Lochinvar Knight, Supply sensor, output sensor and input sensor

russiand

Another question on the Knight. Thanks to the folks here we tackled the TACO circ controller install with this boiler quite well. I did notice one thing that alarmed me quite a bit. The installer put the supply sensor on the return side of the piping. I believe this was the first time they installed a high efficiency mod/con and so it is somewhat understandable. Anywho, the manual is not perfectly clear on the three sesnsors. The supply (external), output, and input. I am trying to find out if I should simply disconnect the supply sensor and this point and reinstall it correctly when time permits. The  manual mentions being able to switch controlling sensors from output to input but that confused me further as to how that relates to the supply sensor. I was thinking that by disconnecting the supply sensor I would help the current situation as having it in the return piping probably "confuses" the logic board. Any thoughts or input on this are much appreciated.

russiand

Anyone?

I really need to understand the dynamics of the 3 sensors...

paul_79

sensor

need more information and pictures would help. the sensors i can think of come mounted inside the boiler except the outdoor temp sensor. the rest ,flue gas sensor, outlet sensor , inlet sensor ,   high limit sensor are factory mounted on the floor standing models.

russiand

Don't have pictures but

It's piped correctly as far as I can tell except for the supply sensor being plumbed in on the return. When we go into the advanced menu one can select controlling sensors to be output/supply or input. My question was until we get a chance to replumb the thing would it be best to unplug the supply sensor and leave the setting on output/suply or switch controlling sensor to the input one.

ColoradoDave

Supply Sensor on the return

Are you sure it's a Supply Temperature Sensor and not a field supplied LWCO or something else?

One way to test it would be to put a temperature clamp on the return pipe and run a cycle to monitor if the boiler shuts off when it sees the "supply" sensor reach the right temperature.

Also, try disconnecting the rogue sensor from the control board and see what error code you get.

russiand

I am abosulutely is the supply sensor that ships with

Just looking for input on how the 3 sensors work. 2 internal output and input and the external supply one.

Slimpickins

sensor

On the last Knight I installed, the local manufactures rep told me you didn't need the supply sensor unless you're using two boilers. It worked beautifully last winter.

Limamikemike

supply sensor

If this is configured as a "system" sensor (as the manual calls it) rather than a "supply" sensor  you should have three temps on your control screen that concern you: inlet, outlet and system. Is this what you have?

Are you piped primary/secondary?

russiand

We would be in real trouble if not piped primary secondary

The installer got that part right but plumbed the system sensor into the return piping. Obviously this has to be fixed but i was trying to see if we can get by if we switch controllling sensor to input in the mean time

RobG

Supply Sensor

From the lochnivar manual:

12. System temperature sensor:

Lochinvar supplies a system temperature sensor.

The sensor is to be installed in the heating loop

downstream from the boiler hot water piping and

heating loop junction. Typically the sensor will be

located far enough downstream to sense system diluted

water temperature.

From the instalation drawings the sensor should be installed on the supply side of the secondary loop. I dont know if it is a strap on sensor or in a well. If it is a strap on, simply move it. If it is in a well, remove the sensor from the well, strap it on to the supply side and insulate it well. Then when the time is right, have your installer relocate the well, and reinstall sensor. It wont be as accurate if it is strapped on, but it should be close.

Rob