Mendota DXV45 Delayed Ignition Problem

[teddybaehr]

I'm new to the Forum, so let me start off by saying "hello" to everyone - this is a great source of advice and am happy to be here.

My house was built in 2008 and I chose a Mendota DXV45 in my living room. It's been a so-so performer since new. I'm running propane and the fireplace was converted (supposedly) from NG when installed. I purchased the Mendota because of its heating ability and general excellent quality rating. I saw many video-commercials of Mendota fireplaces and the local store had display items that looked great. Mine has never achieved the look of a woodburning fire - it's always looked more like my gas range!

But putting aside the look of the flame for a moment, it's also always been a slow starter. From Day 1 it's started with a "whooph". From the time the unit is turned "on" there's been a lag of 5-7 seconds and then boom, it ignites. When the fireplace was new I had the technicians out twice with no improvement; they said it's pretty normal for these fireplaces and wouldn't hurt anything. The technicians didn't seem too savvy, so I tried another company and paid another chunk of cash to have them clean and address the delayed ignition problem with no better a result. So I put up with it for years, but was always uncomfortable - the fireplace didn't get used much mostly because of the starting problem (my wife won't go near it). Last season the pilot wouldn't light. When I called the techs I was told they were swamped and it would be a month or two before they could schedule an appointment. I'd had enough... I generally don't mess with gas, but time for tools.

It took me about 30 seconds to see the problem - the thermocouple was burned through. A little research revealed that a hi-temp thermocouple should have been installed when the unit was converted to LP... it wasn't. I had to remove everything to get the thermocouple out - a very tight fit. I was hardly impressed with Mendota's design; hard to get at things and a flimsy arrangement for the pilot assembly and unfriendly to maintenance. I elected to install a new pilot assembly since I found the flame hood on the pilot was bent and cracked (probably during a ham-fisted installation) and didn't want to have to do the job again if the thermopile needed replacement. I sealed everything up with hi-temp sealant, re-installed the logs per instructions, and fired it up.

It worked as it did before... started a little faster, but still a lag and a "whoomph". This season when I started the fireplace I got a bit more than a whoomph, I got a fireball and what I would call an explosion. One thing about Mendotas - the glass can definitely take an overpressure!

Here's my question - how can I get rid of this delayed start once and for all? It's definitely not normal and has been there since new. Here's what I can tell you:

1. The pilot, thermocouple, and thermopile are clean, good clean flame (although it hits the thermopile at the base - I've read it should engulf the thermopile or hit it more towards the tip)
2. The thermocouple is operating correctly - voltage is spot on; pilot is stable
3. The thermopile puts out around 330mv which is above the 250mv requirement stated in the manual
4. The logs are installed following the manual to the letter - everything matches the placement photos
5. Nothing is blocking the pilot assembly

At this point I'm wondering whether I've been fighting an uphill battle with this fireplace from the start, and whether it was installed, and converted to LP, correctly. I'm also wondering whether I have an issue with the gas valve, or whether the mixture is somehow wrong. I don't have any issue with sooting, but the unit has always produced a pretty meager flame compared the tall, licking flames you see on the videos.

When you build a new house it can be frustrating dealing with system installers. I've had to sort out perplexing issues with improperly installed heat pumps, well pump, garage door openers, and a host of other items that required significant rework. Time now to fix this *&$#%(@# fireplace!

I appreciate any advice you can provide - thanks in advance!!

 

[DAKSY]

I take it you still have the manual, since you've managed to find & replace the pilot assembly.
You are correct in that the pilot flame should engulf the top 3/8" of the T-pile. The pilot being low on it may
account for the low mV putput. It should be more in the 550 mV range with the burner off.
There should be a pilot adjustment screw on the valve. You should be able to adjust the flame
& read what you're getting with your multimeter. Try to bring the mV up.
Your blue flames indicate a lean ATF ratio. That can be adjusted by tweaking the air shutter.
It should be cited in the initial setup instructions in the manual, under "Air Shutter" or "Aeration."
Try closing it in small incements, say 1/16" at a time until you get the flame presentation you want.
The correct flames should be blue at the bottom & yellow at the top.
Once you get orange tips with a little bit of black, you've gotten it too rich. Gradually back it off to yellow.
The ATF mix may also be causing your delayed ignition.
HTH.

