Pizza oven over fireplace. Poor draw.

[DaveT]

I had a local contractor build a fireplace/pizza oven (see attached picture). The pizza oven sits over the fireplace. The fireplace has two flues/chimneys that route around the pizza oven on each side. Looking at the picture, the pizza oven chimney is in the middle at the top, and the fireplace flues come out in the next level down, on either side.

The problem is that I am having poor draw with the fireplace. Smoke comes out the front. My contractor says I should not build a fire in the middle of the fireplace, and should instead have two small fires on each side, under each of the side flues. I am not crazy about this idea.

Any suggestions as to how to solve this? I defer to the experts here, but all I can think of is to have fans put in at the top of the fireplace chimneys. It would be a pain to run power out to the fans, but I could do it if necessary. Or isn't there a kind of passive fan that could help?

Thanks in advance!

- Dave

 

[Sailrmike]

I'm no expert here, but I think part of the issue is that the chimney (s) needs to be pre-heated before they will provide substantial draft. You could try preheating the flues with a propane burner

 

[DaveT]

I wouldn’t think that would work, but I’m no expert either. It seems like a torch wouldn’t be able to warm the chimneys. I don’t know if you can tell the scale of it from the picture, but it is BIG.

 

[double-d]

The smoke could be from a couple of problems,
The wood could be wet or not as dry as needed.
The 2 side flues have to many jogs, and slowing the draft.
The side flues may be to small and restricting the draft.
The chimney height too short, and not creating a strong enough draft.
An Enervex fan could run $1500 to $2800, plus Installation and wiring

 

[DaveT]

The wood is fine. I do think the issue is the jogs or size of the side flues, it’s probably a bad design. But at this point, it is what it is.

 

[begreen]

The smoke could be from a couple of problems,
The wood could be wet or not as dry as needed.
The 2 side flues have to many jogs, and slowing the draft.
The side flues may be to small and restricting the draft.
The chimney height too short, and not creating a strong enough draft.

I'd start by adding a 4' temporary extension on the chimney to see if that improves draft sufficiently. It could be 10" duct pipe. Use only very dry firewood.

it’s probably a bad design

That thought came to mind. The temp pipe should assist draft somewhat. If it works, extend the chimney using masonry.

 

[Ashful]

Holy cow, that chimney top opening looks awful small for that fireplace opening.

What is your chimney size and height? What is the fireplace opening W x H?

Paging @bholler.

 

[Jags]

Just a normal fireplace of that size would have a pretty big clay liner. Throw in kinks and curves running through piles of (relatively) cold stonework and its gonna need to breath even easier for it not to smoke out the front. I also wonder if the top of the smoke chamber is deep (tall) enough.

 

[DaveT]

You can’t see the fireplace chimney openings in the picture. That chimney top you see is for the pizza oven above the fireplace. Unfortunately I am now going to be away for the next week. I will take some measurements when I get back, and revive this thread.

Thanks everyone!

 

[bholler]

It is to short there is no way that there is any room for a smoke chamber and 2 flues rarely work well. It is bad design. Get your money back and get someone in who knows how to design a fireplace. The pizza oven will probably have to be beside the fireplace.

 

[Prof]

I'm not sure how you would establish any draft with the flues situated where they are--I would think they would have to be well above the main structure. Have you tried the two fires as the contractor suggested. I agree, this is an odd suggestion and really impractical, but I'm just curious if it would work or if he just made this up. I wish I could be more optimistic, but my thoughts are in line with others who have noted that the design seems off.

 

[DaveT]

This took months to build, and cost 10s of thousands of $$. I’m not going to be able to have it rebuilt. I will try the two fires thing. But what about electric fans at the top of the flues? There hasn’t been much discussion about that.

 

[bholler]

This took months to build, and cost 10s of thousands of $$. I’m not going to be able to have it rebuilt. I will try the two fires thing. But what about electric fans at the top of the flues? There hasn’t been much discussion about that.

If you paid that much for it it should work make the contractor come over and see if he can get it to work if he cant it is his problem to make it work. Fans are not a fix they are a bandaid. They also cost lots of money are noisy and are a pain to maintain.

 

[EatenByLimestone]

^^^^^^^^

This.

 

[begreen]

And try extending the flue temporarily to see if that improves the situation or not. If it does, then that is something the mason can do to make it permanent. If not, hold the contractor's feet to the fire.

I'd also try a starter fire using compressed logs from the grocery store. 2 or 3 on each side. They will smoke less and may help to start warming up the masonry.

All of these approaches may fail. The design is poor. Pizza ovens are usually well insulated and designed to get very hot inside. Normally a pizza oven has the fire built on the pizza oven floor and it has its own flue.

 

[Ashful]

make the contractor come over and see if he can get it to work

Can’t be said enough times. The guy who designed it and built it should be able to demonstrate it’s functionality, or lack thereof.

