By door, I'm guessing the barometric damper on the flue pipe. If so, it could be from a cold chimney or poor flame in the chamber. Something that has to be seen on site.

As for the domestic hot water, pressure has nothing to do with cold showers. It doesn't seem to be a problem with the coil itself. Maybe a mixing valve malfunction, if you have one? Maybe a bad Moen faucet somewhere in the house? If you have shutoff valves at sinks that use Moen faucets, close them at every sink and especially, close the supply valves for the washing machine, if you have one.

Then try the shower and report back.

Rattling Door:
The door that rattles is the door that if opened would allow me to see the flame from the burning oil, I believe called the combustion chamber. I do not have a barometric damper between the furnace and the chimney. Don't know if it helps but I have a National U.S. Heating Boiler "12 W" Series Oil fired 65000 BTU/HR Water with heat conserver from National - U.S. Radiator Corporation.

Cold Shower:
I don't have a mixing valve (although after reading about what it is, I believe it would be a great addition to my heating system). The water supply to the washing machine is always off unless I am doing laundry. I do have a Moen faucet in my kitchen sink. I shut off the water supply to the kitchen sink and ran the shower with the outcome of a hot shower. I turned the water supply back on to the Moen kitchen faucet and ran the shower with the outcome of a hot shower. My thoughts are that this could be a bad test case. I'm doing this experiment in the afternoon while the furnace has been running some time to heat the house; normally I do have a hot shower after/while the furnace has been running to heat the house. It's in the mornings that I have problems or when the furnace hasn't been running. Therefore I will try the experiment again tomorrow morning with the supply turned off to the Moen faucet and report back.

Just curious, what would make a Moen faucet bad? How does this impact the water temperature to the shower?

Thanks for the help. I can't tell you how excited I am by the possibility of being able to get consistently hot showers!

When the Moen valves start to leak internally, the cold and hot water mix and one will push backward into the pipe, depending on pressure balance. Usually it results in cold showers.

If you set back the temperature at night, your boiler could be working hard in the morning, flooding the boiler with cold return water. The aquastat is supposed to prevent this by shutting down the circulator until the boiler temp catches up. Usual settings are 160 low and 180 high and a differential setting of 10 for copper baseboard and 15 for cast iron radiators. The boiler water will drop down to 150 before the circulator shuts down, but that is more than enough for the domestic water coil. But if you are flooding your boiler with cold radiator water, you could see drops to 100 degrees in the boiler. This can be controlled to a certain extent with a bypass line, to force cold water back into the supply line and only return a smaller portion to the boiler.

Go down in the morning and watch the temperature gauge and see what it says when the boiler is catching up in the morning. If it's below 130/140, you'll have a hard time making domestic hot water.

That would indicate the boiler is undersized for the demand. You might be able to increase the oil nozzle size to make heat quicker, but then you lose a little efficiency.

If this is the problem, have the heater start catching up earlier in the night. If your setback is more than 5 degrees, you aren't saving much oil.

The inspection plate rattle isn't unusual on startup. Caused by pulsating flame and draft. If the tech says the combustion efficiency is good, don't worry about it.

By the way. Don't feel pressured to give up your old boiler. You will most likely never recoup the cost of a new installation unless you live there for the rest of your life. The old boilers were less efficient, but keep in mind that it's lasted twice as long as many newer models will, and it's simplicity at its best.

Cold Shower:
Its Sunday evening the heater hasn't run in awhile since the temperature in the house is reading at 69 degrees and the furnace is set to keep the house at 68 degrees right now. The temperature on the furnace is 120 degrees, the low limit circulator is set to 140 degrees, and the high limit set to 170 degrees. I have cast iron radiators. I anticipate that if I took a shower right now it would start out hot, then go cold, and then go back to hot. Sounds like I need to change the low and high settings. What do you mean by a differential setting of 15? Does that mean I need to add or subtract 15 degrees to/from 160 low and 180 high?

