me again v/c question temp b-vent

[k0wtz]

in firing up the v/c stardance b-vent in sort of a test mode when burning it seems an awful lot of heat going up the flue. is this normal in a b-vent set up? if the top of the pipe will be say 15f I wonder what the temp will be then and if that will cool the flue down at the stove? I wonder what that temp will be at the top of the stove?

I have felt the water heater flue temp and its hot also so must be the way it works.

I guess at 77% efficiency I can see where the money is going

thanks

bob

 

[k0wtz]

well to sort of answer my own questions I guess that pipe can go up to 400d no way my stove was that hot but I am going to be watching it when I do the final hook up. I am sort of amazed that much heat going up the stack lost forever!

 

[coaly]

It should not be that hot.
How do you know how hot the flue gasses are entering the exhaust pipe?
Are you sure you're not missing a divertor hood?

That is an INTAKE on the exhaust allowing indoor air to mix with the hot exhaust gasses rising up the pipe.

Notice on the water heater you mentioned, there should be a large air intake around the exiting pipe. This is found on all vented gas appliances. This keeps the inner pipe cool which could be aluminum that melts easily.

As hot exhaust gasses rise up the pipe, it creates a low pressure area in pipe and appliance connector. This is called and measured as draft.

Atmospheric air pressure is greater outside of the flue pipe, so air rushes in mixing with flue gasses. This cools the gasses as they rise, slowing them down, reducing draft. Too much draft causes too much heat loss up the flue pipe, lowering efficiency of appliance.
Exhaust gas temperature from the stove should be much lower. That efficiency rating is when connected properly. You are probably much lower.

Excessive draft also affects air flow over burner and can affect the correct air pressure needed (atmospheric pressure) to push into air intake of burner.

The connector parts for natural venting in the manuals you've read are for admitting this indoor air up the stack to cool it. Called a "divertor hood".
There may be a built in divertor (intake) in your appliance. This is only used with natural vented appliance. The test to see if the flue pipe is drafting properly on a gas appliance is to light appliance and shake out a match to watch the smoke rush into divertor and up the stack. This shows air flow moving into exhaust. Without proper draft, CO from combustion can leak back into home. It should have a spillage switch. (a high temperature switch that senses high temp exhaust gasses in divertor hood which should be cool incoming air from room) This switch is connected through thermocouple circuit to shut down appliance when the correct draft is not sensed. Since you changed the gas valve, are you sure all safety switches are connected in the circuit properly?

I'm not sure what you mean by "test mode", but the appliance shouldn't work properly connected to a short test exhaust pipe. With proper venting and divertor, it requires enough vertical pipe above roof to cause enough draft to exhaust products of combustion. This height will be specified in manual. The appliance won't work properly without it. The exhaust isn't just a pipe to let the exhaust fumes and CO out. It serves other purposes to make the appliance work.

 

[k0wtz]

It should not be that hot.
How do you know how hot the flue gasses are entering the exhaust pipe?
Are you sure you're not missing a divertor hood?

That is an INTAKE on the exhaust allowing indoor air to mix with the hot exhaust gasses rising up the pipe.

Notice on the water heater you mentioned, there should be a large air intake around the exiting pipe. This is found on all vented gas appliances. This keeps the inner pipe cool which could be aluminum that melts easily.

As hot exhaust gasses rise up the pipe, it creates a low pressure area in pipe and appliance connector. This is called and measured as draft.

Atmospheric air pressure is greater outside of the flue pipe, so air rushes in mixing with flue gasses. This cools the gasses as they rise, slowing them down, reducing draft. Too much draft causes too much heat loss up the flue pipe, lowering efficiency of appliance.
Exhaust gas temperature from the stove should be much lower. That efficiency rating is when connected properly. You are probably much lower.

Excessive draft also affects air flow over burner and can affect the correct air pressure needed (atmospheric pressure) to push into air intake of burner.

The connector parts for natural venting in the manuals you've read are for admitting this indoor air up the stack to cool it. Called a "divertor hood".
There may be a built in divertor (intake) in your appliance. This is only used with natural vented appliance. The test to see if the flue pipe is drafting properly on a gas appliance is to light appliance and shake out a match to watch the smoke rush into divertor and up the stack. This shows air flow moving into exhaust. Without proper draft, CO from combustion can leak back into home. It should have a spillage switch. (a high temperature switch that senses high temp exhaust gasses in divertor hood which should be cool incoming air from room) This switch is connected through thermocouple circuit to shut down appliance when the correct draft is not sensed. Since you changed the gas valve, are you sure all safety switches are connected in the circuit properly?

I'm not sure what you mean by "test mode", but the appliance shouldn't work properly connected to a short test exhaust pipe. With proper venting and divertor, it requires enough vertical pipe above roof to cause enough draft to exhaust products of combustion. This height will be specified in manual. The appliance won't work properly without it. The exhaust isn't just a pipe to let the exhaust fumes and CO out. It serves other purposes to make the appliance work.

coaly thanks for the information I lite the stove with a piece of b-vent on top apparently running it the total length up the roof will tell the truth as to what is going on. as you say once the pipe is up and ventilated apparenty it cools down the flue at the top of the stove. I was just curious as so much heat in that area. my water heater is right there going up a vent and its hot at the heater too. as I read those high tempatures are normal in the 400d range! thanks bob

 

[k0wtz]

by the way I am excited about getting those stove up and going next fall too much ice on the roof to deal with now and I will have to get into the attic also. life is going to be good with a Vermont castings stove and getting rid of the unvented heater. it goes to my neighbors to use furnished free of charge plus paying for the first gas and installation.