single black pipe length limits

I am having problems with low stove top temps on my stove. I can not get over 400 degrees.

Oldspark from forum has told me that single wall black pipe should not be run over 8 ft.. That much of a single wall pipe will reduce the temp of the chimney and the draft.

I have 15 ft of single run inside and 12 ft of double stainless up top.

Can anyone else chime in with more info on this problem.

Yes, I have an inline damper about 2 1/2 ft ( 30 inches ) above the stove and I use.

Wood supply is around 16 to 18 %.

I also got a load of oak from a friend and tried and had same results low stove top temp.

I checked and sealed up 4 small leaks at joints of pipe.

It depends on temps outside and who is home and for how long.

I sometimes run 24/7 and sometimes let go out if daytime temps are high enough and start again in early evening. Sometimes during the day I might only throw 2 or 3 splits on to keep going till later then will load up good for evening.

Yes, I have tried using the damper all the way open and different degrees of closed.

I have not with a full load going strong been able to get my stove top over 400 degrees no matter what I do and have tried different type of wood and loading techniques n/s and e/w.

I mentioned to oldspark I keep air at about 25% or any lower and the glass will dirty up.

I am mistified. I have brought this issue up before on forum. I know sounds like wood supply or fuel problem. But this 8 ft limit on single black pipe is a new one.