HTP, MC Series, Cracked Swirl Plate

Harvey Ramer

So that is what I found while servicing the ModCon. The swirl plate had a semi circular crack, maybe about 1-1/4" diameter, around the center cone. It didn't look like a normal crack, where there's a nice clean break, but with the pieces still in contact. It had more of a ripped, jagged look with some of the plastic pieces still attached to both sides of the crack. The separation of the crack may be about a millimeter or slightly less.

So what makes this happen?

I called the local HTP distributer and they told me that the control had the incorrect post purge parameters set and that was what was cracking the swirl plate. They said I need to bring the control in and they would flash in the correct parameters.

Anybody heard or experienced this before?

wogpa67

Only on Recirc flue gases usually.

Harvey Ramer

It was recirculating the flue gasses. I corrected that. What I'm saying is, what the heck does the post purge have to do with cracking the swirl plate?

wogpa67

I would say nothing. Since they have reduced the post purge and made it installer config now.

I have a Rev 2 Pinnacle and I wish I could Lessen my post purge of the inducer so I lose less heat. I post purge my circs to 100.

Tim McElwain

Understanding the Swirl Plate in your Boiler or Water Heater
Posted by Peter Seddon on Jul 17, 2014 4:42:54 PM
Swirl Plates are a staple in the design of high efficiency boilers and water heaters. They are present in most, but not all, gas burning units. The majority of our units use the Swirl Plate. It is found in most cases attached to the outlet plate of the gas valve and sandwiched in between the gas valve and the blower (inducer) housing. Swirl plates provide a vortexed air flow supply to the gas coming out of the gas valve outlet. The swirl plate adds turbulence, mixing the gas and air to provide a blended mix to the blower.

Swirl plates are plastic, are different colors, are round like a “plate” and have fins and orifice openings of different sizes. The swirl plate is open to the atmosphere at the gas valve outlet as our valves are negative pressure valves that only emit gas with the presence of blower “vacuum” drawing on the valve. The blower at the same time draws air into the swirl plate openings which are on the circumference of the plate. The air/gas mixture is then “swirled” around together and drawn into the opening in the plate and on to the blower.

Swirl plate problems occur for several reasons, but mostly swirl plate failure is the result of exhaust gas recirculation. The corrosive nature of the exhaust gases which can be drawn into the intake air piping and sent to the swirl plate as clean intake air, when it is not, can begin to erode the swirl plate eventually rendering it cracked, broken, disintegrated and even in very rare cases almost completely gone!

It is important that the swirl plate be inspected at least annually, along with other routine inspection of the boiler or water heater combustion apparatus. If you see that the swirl plate has discolored it is wise to remove it and check its condition. There are several of our boilers and water heaters that have the swirl plate contained inside a housing or “cowling” cover that is a round black plastic cover which comes apart in two pieces. Inside the cowling is the swirl plate.

To ensure that your boiler or water heater is maintained properly and gives you years of trouble free service, we suggest that the swirl plate be part of your annual inspection.

Harvey Ramer

Thanks Tim. Good info as always.

Boiler is only a couple years old. It would have kicked the bucket in a few more, if it was left unattended or serviced by the installer. Had to replace the ECO stack limit (corrosion), manifold O-rings and clean out a bucket load of flux from inside the system.

I'm still curious what kind of magic the tech at the distributer hopes to achieve with the post purge adjustment.

Bob Bona_4

Just had a Burnham Freedom with same prob. Venting appears normal, ala Rinnai concentric. About 5 years in. Never serviced, was wondering if not recirc, then possible heat spillage back up thru the horn on off cycles.