What do you mean by "If your setback is more than 5 degrees, you aren't saving much oil."? Are you implying that if the thermostat is set more than 5 degrees lower at night (say 60 degrees) than the daytime temperature (say 68 degrees) it costs as much oil to raise the furnace from the lower temperature than to maintain the temperature at a slightly higher temperature (say 64 degrees) throughout the night?

Rattling door:
If a technician tells me that the combustion efficiency is good, it still won't be acceptable. I can hear the noise throughout the house, it seems to be getting louder, and frankly it's maddening. I am losing my sanity over it. Is it ok if I use some substance to tighten the hatch door?

Thanks again for your time and help!

I guess we would need to see a picture of the rattling door to identify it.

Your boiler should have a triple aquastat, but maybe you have old controls and use separate aquastats. The triple A has three knobs. Normal settings are 160 low, 180 high. There is a third knob marked Diff. Set this knob at either 10 or 15. Usually 15 for cast iron rads.

Your boiler is not supposed to be off and sitting at 120. It should be at least 140 (per your current settings), or 160 (per normal settings). If your thermostat is calling for heat and the burner and circulator are running, your temperature could be anywhere on the dial below 180, per normal settings.

There is a limit where setting back the temp at night doesn't save money. In this area of PA, it's 5 degrees. At work, where we have a new coal boiler, it can take 8-12 hours of steady running to make up 5 degrees in 20-30 degree weather; hardly worth turning it back at night.

At 120, you will have marginally warm water made by the coil, then apparently the burner kicks in and eventually you get hot water. I would expect this with your settings. Move them up and see what happens. Without a mixing valve, it is possible to get scalding water, so be careful.

Here's how to understand your aquastat, if it's a triple. Maybe a pic would help.

Low Limit Controls and the Differential

With NO call for heat:

On a temperature rise (water temperature is below the low limit) the burner circuit breaks at the low limit setpoint. The burner will maintain the low limit setting if the domestic hot water use requires it to do so.

With a call for heat and differential setting of 10:

Below, or at the low limit, the burner will start immediately and continue to run until the thermostat is. The circulator will run if the boiler water temperature is at, or above the low limit.

The circulator will when the water temperature reaches 10 degrees below the low limit setpoint to preserve hot water for the domestic water coil. The circulator will resume operation when the water temperature is again at the low limit setpoint.

With a call for heat and differential setting above 10"

At any differential setting greater than 10 degrees, the circulator will start when the temperature rises to the difference between the differential setting and 10 degrees.

Example: With the differential set at 25 degrees and the low limit set at 160 degrees, on a temperature rise, the circulator will begin again at 175 degrees. 160 degrees plus (25-10 = 15 degrees).

Temperature goes above High Limit:

If the boiler temperature should go above the high limit, the burner will shut off and the circulator will continue to run until the boiler temperature is 10 degrees below the high limit setting, at which point the burner will restart.

Honeywell 8124A Literature:

On a temperature rise, with the adjustable differential at the minimum setting of 10 degrees F, the burner circuit (R-B) breaks and the circulator circuit (R-W) makes at the control setpoint. On a temperature drop of 10 degrees F below the setpoint, the R-B circuit makes and the R-W circuit breaks.
At any differential setting greater than 10 degrees F, the R-B make temperature and the R-W break temperature remain the same (control setting minus 10 degrees F). The R-B break and R-W make temperature are the setpoint temperature plus the difference between the differential setting and 10 degrees F.

Sunday evening I changed the low limit circulator to 160 degrees and the high limit to 180 degrees. This morning, Monday, when I got up the heater had already been running on and off for 2 hours. The temperature in the house was 67 degrees while the target was 68 degreees. I checked the temperature on the furnace and it said 150 degrees. Next I showered. The water was hot (YEAH!) and when I checked the temperature afterwards, the furnace still said 150 degrees.

- What does it mean that the temperature is reading lower than the lower limit? Is something failing?
- Is it normal/suggested to turn the low limit and high limit down during the summer time when the house heating isn't being used (since the tap water can get so hot)?
- The furnace has a Honeywell Triple Aquastat, however, I can not find a place/knob to adjust the differential. I can take some pictures but I don't see a way to attach them to the forum. Is it possible to upload pictures?

