Question about Grundfos RCP-96 Recirculation Pump for Tankless Water Heaters

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3 speed Recirculation pump lost middle speed

I have a Wilo 3 speed recirculation pump for a heating system. The middle speed has quit. Wondering if it's just a simple fix, change a capacitor or something, or replace the pump. It still works on high speed.

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  • danlawrence_ Mar 24, 2009

    Thank you. I already went and pulled the control off, tested and found a burnt winding. Ironically the other pump of 2 went the day after that on all speeds and the lady at the house described an incident with a surge. I replaced them both with Grundfos.

    Thanks again.

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It sounds like you might have had a power surge and burnt the windings on the medium speed. If it is bothersome, you will need to replace either the motor or the whole pump. (not sure if replacing just the motor is an option.)

Posted on Mar 20, 2009

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Does anybody have a diagram for the flow of a back boiler pump


Did you install the pump so it flows in the correct direction? Check the arrows on the unit.

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I have a Navien NR 240A tankless which has been in use for about a year. My only complaint is that when the internal recirculation pump turns on I can hear a waterflow or pump noise throughout the house...


Hi Bruce
No its not normal it shud b isolated by lagging the noise travels through the timber lagging between pipes will help also how old is the pump shud only b a hum if pump ok any more and u need to replace , also u mite like to check speed of pump mite b on max turn down so long ur flow is ok or ur system mite get to hot

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Cost calculations for recirculation system vary widely.
These systems cost more, and they cause higher operation cost of water heater.

1) When pump is OFF, then hot water is no longer leaving the tank.
Most recirculation systems have choice of timer for setting specific times of operation, or thermostatic operation that activates pump when sensor detects temperature less than 90 degrees
BUT...

2) Condition of plumbing is suspect here because you are not receiving fully 90 degree hot water from the recirculation system.?.

Bad single-handle faucet cartridge, or bad recirculation check valve, are causes of crossover. Clean recirculation check valve with white vinegar. Replace worn faucet cartridge.
Test for crossover.
http://waterheatertimer.org/Crossover.html

3) There are other suspects, such as water leak.
Drips, broken pipe, bad TP valve.
Turn off all taps and put ear against pipe to listen for running water.
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html#listen

4) High costs: Lifting single-handle faucet in middle will immediately cause cold water to enter tank. Even if no hot arrives at tap, because the cartridge is drawing both hot and cold in equal amounts when handle is lifted in middle.
Today it is more efficient to install dual-handle faucets so tank is not receiving constant dose of cold water when single-handle faucet is not used correctly or tediously.
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I have a laing cirulating pump thats is worhing but now making noise so i took it apart see nothing but it was hot when running so is there any thing i can do to fix before it burns out


Open following link for Re-circulation information and resources:
http://waterheatertimer.org/Water-heater-recirculation-system.html

If the unit is getting hot, it may have already slowed and is now spiraling to it end.
Try bleeding air out of water lines, and clean autocirc with CLR calcium lime and rust remover.
Recirculation systems have a built in check valve so cold water side of faucet will work correctly. If this check valve is stuck open or closed, it can affect a lot of things in the plumbing system.
For example, stuck check valve can cause tankless water heater not to operate. It can also cause autocirc pump to overheat.
Lines, or elbows clogged with sediment can also cause same problems with recirculation system. If your system has direct return line to water heater that connects into the water heater drain port, then clog in line can cause overheated pump. Check water flow, check water lines, and clean out autocirc.

Upvote the help.
And take advantage of fixya expert assistance live.
For a price, expert works with you while you work on autocirc or any do-it-yourself project.
Fixya is always less expensive than a service call.


Oct 22, 2010 | Laing Thermotech Autocirc Undersink...

1 Answer

Pump runs 5 minutes and stops


Move the slide switch to ON.
Open following link for recirculation system resources.
http://waterheatertimer.org/Water-heater-recirculation-system.html

The recirculation can work on either the timer or the thermostat using slide switch located next to the timer dial.
First of all, look to see if dial is rotating as time passes.
Next look at position of slide switch. If switch is moved to 'timer,' then the timer controls the on-off function for pump.
Move the pins located on timer dial to control on-off times.
If the switch is moved to ON, then the thermostat controls the pump, and turns on until temperature in pipe reaches 94 or 100 degrees F approximately. I forget exact cutoff temp.

Upvote the help.
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.

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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.

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Wilo 3speed recirt pump for my wood stove


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May 26, 2009 | Grundfos RCP-96 Recirculation Pump for...

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