Fish house ventilation general question

[beer batter]

I had some issues with my vented furnace last season. If it was windy and quite cold, the furnace had a hard time venting out until the pipes warmed up all the way to the top of the fish house. I run the pipes out the house horizontally about 18 inches with a slight upwards grade, then run them straight up to the top of the house about 5 feet, with a vent cap that resembles your non-politically correct "China man's cap". In cold, windy conditions I'd throw an empty case of beer (or something similar) over the top of the vent cap to shield it from the wind and allow the pipes to warm up, then the venting would work properly. You could actually feel the pipes warm to the point where you could barely touch them, then the venting would work. It was touch and go some times where it took ten minutes to get the fumes vented outside properly. Often the CO detector would register some fairly high counts until it started venting out properly.

I called some fireplace stores asking them some questions and they suggested using a better vent cap. Something that will shield the wind more and prevent birds from getting in over the summer months. Also to use double shielded vent pipes. I currently have 3" pipes, they suggested adding a 4" pipe over that with screws securing and centering it over the 3" pipes. This apparently will help the pipes warm up better to get the proper venting started easier.

These things make sense to me. Just wondering if anyone else has had issues like this and what they did to get around them.

Also, where do you find better quality vent caps? Menards, and Fleet Farm both have the "China man hat" style caps (no offense to a China man, sorry for not having a better description). Any suggestions would be appreciated.

[leechlake]

I had a problem with the cheap style chimney caps on my home furnace. The things didn't vent enough and the furnace would just shut down. I got one of the more expensive caps and it fixed the problem immediately. I guess to make sure that is the main problem I'd try to run the thing without a cap and see if it vents correctly and then add a good cap that allows a free air flow. For my situation the cap was the problem.

[Eric Wettschreck]

Sometimes, the outside part of the chimney needs to be insulated for proper draft. If the chimney gets cold the exhaust gas will not flow upward. Cold wind can cool the chimney more than a lot of people think.

Having said all that, I'd look at a better vent cap first.

[minneman]

I had the same problem, I now have the majority of the pipe in the house to keep it warm, problem solved.

[nytelyter]

the other way is to eliminate the horizontal run and keep it mostly verticle

[beer batter]

I thought about running the pipes up within the house but then you lose quite a bit of usable space in the area above the furnace. I'll probably start with adding the 4" pipes outside for an insulator, then get a new cap vent.

Anybody recommend a place to find good cap vents? What style would you recommend?