Grundfos submersible well pump with Grundfos CU301 control. Control box shows no contact to pump. What is the problem or problems?

As far as I know, tankless water heaters fire up when the water pressure DROPS 9opening a faucet). Having FLOW won't achieve that. I have never heard of having a recirc system on one of those water heaters, only with a tank. You would have to ask the maker of the water heater. I would say you have the wrong HEATER and SYSTEM for the application.

Question not 100% clear.

1) The pump is not working? Does the pump make a noise? if pump is not working full-time, it can cause delay in arrival.
If pump motor is suspect, and outlet has power, then check override switch located on timer. Set override to Timer, move some of the trippers outward, then manually rotate timer dial until pump turns ON.
http://waterheatertimer.org/images/IMG_9325-grundfos-timer-800.jpg
If no noise is detected, or noise stops and starts, or seems strained, or if pump is hot, then pump motor may have burned out.

2) If pump is working, and makes noise like a humming sound, and pump motor is not hot, but hot water is not circulating, then unplug pump so it will not overheat and burn up.
Disassemble the pump and cross-over piece. Clean piping with white vinegar or CLR. Do not soak in CLR or it will damage seals. Rinse parts thoroughly. Reassemble and see if problem is resolved.
If pump is vibrating, then suspects include sediment and/or air inside line, and this can be resolved by cleaning as described. Also install air vent to increase life of pump.

3) Other causes for hot water delay at faucet are crossover.
Crossover can be caused by bad single-handled faucet cartridge, and/or by clogged-or-failed check valve on cross-over piece on grundfos.
This type of problem lets cold water enter hot line, and causes delay in arrival of hot water. Clean-or-replace the grundfos cross-over piece, and replace bad faucet cartridge.
Open following link for testing instructions:
http://waterheatertimer.org/Crossover.html

Resources:
http://waterheatertimer.org/Water-heater-recirculation-system.html
http://waterheatertimer.org/pdf/Troubleshoot-recirculation.pdf

Add a comment for more help.

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And take advantage of fixya expert assistance live.
For a price, expert works with you while you work on water heater or any do-it-yourself project.
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Question not 100% clear.

1) The pump is not working? Does the pump make a noise? if pump is not working full-time, it can cause delay in arrival.
If pump motor is suspect, and outlet has power, then check override switch located on timer. Set override to Timer, move some of the trippers outward, then manually rotate timer dial until pump turns ON.
http://waterheatertimer.org/images/IMG_9325-grundfos-timer-800.jpg
If no noise is detected, or noise stops and starts, or seems strained, or if pump is hot, then pump motor may have burned out.

2) If pump is working, and makes noise like a humming sound, and pump motor is not hot, but hot water is not circulating, then unplug pump so it will not overheat and burn up.
Disassemble the pump and cross-over piece. Clean piping with white vinegar or CLR. Do not soak in CLR or it will damage seals. Rinse parts thoroughly. Reassemble and see if problem is resolved.
If pump is vibrating, then suspects include sediment and/or air inside line, and this can be resolved by cleaning as described. Also install air vent to increase life of pump.

3) Other causes for hot water delay at faucet are crossover.
Crossover can be caused by bad single-handled faucet cartridge, and/or by clogged-or-failed check valve on cross-over piece on grundfos.
This type of problem lets cold water enter hot line, and causes delay in arrival of hot water. Clean-or-replace the grundfos cross-over piece, and replace bad faucet cartridge.
Open following link for testing instructions:
http://waterheatertimer.org/Crossover.html

Resources:
http://waterheatertimer.org/Water-heater-recirculation-system.html
http://waterheatertimer.org/pdf/Troubleshoot-recirculation.pdf

Add a comment for more help.

Take a moment and rate answer for accuracy:
And take advantage of fixya expert assistance live.
For a price, expert works with you while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

http://waterheatertimer.org/Water-heater-recirculation-system.html

The circulation system should draw hot water directly from the water heater as shown on illustrations on link above.

The Grundfos pump works on a thermostat, and some work on a timer.
Can you hear the pump working?
There should be a humming sound.
Check the timer -or- thermostat setting.

It is possible the lines are clogged with sediment if you have hard water.

If I was going to fix the problem:
1) check thermostat or timer
2) listen for pump sound
3) check electricity going to unit
4) take apart the pipes and inspect for clogging
If there is a clog, I would flush the line or soak the part in CLR (calcium lime rust remover)

The circulation pumps are sealed and there is no way to take apart the motor, timer, or thermostat for repairs.

add a comment if you need more assistance.

The purpose of an aquastat is to measure the temperature of the water flowing in the piping and regulate the control valve.

Venting of the system is when you re circulate the water or cooling fluid in higher speed to eliminate the air bubbles from the system.
If water circulate on a too higher rate does not have time to dissipate the heat so your floor is cold.
You need to go to 2 or even 1 depending on the length of the heating coil in the floor. Unfortunately the pump only has 2 speeds (setting 1 and setting 2) so whoever install your system had to calculate the length of the pipe for maximum efficiency. Try on 2 and if not satisfactory go to setting 1. If too hot on setting 1 then you can adjust the heat by reducing the amount of water from the shut-off volume control. It is a hit and miss situation, I know but unfortunately that is the only choice remaining now after the system is installed.

Try putting a few teeth either in or out and turn the timer until the arrow points to that setting. You will then know which is which

Yes, you need to replace it.

they have it installed wrong it is pulling from the wrong side, it is supposed to pull ot water up to the fixture but then if it stays hot on the cold side they are backwards

What is your reason to have a recirc line on your water heater does the heater sit to far away from a certain fixture? If you put a pump on your tankless waterheater then your heater will continually fire till the call for hot water is stopped. Yes you normally do need a seperate line installed for a recirc line usually from the water heater to the farthest fixture away. If your problem is taking to long to get hot water then I suggest installing a second heater closer to problem area.