Charlie from wmass

I had one this past winter that had similar issues. The original installer had the exhaust and intake backwards with a side by side configuration.

j a_2

Interesting just had crazy similar, incident at a long time friends house,whom I was helping. We were just doing a yearly on his unit,using my trusty combustion analyzer.... Boilers Installed by me....5 years ago. Along with 2 rinnai wall hung water heaters..never more than a minor issue.....So combustion analyzer in, all is good, on high fire, slight o2 adjustment down, ppm under 75...all was great, until we went to low fire, co off the chart high and climbing 2 k plus.co...oops....back and forth we go....Even went to their other unit mirror image accros basement, just to check myself.. That unit test was perfect...So back to other unit we go....Just kept checking and checking.... Called up my trusty old friends at U S Boiler, they hooked me up with Glen, Glen is one smart guy,best I ever dealt with....Glen says Jim,open up the cover, it was open....look inside, he says, what do u see? I saw corrosion,he says remove and check swirl plate, so I did. Check if for wear, it looked great,but I had noting to compare it to...Back in it goes, same readings, calls Glen back.He says order swirl plate ,and I did. I stalled new swirl plate, rechecked readings, with minor tweaks of gas and air screw adjustment's all was perfect....Glen is outstanding, u s boiler is lucky to have him....those in the business know who I mean....He could use a few well wishes and prayes right now...I gotta say but I am sure all the regular tech posters have one, you can not do this type of work without a combustion analyzer
....2000 ppm can kill someone real quickly.... The funny thing is on low fire it looked and sounded great....Went back for a cold one with my buddy couple days later...Just double checked my work,and Glens trouble shooting. Reading were sot on....
About the cracked swirl plate, I just remember back a few years ago,a problem with swirl plates, something about them being damaged at factory, over younder, and may be a wrong length bolt being the cause...I just can't remember.....

jonny88

@ja interesting I had a conversation with Glen two nights ago,dont know if it is the same guy,I dont want to mention his last name without his permossion.He troubleshooted a problem for me over the phone and after that he sent a long email as a follow up with instructions.He is on Long Island same guy?

j a_2

If u can call me 6176886802

Harvey Ramer

Got an answer. Apparently HTP sent out a bulletin advising that the post purge time be extended to make sure all the gasses are exhausted.

j a_2

Interesting. This is a good thread..Deserves some homework and input....

Bob Bona_4

Makes sense Harvey, possible combustion aftergasses wafting back...

4Johnpipe

Question...How long are the vent lengths I have seen this when pushing the maximum lengths allowed perhaps not accounting for fittings...

j a_2

Cross contamination. is a good possible

Harvey Ramer

John,
The exhaust was roughly 13' with 1 90. The intake being the same. 2" pvc. Boiler MC 120.

So we should be good in that respect.

Bob Bona_4

My case, the vent was concentric pipe, 2 feet max, factory supplied.
It wouldn't be surprising to learn swirl plates may all come from the same vendor. There's deterioration happening for some reason, not so sure it's cross contam. Possible chemical breakdown?

Harvey Ramer

Bob Bona said:

My case, the vent was concentric pipe, 2 feet max, factory supplied.

It wouldn't be surprising to learn swirl plates may all come from the same vendor. There's deterioration happening for some reason, not so sure it's cross contam. Possible chemical breakdown?

This unit is running on propane. On the gas valve side of the plate, there is a clear trail left by the gas. It looks like a reaction between the plastic and the raw gas. Propane is a petroleum based product as is plastic, no.. Maybe that has something to do with it?

Bob Bona_4

I really believe that. My Freedom was lp too. I've been trying to post a pic of its cracked plate but it's not working too well from my smart phone. Not only was mine practically cracked all the way around the hub, it was badly discolored and brittle like an eggshell.

Harvey Ramer

I will post high quality pics of this plate within the next couple days. We can compare notes and see if the plates suffered the same type of failure.

Bob Bona_4

I will try again too. Mine are high quality also, and there's one of the backing plate and it's deterioration.

SWEI

LPG consists of a portion of the liquids known as "natural gas condensates." Many are solvents.

BobC

i wonder if some supplier made an unauthorized change to the material used for these plates. Back in the day companies bought from local suppliers that they knew and worked with, when you go across the pond to save money you give up a lot of control - If you don't keep a very close eye on them they will try to get away with almost anything.

