Earthlinked DX SD model - desuperheater problems
Last Post 15 Sep 2011 10:29 AM by foaf. 8 Replies.
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15 Jan 2011 11:51 AM

see below

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15 Jan 2011 12:44 PM
Posted By foaf on 15 Jan 2011 11:51 AM
I am hoping that there is an Expert on Earthlinked DX SD systems on this group who can help me out. I have problems with no power to the hot water circulating pump, in either cooling or heating modes.

I am dealing with a contractor named Gary, from Geothermal Experts in Ottawa. 

The custom controller I thought I was getting from Earthlinked, to make hot water year around, turned out to be Gary being misinformed. Only on commercial quad systems he says.

So, I have the standard SD model desuperheater configuration.

I noticed from day one that it was not working right. I told Gary over and over again that something was not right. He kept insisting that all was OK, and would not even look at it.

My problem is this. There are two waterpipes connecting the preheat hot water tank to the compressor box. When the air handler starts making heat, randomly either of these two pipes may become quite hot, while the other stays cold. From a cold start you never know which pipe will get hot. Further, the heat starts slowly at the compressor box end of the pipe, and spreads very slowly along the hot pipe towards the pre-heat tank, until the pipe gets too hot to touch for long. By the time the heat reaches the tank, the air handler and desuperheater shut off shortly after. I do not seem to be making much hot water.

Further, in home airconditioning-cooling mode the desuperheater does not seem to heat up much at all, compared to in the home heating mode.

I pointed out to Gary, that he had installed the water circulation backwards compared to the manufacturers specification, since he made the desuperheater draw water, from the pre-heat water tank, using the cold water input at the top of the tank. The hot water feeds out of the desuperheater into the bottom of the pre-heat hot water tank at the tank drain. This is reverse of what the manufacturer specifies.

He insists that the manufacturer is wrong and he is right! You could not convince him otherwise. However, I do not think this is causing my problem.

I downloaded the installation manual, traced out the wiring and measured voltages.

There is a hot water circulating pump which is supposed to push the water through the desuperheater and circulate the water through the preheat hot water tank. The problem is that the hot water circulating pump never gets any power, ever, under any conditions.

There is a water heater relay, which is supposed to turn on power to the circulating pump. I can measure the proper power feeds for the pump on one side of the relay, but the relay never operates, to send that power to the pump.

I found a loose orange and black wire on TB-1. Two orange and black wires are supposed to be inserted into the terminal block and the screw tightened. Only one wire was properly inserted. The other was loose. I corrected this problem.  However, this wire supplies 24 V AC to actuate the water heater relay when in cooling mode, and does not affect heating mode. 

I also found a loose screw on TB-2, the red and red-white wires that supply the 24v AC to operate the water heater relay when in heating mode. I tightened that down. With the loose wires that I found, no power could ever reach the water heater relay, and power the circulating pump. Strange that these were the only loose connections that I could find. One might almost think it was done deliberately.

However, this did not fix the problem.

For the water heater relay to operate, 24v AC must be supplied to the yellow-green wire on TB-3, which connects to the supply side of the relay coil. 24 v AC is supplied from the red-white wire on TB-3, and the orange-black wire on TB-3, to 3 temperature sensors connected about the desuperheater. Two of the sensors are used only for cooling mode and being in series both must actuate for power to be supplied to the relay coil. They work off the orange-black wire.

This does not seem to be working, possibly because the desuperheater is not heating up much, if at all, in air handler cooling mode. Whatever the cause, the water heater relay never actuates, in air handler cooling mode. I can measure 25 V AC at TB-3 on the orange and black wires, so power now gets to TB-3.

The third temperature sensor is used in air handler heating mode. If it actuates, 24v AC should be supplied to operate the water heater relay. 

I can measure the 24v AC power on the red-white wires of TB-3, and at the temperature sensor. However, the temperature sensor never trips to supply power for the relay, which should then actuate to provide power for the circulating pump.

So power is measured going into the temperature sensor, but nothing ever comes out. The pipe to which it connects gets very hot, so you would expect the sensor to actuate. However, I am not certain of this, and I still do not understand why the desuperheater does not heat up much when the air handler is in cooling mode, and why the hot water relay will not actuate in cooling mode either.

No matter what I look at, or how I run the air handler, I never get power to the hot water circulating pump.

I have 24 V AC power at TB-3 on the two wires that feed the power to the temperature sensors, one for heating and one for cooling, but nothing ever comes back from the temperature sensors, connected to the third wire. That power is needed to actuate the water heater relay and provide power to the circulating pump.

I find it hard to believe I have two or three bad temperature sensors.

Help!





engineerUser is Offline
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15 Jan 2011 08:21 PM
"I pointed out to Gary, that he had installed the water circulation backwards compared to the manufacturers specification, since he made the desuperheater draw water, from the pre-heat water tank, using the cold water input at the top of the tank. The hot water feeds out of the desuperheater into the bottom of the pre-heat hot water tank at the tank drain. This is reverse of what the manufacturer specifies."

I can't help you with the specifics of the circ pump wiring, but the above description is how most of us plumb desupers and buffers. Our reasoning is that we don't want to draw any crud or sediment from the very bottom of the tank into the desuper or circ pump. Note that the CW inlet typically has a dip tube such that water withdrawn from it is taken from NEAR but not at the very bottom.

