sure if this is the same with your unit.

Low grade heat is hard (ie, often not worth it) to make use of. But a buffer tank and correct logic in the heat pump will make use of some of it.

Some people aren't aware of this which is why WF writes:

Note: Under certain conditions, Envision dual capacity units operate with very low refrigerant discharge temperatures,
producing little or no water heating capability. This scenario occurs when the unit is operating with cold entering source
water (loop or well).

I can see this being an issue in winter, but not summer. So much extra heat is available in summer from the house. Weird. I do need to verify that it even tries to come on, though.

Our loop temp is 75.3f this morning and our WF DSH is producing hot water (from feeling the lines). Fortunately, we have always had good luck with our DSH producing hot water. Maybe our units were made on a Tuesday (reference anyone?)

I'm sure my unit was installed on a Thursday. Never could get the hang of Thursdays... (reference anyone?)

Geome, is that 75.3F your EWT or LWT? And your DSH OUT is definitely hotter than your IN, right?

I hesitate saying this not knowing your level of expertise.

There is a fairly easy way to tell what is going on. Ideally your installer should do this.

You could hot wire the DSH pump to come on when the compressor starts.

Make sure that the voltage on the pump is 208/220, then wire it onto the load side of the compressor contactor.

Then when the compressor starts, the DSH pump will start. Then you can check the lines and see if any heat is being exchanged.

Be very careful doing this. Make sure that the breaker is turned off before doing anything. Make sure that you know where to hook the wires.

If you do something wrong, you could be seriously injured and so could the heat pump.

That might be a last resort, as I would not want to damage anything or risk voiding the warranty. Could I just bypass the thermostatic switches with a piece of 12 ga. wire? I mean, the worst thing that would happen is the pump would turn on and possibly the system wouldn't produce much HW if I was watching it. I'd certainly make sure the DSH wasn't exceeding 125 on the output.

I'm also looking into getting a WELserver...expensive....SIGH.

Maybe bypassing the switches would work. I have never done that, so I can't say for sure. You don't need a WEL server to tell you if the DSH is working. At this point we are pretty sure that it is not working. Get the DSH pump to run and then you can check the in and out and see if you are getting any hot water.

Posted By stuart.wyss on 30 Aug 2010 01:16 PM
Geome, is that 75.3F your EWT or LWT? And your DSH OUT is definitely hotter than your IN, right?

Sorry, EWT.

Yes, our DSH Out is hotter than the In.  We have systems from different manufacturers, and possible a different sensor set up and different programming, but I think I see where you're going with this - if our DSH can make hot water, then why not yours since we have similar EWT's.

Check your manual about DSH test mode.  I don't have confidence in my ability to jump wires without harming myself, but I could certainly switch my thermostat to heating mode and feel the pex lines.  If the DSH Out still isn't hotter than the In, maybe the issue isn't EWT?  The only other step I would take is purging the line with the bleeder valve that is already installed on our pipe with all surrounding power turned off until the entire area is thoroughly dry and being sure to not get any equipment wet in the process.  You may be more skilled than I am with this sort of thing.

The WELserver was more just to post all my data to the web like many others, not for troubleshooting....sadly, I know my system isn't working properly :-(

I suppose if one wanted to force up the temperatures, they could bypass the ground loop circuit to some extent. Might even be worth it in some cases.

.

I can verify that the terminals to which the DSH pump and thermostatic switches does get power as soon as the compressor activates. I can also confirm that the circulator pump itself does *NOT* get power, which means one of the two t-switches are open. I know by testing it's not the 125 F cutoff of the HWG IN line, therefore, it must be the other t-switch on the refrigerant lines. These lines seem too far back in the cabinet to reach, so I can't test them by touch.

Your low LWT may well be keeping the DSH off, perhaps rightly so.