Laars Lite 2: Flame Sensor issue

NOVApool

LifeTime Supporter
Sep 29, 2014
20
Northern Virginia
Hello all,

I was recently having an issue with my pool heater (Laars Lite 2 - Natural Gas, LD), in that it would ignite, and then turn off w/n 1-2 seconds. After some research, it seemed it might be a faulty flame sensor. I started cleaning it off in place but the contraption with the flame sensor came off. I cleaned it off, and and when I was looking at where to replace it by running a presumably quick 1-2 second cycle beforehand, I was surprised to see that the heater stayed lit without the flame sensor in place. I then performed a quick test where I unplugged the flame sensor altogether, and sure enough the heater still ran with no problems. I'm happy that my heater appears to be working again, but now quite worried that my system has no working flame sensor.

Does anyone have any suggestions at the next step forward? Should my control board work with an unplugged flame sensor, and only stop if one is plugged in and not sensing flame? Do I need a new flame sensor? Do I need to try and clean the contacts more? New control board?

Note sure if this is relevant, but the LD manual states that the flame sensor is an "optional" retrofit (bottom right of p. 36 of manual: Lite2 | Jandy).

More than happy to provide additional information, tests, pictures, etc.

Many thanks for any help!
 

swamprat69

Well-known member
Mar 30, 2019
600
Las Vegas, NV
Do you have the manual for your heater? Originally when silicon carbide hot surface ignitors came out, the flame was sensed through the ignitor itself after the ignitor heat up time ( the Fenwal ignition control switched from powering the ignitor to using it as the flame sensor). This proved to be somewhat "iffy" for flame sensing as the ignitor aged and got dirty, The solution was to add a dedicated flame sensor into the ignitor circuit to make it more reliable. Yours may be one of these, if the wiring diagram shows the flame sensor tapped into one leg of the ignitor power. There can be other reasons for lack of or intermittent flame sensing though, including dirt (accumulation in/on burner slots) or blocked burners (spider webs in the burner tubes), blocked manifold orifices (spider webs) or poor system grounds etc.. If your heater hasn't been cleaned in a while, I would also check these other possible sources.
 

NOVApool

LifeTime Supporter
Sep 29, 2014
20
Northern Virginia
Thanks for the quick response! I've seen at least two manuals floating around, but this one has the wiring diagram that looks exactly like the one inside the heater: https://shop.solardirect.com/pdf/pool-heaters/gas-pool-heaters/jandy-lite2manual.pdf . Page 7 has the wiring diagram. The other one on the jandy website (Lite2 | Jandy : first hit, p. 18) labels the "FS" input as "IGN/FS" so I think you are exactly right that at least this type of unit at some point in its lifetime used the ignitor as the flame sensor.

I'm not sure if this helps, but my Fenwal unit looks like this one, which says "Pre purge 0 seconds", "Ignition 7 second seconds" and also my unit says "Heat up 40 seconds":

One question I have is: when does the unit call for flame sensing? Do I have it right that the unit will: energize the ignitor for 40 seconds, open the gas valve, wait 7 seconds for the flame sensor, if no flame sensed-->close gas valve?

When the flame are going they look very strong, so I don't think it is likely there are any blockages. However, I have seen quite a bit on ground wire issues poking around for pool heater problems. Is there anything you think I should start with to check for issues with the ground wire? I'm really not sure where to start on that one.

Thanks again!
 

swamprat69

Well-known member
Mar 30, 2019
600
Las Vegas, NV
Curious as to how old the heater is. Many gas valves have a 4 digit date code on them that read as year/week such as 0422 meaning the 22nd week of 2004. You may also find this type of date code on other parts such as circuit boards and Fenwal igniton controls etc.. Since your heater is a natural draft heater ( no combustion air or induced draft motor ) it will not have a prepurge or postpurge listed. Yes you will have a 40 second ignitor warmup after which the gas valve will be powered and the ignition control will look for a proven flame for 7 seconds before shutting down the gas valve if flame hasen't been proven. Flame is sensed through either the ignitor or flame sensor to "ground" which is the reason that all heater grounds ( Fenwal, Heater Cabinet and others e.g. ) need to bare metal to bare metal with no dirt or corrosion at the connections.
 

NOVApool

LifeTime Supporter
Sep 29, 2014
20
Northern Virginia
I just checked the gas valve which has a "VR8305H 4013" code on it. I can't find a serial number on the heater itself. The Fenwal unit has catalog number 05-339013-003 and also E0201300, not sure if those can help. I moved into the house in 2014, and the heater looked like it had been used fairly well prior to that. I wouldn't be surprised if it was the original heater from 2003ish when the pool was installed.

I looked at the TFP flame sensor article, and tried to locate and clean all ground wires. No change. I ran one more test where I plugged in the flame sensor and ran the heater on. The heater started and continued as normal, but as I touched the flame sensor to various parts of the heater, it could actually trip the system to turn off the gas. So the Fenwal system is looking for something, and the flame sensor is providing something, I'm just not sure exactly what. I'm kind of afraid that I will reinstall the flame sensor in its intended position, but there is nothing that would actually trigger the system to stop if flame is not being sensed, and I'm not sure how one would test the system to prove that lack of flame would actually shut off the system.

I think I will try what you suggested above, which is cleaning the actual burners to see if that makes a difference.

Any additional suggestions or thoughts more than welcome. I'm not opposed to getting a new Fenwal unit if there is at least a reasonable chance that would fix the problem, but I don't want to go that route if there is zero chance of success. I also realize that with my heater's age it may be time to move on, but I'd prefer to exhaust all other possibilities first, if nothing else because I am having a heck of a time to get any pool service companies to respond to me.

