gas furnace chimney need a cap? (Combined Posts)


Old 11-11-04, 12:10 PM
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Does a gas furnace chimney need a cap?

Mine doesn't have one. My other chimney (for the wood fireplace) does have one though.

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Old 11-11-04, 12:13 PM
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Can I use my existing chimney for a new condensing furnace?

I realize the new furnace can be vented simply with PVC pipe. That is I realize a chimney is overkill, but I already have a chimney. It seems dumb to abandon a perfectly good chimney and chop another hole in my house for PVC just because the chimney is overkill. Am I missing something?

Old 11-11-04, 12:21 PM
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I would put a cap on it. Keeps the elements and critters (looking for a warm place) out of it. Rain will not do the pipe any good so it's best to use a cover.Good luck.
Old 11-11-04, 01:02 PM
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Arrow FYI: Installing A Flue Cap Info Only

Information only post.
Background info & Tips installing a flue cap.

Customers who had furnaces problems and I made calls on, used the word chimney when they really meant flu pipe while placing the call to the office personal answering calls for service. Upon arrival at the home, sure enough the furnace has problems. Failure to vent fumes out of the flu pipe.

Primary reason I found out was by asking this question to them while still in the house or business. Have you or has anyone else recently installed or reinstalled cap on the exhaust pipe/vent? Sure enough one had been installed or reinstalled recently. Reinstalled applies when repairs are made to roofs or roofs where replaced.

Condition found was cap was forced down too far onto the flue pipe. Which blocked and or restricted the exhaust of the furnace. On newer furnaces with power vent fans, a restricted and or blocked flue, causes conditions which adversly effects normal furnace opertions.

Power exhaust vented furnaces will shut down quickly or never fire up at all, if flu is blocked. If flue is slightly restricted only, furnace likely to fire up but shuts down very soon after burners fire up. Or may not fire up at all. If vent pipe or exhaust flue is restricted enough, furnace likely to shut down very soon or not fire up at all.

Conditions can vary widely as it pertains to flue restrictions or blockages. As well as furnace operation, based upon the above conditions. A furnace problem is not always directly related to the furnace having a problem. In some instances the conditions are incorrect and it is the safety devices shuting a furnace down to prevent hazards or damages, etc.

On older model furnaces without power vent fans, a restricted and or blocked roof top flue pipe, the furnaces fumes from the burning process are spilled out of the downdrift divertor. Fumes will fill the furnaces inclosure area. Noticeable easily but excessive heat in the area immediately around the furnace, if in a closed closet or small area. Other signs not so easily noticeable to the untrained eye. All above conditions are unsafe and must be corrected as soon as possible.

When installing a flue cap, onto a flue pipe on the roof, never force the cap down onto the pipe fully. Inside the cap are small stop pins. Once the stop pins or tabs are in contact with the vent flue pipe, the cap is fully seated. Install screws per instructions and job done.
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