I used to deal with a metal fabricator about 25 miles away and from time to time I'd get something in that was just wrong. I'd call him up and if he recognized the error the new part would be on my doorstep in 2 days; if it was more involved I'd get inn the car and we would straighten things out in short order. We were a small shop but we used them for almost all of our work so he was very responsive and his pricing was usually pretty good.

I once ordered some machined heat sinks (17X6X2") from a Chinese supplier because he could supply the finished part for less than I could buy the raw aluminum for (quick rule of thumb was finished parts cost 3X material costs). I got 675 heatsinks in that were absolutely beautiful BUT some hole dimensions were off by about 3/8". No way i could send them back so I had to modify them and add a aluminum plate to "move" those mounting holes. We were able to recover from that error without losing our shirts but it taught me a lesson; have parts fabricated close enough so you can reach out and touch the supplier.

Bob

Bob Bona_4

In our case it would be "we've never seen this before, it's obviously a field problem". Click.

Harvey Ramer

Here are pics of the swirl plate.
https://www.dropbox.com/s/jzpxl1ljxbz63j4/20150522_180958.jpg?dl=0
https://www.dropbox.com/s/n2bfk97g8pro93q/20150522_181010.jpg?dl=0

AlCorelliNY

Certainly looks like it has seen some "products of combustion".

j a_2

Clearly its cracked at the hub, correct? About being worn or deteriorated, other than the obvious, are there specific measurements for that...As u know the swirl plate is ultra critical, my simple thinking is there is more to come on this subject....Great and very imformitive thread by you

Harvey Ramer

I would also note, that the plastic air inlet air shroud that encases the swirl plate, does not appear to be damaged in any way.

j a_2

So whats you thinking?

Bob Bona_4

I still can't post a pic. But that's identical to my swirl plate damage, plus I had discoloration, a blue faded to light blue

Bob Bona_4

.....freedom boiler<img src="https://us.v-cdn.net/5021738/uploads/FileUpload/64/05561a19ae219e3bf4ab6664d9afab.jpg" />

Tim McElwain

I had talked to Harvey at the OESP Show and told him I have some info that may help with this. This material is taken from my Manual I wrote a while back Mod/Con Equipment Volume I:

Here it sorry for the length I will break it down into different postings but need to get all the correct info.

Swirl plate

The integrated baffle acts as a two stage cascaded signal amplifier and permits safe operation over a modulation range up to 1: 10. The specially designed, patented. Swirl plate changes flow patterns to reduce resonances.

The following info is found on pages 176, 177, 178 and 179 of my manual.

F09

An F09 that appears on initial startup of a Munchkin is usually the result of an improper air/gas mixture. Every unit is fired before delivery, with proper combustion set, however gas has differing calorific values in different areas.

To initially start a challenging boiler, cover the air intake on the left side of the blower ½ to ¾ of the way with your hand (essentially choking the emit). The unit should fire. Once a solid flame is established, you should be able to set the CO levels to 105 to 110 ppm on high fire by adjusting the throttle adjustment screw (See Figure 4, 5 and 6).

Check through the viewing port that the ignitor (11 o'clock position on the face plate) is sparking. Ascertain that the gap is 1/4 inch.

Be sure that the ignitor is directed downward toward the burner. The spark should be visible through the viewing port.

The F09 fault actually means that the boiler does not see flame rectification; it does not necessarily mean the boiler failed to light.

There are three possible causes for failure to rectify.

1) Spark, but no gas boiler wont light, therefore no flame rectification.

a) Frequently a result of poor gas pressure or a bad regulator, it may be that the gas line needs to be purged (start up).

b) Verify spark gap (114")

2) No Spark, but you have gas boiler wont light, therefore no flame rectification.

a) Frequently a result of condensate back up. Verify the spark igniter works out side the boiler, use caution as there is a large voltage present

b) If there was a condensate back up it may be necessary to gently push the refractory aside using a small screw driver. This may prevent the spark from grounding out through a moist material. You may then need to address a condensate back up.