 

[teddybaehr]

I take it you still have the manual, since you've managed to find & replace the pilot assembly.
You are correct in that the pilot flame should engulf the top 3/8" of the T-pile. The pilot being low on it may
account for the low mV putput. It should be more in the 550 mV range with the burner off.
There should be a pilot adjustment screw on the valve. You should be able to adjust the flame
& read what you're getting with your multimeter. Try to bring the mV up.
Your blue flames indicate a lean ATF ratio. That can be adjusted by tweaking the air shutter.
It should be cited in the initial setup instructions in the manual, under "Air Shutter" or "Aeration."
Try closing it in small incements, say 1/16" at a time until you get the flame presentation you want.
The correct flames should be blue at the bottom & yellow at the top.
Once you get orange tips with a little bit of black, you've gotten it too rich. Gradually back it off to yellow.
The ATF mix may also be causing your delayed ignition.
HTH.

Thanks Bob,

Yep - I have the original manual and have been going by it.

The pilot on this unit has never made much sense to me. It has a three-way hood - one pointed at the burner tube, one at the TC and the other at the TP. It's not adjustable. When I found the hood bent on the original pilot assembly it looked like someone put pliers on it to get it to point higher up on the TC and TP and probably get the flame closer to the burner. The hood is actually welded on and bending it caused a crack, so I replaced the whole assembly. But I can see what the tech was trying to do. If the hood sat a little higher the flames would cleanly hit the upper part of the TC and TP which would help kick up the voltage.

I see the pilot adjustment screw and the air shutter damper. With the glass back on I'll try adjusting the air mix and report back with the millivolt readings.

The fact this this unit has had delayed ignition problems makes me wonder if I'm missing something fundamental. I know the techs fiddled with everything and it was still a hard starter. They finally gave up and declared it normal!

 

[DAKSY]

I have a Heat & Glo 6000TRXI-IPI-LP had a delayed ignition when I replaced a cracked ceramic burner.
I eliminated the problem by sizing the closest burner ports to the pilot & by drilling the same diameter
into the burner even CLOSER to the pilot flame. That allowed the first burst of LP to ignite almost immediately.
I'm not telling you to modify your burner, but it worked for me.

 

[teddybaehr]

I have a Heat & Glo 6000TRXI-IPI-LP had a delayed ignition when I replaced a cracked ceramic burner.
I eliminated the problem by sizing the closest burner ports to the pilot & by drilling the same diameter
into the burner even CLOSER to the pilot flame. That allowed the first burst of LP to ignite almost immediately.
I'm not telling you to modify your burner, but it worked for me.

Yeah, I noticed that you mentioned doing that in response to another fellow with a 'boom box'. What's really drove me nuts is an acquaintance with the exact same unit installed around the same time and also on propane. His ignites immediately, within a second of hitting start. I noticed his logs were laid out the same way, but the coals, vermiculite, and inswool were set up differently. I never thought it made any difference, but maybe that's plain wrong. I went back and found three different manuals from Mendota on the DXV45; all three have different instructions on how to set up this material during the lay-up. I believe the 3 versions of the manual represent different variations of the DVX45, but it's interesting that they keep changing this step.

 

[DAKSY]

You DEFINITELY don't want ANY ember material near the pilot.
That can help in the delaying the ignition,
by diverting the burner LP away from the pilot flame.

 

[teddybaehr]

Okay - I performed everything suggested - attached a few pictures to show what's going on. I tweaked the pilot jet, adjusted the damper, cleaned the thermopile (it was pretty clean already), and fired up the pilot. I registering around 800 mv with the unit off, double what I measured before. You were right on the money.

