I have a desuperheater to Marathon buffer to Marathon finish tank. I had a geo tech check the system. He says water is not circulating thru the buffer tank. The geo,pump etc. is working fine. I believe the lines might need purged, or possibly the vacuum valve or check valve causing the problem. Is there a separate check valve/flap in the cold water inlet on the Marathon? Any advice is appreciated. Picture attached.

Posted By Newbie1 on 17 Aug 2015 09:34 PM
I have a desuperheater to Marathon buffer to Marathon finish tank. I had a geo tech check the system. He says water is not circulating thru the buffer tank. The geo,pump etc. is working fine. I believe the lines might need purged, or possibly the vacuum valve or check valve causing the problem. Is there a separate check valve/flap in the cold water inlet on the Marathon? ...

Not at the time we purchased our Marathon.  Call Marathon customer service to be sure.  They were extremely helpful to me in the past.

Could be air locked, or something else.  Is this a new installation?  A complete drawing of the plumbing indicating check valves, etc., wouldn't hurt.

I called Marathon today. They said there was not a check valve in the cold inlet. The plumbing setup: DSH out to buffer tank drain; Tee,from buffer tank cold water in, to DSH in; buffer tank hot water out to finish tank cold in. Basically the Bergy drawing minus the air check at the highest point. The geo tech said the lines going to the buffer tank should be hotter. I drained some water today the temp was 90 deg. so apparently water is circulating. What temperatures should I expect? The unit doesn't run very long per cycle. Thanks for the response.

Posted By Newbie1 on 18 Aug 2015 05:52 PM
I called Marathon today. They said there was not a check valve in the cold inlet. The plumbing setup: DSH out to buffer tank drain; Tee,from buffer tank cold water in, to DSH in; buffer tank hot water out to finish tank cold in. Basically the Bergy drawing minus the air check at the highest point. The geo tech said the lines going to the buffer tank should be hotter. I drained some water today the temp was 90 deg. so apparently water is circulating. What temperatures should I expect? The unit doesn't run very long per cycle. Thanks for the response.

In water to air systems, the DSH raises the water temp going into the DSH by a few degrees.  Insulate the DSH lines to minimize heat loss.

I, and others here, have noticed better DSH performance with longer run times that we achieved by reducing cycles per hour on 2 stage water to air systems.  House temperature swings will increase as a result of reducing CPH.  I don't have and am not familiar with inverter based and radiant units.  Not sure what type of system you have.

I'll let the pros comment on plumbing, etc.

If you measured 90 degree water from your buffer tank, I would think the DSH is working and circulating. As geome said above, longer heat pump run times yield more DSH output. Here is a link to a 24 hour graph of my buffer tank temperature:

http://www.welserver.com/perl/plot/WEL0899/BufferTemp.png

And here is a link to a 24 hour graph of my heat pump run times

http://www.welserver.com/perl/plot/WEL0899/Stages.png

HW usage is a factor and one I cannot graph. Mine is a 6 person household, so lots of showers, laundry...

To Stickman: Parenthetically, your WEL charts are nicely informative. Looks like so far so good on your overall performance. Your capacity looks to be adequate or more than adequate. EWT looks to be in low 40s in Winter time and so far you look to be under 75 degrees F this Summer. Assuming your 'swing' above/below down deep earth temperature is sizable (20 degrees plus or minus, or more) then you can further conclude that your design is 'right sized' to the heat load your structure presents. Best regards, Bill

Bill - thank you for the positive assessment. It's comforting to know that from a distance it looks like my system is as it should be. I had a very difficult time with the installing company (not the workers themselves). They did the drilling and commissioning, and I've been wondering if they did the right thing. I've been told that 4 tons is a lot for my 1954 built ~2000 ft2 home. But the manual J they did called for it. And based on the design temps, the heat pump and aux strip has been staging as I've learned it should.

Best, Steve

PS - sorry to the OP for sidetracking this thread

By reducing the CPH, I assume you increased the setback on the thermostat? I considered the same idea. My thermostat is the standard Geocomfort non-programmable. When I hold the menu button I can scroll thru 22 modes, each with abbreviated descriptions that I don't know. I've looked in the owners manual and contacted the manufacturer with no luck. So I've not been able to try the reduced CPH, but would like to. Stickman, how did you monitor the buffer tank temps?

CPH is usually an installer setting. Most owners manuals don't reveal access to these types of settings as they are critical to system performance, thus left for installer use. You would need to seek out the installation manual for your thermostat.

Monitoring of my buffer tank temp is done with a WEL. It's a data logger that can be used to monitor many different facets of our type of HVAC system, plus solar, etc. I put mine in a year after my geo system was installed because I wanted to be sure it was operating to the best of its ability. I am very glad I did. There are other manufacturers of this type of tech out there, but the WEL has served me "well", and is very prevalent in these forums. www.welserver.com