Just checked the temperature on the furnace on Monday evening, when the house is no longer being heated, and the temperature on the furnace is 125 degrees. Should it be that low?

What does the pressure valve on the furnace change? Could this have any impact on the rattling chamber door?

Thanks again for all the information and expertise!

sign up for Photobucket or a similar site. Upload the digital picture and copy and paste the HTML link on a separate line in the body of your forum text. Your picture will appear on the thread.

The pressure relief valve should be doing nothing. No leaks, no rattling. Doubt that is a problem.

If the circulator wasn't running late at night, your boiler should be maintaining the low limit of 160.

I suspect a malfunction in the aquastat for failure to maintain the low limit when no circulator or hot water use is occurring.

Yes, you can reduce the low limit setting to any temperature in the warmer months. High limit can remain at 180; it's only a safety device.

The water temp should not be below the low limit setting by more than 10 degrees at any point, unless you are flooding the boiler with cold return water from the radiators.

The differential setting knob is usually at the very top right hand corner of the aquastat if it's an L8124A Honeywell.

I'm a manufacturer's rep for a boiler manufacturer. I help our dealer's service guys every day to fix problems. I'm surprised at the lack of knowledge some of these guys have, but I'm there to help them learn, even the simple stuff.

Is there an update on this issue?

Sorry been working 12 hour days and trying to get ready for the holiday. I've taken many pictures and will post. Can we postpone until after Christmas?

Sure! As long as you are getting your hot water. :)

Hello. Hope you are enjoying a wonderful holiday. Things have calmed down on my end, so here's an update:
- Low set at 160. High set at 180. Under the cover it says "Triple Aquastat Type L6010A3X0A4". I believe I also see the differential lever which is set at 15.
- I've observed the temperature on the furnace being anywhere from 130 to 155.
- Showers are hot when the furnace has been running to heat the house. If furnace hasn't been running then shower starts out hot, goes cold, and then comes back hot when you are about to turn shower off.
- Furnace rattling sounds more like a jackhammer now when running. It's definitely worse. If I open the peep hole to view the flame then it stops.
I've uploaded some pictures. Hopefully this helps. I can always take more.

Here is a link that might be useful: pictures

Very good that you posted pictures. You have some serious
code violations on your furnace install. Your flue pipe must NEVER NEVER be down sized. Looks like it went from 7 inch to 6 inch. Looks like your oil shut off to the filter is on the wrong side. Your stack controler is in the wrong place. " if i open the peep hole to view the flame then it stops ". tells me you don't have enough combustion air.

The flue pipe CAN be downsized by 1 inch depending upon the firing rate. This boiler is really fired and sized small.

I think that is the whole problem. The house saps everything out of it that it can in the morning and the boiler is flooded with cold water. The aquastat is supposed to leave some water for domestic hot water, but the boiler may get too cool, too fast, to even catch it in time.

Is the rattling door the tine peep hole in the large door? A pulsating flame can cause this and there can be many reasons. I have it too because my chimney base is open well below the flue inlet and it causes turbulence. Not a big deal to me. If it bothers you, put a drop of high temp silicone under the peep door and let it cure.

Turn on your shower, go down and look at the temperatures and see what's happening. I expect that you'll see the water temperature drop below 130 until the boiler catches up. If that's the case, you'll have to start heating the house a little earlier than your shower time.

It's really a small boiler. Must also be a small house.

Yes it is a small single family house, one floor with basement. It's the afternoon, heat hasn't been running since morning and the temperature on the furnace says 130. Furnace runs for a few minutes (without my trigger) and temperature then rises to 145. Furnace sits for a few minutes and temperature rises to 153. I turn on the shower. Three minutes in and I turn off the cold water. Six minutes in the furnace starts running. Water temperature stays at a good temperature - not burning hot but not lukewarm for the remainder of the shower (using only hot water, no cold water running). After my shower the furnace reads 150. This is the exact scenario where I would expect a cold shower. My guess is that since the furnace heated up from 130 to 153 immediately prior to me showering it created a good shower.

