Vented Fireplace Log Set Problem


  #1  
Old 01-02-03, 06:13 PM
Rick Mangione
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Question Majestic G36DVpi furnace repair

Forgive me if I'm long-winded, but I am frustrated with my Majestic G36DVpi direct-vent continuous pilot fireplace. I've emailed and spoken with several professionals, and I would like other opinions and suggestions. Thanks very much for any replies!! Rick

Symptoms: Installed around 1992. I moved here in September 1994. I've had several problems every winter. We've replaced the thermostat several times, the switch several times, the glass several times, injected methane into the propane tank several times, all to ultimately no avail. Two weeks ago the glass cracked and later shattered. I think the installation is bad.

(Reply1: I believe you might have a venting problem, with delayed ignition, which may be the reason the glass was damaged. It is possible that too much air is entering the firebox, or that not enough air is coming in. Was the pilot going out often? If so, the excess air may have been blowing it out. This extra air can also move the gas across the burner away from the pilot flame long enough to allow too much gas into the box before lightoff,. (delayed ignition) Not enough air can cause the same effect, but for a different reason. )

(My response: The flue extends 1.5 feet out chest high on the side of our house. We do have significant wind gusts from time to time, although I've not correlated them with fireplace problems (I've never checked this idea).
The unit does have a shut off switch for when it gets too hot....
Also, the face plate does not have louvers below the glass. The metal face is solid, with a hinged bottom section (with a single louver) allowing access to the gas plumbing below. This may restrict the air intake. The upper section is solid, with merely an open 1.5 inch space partly obscured by a metal strip at 45 degrees (like the roof of a house where the first foot below the roof edge is open....) Thus, you suggest this air-flow restriction keeps the heat from radiating away from the firebox, which allow heat to build and thus overheat the firebox and the glass? Perhaps the solid metal base plate could be replaced with a properly vented piece.)

(Reply2: I have waited for MONTHS for a single piece of glass, yet I can usually get an entire unit in 2-3 weeks. Majestic makes good equipment for the most part, but sometimes getting it serviced can be an ordeal. You may want to attempt to order the parts locally, as they may have a better distributor, and then let me know if you feel you need me to come up. replacing the glass and the louvers may be something you can do, as well as checking the switch. You may want to see if you can remove the vent cap as well, in order to know if you'd be able to install a draft restrictor plate or a wind guard.)

(Reply3: do you have an owner's manual for this unit? I am unfamiliar with any direct-vent fireplace built without at least as much convection intake area as it has outflow area.The hot air coming out of that "hood" would naturally be very warm anyway, and if it is slowed down because of an altered intake area, or a poorly designed one to begin with, this could easily cause it to overheat the switch, which would cut off the pilot and shut the valve. this would also expain why it sometimes can't be started right away, because the switch would have to cool down before the pilot circuit would "close" and stay lit. An easy experiment would be to bridge the two wires accross the switch, and see if the unit burns OK> (but you need to be aware that you may overheat the unit and/or the wall framing, so you should be very careful to monitor them) The switch may be worn out to the point that it trips out at too low a temperature, and need replacement. If this is not the case, the unit IS getting too hot, a louvered lower door may allow the needed air flow. I doubt you need to replace anything inside, and if you do, you are only allowed to use the identical burner and logs. If you want to replace the unit, the entire unit must be replaced. I am sure you can Save the one you have pretty cheaply.)

(My next reply: You are providing loads of help. Thanks.
The vent out the side is a tube in a tube, as you are probably aware. The unit is sealed, so no air that contacts the logs and flame can escape into the room. I've heard the descriptions decorative vs. heat source. The firebox certainly gets hot on the exterior, and the face metal plate does also, as does the glass. Thus, a fair bit of heat comes from radiation. Although air can flow around the unit from below and out above, there is no directed air flow as such. I have two documents from Majestic: "Installation and Operation Instructions", and "How to enjoy your built-in fireplace." However, the model number, G36DVpi, does not appear in the "How to enjoy..." homeowner's manual. Also, the "Louver Weld Ass'y Painted" which is in the installation instructions is not installed on my unit, and I do not have this item. Since I have no glass, I'd prefer not to use the test you mentioned. It appears, however, that the louver for convection air intake beneath the unit is not installed, so then 1. less air moves around the firebox to move the heat away, and 2. the higher operating temperature may be causing problems with the glass, the logs, and the electronics beneath the box.)

