Lochinvar 80 not lighting, many new parts already

ColdCanuck

Our Lochinvar 80 which has provided great service for many years has been acting up, and now failed completely. Many service calls - however, we live in a small mountain village and service providers are scarce. Unit provides heat to both DHW and SH in our radiant floors and domestic water storage tank. Has had fairly regular maintenance.

History: Unit began to fail to light or run, Resets would get it to run for a while then quit. Boiler would light, but when the fan ramped up the flame would go out, but sometimes it would light and heat for a few hours. Unit would show "No Flame Ign" or "No Flame Running" codes. The boiler was cleaned, new igniter and flame sensor. When this failed to solve the problems service tech then did manometer gas supply and Gas Valve checks, told us we needed a new gas valve and maybe a new burner as well. This not only failed to solve the problem but now the boiler won't light at all. The service provider then sent their "best tech" to look at the problem, he was very thorough, spending hours doing many checks with manometer, voltage, piping, etc. but came away stumped.

Next was to replace the Control Board. Have spent big $$$$ and still have a dead boiler, still throwing "No Flame Ign" code. However it did once show a "G/V Relay Fail" which lead me to find a couple references to a bad Gas Valve Harness. The part number WRE2205 or 100208619 shows a harness which differs from what we have. Ours is two part, with a basic 2 wire from Control Board to GV but connects to a small gray plastic cube with a On/Off switch with a small circuit board inside. The new ones look to be one piece moulded black rubber.

Before we throw more money at this any ideas? Is this harness a known failure point which necessitated a re-design? Any help much appreciated!

GroundUp

I'm guessing this is an NKB-80 model Noble? Or the Canadian equivalent which is an Epic? I can't think of another 80k model they made. When these "techs" cleaned the unit, did they completely disassemble the top half and scrub the heat exchanger, clean out the venturi, replace the burner, etc or simply flush it out and tell you they cleaned it? Did they use a combustion analyzer to adjust the gas valve to proper spec? 99% of the time, flame fail: ignition/running are a combustion problem and based on your feedback of it locking out toward the top end, I would still stand by that assumption. Often the mixture runs lean (low CO2 readings) and locks out on flame fail: running, when the high fire is out of adjustment. If they replaced the burner and gas valve without an analyzer, I'd bet my house that's the problem here. Are they simply firing the parts cannon at it or are they actually working through and documenting the issues with tech support? Tech support can't/won't do anything unless the technician is standing there with a combustion analyzer and since you never mentioned a combustion analyzer, I'm wondering if they may have been just guessing and hoping… Can you clarify this, please? If they had an analyzer, they should have left a printout or two with the unit (looks like a paper receipt). If you can find those, please share photos or at least the CO2 & O2 readings. Also, there is a 3A fuse plugged into two female spade connectors located behind the transformer (to the right of the display, there are 4 spot welds that hold the transformer behind that gray cross bar) which will sometimes cause the GV relay fail message if the fuse is bad or loose.

JUGHNE

I did get that code on my Lochinvar 80 after several failed flame codes and resets.

The tiny wire pulled out of Molex cube.

It was the 100208619 cable you can see on the SupplyHouse.com site.

I did manage to force the stabs out of the grey cube/plug with small nail. Then solder the wires on the stabs and force them back inside.

Still working months later.

The small on/off switch does not seem to be present, Can you post pictures of that part?

I believe the board monitors the continuity of that cable. If hanging on by one thread of copper it may work, but vibration while operating could open the circuit, drop out the gas valve giving the flame failure code.

But then recompleting the monitoring circuit to NOT show the failed GV code.

ColdCanuck

GroundUp - Lochinvar-Knight WBN 080 is the full name. Yes the burner assembly was completely opened up and cleaned. New burner and gas valve were ordered and installed after tech thought some of the manometer readings of the G/V were suspect. The day the new burner and G/V were installed the unit fired right up and ran, all seemed good until later that night when it failed again "No Flame Running" code. After a couple resets we got it fire again but it continued to fail. "No Flame Ign" code.