Will replacing the aquastat keep the furnace temperature from dropping below the low limit?

It's the big door that rattles when the furnace is running. I uploaded a video of the rattling, the sound my little camera picks up does not do it justice as it was enough to wake me up at 5am this morning. video If I open the peep hole then the rattling stops. What gets me is that I didn't have this problem prior to the cleaning when they changed a part in the burner motor/blower. I read that "Excessive noise (pulsation, thumping, rumbling, etc.) in the heating unit is generally caused by a problem with the oil burner nozzle." Is the oil burner nozzle inside the burner motor/blower?

What other changes can be made to help the combustion air?

Here is a link that might be useful:

Your unit looks like a coal boiler that the company made into an oil boiler. A hand-fired coal boiler, at that.

The location on the burner is possibly where the nozzle line is located. It's so old, I've never seen a model like that. I don't know what else would be in that area but the nozzle. Pulsation can come from a few causes, one of them being a dirty nozzle. You might want to have the guy come back and change it.

The video doesn't work.

Back to the water temperature. If the burner runs without a call from the tstat, it should go up to the low limit setting of 160. If the circulator starts, it should drop to 150 and no lower, unless the boiler is being flooded with cold radiator water.

Maybe the aquastat says 160, but it's only 150. They can be off calibration or not reading properly. Try going to 170/190 and see if there is an improvement.

The tech should have set up the unit and air settings when he was there, so don't mess with that.

Yes, replacing the aquastat could stop the problem. The more modern aquastat is the Honeywell L7224A or L8124A, (better) if you can get it. We have a few left, but they are phased out and few are available. Not sure if you'll have to change the aquastat's well.

Test: Seems like some posts are missing now.

No air testing was done on the furnace. Just came across the bill for the service. Here's what it says and I quote:
-Vacummed All
-Replaced: .85 X 70 degrees nozzle, 1A Filter, J Strainer
-Made sure boiler is ok
-Raised press. from 6 to 12/14p
end quote.

Looks like the nozzle .85 matches. What does the 70 degrees mean?

What does the pressure valve do? On the furnace one says "reducing valve" and the other says "relief valve". I believe the tech changed the "reducing valve".

Aquastat low set to 170 and high set to 190 as of last night. Temperature on furnace after running for about 30 minutes this morning was 160. The furnace sits for about an hour and the temperature still says 160. I'm going to shower, I have a good feeling about this!

Here is a link that might be useful:

That's a pressure reducing valve, and possible a backflow preventer.

70 degrees is the angle of the spray. It can be a hollow (A) or solid (B) nozzle. It does matter. Your boiler pressure was a bit low, but that would only affect the circulation to high places.

The pressure relief valve is the safety that will allow pressure to safely escape if it goes over 30 pounds. Pipe goes towards the floor for discharge.

Yes, I also see that posts are missing. The front page of the forum says: 'Wednesday, December 30, 11:00am ET: During our maintenance window, we experienced issues that required restoring yesterday's backup files. Unfortunately, this means that anything that was posted since midnight was lost. We apologize for the inconvenience, but in order to bring back site functionality, this was a necessary evil.' So I guess the posted are gone for good.

I'm learning a lot and feel comforted that the cold shower problem has been troubleshooted. My shower today was hot, even had to keep the cold water on a touch throughout the shower. So it seems the aquastat is not calibrated correctly or is failing. I see the honeywell part online and will call some local techs to get an installation estimate.

If the furnace is being flooded with cold radiator water, is there another part(s) that need to be replaced?

As for the nozzle, how does one figure out what angle the spray should be at? Or whether it should be hollow or solid?

I've uploaded a few additional pictures/questions. Thanks again for your help.

Here is a link that might be useful: Photo Album

I wouldn't be in a hurry to change the aquastat if your shower water is OK. Try it for awhile.

I see you boiler has an H stamp, meaning it was built to "code" and usable in a commercial setting. Nowadays, an H stamp can add $2000 to the cost of a boiler unless there is quantity discount. Even at mass quantities, it can cost $500.

Did you get an email response from this site about the door gasket? A missing post.

