Lochinvar WB80 not lighting, many new parts already. SOLVED

EBEBRATT-Ed

I know this is tricky but to track down an intermitant control that is not closing or is shutting something down we use to wire a tattle tale (usually a fuse) across the control you are suspicious of tripping.

We use to use small fuses.

The issue is you need to know how many amps is going through the wire and pic a fuse with a lower amp rating to wire across the control (in parallel) If the control opens when it should not the fuse will blow and when you return and find the blown fuse you will know what is tripping.

This will not work sometimes as the control logic knows when an air pressure switch has been jumped or not.

ColdCanuck

109A_5 - Yes, there are four wires going to the outlet sensor (#7 in drawing you posted) Yellow,Red,Orange, and Gray. You're right, the wiring diagrams are not very helpful in this case! That sensor only seems to throw a code if it's completely disconnected ("Sensor 1 Open") Even at the time this unit was built they could easily have provided better fault feedback - like the OBDII in cars. (by the way, where did you find that drawing/explantion? Have not seen that before, it would have helped troubleshooting)

Looking at the current track you laid out it's starting to make sense. I'm used to following the current tracks on old cars - no integrated circuit boards!

Hot_Rod - yep, I've been thinking about making up a whole new harness during the summer. Lochinvar has a part number for the cabinet wide harness, it's listed at $400, but nobody seems to have stock. Finding the correct connectors will be the challenge, but a good electrical parts catalog should list, they don't seem to be proprietary.

Alan - Thanks, being cold gives incentive! Living in a small mountain village we're limited on services available. The grounds were checked at the start, both in cabinet and the hardwire to house.

EBEBRATT-Ed - Thanks for the ideas, but hopefully this sensor is the problem and I won't have to keep chasing. Time will tell.

As usual, many thanks!

hot_rod

https://forum.heatinghelp.com/discussion/comment/1847858#Comment_1847858

Hot_Rod - yep, I've been thinking about making up a whole new harness during the summer. Lochinvar has a part number for the cabinet wide harness, it's listed at $400, but nobody seems to have stock. Finding the correct connectors will be the challenge, but a good electrical parts catalog should list, they don't seem to be proprietary.

The harness comes with all the correct plugs on it, remove the old one, replace with the new. Unless someone changed connectors on switches or sensors?

109A_5

Funny you mention OBDII, it still can leave you guessing if good troubleshooting strategy is not used, often just the sensor is changed only to have the same problem or even another problem with the poor quality of automotive aftermarket products. And with OBDII you still need the scan tool.

That version of the manual was found using Google. It is on the Supplyhouse.com page of a discontinued boiler like yours. Going by the revision letters I think it is newer than your unit. I don't think I ever found a version that was your exact unit, older and newer but not yours. Supplyhouse.com often has many documents.

Page 4.

https://s3.amazonaws.com/s3.supplyhouse.com/manuals/1249544894162/Lochinvar-KnightBoiler-Installation2.pdf

Old cars versus new cars, old cars battery, wires, switch, and a load, new cars, when you think about it are about the same except there is a black box (or many) in the middle (between the switch and the load) supplying logic functions to further manipulate things. So more wires and sensors. Most folks don't go into the back box anyway, but often you need to test up to the black box. Networks and CAN bus can make things interesting too.

Personally if the new sensor returns the unit to proper operation I would not bother with the building of a wiring harness for the whole boiler. By the time you source the needed wire with the proper colors, the proper connectors and pins, the proper pin extraction and crimping tool(s), etc. you may have spent more than $400 and spent a lot of time doing so.

If you think you have or will have connector issues, I would figure out what connector manufacture and series the connectors are (MOLEX, AMP, TE connectivity, etc.), there are many. Check out Digikey.com or Mouser.com. I would simply repair the harness if needed. Also if you don't build the replacement harness perfectly you could damage something expensive.

@EBEBRATT-Ed As much as your 'Fuse' technique will work I always regard more than one blown fuse as the onset of frustration. I much prefer an appropriate incandescent lamp, it indicates and current limits, and does not blow, so it is reusable (as long as you don't drop it or abuse it too much).

ColdCanuck

Update: It works!

After getting the new Output Temp/Hi-Limit sensor a couple days ago I can finally say the unit is fixed. I opted to install myself; it was pretty basic, just drain off the pressure and let a little glycol out. I also replaced the Inlet Temp sensor, figured might as well, now just about everything is new. Crazy, all that money spent on parts because the Service Tech didn't make the correct diagnosis of the fault in the first place.

Since I got it to fire interminably back on March 10 I had the Service Tech dude out to conduct the combustion test and asked him to also program the parameters. I told him specifically that the SH temp should be 110. Well, he couldn't even get that right! When I first got the new sensor in and fired up the boiler DWH seem to work fine, but when it switched to SH the output temp would start rising over 140 so I knew I had to reprogram the thing.

Had a bit of fun figuring out the programing of parameters - the Service Manual was pretty vague but now it's set to 110 and seems to be working fine. The Service guy had it set at 180 for SH on radiant floors! I suspect he didn't do anything except change the date since beyond that point was when the guide got pretty vague on how to switch screens. That 180 was the default setting.

I'm a little bit confused why the DHW gets priority even when the thermostat on the tank has met set point. I must have something not quite right. The boiler will always fire and heat DHW first for twenty minutes, then switch to SH but after a bit switch back to DHW even though the tank is hot. The parameters allow me to set the switch over time from SH to DHW at twenty minutes,(EDIT: oops, I meant from DHW to SH) but not the other way around. (EDIT: I guess it's the same for both?)

In any case it's nice to have warm floors again - although heating season is almost over!

Thanks everyone for your help!

109A_5

Thanks for the update, I'm glad that fixed it.

As far as the " DHW gets priority ", it should, but only if there is a DHW call. Could the thermostat input connections to the boiler mistakenly been reversed ?

ColdCanuck

https://forum.heatinghelp.com/discussion/comment/1850532#Comment_1850532

I checked the wires. Maybe it keeps switching back and forth ever twenty minutes regardless of DHW need? Seems like if DWH temp is met it should just stay on SH until that temp is reached?

109A_5

Well one question I would have is, did it behave that way with the old control board ? If not, maybe it is a setting, but that seems odd.

What if you (as a test) just disconnect the DHW thermostat from the boiler. What does it do ?