Another common error is failure to remove the anti-thermal syphon widget from the CW inlet nipple on a typical electric storage water heater tank commonly used for buffer tank service.


Curt Kinder

The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is - Winston Churchill

www.greenersolutionsair.com
tuffluckdrillerUser is Offline
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20 Jan 2011 03:32 PM
The thing that first comes to mind is the water tank temp. The circulator pump will never get power if the tank is already hot. I'm not sure I'm following your post all the way as to whether the tank is in need/demand of hotter water at the time the heat pump runs.

Do you have 2 water tanks? One as a buffer/desuperheater tank and the other as a water heater?
Clark Timothy (clark@pinksgeothermal.com)
Geothermal Heat Pumps: Heating and Cooling that's Dirt Cheap!
www.pinksgeothermal.com
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31 Aug 2011 12:23 PM
OK there are two problems with the desuperheater. One of them is now fixed, but it still doesn't work, because of the other. The fixed problem was that the system was not designed to run the preheat hot water circulating pump when the system was in heating mode. The circulating pump could only work in cooling mode, by design. Goethermal Experts, working with the local Earthlinked Rep, and Earthlinked, were able to provide a wiring modification that would allow the circulating pump to operate in heating mode. The other problem is that the fixed thermostats, for turning on the circulating pump are set at too high temperatures for our geographic location in Ottawa, Canada. In heating mode, when the wall theomostat is set for a 0.5 C temperature differential, the circulating pump never comes on. If the differential is raised to 1 C. Then the system will run for ten minutes and the circulating pump will come on for the last 15 seconds. I have run the system with the circulating pump forced on, and could not feel any drop in the air temperature coming from the air handler. The system can heat both water and the house at the same time. In the summer, the circulating pump never comes on, ever. The pipes never get hot enough to trip the fixed thermostats. So, the desuperheater, works for 15 seconds a ten minute cycle in the winter, and not at all in the summer. Both of these issues could be corrected by lowering the fixed thermostat tempertures to match the geographic and climate profile of this region. This thing was designed to run in Florida under heavy cooling loads with higher ground temperature and higher ambient air temperatures. To operate realistically in this climate the fixed thermostats should be dropped about 20F for their operating tempertures. Otherwise the desuperheater on this unit is a waste of time and money, and is no selling point in Canada. To me, in the summer, all heat from the air handler is superheat. I am not sure I have anything to gain by heating up the ground. I could run the circulating pump at a much lower temperature and at least get some hot water preheat, which is better at a lower temperature, than none at all.
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01 Sep 2011 10:11 AM
I've tried to follow but I may have missed something in the giant paragraph, but lemme summarize my thoughts:
If system design is not a good fit with application, I blame dealer not manufacturer.

If your intent is to educate us on changes in manufacturer design that make it work in your area, us dealer types aren't likely to change presets without manufacturer's say so.

I'm glad you got it working better for you.
j
Joe Hardin www.amicontracting.com We Dig Comfort! www.doityourselfgeothermal.com Dig Your Own Comfort!
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01 Sep 2011 06:19 PM
I see a few options.

Convince manufacturer to fix it
Make your own controller for the circulation pump
Wire the circ pump to run whenever the compressor is on. Disable during any long periods where this loses more than it gains.


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02 Sep 2011 09:17 AM
Posted By jonr on 01 Sep 2011 06:19 PM
Convince manufacturer to fix it 





Again, manufacturer has a list of applications, if dealer chose to color outside the lines, it is the dealer who owes the fix not the manufacturer.
j
Joe Hardin www.amicontracting.com We Dig Comfort! www.doityourselfgeothermal.com Dig Your Own Comfort!
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15 Sep 2011 10:29 AM
(For some reason, this text editor does not like my carriage returns and clumps my paragraphs together into one big paragraph. Sorry.) An update. Let mean explain our usage pattern. We use cooling mode occasionally in June, have it on most of July, and the first week or two in August, then we only use it ocassionally until the second week in September. I checked the circulating pump in the first half of July, and it was not coming on. However, after posting the last update, I had occasion to check it again when the cooling mode was on for a couple hot days. The circulating pump seems to be working now, but now we are no longer using the cooling mode. We are now in the shoulder season. I would guess that heating the ground may have eventually increased the refrigerant return temperature enough to get some super heat. I would guess this happened sometime in July and improved over time as the ground go warmer. So I would guess that I might actually have been producing some hot water for about a month. The desuperheater was not modified to work in the winter, until February, so by then the ground would have been made colder, by drawing heat from it for a couple months. I would guess that the reverse will happen in heating season. We will get longer pump cycle times in the beginning and it will get shorter as the ground gets colder. So we get hot water increasingly after a warm up period, in the summer, and likely will get hot water decreasingly in the winter, for perhaps a couple months, until the ground cools down, I am guessing. So, it is sort of working, but would work better with lower temperature thermostats, or perhaps have the pump come on whenever the refrigerant is hotter than the water in the tank, by say 10 degrees F. At some temperature differential, the heat transfer will not be enough to compensate for the energy used to power the pump. At that point there is no value in running the pump. Ground loop capacity is also a concern. In my case, there are 4 x 100' vertical wells in a twelve foot box, plus about fifty feet of horizontal ground loop to the house.
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