The aquastat is supposed to shut down the circulator so you don't loose hot domestic water. Start with a cold house, turn on the shower and the heat, go to the boiler and watch the temperature drop and listen for whent he circ stops and note the temp. It should be 10 degrees below 170 or 160, meaning 160 or 150, depending how your aquastat is working.

I'll see if I can find specs for the nozzle. Unlikely, due to the age of the boiler.

The combustion chamber looks clean, so it must be set up correctly. You've found the electrodes and nozzle under the round cover. Don't know what's under the oil pump cover. Don't mess with it.

The best thing you could do would be to change out the burner and install a Beckett AFG or similar for more combustion efficiency, but there again, figure $500+ to do that. Sometimes it's better to leave well enough, alone.

The heat was off for 3.5 hours, I turned up the thermostat and turned the hot water on in the shower. The temperature on the furnace went from 150 to a hair over the 130 line. It probably took 15 or so minutes to drop and then some time for the temperature to start rising. The shower water went from hot, lukewarm, somewhat warm, and then I turned it the shower water off when the temperature on the furnace started to rise. The furnace ran for approximately an hour and when it stopped the temperature was 160. Now it has been going on and off every few minutes. I'm not sure what sound the circulator makes so I don't know when/if it stopped. Is there another way I can test the circulator shutoff?

I searched a little online for a door gasket and didn't see anything. I'll go to a local plumbing store on Saturday and see if they have any.

(While I was watching the furnace I notice a valve dripping. The tag on it says its the fast fill. I'll have to add that to the list.)

Here is a link that might be useful:

Your boiler should recover in 10 minutes. Was it always like this? If not, something wasn't done right during the service. I realize a .85 nozzle is small, but the recovery time is ridiculous.

First you'd have to know what gasket you need for the door, if any. It would be fiberglass rope and some contact cement to hold it in place.

The valve leaking looks like a fill valve. If it isn't leaking much, I'd worry about other things first.

Your circulator is the green Taco 007. They are very quiet and you almost have to put some solid object between your ear and circulator to hear them.

Happy New Year! I've never paid much attention to the furnace before so I don't know if it used to take long for the recover time. If you are asking if the boiler recovered from 130 to 150 or 160 in ten minutes I would say no. The furnace probably ran for 10 minutes just holding the 130 temperature and then maybe raised one degree in that amount of time. I'll try the experiment again tomorrow morning when the heat first kicks on.

I wish I could find a manual on this furnace; that would tell me whether it requires a gasket and what it was. Unfortunately, from internet searches it doesn't appear that the manufacturing company exists any more. Will ask at the plumbing store.

A few positive notes. Had a hot shower today. Was wonderful!

Read in a HVAC fundamentals book if the combustion chamber is 10 inches in length, 8 inches wide, and 12 inches high (which is what I measured the pinkish/orangish area in the bottom of the furnace to be) then the nozzle size of rating (gph) should be .75-.85 with a spray angle 60 degrees. So the nozzle should be .85 with a spray angle of 60 degrees. Now I just need to find out if it should be hollow or cone (and how to change the nozzle once I find the part). :)

Do you think the degree of the spray changing from 60 degrees to 70 degrees could cause the air dynamics in the chamber to change? thus causing the rattling door?

Nozzles can be funny animals. At one time on certain models we always used a hollow (A). After years of production the evidence said that we should use solid (B). Sometimes a third choice is used which combines sort of both nozzles, but Delavan doesn't make them.

I didn't find any information in the Beckett book and you'll have to do some detective work on the door. The entire unit has to be shut down before looking at the door.

You'd have to have a tech try both nozzles in a test, because equipment must be used to check combustion after changing the nozzle. It's possible that the new nozzle is defective. They can be contaminated during installation by putting a finger over the orfice; that's all it takes.

The boiler really shouldn't be going to 130. I would suspect flooding cold radiator water, or a low limit control that is no longer working.

Years ago, I removed my old burner and installed a new Beckett burner. It brought up the combustion efficiency by about 7%. It's alot cheaper than replacing an otherwise good boiler.