The second picture shows the flame output from the pilot - this is with the door off (so I could get a clear shot), with the door on the flame has more yellow in it. I removed the logs to show that the flame clearly envelopes the lower burner tube. As you can see in the third picture, this unit has two burner tubes; the rear unit is engaged separately from the front burner if you desire more heat.

Before I try to fire the main burners... a question. Can I try to fire it without the logs - just the tubes alone installed? The reason I ask is some stuff I've read suggest the logs are required in order to properly flow the gas for quick ignition. I can't understand why this would be true since the gas should flow quickly to the short tube adjacent to the pilot and get things going. I'd like to eliminate all potential reasons for delayed ignition by starting as simple as I can and testing in steps - it seems to make sense to first try with bare burners and establish if it ignites quickly. If it doesn't, then it would seem to me that something is fundamentally wrong.

 

[DAKSY]

815 mV will absolutely SMOKE the T-P & the T-C. Turn it down to about 550mV.
You CAN safely light the unit without the logset installed.

 

[barmstrong2]

I would want to know the manifold gas pressure after the gas valve. For propane, it should be 10" WC. If the technician missed a step in the conversion, it would be low, around 3.5" WC. This could cause poor flame picture and delayed ignition.

What daksy said about drilling a couple extra holes closer to the pilot flame sounds extreme, but, I have done this also. Gas appliances are manufactured for use with natural gas and don't always translate to propane. The big difference is the natural properties of the two. Natural gas is lighter than air and will float up. Propane is heavier than air and sinks. Many times, the burner/pilot design works well natural, but, with propane being heavier, it drops away from the pilot flame, thus needing to build until... Boom! Any more than 3 seconds is unacceptable, for my liking.
Regarding doing this, with a new unit, I have contacted the manufacturer tech support and obtained authorization to do so, so as not to void warranty. With an older unit that's not a concern, but, just to add some credibility to what we're telling you.

 

[teddybaehr]

Thanks to you both for your advice. I'll do some more tuning and try to get the mv reading where it's supposed to be. On this unit I've noticed that the difference between a clean and dirty TP is almost a factor of 2. The TP never gets that dirty, but even when it looks clean if I wipe it down and give it a quick cleaning with crocus cloth or fine steel wool the readings shoot up. Annual maintenance is clearly needed in this department.

The pilot flame completely engulfs 3 or 4 holes of the burner tube segment adjacent to the pilot - any gas getting there is going to ignite immediately. The area around the pilot has always been clear, so that's not an issue. Since the rear burner tube is never receiving gas during start-up, the build-up of propane that ignites with a boom must be coming from the bottom main burner tube. It's hard to see in the picture I posted, but the segment of the burner tube running to the pilot is angled up... so propane has to run up hill a bit to get to the pilot. This has always troubled me since, as you point out, LP is heavier than air. If indeed the manifold pressure is low, the flow of propane into the burner tube might be slower that it should be without enough pressure to "push" it up the segment of the tube to the pilot. That would explain the persistent delayed ignition and the meager flame I've been experiencing. Great catch on that important point about checking manifold pressure - I feel dumb for not thinking of that!

I've long felt that my woes with this fireplace started with a bad installer; it wouldn't surprise me one bit that he missed this important step. I have a lot of LP appliances in my house: 2 fireplaces, furnace, range, generator, and garage heater supplied from an underground 500 gallon tank. All the other units work flawlessly. I don't have the tools needed to check the manifold pressure, so I'll locate someone who can.

 

[DAKSY]

One other thing to take a look at while you have it apart is the alignment
between the burner orifice & the primary burner. If your burner points UP
& the burner orifice is nearly horizontal, there's your issue.
They BOTH need to be pointed in the same direction.