(Recent discussion today, summary: I could order the glass, the lower louvered grill (that sits above the hinged access panel), a fan to draw air, and the intake restrictor for the flue, and install all these myself or with a local contracter. This does not involve any changes in gas plumbing.)

Does this sound like a do-able project? Thanks again!
 
  #2  
Old 01-02-03, 06:35 PM
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Hello: Rick

I too suspect an overheating problem exists. Try the fireplace with the lower door proped up or open to allow much air to entire the lower section.

Doing so should allow more heat to flow through the space between the fireplace and the hearth, thus more warm air out the above louvers.

The problem may be do to an air circulation restriction. Check for air flow restrictions at the top louvers also.

You may need to remove the vent outside if it is possible. Some cannot be removed from outside while others attach to the vent pipe extending outside. There could be a restriction in one of the tubes.

I doubt wind flow past the vent would cause this problem. The others offering possible suggestions do make some points which could be valid but not likely.

Delayed ignition creates an explosion which would be heard and cause the glass damage at start up not after hours of usage and the glass becoming overheated.

Improper installation can be a critical factor which you may not notice or be aware of. Professional help may be required. Check the local phone book for fireplace retail sales dealers. These shops may have a private agent who is a pro dealing with these types of problems.

The factory may not be willing to provide the service granted but they should at least state why.
 
  #3  
Old 01-03-03, 08:59 PM
Rick Mangione
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Thanks, Tom!

Tom, that does make sense. The likely cause of glass breaking is the heat; whether too much, or that coupled with frequent cool air blasts from the outside. Yet another contractor suggested that this might be an issue, that he has heard of similar, and that a 'cap' shaped not unlike an inverted 'U', sideways (or something like that, he said), when put on the flue, will all but eliminate any inflow of cold air gusts.

He also suggested a small fan to move more air around the box, along with adding louvers below. All the pictures of the unit, alone or installed, only show the single 'vent' overtop of the fire box. I am not familiar with a set of louvers to go overhead, but it might make sense (especially if I do install the fan).

I'll try to inspect the outside 'pipe-in-a-pipe' flue. I cannot test the air flow until I replace the glass, however.

Do you know of a supplier that might have the parts listed in the previous message? Thanks again!

Rick Mangione
rlm6m@hotmail.com
 
  #4  
Old 01-04-03, 05:18 AM
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Rick

The exhaust vent is a tube inside a tube, as you mentioned. The purpose is to allow intake air into the firebox chamber for combustion and also an exhaust vent for fumes and products of combustion to vent.

This method is termed direct venting or direct vent. Some styles of wall mounted furnaces and water heaters use this type of venting system. The outside vent cap used in this type of system must be installed correctly or problems develope. The caps are not prone to cause any types of problems due to winds.

However, if not installed correctly or the vent tubing connections from the fireplace to the cap, will cause problems, if not installed correctly. Smothering flames are the most common.

Smothering flames cause the flames to burn incorrectly and produce large quantities of odors which are very toxic. But they cannot burn hot enough to produce the heat in the problem you are describing. So it cannot be the problem in the fireplace.

The fact that there is so much heat would indicate to me that the problem is a lack of air flow around the circumfirence of the fireplace insert. Could be a lack of clearence, restriction of air from the intake & exhaust vents, etc.

A small fan may provide the solution, since issues of air flow and clearences may not be as easily corrected. I do not know of suppliers but a source may be a heating agent who deals in direct venting heaters and water heaters.
 
  #5  
Old 01-04-03, 02:41 PM
Rick Mangione
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Cool Thanks again, Tom!

Rick
 
 

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