I don't see any remnants indicating that there was a gasket behind the door but that doesn't mean there shouldn't be one. Here's a pic:

Here is a link that might be useful:

It doesn't look like a gasket isn't used. I can't really tell what the area above the combustion chamber looks like; the pic is too small.

Do you see any smoke during combustion? Is the flame a lazy yellow or white and clear?

But the most important question is still: Did all these problems occur after the last service?

Went to the plumbing store yesterday - they didn't have any gaskets and they didn't have the right nozzle size. However, they did recommend another store a town over who carries furnace supplies. Unfortunately they weren't open so have to go another day.

Ran the test again of having the furnace off for awhile, then turning on the furnace and the shower at the same time. Here's the results:
start - furnace temperature reads 162
5 minutes passes - 145 temp, shower water warm but not hot enough for a good shower.
5 minutes passes - 141 temp, shower water warm but not hot enough for a good shower.
5 minutes passes - 137 temp, shower water seems a little warmer but still not hot.
5 minutes passes - 135 temp, shower water same / no change.
5 minutes passes - 134 temp, shower water same / no change.
5 minutes passes - 132 temp, shower water feels warmer.
5 minutes passes - 131 temp, shower water same / no change.
5 minutes passes - 131 temp, shower water feels like it got a little cooler, back to warm but not enough for a shower.
5 minutes passes - 132 temp, shower water hot. Turned shower off.
5 minutes passes - 142 temp.
5 minutes passes - 160 temp.
5 minutes passes - 155 temp.
5 minutes passes - 158 temp.
5 minutes passes - 165 temp.
furnace still running but stopped monitoring

I thought I heard the circulator make some noise when the temperature was at 134. However at the end of the test, temp 165, the circulator was making a louder sound. Now that I know what I'm listening for I think I need to do it again. What should be happening is that when the temperature drops to a certain level the circulator should stop running in order to preserve the existing hot water for the shower. Is that right?

This morning I was woken up by the doorbell. It was the fuel & heating company that last serviced the furnace, since they didn't return my calls and was in the area they figured they would drop by. The owner looked at the furnace. The flame looked to be a bright orange. Then he opened the air vents found between the oil pump cover and the housing that contains the electrodes, see pic. This lessoned the rattling door and I believe the flame became more of a bright yellow. Both flames are tall, perhaps a little taller than the 'brick' liner.

He said they don't test the combustion chamber as his kit is 30 years old. Basically they do they set the flame by eye.

He said there may be a blockage in the fuel line that is causing the door to rattle, soot to come out any small opening, and flame when viewed through the vents to flicker, see same pic. (Tank & fuel line are from Aug 2005) He's going to send someone tomorrow to blow air through the line. He also pointed to the flow control, said that might be slowing the oil fuel, and suggested removing it - part also from 2005 and I will not remove, replace but not remove. He thought that the thermometer may not be reading right instead of the aquastat not being calibrated.

I think that is everything. So as it stands: Leaving aquastat alone. Still a question as to whether the circulator is working. Furnace tech is going to replace filters, try new nozzle, put a soot bomb in the chamber, and blow the fuel line (provided the earlier items don't prove successful) tomorrow. I'm going to call a plumber to change the leaking valve. Finally, depending on outcomes, get estimates on replacing the burner.

What do you think of the next steps?

Here is a link that might be useful:

To answer your other question - The hot water was always a problem. The rattling door started immediately following the last service.

and I don't see smoke from the flame but soot is coming out any small openings at a faster rate than before.

almost but didn't forget about following up with the plumbing store about the gasket. As well as two nice to haves - adding a mixing valve and adding a dishwasher into the system. :)

Ask him to test the temp of the supply water right where it comes out of the boiler. If it's close in temp to the gauge reading, I'd say the aquastat is bad.

Since adding air made the flame brighter, the air setting could have been set wrong and will create soot, another insulator inside the boiler and a mess $$$ to clean up if the boiler blocks up.

The bleed valve on the fuel pump should be a good indicator of the condition of the fuel line. If oil comes out in a good stream I would not suspect the fuel line. If it doesn't, it could be the fuel line, valve, filter, or the internal oil pump filter, if any.

