Gas logs in a pre-fabbed fireplace

[herd]

Hello, I need some adcice on gas logs. A few years back, I bought a manufactured house, basically a double-wide but with a 7/12 roof pitch and I have added a full porch on the front and earlier this year, about 1000sf on the back to include a 240sf expansion to my den.

I bought the house with a pre-fab fireplace, one that is typical in manufactured homes, I think a Tamco 36" model. Anyways, I am going to move the fireplace into the new addition and plan to install gas logs, no woodburning. It will be a vent-free gas log system.

As I was telling my wife about this, she actually came up with an intelligent question: "Why do you need to reinstall the chimney (flue) in the new section if the logs are ventfree?" Well, that stumped me, so I am wondering if any of you folks would know the answer to that?

If this would work, I would really like it if I didn't have to cut thru the new roof and build a chimney chase, which is another possible opening for rainwater. Tks in advance for any input and this is a great site.

 

[k0ua]

YMMV, but I am not all that happy with my "ventfree" gas logs..they still seem to require venting, Just too much noxious emissions without opening the vent flue. of course when you do that the heat output goes way down. I can stand them for a while, but in a tight house, there is a gas build up after a while and your eyes can start to water. Should not be this way, as they are supposed to burn clean, with just Co2 and water vapor as the byproducts. I did have vented logs, and of course they burned yellow and made pretty flames, but you had to have the vent flue completely open or you would die quick. These burn mostly blue, with some yellow tops of the flames. not all that pretty, but much cleaner.. But still not as clean as a little wall heater in the basement, which makes practically no smell, and lots of heat.
just my 2 cents.
James K0UA

 

[ragkar]

The difference is that vented gas logs lick the fake logs and unvented ones do not. The vented gas logs are more realistic.
I put unvented logs in my stone fireplace and blocked the flue/chimney eight years ago. I do have a carbon monoxide monitor in the room and it hasn't beeped yet.
For realism, they sell on the web a burning log noisemaker. It's real clever with gradually growing volume and crackling as you might expect from an actual fire.

 

[johnrex62]

My gas log set is unvented and the flames contact the logs. It does give off an odor similar to dust burning (like the first use of a furnace after a summer off but does not dissapate). I tend to crack the flue a bit to bleed off the off-gassing I suspect to be the source of the odor.

I would be hesitant to install a fireplace box without a chimney even for a ventless log set simply because the firebox will have a substantial insulation gap at the firebox vent. Heat will escape the firebox at that point and absent a chimney will build up in your surround.

 

[sodamo]

I have 2 types, one is the vented stove type and instead of going thru the ceiling/roof, for same reasons you stated, I went horizontally thru the wall. My 2nd is a fireplace type but has the vents built in - drove the building inspector nuts Neither would replace the ambience of a real wood fire, but both do their job well - instant on, warmth & glow, instant off.

Some friends had the ventless for awhile. In addition to the noxious fumes, they also felt it added too much moisture to the air giving a clammy, damp feeling.

 

[AHNC]

I sell gas heating equipment for a living and represent Rinnai in my home market. We never sold unvented gas logs. As such I cannot speak to which log is best but can speak about unvented (uv) units. First off, no matter what unit you have, vented or no, do get a good quality CO detector. I also run a combustible gas detector. Personally, I am sensitive to the by-products of combustion from vf units, as is my wife. It kinda hits me right in the back of the throat.

My problem with vf is that they are consistently oversized. Check the DOE sizing guidlines. Here in New England, Zone 5, the coldest, for an average house with a thermostatic equipped unit you should provide 3.85btu/cuft. If you look at a 20x20x8' room you are looking at 3200cuft. Tmes about 4 you end up with 12,000 btu or so. The log manuf sells flame effect. A 12kbtu log would look like two bic lighters on low, so they make them a minimum of 25k btu. As a result, they are grossly oversized. In SC you are even more oversized.

There are millions of these installed. As you can see from the previous posts, some like them, some hate them. Vf are intended as supplemental heat not primary. If you want one for ambiance and understand the limitations, then go for it. The best vent frees on the market today are the infrareds. You burn at about 2000 degrees down in the meniscus of the plaque, so you get a very clean burn, but it is still venting into the room. You have to keep the plaque clean. Compressed air is the answer. Don't hit it with 100# or you can blow the ceramic away. Make up air is critical. Put a vf in a real tight space and you can have odor and moisture problems. For every gallon of lp burned you have about 1.1 gallons of water vapor entrained in the flue gases. If you end up with sweating windows/heavy air you need ventilation. Empire makes abut the best infrareds now that Rinnai got out of the vf business a several years ago. A lot of odor issues on vf's are due to dirty pilot assemblies. Again follow the manuf service guidelines.

If you are looking for good efficient heat, look at the Rinnai Energysavers. They are the most expensive in the direct vent catagory, but by far the best technology, durability, value. You can get cheaper. You can't get better! I've sold over 165,000 of them in NE over the past 20 yrs and at least 90% of what I sold in 1991 is still in the field. Show me a pellet stove that can say that, or a vf for that matter. Sorry for the pitch, but they have been good enough that I kinda look at it like a public service announcement and they are what I heat both my homes with.

