Recently i had a Watts instant hot water circulatering system installed to resolve an issue where the hot water wasn't hot until i ran it at the kitchen sink
for at least 3 minutes, it seemed ok at the shower which is only about 12 feet from the water heater.  Now the water feels luke warm and measures 101
degrees at the sink.
The recircuilating system installer says it could  be an element in the Marathon water heater, geeze!  this thing is only 2 years old, is there any other tests i
can make ? shut down the circulating pump ? I will have to try it but it takes 3 days for the water to even get warm.

Perhaps a thermostat on the Marathon has drifted a bit - have you tried adjusting the setpoint up a bit? Put a hand on the metal part of the hot water outlet of the heater while hot water is being drawn - if it is lukewarm, there's your problem

A burnt out element (uncommon in a newer heater) may be detected by measuring resistance across its terminals - be sure to disconnect other wires from element first. You need to be comfortable with exposed high voltages and / or sure of your ability to de-energize the heater.

On first blush I'm reluctant to blame the circ pump - it only circulates what's in the tank.

So if you do leave the kitchen sink on for 3 minutes does it ever get hot? If so then the re-circ pump is just set to low. If the water never gets hot but you still have nice hot showers my guess would be the circ pump is somehow allowing cold water to flow back in to the hot line thus mixing cold and hot when you turn the hot on. It should be a simple check valve near the circ pump to not allow the cold water line to run backwards in to the hot water line.

I have not messed with the setpoint (being completely unfamilar with it) I will have to try the hand test but will wait until daylight.  I think I know where the power
is to the water heater but will reserve testing the elements as last test, not much i could do if it is broken anyways except call for a repairman, lets hope this doesnt get any worse, heating a pot of water on the stove and dumping it int the sink to wash will have to work until i can afford paying someone, then the biggest problem will be finding that person ;(
I agree with your first thoughts on the element it really seems unlikely, it sure is curious this luke warm water showed up right after this high priced installer put
the re-circulating pump in.

I am wondering now if the water is being drawn through the Desuperheater, the Geothermal people have it plumbed from the bottom of the water tank into the
desuperheater and the out is connected to the hot water side of the marathon, this seems to me to be incorrect and should of gone to the cold water input.

I had the hot water running for 10 minutes, it actually felt cooler than when it was on for the first 3 minutes. The showers are actually cooler than before re-circulator was installed, I can have the hot water knob fully open and not have the water too hot for a shower, although its sort of nice not to worry about
it being too hot now but it does indicate something has changed. here are some sample photos, one shows the connections.
http://picasaweb.google.com/silvermachineman/GeothermalMisc#

This morning I checked the water temp entering the Hot water side from the Geo Dsuperheater, it was 111 degs! the water was too
hot to hold on to, however the hot water out pipe about 6 inches above the tank was luke warm to the touch, I then shut off the return to the circulator and turned it off so no return water was flowing, went back to the kitchen, I waited about 30 minutes and tried the
hot water test, it did indicate the water was warm after 3mins, it was cooler prior to that, it is cold downstairs.. I now have returned
to where the circulator is back on. (shakes heads) I have learned a hard lesson on how to waste $800 with plumbing contractors.

A DSH without a buffer and a circulator added to it, Hmmmm. Is the lower element on the tank disabled? Not really familiar with Marathons. But you may be circulating your heat away.
DSH piping is a seperate issue. You may have the worst of all worlds here....water heater giving up heat to heat pump, losing heat to circulator loop......may have low setting or single element configuration....
yow.
I could offer to help, but we are pretty bombed right now and you are a little off my beaten track.
Good luck,
joe

Circulation lines are great for comfort and save water, but they are energy hogs. That is OK since they are usually all within your thermal envelope. That is good in the winter. Summer is a different story.

The way you have it set up you make most of the hot water for the circulation lines with your resistance heat. Very inefficient.
Apart from efficiency, your water tank does not seem to heat up properly, usually the load of a tank
Do yourself a favor and get a buffer tank (a reasonable cheap electric tank with sprayed on insulation will do), you can wire it but keep the breakers off except in the shoulder season. And you can run the circulation line off the buffer tank. In the shoulder season you can flip on the breakers for the circulation pump.

It is confusing, without knowing how this marathon is configured all that can be done is speculate, I don't even have information on the Marathon, perhaps google will help me, I agree though with one thought and that is im circulating the heat away. I have since configured the little dips so that from 12mn to about 5am its not circulating, hoping that during that time the heat will build back up inside the tank and then get pushed out over the next period of time 5am to 10pm. The question of the lower element being disabled is certainly a good thought though, im really at a disadvantage since I really dont know what the heck the installer did on this (i doubt he even knew) If i were younger I would learn and learn how to make the changes in the copper so its plumbed correctly, being on a fixed income im really limited on what i can pay to have changed. I am thinking though that its probably better for the life of the Marathon not
to have the heat in the water continuously flowin away, it would seem that the heaters would be on much longer and make for a more expensive use of heated water. I can see though that haveing a second tank as a buffer would be a much better approach, maybe Obama will give seniors another $250 bucks and i can do something .....

If you're looking for information on the Marathon regarding the original configuration from the factory, I'm sure they can provide you with a manual. Their web site is:
http://www.marathonheaters.com/

They have troubleshooting guides listed under the dealer and contractor sections of their site.

I called them a few times with questions and have always found them to be helpful. Their phone number is 800-321-6718. It's possible their technical department may be able to give you some advise as well.

P.S.  While the installer may not (or may) have installed the circulation pump correctly, he should at least be able to explain to you what how he plumbed it.  Also, make sure anyone draining or working on the Marathon follows the manual since damage can occur to the tank if instructions are not followed.

I didn't re-read your entire post, but I wonder if air is now in the desuperheater lines (as a result of the work that was done) that needs to be purged.  An air locked DSH won't function.

Your Marathon is simply piped WRONG!!! Your photos show the DHW "OUT" re-injecting into the bottom of the Marathon...this is correct. The DHW "IN" is coming off the top of the Marathon's "HOT OUT" supply... This is incorrect. It should be piped to the "COLD IN" pipe, drawing cooler water from the bottom of the Marathon, circulating through the Desuperheater and going back into the bottom of the Marathon.

The hot water recirc line is piped into the cold water side of the Marathon. It is drawing cooler water from the bottom of the tank UNTIL...someone turnes on some cold water! Then it starts to circulate even cooler water through your pipes!!

You would be best served with a "Buffer Tank". If you get one pipe it like the attachment.

Bergy

Another point about your system. The twin Temperature/Pressure gauges are useless for any type of diagnostic work. The same pressure gauge and the same thermometer must be used to read both entering and leaving parameters.

Bergy

Very nice, i am bookmarking and saveing all of this for future repairs and upgrade. It is clear to me the installer was clueless as to how to hook this thing up, no wonder they went out of business, yet another good reason to check out the creditials of those who you select to do this install, we are very very lucky that this system works at all. I agree with your comments on makeing sure whoever does this knows how to drain that tank and re-plumb it (shakes head) what a mess they made. Thank you Bergy and all who have commented..