That's when they sent out their "best tech" who did work very diligently at trying to figure out what's wrong - many electrical tests, more manometer tests, etc. He even changed the slope of the exhaust vent pipe to achieve better drainage of condensate and vacuumed the inlet vent pipe to clean (was fine). All fuses are fine.

They did not do a combustion analysis at time of first G/V manometer readings, and not able now since it won't run. I did talk to a Lochinvar Technical phone support guy today, (although he was very reluctant to deal with a homeowner) he seemed to think the new G/V should have been adjusted and that's why boiler not firing, however that doesn't account for the fact that it started right up and ran fine for several hours before going back to original symptoms and is now dead. I was able to get it to ignite once by wiggling the G/V harness cube, but it failed to stay lit. That trick has not worked since and was the reason I suspected the harness.

JUGHNE I will try to figure out how to post photos of the G/V harness and cube and some general pictures of the setup. Thanks both for the help so far!

EBEBRATT-Ed

Not familiar with the boiler but as @JUGHNE said and your wiggling the harness shows the harness could be the issue.

mattmia2

you absolutely must adjust the new gas valve with a combustion analyzer or it won't fire properly or likely at all.

probably could put the old gas valve back in and set the combustion properly and be on your way.

the readings on the manometer would be the result of the house regulator and the pipe sizing. there isn't anything really useful to measure pressure wise on the outlet side of the gas valve.

it would be easy enough to test for voltage at the gas valve to see if the harness is intact.

ColdCanuck

Hey mattmia2 remember the boiler was working fine before it started dying and throwing these no ignition and no flame codes. Can't get a combustion analysis with it not running. Tech tested for 24vac at control board like the Lochinvar Service Manual instructed.

OK, got some pictures.

Gas valve and plug.

I found a Honeywell part number 50015704-001 on it, looked up, it's listed as Gas Valve Rectifier. 24vac to dc

General layout:

Also, can the Air Pressure device go bad?

Thanks for looking!

109A_5

Don't know how handy you are, maybe you can review some things on your own, multi-meters are inexpensive and a water manometer can be made inexpensively. The service tech should have gone through all of this.

I'd identify the point in the ignition sequence that the process stops.

https://www.lochinvar.com/lit/0948421000288296_2000546130_SERVICE%20MANUAL_WH56-WH400_Rev%20A.pdf

And does it fire up this way ?

https://www.lochinvar.com/lit/WBII-I-O%20Rev%20J.pdf

GroundUp

The gas valve, especially a new one, NEEDS adjustment. Unreal that any supposed "technician" would even think about walking away from this unit without doing a combustion analysis and adjustment. They need to come back and take care of that for FREE. There may also be something going on with the harness, but the gas valve is most definitely out of adjustment.

hot_rod

There are a number of different tricks you can do to get it to fire once you confirm gas pressure.

Remove the air intake rubber coupling and partially cover the opening will some times work. Or get tech support on the phone as you go through all the steps.

At the very least a manometer and combustion analyzer is needed to do it properly.

Those molex plugs can be problematic. The wire isn't always crimped onto the pin inside the plastic, and you get an intermittent connection. Tug gently on the wires at all those plugs to see if it crimped properly.

mattmia2

testing for voltage at the valve will tell you if the connections are a problem….

also if you smell gas in the exhaust when it is trying to fire

JUGHNE

I have the KBN 80, floor model, maybe newer than yours.

It has the one piece molded gas valve plug, as shown on the SupplyHouse.com site.

The wires pulled out of the small end that connect to the control board. The stranded wire is very small gauge and was crimped into the pins.

As stated above I was able to get the pins out of the Molex and solder back in place.

My best guess for what happens is that the intermittent connections on the pin let the gas valve drop out, losing flame. But the intermittent connection then "repaired" itself enough to not trigger the "GV relay failure" code. That code alone would make one think the GV itself needed replaced, it could be how you ended up with a new GV.

Then it may or may not have enough continuity to activate the GV for the next try.

If GV is activated it may run until the connection is opened again and shut down for retry. Vibration may open the bad connection.