 

[barmstrong2]

Do you have rock wool, burning ember material, to place over the burner ports? I always put that ember material across the burner ports, mostly to improve the flame picture, but, it would also create just enough of a restriction to maybe push the flow of gas up the lighter tube a bit quicker. There ember material should be dime size pieces, in shape and thickness. They lay loosely over the burner ports.

 

[teddybaehr]

I wish I had uploaded a clearer picture... the main orifice delivers to the front burner tube which is a downhill run, so that's good. However, the branch off the front burner tube running to the pilot is back uphill, a pretty good angle too. That might be great for NG, but might be an issue with LP. The rear burner tube runs downhill from it's orifice and then sharply uphill along the 'c' bend. The pilot flame catches the rear tube nicely and the rear burner has always ignited immediately with the flame running around the tube quickly from the pilot outward.

I think barmstrong2 is on to something with the manifold pressure. If the pressure is low the LP could be filling the main burner tube and pooling but taking its sweet time to wander up to the pilot - the result is a late ignition and boom. I did try firing it up with the unit with bare tubes... marginally better, but still a delayed ignition - 6-8 seconds and a strong boom. So I doubt loading logs, vermiculite, rocks, and inswool is going to improve things. I did tune down the pilot flame, but I can't get the TP voltage below 620 mv.

The inswool was never installed over the burner tube port holes, but laid adjacent to them. I tried once placing inswool over the ports with exactly that thought in mind, but it didn't seem to help. And one good 'boom' sent the inswool flying!

I suspect that the LP conversion on these units has to be done with precision. If properly done everything's all set; but if errors are made you wind up walking down the road I've been on. I'm waiting to get help testing the manifold pressure - I'm betting it'll wind up being low. It explains both late ignition and a weak flame.

Thanks for your continued help - it's very much appreciated!!

 

[BDScott]

I could not have written thread any better than teddybaehr. This is precisely my experience with this model. My only difference is that I have drilled additional gas holes nearer the pilot for a faster ignition, but with no different results. I believe the angle of the main burn tube is a design flaw for use with PG. If accurate, it is a latent design defect for LP conversions. If true, it will always be defective. I was hoping this thread had a resolution. Did we ever learn how to get the 'WHUMMPP!' to stop? Any remedy?

 

[DAKSY]

Has the Burner orifice been removed & inspected? I'm wondering if it is correctly sized for LP gas.
LP burner orifices have smaller holes due to the higher line pressure. If you still have an NG orifice,
the larger diameter hole may be allowing the LP to disperse before getting to the pilot flame.
The smaller hole in the LP orifice would tend to create higher pressure & a "jet" of gas shooting
further into the burner tube...

 

[Millbilly]

I would take the burner out and inspect the burner orifice size, should have a number stamped on it and check for partial blockage. While you are at it inspect inside burner tube at the air shutter and make sure there is no soot or insects obstructing air flow. Then make sure installer replaced gas flow regulator tower to lpg one. It would be right on the valve and should be obviouus because the torque screws will likely not be safety heads and lack the factory indicating paint seals on screw heads, and check pressure.

 

[JIContender]

Good morning!
New to this forum, searching for answers to my 2008 propane DXV45 'whoomp' that had been very intermittent, then gone once unit fully heated up; now it is more persistent.
My questions:
Since this model is 'discontinued' is there an upgrade to the pilot/starter which seems to be the problem? Otherwise great looking unit with perfect heat output for my room from 40° to -10°, even with multiple large windows.
When it's on, you always know where to find our Bully!
Thanks in advance!

 

[DAKSY]

Are you burning LP?
Do you have glowing embers on the burner?
Try moving the embers away from the holes nearest the pilot flame.

