Here's hoping you saved some pics of the flowmeter wiring as it is, most definitely, very specific. Here is how I BELIEVE it should be, based on a view of LM wiring diagrams.



The red wire goes to the plus side and the white to the negative. Reversing these would ruin the flowmeter circuitry.

Thanks for pointing that out Eric. You are correct.
I posted a very clear pic of that here.
Here is the detail on the flow meter from that pic before I coiled the wires :
Image: Flow Meter Wiring Detail

Cheers!

- Jake

erics wrote:The red wire goes to the plus side and the white to the negative. Reversing these would ruin the flowmeter circuitry.

Not that I would recommend reversing the leads, but I'm not sure it's correct that it would damage the logic board. I haven't checked, but I don't believe the negative lead is connected to the ground lug. The counter might not work with the leads reversed, but I don't think it would cause a short if the negative lead isn't grounded. Assaf would probably know.

. . . but I'm not sure it's correct that it would damage the logic board.

It will render it useless. This has been addressed before but I am too lazy to find the correct link.

Certainly(?), Digmesa makes the flowmeter for LM and I thought I had found that warning on their site but . . . no such luck after a quick search.

Yes, Assaf would know.

I think it won't ruin it - but definitely not recommended.

So there are 3 wires (not two!):
5V DC supply: The red wire is the 5V supply.
Out: The white is actually an open collector output (biased with a resistor so when the hall effect sensor triggers, the collector ties the white line to ground).
Ground: this is the third wire and is routed through the chassis to the GND lug near the steam boiler ball valve.

If you reverse the red and white you are not reversing (and frying) the hall effect sensor since its ground is still the chassis, and the collector bias voltage is still 5V.
However, if you cause the impeller to rotate, the open collector would try to pulse the 5V supply (the red wire) to ground. That isn't good. Now I seem to remember that the 3d5 does have a resistor on the 5V supply as well (but I am not 100% certain) so it may not be an issue - apart from the flowmeter alarm. But then again - I wouldn't...

NB - these lugs break off easily. Then you are screwed. So be careful....

Edit - looked at the board and it doesn't look like the 5V is protected by a resistor. So I'd be wary of connecting the Out to a 5V without a resistor to limit the collector current (Out and +5V marked below - as is the bias circuit to the Out):

My error - I did not mean to say the logic board would be destroyed. It is the 'electronics' within the flow meter that would be rendered useless.

Check Valves:

Ok, my big bag of O-rings finally arrived today. Here's the story on the check valves.

Begin by disassembling the check valves. First, get a grasp on the internal retaining ring. Here I'm using an angled pick that fits into the hole as my snap ring pliers are a wee bit too large to work:

Image: Check Valve Retaining Ring


Then pull it out:

Image: Check Valve Retaining Ring-Removed


Next it's time to get the plunger out, which means shearing the old O-ring. I used a 5/16 nut driver extension in my vice with some protective cardboard over the sealing end of the check valve:

Image: Pressing the Plunger out

You dont have to press very far. The O-ring cross section is less than 2mm. Just press until the O-ring gives and then pull the valve out of the vise. If the plunger doesn't fall out of the valve, it should look like this:

Image: Check Valve-Sheared O-ring


From here you can tap out the plunger and get a pick under the O-ring to remove it:

Image: Check Valve-Removing the O-ring


Here you have a disassembled check valve:

Image: Check Valve-Disassembled


And here are all 6 of them:

Image: Check Valves-Ready for Repair


First, set the spring back into the check valve body from the inlet side:
Image: Check Valve-Spring Installed


Followed by the plunger:

Image: Check Valve-Plunger Installed


For the next part, I used a frame-mounting screw and the cap that goes on the spare fitting for the steam boiler to hold the plunger open while I insert the new O-ring. First set the screw on the plunger:

Image: Screw Resting on Plunger

And then compress the spring:

Image: Screw Pressed Down


Then carefully install the cap over the screw to keep the spring compressed. This is important:

Image: Boiler Fitting Cap to Keep Plunger Lifted


Next, flip the valve over, set a new -007 O-ring over the top of it and gently press one side of the O-ring down around the piston:

Image: O-ring Partially in Place


The next part was impossible to photograph. You need two picks. One to hold the part of the O-ring you just pressed down in place, and another to walk the exposed portion around the circumference of the plunger and down into the groove below. Here's the best I could do for a pic:

Image: O-ring Nearly Installed


From there, it's one little push and the O-ring all but disappears into the groove of the plunger. Then flip the check valve over and replace the snap ring:

Image: Check Valve Retaining Clip-Ready to Install


From here, I took each and every check valve over to the bathroom sink and left it charged to check for leaks while I rebuilt the next one:

Image: Check Valve Passing Leak Test


Each valve passed the test and now I have 6 rebuilt check valves, ready to be installed:

Image: 6 Rebuilt Check Valves


Whew.


I've got issues...

Cheers!

- Jake

Save that series of images to apply for a job with LM factory. Who knows, maybe some day you can do a work play in Florence. Build check valves mornings and check out the Duomo and other sites afternoons...

This is like a spa for check valves.

As regards the reversing of the plus and minus on the flowmeter, please see the measurement tips on page 4 of this:
http://www.digmesa.com/wp-content/uploa ... V08_GB.pdf wherein it says:

Incorrect cabling of power supply +, signal and ground will destroy the flowmeter