3) Spark and gas then flame however it wont stay burning, therefore no flame rectification.

a) The Munchkin must be properly grounded; MX or BX cable does not make a proper ground.

b) Verify there is 48VAC from the flame rod to chassis ground.

c) Check the status menu (d7) to verify current (light off should be approximately 1.5 µA, low fire should be 3.0- 3.4 µA, high fire should be 3.8-4.2 µA

d) Remove the X6 plug and check for corrosion

e) Remove and clean the screws that hold the burner tube to the face plate (this may also fix an F10). When replacing them us a conductive anti seize compound to coat the screws as this will help complete the path back to ground for the flame signal.

f) Verify combustion numbers.

F10

F10 is indicative of a failure while running.

Check that the condensate drain is clear, and that condensate can flow freely from the boiler. Back ups create steam which suffocates the flame, throws off rectification, or in the worst case, soaks the refractory plates, causing the spark to ground out instead of sparking.

Check what the flame rod is reading by depressing and holding the S4 button. It will display d1. Press and release the button until d7 appears. The d7 reading should be 4.0 or stronger, and is directly related to the CO output of the boiler (see below).

The CO levels at the exhaust breach should be 105-110 ppm on high fire on all units. See Figure 4, 5 and 6 for adjustment procedures.

If you have the CO set properly with the flame current holding steadily, then suddenly the flame current begins to swing in large amounts, check the burner gasket. At higher temperatures, the burner flange can shift, causing gas (flame) leakage at the rear of the burner itself. This is rare, but it has been seen.

If there is a concentric vent kit installed, check that it has been properly assembled and GLUED. Exhaust gas recirculation will cause the unit to fire then fail almost immediately.

On a Munchkin 80, check that the brass vent barb on the rear of the gas valve is not blocked by the rear of the boiler cabinet. If so, shift the boiler slightly forward in the cabinet.

Tim McElwain

Here is the rest:

MUNCHKIN SWIRL PLATE PROBLEMS WITH DUNGS GAS VALVE AFTER 11-11-04 (Note Honeywell Gas Valve did not have swirl plate but used a venturi cone)

The problem may show up as an F09 code or just a noisy blower may be an indication of something wrong. It will typically be a very deep sounding noise and typically loud enough that the customer may hear it upstairs. Another symptom maybe a lot of restarts/recycling and it as another described it "moans" when running or before it shuts off.

What to look for:

Take the cover off and look carefully in to the blower assembly. The air and gas come in from the left. The gas mixture goes out from the right. Between the fan and the mixing chamber, notice a white plastic spacer plate. Between the blower and the collector, notice that there is a white plastic spacer about 1/4" wide.

That white thing is the swirl plate (some later were grey and then black or red). What you see are vanes like the volute case on an injector water pump. The gas goes into the middle where it goes through a venturi nozzle that is part of the plate. Air is added to the gas and "swirls" and recirculates, mixing the air and gas.

Look very carefully at the plate and notice that it has curling vanes. See if they are deteriorated. This is the" Swirl Plate". It may need to be replaced. You can take the cover off and try to see what is happening when it makes the noise but experience seems to show that it doesn't happen as often when the cover is off. If it will do it for you, look carefully at the plate. Get a narrow flame mirror and look all around it. If you see a place on the outside of the swirl plate that is a different color from the rest, it may be "backfiring". The flame is being pushed back through the burner cone and igniting in the mixing chamber. Where the fan mixes the air and gas, then being recirculated as a flame. You may be able to see it with a flame mirror.

It is then supposed to go into the burner. It will appear that there is flame damage to the swirl plate with burn evidence running from a passage to the other side of the plate and all the fins of the volute/plate are seriously worn. Take a flame mirror and look carefully at the white part you can see. The spot that is the worst is where you need a mirror to see. If the vanes are all worn, then you will see it.

Heat Transfer Products has replacement plates that have a higher heat resistance to improve this problem. It is not "Backfiring" though. , It is recycling exhaust gas through the intake. Even when the cover is off and it is getting its combustion air from inside. The other thing is be sure that there is no obstruction in front of the exhaust. Look for bushes planted in front of the concentric exhaust or any kind of decorative lawn figure used to hide the termination. The moaning noise when running is the symptom. The swirl plate is
the solution.