 

[JIContender]

Yes, propane home with fireplace, Navien tankless water heater & 2 stage heat pump furnace so we burn a moderate amount.
Removed all embers & wool as I do with yearly cleaning. Lightly brushed small amount of soot around pilot and 'cleaned' igniter with fine emery cloth and replaced. Always take care to not obstruct pilot so i can fully see it always.
Funny thing that the whoomp only occurs when the rear burner is on from cold startup, esp. after we have been away & not used it for a week or more. We have found that if the front burner alone is used for awhile, say 1 hr., then adding the rear burner it works normally. On start-up with front & rear the whoomp will occur every 30 seconds for up to 10 minutes, or until I give up & burn front only for awhile. After both heated up, 1hr or overnite I cannot get it to whoomp any combo. Is there a mechanical solenoid type valve that misfires when cold? After constant use over a few days I can also turn it off in the evening as the room gets quite warm with sunset heat, then when turning back on 10pm it never whoomps regardless of front or both burners used. Flame looks perfect like the brochures, and soot production is very minimal. Have used it regularly in the past week, and @ 37° outside this morning, burner was on low all night and it works perfectly.
Go figure?

 

[DAKSY]

I am not really familiar with your unit, but it's a common occurrence with LP units.
LP is heavier than air & can puddle below the burner. It can build up until there's enough
of it that it reaches the pilot flame, & the entire "puddle" will ignite at once, with an audible
"Whoomph." Once that puddle has ignited, it shouldn't happen again during use.
Sometimes, drilling an additional hole near the pilot flame can help to mitigate this issue,
but I wouldn't recommend that being done by the everyday homeowner.
As I have stated in previous posts on this issue, sometimes it's an alignment problem between
the burner tube & the burner orifice. If they are not exactly aligned, fuel will escape the air shutter
instead of being directed into the burner tube. Again, performing this inspection, & re-alignment is
best handled by a professional.

 

[dbr549]

Hi!
I started having problems with the exact same unit as the OP (Mendota DVX45). We bought the unit in 2018 (converted to LP) and used it about a half a dozen times that season because it was installed mid-season. Last year it started with the small explosion. Talked to the place we bought it which is about 2 hours away and never got the issue resolved. I blew out around the pilot hood and it seemed to help. This year- I cleaned the unit and it started up fine. I set the pilot light to stay on and tried it about a week later and whoomf- back to the same thing.

I looked at this thread again and I see a difference in the picture in thread #7 and the pilot hood compared to mine. His setup is different to where it appears the pilot flame is directed at the TP, TH and the burner. Mine's directed the two thin wires and a gas log- not the burner. Is this a faulty conversion done at the dealer or is this correct?

Here's a link to a video of what was happening last year. The same thing is happening now but the pilot light is also being extinguished half the time. The unit then locks me out and has to be reset in order to start the pilot light. This doesn't happen every time but it is happening. Here's a link to the video- Mendota. That fireball is loud and freaks me out when lighting it as it sounds like the whole unit is going to explode

The dealer suggested drilling a hole in the burner closer to the pilot light- I'm now thinking this is an incorrect conversion or pilot assembly. Any suggestions?

Does anyone know how to remove this pilot hood? I'd like to get it off to clean it if possible.

 

[Millbilly]

Remove burner. Remove and clean burner orifice. Inspect burner line. Clean air shutter. Position air shutter to factory recommended setting. Reassemble and test.

 

[t c]

Hi!
I started having problems with the exact same unit as the OP (Mendota DVX45). We bought the unit in 2018 (converted to LP) and used it about a half a dozen times that season because it was installed mid-season. Last year it started with the small explosion. Talked to the place we bought it which is about 2 hours away and never got the issue resolved. I blew out around the pilot hood and it seemed to help. This year- I cleaned the unit and it started up fine. I set the pilot light to stay on and tried it about a week later and whoomf- back to the same thing.

I looked at this thread again and I see a difference in the picture in thread #7 and the pilot hood compared to mine. His setup is different to where it appears the pilot flame is directed at the TP, TH and the burner. Mine's directed the two thin wires and a gas log- not the burner. Is this a faulty conversion done at the dealer or is this correct?

