Central Heating Option

[jma24]

I’m having another go at getting my kitchen fireplace upgraded from a regular prefab to a ZC high-efficiency wood burner this year.

The problem I’m running into is the amount of space available to run a heat dump or central heating option into the basement. This is a must for me because the room is small and I need to be able to move heat elsewhere in the house.

I should be good on depth, I have a decent chase (29x29” external) but I’m worried about the width available.

The fireplace is 54” wide, I have to subtract 4” for framing and 1” for cement board, so let’s say 48” interior width to be safe. A stove like the RSF Opel or Pearl would fit at 36”, but that leaves just 6” either side for anything needing to pass the stove.

RSF specify 12” clearance to pass the stove, although that seems odd given it’s zero clearance.

If anyone has experience running heat dumps in a narrow space that would be much appreciated!

 

[jma24]

I think I may have solved my own problem. Looks like you can use HVAC ducting with zero clearance provided it’s a minimum of 50 sqin. So a standard 4x14 rectangular duct would easily fit on either/both sides for the heat dump and central heating.

 

[jma24]

Following on from my last thread, a number of ZC fireplaces have a central heating option. Basically it looks like the gravity vent is connected into the HVAC ducting with a blower.

Are there any safety considerations when connecting this? In my configuration, I have the furnace on one side of the house and the fireplace on the other. I was thinking to connect the HVAC to the duct which feeds the far side of the house. Because of the design, this side is inadequately heated.

In theory this could cause back pressure to the main plenum on that HVAC duct, and this could reduce the airflow through the furnace if the furnace is running at the same time?

I couldn’t find any literature about this though. It may be a moot point in reality because the furnace has 2 0.5hp blowers and a central heating option is about 1/10 of that. In this case the fireplace might just warm up the air nicely.

 

[begreen]

Yes, this could unbalance the system. But even if not, it may not provide the best results. If the goal is to try and dump excess heat in the basement then having a blower intaking basement air and blowing through the fireplace to a heat dump in the basement may provide more satisfying results. Always follow the manual's guidance for this type of installation.

 

[jma24]

Yes, this could unbalance the system. But even if not, it may not provide the best results. If the goal is to try and dump excess heat in the basement then having a blower intaking basement air and blowing through the fireplace to a heat dump in the basement may provide more satisfying results. Always follow the manual's guidance for this type of installation.

Understood that a heat dump would work to heat the basement (and ensure the kitchen isn't a furnace. That would be better than nothing.

My ideal goal though is to heat the rooms above the kitchen. A gravity vent is (probably) not a workable solution and so I was thinking to tee the central heat output from the fireplace into the HVAC pipe which supplies the far two rooms. That tee would have to happen in the basement below the fireplace and should be logistically straightforward.

These two rooms were added to the house last and are furthest away from the furnace and always cold.

 

[begreen]

Why is it impractical to heat upstairs by gravity? Is it because right above is only one room or a hallway? Does the upstairs supply duct go up an exterior wall?

Help me out so that I understand what is being proposed, the layout and challenges. A floorplan sketch might help too. You are asking if it would it work to run the line to the basement (at least 2 90º turns) to tie into a duct going upstairs (through the walls?) Is that correct? Too many turns is going to greatly reduce output. How many 90º turns total in the air path would there be from the fireplace to the rooms?

 

[jma24]

Why is it impractical to heat upstairs by gravity? Is it because right above is only one room or a hallway? Does the upstairs supply duct go up an exterior wall?

Let me make sure I understand what is being proposed. You are asking if it would it work to run the line to the basement (at least 2 90º turns) to tie into a duct going upstairs (through the walls?) Is that correct? Too many turns is going to greatly reduce output. How many 90º turns total in the air path would there be from the fireplace to the rooms?

The two cold rooms are above the garage (above and next to the kitchen) and the only way to duct to them is through the garage ceiling. That's how the HVAC did it - through the basement, up the garage wall and across the garage ceiling into the rooms.

If I go straight up from the kitchen it will come out in the bedroom above the kitchen, but that room is already warm.

There are already 3 90 degree turns in place from the plenum to the far rooms. This would add two more, as you say.

One option would be to add a booster to the duct between the tee to the fireplace and the rooms. I could place that one in the garage and push additional air into the old rooms and avoid any back pressure?

 

[begreen]

I hear you, but this is a losing situation. Bedrooms over garages are often cold due to poor insulation in the floor and ceiling and being disconnected from the house. Ducting heat through the basement I'm afraid is going to be poor due to the number of turns and large heat loss in the duct run. If possible, much better heating would be possible if the ducts could come up from the fireplace and then 90º into the rooms. This may mean boxing in the ducts in the bedroom above, but maybe that could become a seat?