The LP Munchkins seem to be more susceptible to this. You need to get the gas valve pressure just right. The quality of the LP gas may be part of the problem. This along with making sure the piping is at least 10 feet of 3/4" pipe before entering the Munchkin. Gas pressure from the second stage regulator in and gas pressure from the valve to the burner could be variable and contribute. Even composition of the LP could contribute especially if it has a lot of condensables in the-gas.

When this problem was presented to Heat Transfer Products they reported the following:

I believe pre mature failure is due to two reasons:

1. The back draft of flue gases from venting system through heat exchanger and back out through swirl plate. The spent flue gases contain a great deal of corrosive condensate. The fix we used was to increase post purge on fan to clear all spent flue gases from venting system.

2. Another cause can be recirculation of flue gasses entering the cabinet and being drawn into swirl plate. Same material just from another direction. About two years (2009) ago the manufacturer of the swirl plates changed what they are made of. They switched to Poly Propylene a more durable product that can also take higher temperatures. Swirl plates made of this newer material can be identified by the letters PP under the triangle on the back side of swirl plate.

3. You may also need to raise the exhaust pipe. Cut off the end of the funnel and put it back onto the pipe then install an elbow straight up with a piece of pipe 18 inches long. Then put a 45° elbow on top to direct the gasses up and away. Put a 112 mesh stainless steel screen in the 45° elbow. You do not have to worry about rain getting into the intake.

4. Check for a bad burner gasket and bad gaskets between the blower and the burner. The opaque rubber gasket can get blown out.

5. An upgrade that can help prevent this. The new 926 ignition control has a longer post purge time built in. Sometimes the problem with the swirl plate is that when the unit shuts off after firing, heat from the heat exchanger can migrate up and overheat the swirl plate causing its early demise. The longer post purge helps remove more heat to prevent this. A change out to the 926 controller has had great results. A new 926 control also brings with it a higher voltage flame sensing circuit. It will also use the sparker as a 2nd flame sensor. This should eliminate the F09's.

6. It is also a good idea to upgrade both refractories, target wall and burner door, along with a new burner gasket.


I hope this helps!

Bob Bona_4

My money is on back spillage due to short post purge, as I always suspected. Thanks for the info Tim!

Harvey Ramer

This particular plate is made from Polyoxymethylene. Very short vents. Can't see extended post purge helping. Was recirculating flue gasses prior to the repairs I made.

SWEI

POM (acetyl, Delrin) has issues with depolymerization caused by exposure to acids and also stress cracking from exposure to chlorine.

Side note: some rather infamous PB fittings were made from the stuff.

Polypropylene is somewhat less rigid, but is resistant to the overwhelming majority of chemical attacks.

Harvey Ramer

So let's put 2 and 2 together. PVC vents, (polyvinyl chloride) getting heated up and off gassing chlorine. Some recirculation resulting in the chlorine attacking the Polyoxymethylene. Stress fractures, which is certainly what the plates appear to have. My first thought was chemical absorbtion resulting in the shrinking and cracking appearance. Might still be some of that going on? Depends how chlorine reacts with Polyoxymethylene.

By the way, I am just theorizing here.

j a_2

Well I am going to do some research on this...Just because I find it interesting

j a_2

This and all the info posted here about close calls on modcons made me think...These boilers must be serviced annually, and updated as required..... Just thinking out loud,,,,maybe a trip sw. That shuts it down after 365 days, or an annoying noise that can only be reset after a service...they can program these things to do whatever they want...even install an internal combustion analyzer.....these computer geegs are pretty smart.....Here in Mass. If you don't get your car inspected once a year, the state will fine you and your insurance goes up..Car owners can't inspect there own cars and install a sticker. Kinda crazy what has become of what was once a real friendly simple job...But its to the point of everyone wants to make money off of those of us down in the trenches....the is a need for more accountability, a free jacket or gift card or hat, never made me buy some of the crap out there on the market....Reliability, support, part availibilty, training, are the most important...