Unless you are handy enough to repair the pins, IIWM, I would order the replacement cable. About $70. No switch and one piece cable/connector.

ColdCanuck

Hi folks, thanks for the replies so far. Please keep in mind that as the homeowner (and not wanting to hover over the tech's shoulder while working) I may have missed some of the steps they took. I do know they didn't do a combustion check.

109A_5 - here's the proper service manual for our unit: https://www.lochinvar.com/lit/WB-SER-Rev%20D.pdf Have gone down the list.

I will try the service only mode (pin in hole) to fire the boiler later today.

mattmia2 - as you can see in the "No Flame Ign" part of the trouble shooting guide, point seven, that Lochinvar said not to test for voltage at G/V (seems nuts to me, how else are you gonna know if that G/V rectifier plug is still good?). But that's the list the tech was following. The connection at Control Board shows 24vac, but it did drop during start attempt, is that normal? Also, if the G/V rectifier plug is to convert 24vac to dc, what should the reading be at the output of the plug? There are two wires going in and four pins going out. Any idea which should show what?

GroundUp - if we can get the darn thing to fire up I will insist they test combustion.

hot_rod - I will let the service guys do the gas pressure tests and they'll need to deal with Lochinvar service support as they don't want to deal with homeowners. Have already tried all the wire tugging, squeezing attempts. Plug seems outwardly good, not enough information to tell if the circuit board inside plug is still good.

mattmia2 - I'm waiting for the "best" tech to call back and make an appointment to come out again. I'm reluctant to poke around too much with electrical so that they can't claim I screwed something up.

I do noticed that there's no smell of gas anymore coming from exhaust vent during start attempts, which would seem to indicate the G/V is not opening at all. Before, when it would fire intermittently and fail, you could smell gas after ignition fail.

JUGHNE - All the pins are good on both the plug and the G/V. Being in Canada getting parts is a slow process and expensive, but replacing that rectifier plug does seem to be the next step. Weird - I have seen the black moulded plug shown under a general "G/V rectifier plug" search come up for many different units (but with different part number) for as little as $29. Is it possible it's the same plug or are there different electronics inside? Here in Canada the plug sells for $155 - $190!

Here's another look at that plug:

Again - is it possible the Air Pressure puck can go bad? How to test?

Thanks for help, sorry if I miss-read or mixed up responses to someone.

JUGHNE

The air pressure switch is normally closed.

It can open if your air inlet becomes obstructed.

The fault code is "APS Open" and requires a manual reset after correction of the problem.

Page 32 of Knight Service Manual.

mattmia2

That switch can get dicey as well as bad joints on the pcb. I would test it by taking 2 pieces of very small wire and stripping enough to wrap around the terminals or slip in with the terminals on the gas valve then put the plug back on and test with a voltmeter. or use 2 test leads from the pins on the connector to the sockets on the gas valve and tap that with the meter.

If the board is a rectifier to chance it to dc then it will be either about 12vdc or 24vdc depending on if it is a half or full wave rectifier(one diode or 4 or an ic with 4 diodes in one package). I would try reading with dc and ac with the meter forced to the right range for about 5-50 v if it is autoranging.

different companies make the innards and the control and someone like lochinvar buys them and puts them in a cabinet so likely some boilers of other makes use the same part.

page 79 of the manual shows the pinout of the connectors. what 4 pin connector are you referring to?

ColdCanuck

mattmia2 wrote: (page 79 of the manual shows the pinout of the connectors. what 4 pin connector are you referring to?)

That's one of the weird things - the wiring diagram doesn't show the rectifier plug, and the two wires coming off the Control Board are yellow and red, not Y and BK.

Here's a shot of the four pins on the original G/V (both the old and new G/V have only four pins) and the plug.

As you can see in the earlier pictures getting at those pins while the G/V is in the cabinet will be a pain.

mattmia2

not at all. hook a piece of about 30 awg wire around the base of each pin and plug the connector in on top of it.

mattmia2

might have to find the manufacturer's data sheet for the gas valve to figure out the pinout of that from the numbers on the valve.

