see below

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!

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