 

[herd]

Ok, great info and tks all for replies. You have me convinced that VF is not what I want to do so now my question is, how can I vent the fireplace without going thru the roof, if I do some kind of sideventing, it seems like I'd need a 90degree elbow for the 8'' flue.

 

[Opti-Mist]

Go the direct vent route which is through the wall as used with high efficience gas fireplaces, if allowed by code and insurance carrier.

 

[herd]

I sell gas heating equipment for a living and represent Rinnai in my home market. We never sold unvented gas logs. As such I cannot speak to which log is best but can speak about unvented (uv) units. First off, no matter what unit you have, vented or no, do get a good quality CO detector. I also run a combustible gas detector. Personally, I am sensitive to the by-products of combustion from vf units, as is my wife. It kinda hits me right in the back of the throat.

My problem with vf is that they are consistently oversized. Check the DOE sizing guidlines. Here in New England, Zone 5, the coldest, for an average house with a thermostatic equipped unit you should provide 3.85btu/cuft. If you look at a 20x20x8' room you are looking at 3200cuft. Tmes about 4 you end up with 12,000 btu or so. The log manuf sells flame effect. A 12kbtu log would look like two bic lighters on low, so they make them a minimum of 25k btu. As a result, they are grossly oversized. In SC you are even more oversized.

There are millions of these installed. As you can see from the previous posts, some like them, some hate them. Vf are intended as supplemental heat not primary. If you want one for ambiance and understand the limitations, then go for it. The best vent frees on the market today are the infrareds. You burn at about 2000 degrees down in the meniscus of the plaque, so you get a very clean burn, but it is still venting into the room. You have to keep the plaque clean. Compressed air is the answer. Don't hit it with 100# or you can blow the ceramic away. Make up air is critical. Put a vf in a real tight space and you can have odor and moisture problems. For every gallon of lp burned you have about 1.1 gallons of water vapor entrained in the flue gases. If you end up with sweating windows/heavy air you need ventilation. Empire makes abut the best infrareds now that Rinnai got out of the vf business a several years ago. A lot of odor issues on vf's are due to dirty pilot assemblies. Again follow the manuf service guidelines.

If you are looking for good efficient heat, look at the Rinnai Energysavers. They are the most expensive in the direct vent catagory, but by far the best technology, durability, value. You can get cheaper. You can't get better! I've sold over 165,000 of them in NE over the past 20 yrs and at least 90% of what I sold in 1991 is still in the field. Show me a pellet stove that can say that, or a vf for that matter. Sorry for the pitch, but they have been good enough that I kinda look at it like a public service announcement and they are what I heat both my homes with.

Ok, you have sold me on the DV's, and I appreciate your sharing your vast knowledge on this subject. My den, once the addition is completed, will be 16'W and 28'D, plus a 3' open Bay. The old part, 16'w x 13;D is an 8' ceiling; the addon is 16' W by 15'D and is a vaulted ceiling 12' at the ridge. So what size DV would you recommend and could you give me a ballpark $'s on the cost.

Also, since I am primarily using this for ambivience although I live in the country and subject to Co-Op outages, I may a few times need some extra heat source. So, I was wondering about gas consumption. I really don't want an unsightly tank in the yard and thought maybe I might be ok with two 30# bottles like I have in the camper. They last a long time even when we use the heater. I could conceal these two bottles under the deck adjacent to the fireplace chase.

That you so much again for the info;

 

[AHNC]

Ok, you have sold me on the DV's, and I appreciate your sharing your vast knowledge on this subject. My den, once the addition is completed, will be 16'W and 28'D, plus a 3' open Bay. The old part, 16'w x 13;D is an 8' ceiling; the addon is 16' W by 15'D and is a vaulted ceiling 12' at the ridge. So what size DV would you recommend and could you give me a ballpark $'s on the cost.

Also, since I am primarily using this for ambivience although I live in the country and subject to Co-Op outages, I may a few times need some extra heat source. So, I was wondering about gas consumption. I really don't want an unsightly tank in the yard and thought maybe I might be ok with two 30# bottles like I have in the camper. They last a long time even when we use the heater. I could conceal these two bottles under the deck adjacent to the fireplace chase.

That you so much again for the info;

So, the total space will be about 600-650 sq ft. For straight heating I'd look at a EX22C Rinnai Energysaver. This is a straight heating appliance. Not a lot of ambiance, but efficient, reliable and it will last a long time. Again, the best technology in the business. For a better look, check out the model 750. A DV fireplace with a modulating gas valve and blower. It is basically the ambiance version of the DV line. Not inexpensive, but again, you get what you pay for.

As to pricing, I sell containers of these to distributors and honestly do not do retail and don't know your area. Your best local distributor in the Carolinas would be Gardner Marsh. Good company, great folks!

You want to make sure if you go this way that you locate the unit so it can distribute the heat. Put it behind the arm of the chair and it will be warm back there. Give it good open space and it will do a real nice job for you.