109A_5

I bet the circuit board with the bridge rectifier, 2 connectors and the On-Off Switch may slide out of the plastic housing with some coaxing then the meter probes may be able to touch the pins on the 5 circuit connector (one circuit position not populated on the gas valve). Also you can then see the PCB to see where things go and to what pins.

The problem with measuring Pulsating DC, sometimes called RAC (Rectified AC I think it was in some manuals), is different meters may interpret it differently, so hard to publish a specification.

The 24 VAC input voltage to the rectifier assembly should not drop much.

109A_5

The red arrow points to what is most likely a bridge rectifier. The green Printed Circuit board probably sides out of the plastic housing.

mattmia2

since i don't see anything like a snubber in there, if that is actually a br the back emf from the coil frying the rectifier is a strong possibility.

thinking about it more, those connections are probably in parallel to open redundant valves simultaneously

109A_5

I think you will find you don't need a snubber, the series diodes in the bridge rectifier act like a squelch diode or flyback diode.

mattmia2

Didn't seem to work that way on the exciter for the field coil on a generator. the revised version had a mov across the field coil.

109A_5

Using an MOV in place of an actual snubber circuit, where a snubber circuit is actually needed seems like bad engineering to me. I suspect they were trying to mitigate a very different issue, and not the continuous load of a gas valve coil energized only by rectified 24 VAC.

ColdCanuck

Yes the circuit board pulls out of the case, but it's all Greek to me. The G/V is a Honeywell VK8115V.

At this point I just need an idea or consensus that this G/V rectifier plug might be the culprit for why the boiler is not firing and should I go ahead and order a new one? Waiting for the local service guys to call back could take weeks and every time they show up it costs big $$ and they will charge extra for the cable. I can replace the damn harness, if it fires then I get them to come out and do a combustion test and finish programing the Smart control (time of day, temps, etc.) They owe me that much considering how much we've spent and how long this has been going on (since before Christmas)!

mattmia2

here is the data sheet for the gas valve

https://digitalassets.resideo.com/damroot/Original/10017/en1r9134-nl05.pdf?_gl=1*13lyvx1*_up*MQ..*_ga*MjEzOTk0NTkxOC4xNzQwNjMyNTU0*_ga_71MWVRREH9*MTc0MDYzMjU1Mi4xLjAuMTc0MDYzMjU1Mi4wLjAuMTE3MjQzNDUy

it looks like it is just 2 valves, a main and a safety valve. look for 24vdc at both if i'm reading the spec right. you could also test just the harness with the diode test function of the dmm

109A_5

I prefer to Test and not Guess. Every time you change a part you could be introducing a new and/or different defect into the situation. This can be expensive, frustrating and time consuming.

Its funny how the data sheets don't provide useful data. Coil V1 and V2 what is their resistance ? A useful tidbit for a field tech.

Going by the current draw I would suspect the resistance of each coil V1 or V2 to be in the 100 Ohm ballpark, V1 (pins 1, 2) and then V2 (pins 4, 5). I would measure their resistance first. Also Measure each of the 4 pins to the metal body of the gas valve, it should be infinite, open (OL, on some meters) like when the probes are not in contact with each other or anything else that has resistance.

Then take the circuit board out of the plastic case and plug it into the gas valve making sure it can't short against anything metal. This may provide easy access to test the voltage right at the Gas valve connector pins or at the other side of the board where the connector is soldered to the circuit board. Then with everything connected up measure the DC voltage across V1 (pins 1, 2) and then V2 (pins 4, 5) during an ignition attempt. As mattmia2 stated it should be a DC voltage, in a similar scenario my meter reads about 15 % lower measuring Pulsating DC or Vrac than the actual AC voltage on the wiring harness side of the little circuit board.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1845382#Comment_1845382

the problem comes when the power is turned off in both cases.