Here's a link to a video of what was happening last year. The same thing is happening now but the pilot light is also being extinguished half the time. The unit then locks me out and has to be reset in order to start the pilot light. This doesn't happen every time but it is happening. Here's a link to the video- Mendota. That fireball is loud and freaks me out when lighting it as it sounds like the whole unit is going to explode

The dealer suggested drilling a hole in the burner closer to the pilot light- I'm now thinking this is an incorrect conversion or pilot assembly. Any suggestions?

Does anyone know how to remove this pilot hood? I'd like to get it off to clean it if possible.

thats absolutely a problem. there should be a series of smaller holes ( about half the size)that the pilot light completely covers all the time maybe 3 or 4. In mendota set up it clearly states that. the photo you showed is different than what i have always seen but for the pilot to be directed at a log seems stupid. if anyone says that the way your unit lights is normal i would have them put it in writing. i have had issues with a dx35 that never was able to be corrected. there were hole missing in the burner where the flame would stop and sit there and then would boom and jump. i corrected that by drilling the same size holes to complete the burner(about 7). i also had an issue where the pilot wasn't even close to the ignition holes so i had to saw and modify the bracket to move the whole pilot assembly over 3/4 of an inch.it's a beautiful looking fireplace but i will never leave it light on it's own without being in the room. Most of the time it's the first light of the day . mendota has issues with quality control. thats based on my experience with the company. when talking to the head of their operation about the jump in the burner they asked if it looked like holes were missing ,i didn't tell them i already drilled them until then.they knew with no recall notice. sorry i was rambling but there should be ignition holes under the pilot and as soon as you here the click from the thermostat there should be a flame immediately with no boom!

 

[dbr549]

Thanks for the reply TC!

I've been in contact with the dealer. They sent the Mendota manual they used for the conversion from gas to LP. In it, it clearly shows that the photo I posted is the correct installation. The dealer suggested drilling a holes on those burner tube too. I only drilled one hole (same size as all others) on the back burner and one on the side inline with the pilot light. Plus made sure there was no ember material anywhere near the pilot assembly. This has helped. I don't have a booming ignition anymore but I still have a longer delay in ignition than I think their should be (about 4-5 seconds).

The weather is starting to turn cold here and time will tell with more use. But I think I'm going to have to do like you did and drill several more holes to hopefully solve this problem.

Not sure about Mendota's quality control but, I think this is a design flaw. The ignition assembly is simply too far away with this conversion to LP setup and turned the wrong way. It may work fine with natural gas, I don't know. But obviously, people are having issues with LP that Mendota needs to address. Which is to relocate that assembly closer to the gas tubes and drill several more holes lower on the burner tubes, in line with the pilot light.

It's aggravating to spend this kind of money for a premium product only to have problems and try to fix them on your own. The good thing is- my wife is not as afraid to turn it on by herself now.

 

[Brooks89]

Has the Burner orifice been removed & inspected? I'm wondering if it is correctly sized for LP gas.
LP burner orifices have smaller holes due to the higher line pressure. If you still have an NG orifice,
the larger diameter hole may be allowing the LP to disperse before getting to the pilot flame.
The smaller hole in the LP orifice would tend to create higher pressure & a "jet" of gas shooting
further into the burner tube...

I'd second looking at the orifice. Even if it's the correct factory spec'd orifice for propane, I found with my gas fireplace changing it ONE SIZE made a world of difference.
In my case the flames were spectacularly high, and rather than delayed ignition I had an 'extinction' or 'extinguishment' POP that would literally move the log set out of position. Reducing the orifice from a #51 to #52 and rejiggering the glass media installed below my log set made a world of difference. Unit fires up nicely, extinguishes quietly and the flame picture is lowered but looks fine. However my fireplace was not from Mendota. You might want to speak with them about increasing the orifice one size. Likely they can supply you with exactly what you'd need.