Grundfos Mix/Mizer Problem

GW

I'm not familiar with that pump. You'll need to pull it out (obviuosly you have water in the system... no air right?) and make sure its spinning. If it's deathly quite, can you hear anything going on? It may be time for a new pump.

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Eric_31

Grunfos Mix/Mizer Problem

I have a Grudfos Mix/Mizer installed ffrom the main circulating loop to the slab heating. The demand for heat is hooked up to the Wirsbo control unit which has 5 zones and thermostats to each zone. I have an outdoor sensor, supply sensor, & return sensor all hooked up to the Mix/Mizer. I have checked the sensors with an ohm meter to make sure these are not defective. The problem is when a call for heat is registered from the wirsbo control to the mix/mizer the pump display shows the call for heat and the pump performance light flashes and it feels like it is working but it is not drawing enough hot water from the mail circulation. The temperature from the main is between 185 - 170 degrees F. The temperature being supplied to the slab is only 20 degrees celcius. Any suggestions? This only started happening the season (1 month) and is 6 years old.

GW

ahhh yes

I may be able to help; just got done with a head scratcher that took me for a loop. When you say mix/mixer, I assume you mean injection pump? That is, does the control shoot more or less heat into the system (through this pump you're describing) depending on the outdoor temps? What model pump do you have? It should say right on it.

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Eric_31

This is the pump info:
Grundfos MixiMizer Injection Pump UP15-42 www.us.grundfos.com/Web/Download.nsf/Pages/259D73C07BE5C64208256952007F36D5/

Eric_31

Appears to be working

From the sound of the pump and vibration of the pipe it appears to be working however I think it is not mixing enough hot water from the main loop.

hot_rod

something with the piping sounds

like the cause. If the indicator lights are on on the MixiMiser, and it is in fact spinning it has to move fluid.

Do you have a picture or drawing on how you have it piped?

There is always an amount of blending that goes on where the injection loop connects to the heating loop. if the floor loops are cold, real cold, that mixes with the injection temperature. Although you should have a higher injection temperature than 20C.

It needs to be piped P/S and the tees installed correct.

Did you check the internal check valve in the pump body to assure it is not stuck with something to prevent it from opening?

hot rod

Eric_31

The main problem

may be that the pump performance LED stays lit after a few seconds of powering up. I haven't drained the system to inspect the pump...last resort. Please find attached pics and diagram of system.

hot_rod

The Mixi is just a circ with a tekmar

board under the hood. You might bypass the board and run the circ as a normal full speed ahead circ to see if the flow and heat moves that way.

If so it could be, but probably not, the tekmar board.

The indicator lights indicate the faults and operation, as you know.

I have removed them from the volute, with the 4 allen screws, and powered them up and watch the rotation and speed change, while holding them. They can run dry for a short period. Not that I would recommend that, of course

hot rod

Eric_31

Bypass Board

Not sure how to bypass the board to see if pump is working or if it is the board?