Your record seems to indicate a bad aquastat or a substantial distance between the gauge and aquastat, in inches apart.

I was looking at your aquastat. On the left one, what is the differential set at? It goes from 5-45. For most applications, it's set at 10.

And try to find out at what temp the circulator stops on the way down.

I'll ask them to check the water temperature and will check the bleed valve to see the stream of oil. Thanks for the tips.

I still think the rattling door is from the nozzle. I'm going to have them change the nozzle first before tampering with the fuel line.

The differential lever is set at 15.

So the service company came. They did many things to address the rattling door which had no effect:
- changed the filter
- changed the strainer in the pump
- adjusted the air flow next to the pump
- blew air through the fuel line back to the oil tank (the burner whined loudly after this then quieted down)
- bled oil from the burner
- started to remove the flow control from the system then decided it was working fine and put it back

Finally they changed the nozzle. They stepped the nozzle down to .75 by 70 degrees and wouldn't you know the furnace is back to its quiet happy self. What a relief! I can sleep again at night.

(They did not clean/vacuum the furnace.)

The showers have been consistently hot, set at 170, 190, and 15 differential. The tech did not have a tool to test the water temperature. Still need to retest the circulator but much progress!

Congratulations! You've gone from needing a completely new system to an old one that works well.

And you seem to have learned more than some of the techs I know.

I have definitely learned a lot and I want to continue to learn, which I will as I believe I posted too soon - the furnace door still rattles/bangs loudly (woke me up this morning) but now only intermittently. I believe it's the loudest when the furnace first starts and then quiets after running for a bit. Thus far changing the nozzle and opening/closing the air vent has had the most impact on the problem. Going to call the tech back but I'm not sure what they can do...

There's nothing stopping you from applying thin, flat fiberglass rope around the perimeter of the door. Spray with contact cement and affix the rope and close off the door. If rope is too thick, use thin fiberglass insulation, like the kind in your walls. Ask the tech about this.

Until the chimney warms up, it's not unusual for some pulsations.

I went to the plumbing store this weekend. They had rubber gasket, fiberglass rope, and kaowool, however only sold in large quantities. They suggested I go to home depot to see if they had something that I could substitute. Went to home depot and they had a small patch of gasket rubber for sale, which I purchased, picture attached. Not sure if it will hold up or melt but I'm going to give it a try.

Here is a link that might be useful:

That's for water applications, like a coil gasket.

Isn't there a fireplace store near you? Check your email.

Went to Lowes and found Fiberglass Cloth, picture attached.

Here's what the package says:
Elmer's Fiberglass Cloth
Fiberglass Repair
-Superior Strength
-No rusting or rotting
-Great for Use with Polyester or Epoxy Resin Repairs

Elmer's Fiberglass Cloth is ideal for repairing holes or cracks in pools, boats, campers, cars, snowmobiles and more. Use Elmer's Fiberglass Cloth to leminate and reinforce your polyester or epoxy resin repairs on wood, fiberglass, metal and concrete.

Do you think this would be a suitable substitute?

Otherwise, I googled and found a fireplace store a couple towns over and will give them a call tomorrow to see if they have fiberglass rope.

Here is a link that might be useful:

Yes, that should work. Check for flammability. It shouldn't burn. Cut the strips you need to cover the flanges, clean the flanges, apply a water-based contact cement and when cured, apply the fiberglass and close the door.

Was this problem ever resolved?

If the smaller nozzle is keeping up w/ your heating loads then i would keep it, if not, I would switch to .85x80ºAH DANFOSS nozzle; don't worry about a little flame impingement on the firebrick from the wider spray pattern. I would also Install a barometric damper in your conector pipe - I think this is a pretty important thing to do for efficiency and allowing your burner to have a proper flame at all times; I would buy one, install it level and plumb and set it to .02 Also as baymee suggested install a fiberglass gasket on the boiler door this will very simply and easily fix the noise. that's a nice old boiler/burner you have - if it's set up properly it will be a good reliable heating plant.