Again thanks for all your help.
 

NOVApool

LifeTime Supporter
Sep 29, 2014
20
Northern Virginia
Here are the various pictures I've taken to date. Not sure if they help at all. We've got thunderstorm watch for the rest of the day, so I'll snap more pictures when I clean out the burners/orifices. Please let me know if there is anything else that would be particularly helpful when I work on this tomorrow.
 

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swamprat69

Well-known member
Mar 30, 2019
600
Las Vegas, NV
The Fenwal date code in your photo that is stamped on shows 2001/ 50th week Rev. F ( 0150F ). From the second photo of your burners, it looks like something has been nesting on the right hand side (all that fluffy stuff by the burners). Besides a cleaning, you might also want to check all of the wiring to make sure it hasn't been chewed on/through in spots. Closer photos of the wiring and ground/cabinet/control connections would help also. "VR8305H 4013" is actually the honeywell model number for your gas valve.
 

Bperry

Gold Supporter
Aug 20, 2020
1,071
Knoxville, TN
Pool Size
27000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60
Interested in this one as I have what looks like the same model and about the same age. Mine has the same issue starting up but it was the igniter tip that was broken and not starting. Where is the flame sensor on that? I might be able to check it on mine.
 

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NOVApool

LifeTime Supporter
Sep 29, 2014
20
Northern Virginia
Having some trouble with my phone pictures right now, but quick update:

There is definitely some dampness on the bottom of the unit, which is troubling. A lot of what you are seeing down there is wet insulation that has come off. Regardless, it is cleaned up now. I've also checked all the wiring and didn't find any issues.

Cleaned out all the burners and orifices, and there wasn't really any debris of note.

I did finalize realize that the way that the flame sensor is attached could very likely be the issue. Specifically, it looks like the flame sensor assembly is supposed to be metallically adhered to the burner itself, which might explains some of the grounding issues described by swamprat. It looks like mine had corroded to the point where it just fell off when I tried to clean it. I think I'm going to just get a new flame sensor (and associated attached burner) and see if that fixes the issue (sample picture of what unit should look like here: Amazon.com : Zodiac R0334300 Flame Sensor Rod Replacement for Zodiac Jandy Lite2 Pool and Spa Heaters : Swimming Pool Heater And Heat Pump Parts : Patio, Lawn & Garden).

Bperry: if you indeed have the same unit, AND you feel comfortable doing so, would you mind doing a test for me where you unplug the flame sensor from the Fenwal unit, and see if that results in the system shutting down briefly after startup? This probably only applies if you have the exact same Fenwal unit that I do, but I'm curious what the result will be.
 

NOVApool

LifeTime Supporter
Sep 29, 2014
20
Northern Virginia
Various wiring pics. One thing that may be of note is the placement of the ground. Although my tests didn't really find any difference with it's placement, it could go closer to the flame sensor as per the article about flame sensors
 

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Last edited:

Bperry

Gold Supporter
Aug 20, 2020
1,071
Knoxville, TN
Pool Size
27000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60
Upon closer inspection mine is a slightly different model. Doesn’t have a separate flame sensor like that and the Fenway unit PN is a different version. I think my ignitor is also the flame sensor.
 

swamprat69

Well-known member
Mar 30, 2019
600
Las Vegas, NV
Flame sensing is accomplished from the flame sensor (ignitor or separate flame sensor) through the flame to the burner and back through the burner to ground. The burner can be grounded through its connection to the burner > burner tray > heater cabinet connections or through the burner > orifice > gas manifold > heater cabinet conections. In your case I would use a wire brush on the burner ports of the burners and the metal points of connection between the burners and the brass gas manifold orifices ( get rid of the dirt/corrosion down to bare metal). In your photos, It looks like you have a good amount of corrosion in both the burner assembly and the front control section. The green ground wire attachment to the cabinet is dirty and corroded and both the wire crimped spade connector and all screw and metal plate to plate connections need to be cleaned down to bare metal. The crimped on wire connectors at most connections also appear to be dirty and corroded e.g. the transformer, Fenwal and other wired connections. These also need to be cleaned to obtain a good connection. As long as you have the burner tray removed, I would also check the underside of the heat exchanger for sooting and the top side of the heat exchanger for leaves or other debris and any deteriorated insulation that may be blocking flue gas flow through the heat exchanger.
 

NOVApool

LifeTime Supporter
Sep 29, 2014
20
Northern Virginia
Thanks for the detailed review. I had cleaned a few of the ground connections but hadn't really done any of the others. I'll give all the wire connections a good brushing, along with the various burner attachments when the new flame sensor comes in. Unfortunately the new flame sensor doesn't come in for about a week, so I'll give an update then. Again, many thanks for all the help, you have been a great resource!
 

1poolman1

In The Industry
Jul 14, 2014
205
Sacramento
Just a note. Every heater school that I have attended has said that a main gas valve that has been subjected to the amount of water it would take to cause the corrosion on your valve should be replaced. When a valve fails, USUALLY they fail closed. A corroded valve like yours can fail open and the heater won't shut off when the pump does, even if power is cut. Having seen what can happen with a runaway heater, I would never take that chance. Replacement valves are not that expensive.
 

NOVApool

LifeTime Supporter
Sep 29, 2014
20
Northern Virginia
That seems like a very reasonable suggestion. The new flame sensor just came today, so I'm going to clean the wires as suggested and see how that work out tomorrow. I want to convince myself I'm at least making progress before I sink more money into parts like the valve, as if I end up having to replace the flame sensor, ignitor control module, and now valve, that looks like its going to be close to about $700. Definitely would be worth it if I knew I was going to get many more years on this thing, but if its near end of life, I may have to cut my losses.
 

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