109A_5

Yes when the magnetic field collapses. Maybe redrawn this way, it will make more sense to you. When the power is interrupted (even at the peak of the waveform) doubling the forward voltage drop from 0.7 to 1.4 volts is not going to hurt anything.

mattmia2

So there is nothing to conduct the reverse voltage, it can easily exceed the piv of the diodes. There is only conduction in one direction.

If the field collapses such that the induced convectional current is this way, it can easily fry the diodes:

109A_5

You seen to forget the voltage across the inductor reverses so the diode(s) are forward biased. Otherwise in that VERY common protection scheme you would need a Zener diode that is a bit greater than the peak voltage of the circuit.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1845515#Comment_1845515

i usually see small ceramic capacitors. sometimes it is a diode. it is an mov on that generator.

i don't think you can predict exactly what is going to happen once you get magnetic flux through various parts and a moving solenoid

ColdCanuck

Here are a couple close ups of the rectifier plug, you can see there's not much to it.

Question was it possible the tech fried the circuit board while trying to test for 24vac?

Recap; The unit has had the G/V replaced and a new burner, boiler fired right up after these were installed and seemed to be working fine. However, later that same night the unit shut down ("No Flame Running"), after reset failed to relight ("No Flame Ign"), I tried wiggling the wires to the gas valve, it lit briefly - flame went out after just few seconds ("No Flame Running"), reset- dead (No Flame Ign). Has been dead ever since. New Control Board installed. Still dead. There is no smell of gas coming from the exhaust vent after ignition attempts.

After multiple tries I got a new code ("G/V Relay Fail") this lead me to research the plug and find out it's a rectifier.

Question, if it was yours would you suggest a new plug/harness? There is a identical plug on fleabay (no idea if brand new) or there are the black moulded all in one cords available new, WRE2005. However, this part number was listed for similar Lochinvar boiler - no mention of G/V harness on our Lochinvar WB80 parts list. There is a WRE20030 listed as "Harness-connection board" but I'm not sure and can find no pictures.

I'm not very good at electronics, have limited experience, space is very tight around G/V because of condensate trap. Service techs have still not responded to our calls.

What would you do? Thanks for help!

109A_5

With automotive fuel injection technology, using a scope to view the voltage and current waveform it is quite common to see the pintle movement.

With the OP's case that level of diagnostics never happens. Apply power to the gas valve and you should have gas flow, in this case a pressure change monitored by a manometer should be observed.

The AC current to the rectifier board could also be measured, the setup is a bit more complicated than just measuring voltage.

109A_5

" Question was it possible the tech fried the circuit board while trying to test for 24vac? "

Anything is possible, however didn't it quit after the Tech left.

" Question, if it was yours would you suggest a new plug/harness? "

No I would test and inspect. Easy for me but may not be for others.

109A_5

It seems like lack of fuel, since you don't smell any now, so either the boiler is not getting any gas, the gas valve is defective or the electrical control is not energizing the Gas Valve properly.

There may be something to the "G/V Relay Fail" where is the G/V Relay ? Is it on the control board that was replaced ?

mattmia2

i can see some of the solder joints look a little iffy but it is out of focus where i need to see well

109A_5

Well more confusing for me, using the information found in the data sheet provided by mattmia2 the circuit traces on your rectifier board don't seem to line up with the V1 and V2 pins on the Gas Valve, which leads me to wonder how it worked in the first place. I can't see all of it and there may be a trace hidden under a connector body.

109A_5

Things don't seem to line up with the data sheet, and this is the only one rectifier board involved so far, and it worked with the second Gas Valve ?

109A_5

To me these solder joints look poor, although none of them look great, a sharper picture may help.

Did you do the DC voltage test ?

I would at least do it here.

109A_5

Even from this side of the board the solder joints don't look good. Can you re-solder them or do you know someone that can re-solder them for you and do a quality job? Since much has been changed in the boiler with no long term improvement, but not this board (I believe), maybe that is the way to go. I'd re-solder and verify the DC voltage, but that is easy for me to do. The replacement on eBay seems outrageously expensive for what is actually there.

If it was me I would verify the voltage to the Gas Valve and what actual pins are in use, since the data sheet does not seem to agree with what I see on the the board.