 

[Prof]

And try extending the flue temporarily to see if that improves the situation or not. If it does, then that is something the mason can do to make it permanent. If not, hold the contractor's feet to the fire.

I'd also try a starter fire using compressed logs from the grocery store. 2 or 3 on each side. They will smoke less and may help to start warming up the masonry.

All of these approaches may fail. The design is poor. Pizza ovens are usually well insulated and designed to get very hot inside. Normally a pizza oven has the fire built on the pizza oven floor and it has its own flue.

I agree, I'd make it the contractor's problem. The pizza oven would seem to be able to be independently fired and has its own flue that seems more logically placed. Extending the flues for the fireplace would have to be thoughtfully done or it could mess up the draft for the oven! I wonder if the contractor used any type of standard design or just did his own thing?

 

[jetsam]

You could try adding airtight glass fireplace doors with an adjustable intake, and of course extending the flue. You're probably going to want both anyway for cooking purposes.

 

[bholler]

You could try adding airtight glass fireplace doors with an adjustable intake, and of course extending the flue. You're probably going to want both anyway for cooking purposes.

The fireplace and pizza ovens are separate those glass doors have nothing to do with cooking. And if it was me i would do nothing untill the contractor came out and started a fire in it. If he cant get it to work he needs to fix it. Which my guess would mean taking it down and starting over. And it shouldnt cost the homeowner a dime.

 

[jetsam]

The fireplace and pizza ovens are separate those glass doors have nothing to do with cooking. And if it was me i would do nothing untill the contractor came out and started a fire in it. If he cant get it to work he needs to fix it. Which my guess would mean taking it down and starting over. And it shouldnt cost the homeowner a dime.

The fireplace doors restrict airflow so you can slow down combustion in the fireplace so you can (very gradually) moderate the temperature of the oven.

Admittedly you do need to get the combustion air to move from bottom to top instead of top to bottom before you worry too much about temperatures.

Could also just take a core drill and knock a 8" hole right down the middle. Draft will improve, and you can call it a pizza smoker. Maybe that's trendy or something.. You'll also need to leave a hole in the pizzas so they don't block the one working flue.... this is sounding trendier all the time! 'Natural Smoked Organic Pizzrings'. Almost as good as selling "distressed barnwood" to rubes now.

 

[maple1]

The contractor built it but who designed it?

 

[Prof]

Could also just take a core drill and knock a 8" hole right down the middle.

My wife actually said something very similar--stopped short of the trendy doughnut pizza thing though. She did, however, note that you could probably bake a pizza in the fireplace if you'd push the coals back and to the sides and figure out a way to block the opening a bit to retain the heat. This could be a chore since the fireplace looks huge. She does most of the baking in our masonry heater, so I'd defer to her expertise here.

 

[DaveT]

Thanks but many of you aren’t understanding what this is. The pizza oven and fireplace are separate. The pizza oven has its own chimney and works fine. It’s the fireplace under the pizza oven that we are talking about. Burning wood in that has nothing to do with the pizza oven. The pizza oven’s chimney extends vertically and comes out the top of the structure. The fireplace flues go around the sides of the pizza oven. It’s not an option to extend the fireplace flues. The structure is incredibly massive as it is, and is in an area between our patio and pool. We don’t want it any bigger. I’ve talked to the contractor, and he says to burn two fires on either side of the fireplace. He says that he told us that before they built it. That isn’t true, but here we are.

 

[bholler]

The fireplace doors restrict airflow so you can slow down combustion in the fireplace so you can (very gradually) moderate the temperature of the oven.

Admittedly you do need to get the combustion air to move from bottom to top instead of top to bottom before you worry too much about temperatures.

Could also just take a core drill and knock a 8" hole right down the middle. Draft will improve, and you can call it a pizza smoker. Maybe that's trendy or something.. You'll also need to leave a hole in the pizzas so they don't block the one working flue.... this is sounding trendier all the time! 'Natural Smoked Organic Pizzrings'. Almost as good as selling "distressed barnwood" to rubes now.

The pizza oven is completly seperate. It has its own flue you burn wood in the oven. The fireplace has nothing to do with it other than the oven interferes with the fireplace flue due to its placement

 

[bholler]

Thanks but many of you aren’t understanding what this is. The pizza oven and fireplace are separate. The pizza oven has its own chimney and works fine. It’s the fireplace under the pizza oven that we are talking about. Burning wood in that has nothing to do with the pizza oven. The pizza oven’s chimney extends vertically and comes out the top of the structure. The fireplace flues go around the sides of the pizza oven. It’s not an option to extend the fireplace flues. The structure is incredibly massive as it is, and is in an area between our patio and pool. We don’t want it any bigger. I’ve talked to the contractor, and he says to burn two fires on either side of the fireplace. He says that he told us that before they built it. That isn’t true, but here we are.

I understand all of that. You need to tell the contractor to come out and show you how to burn it without getting smoke spillage. If he cant he needs to fix it.