Vent Hood Termination for Heat n Glo Gas Fireplace

**Nick Ostrowski** · 03-30-2013, 11:35 AM

If I am understanding the installation instructions correctly on page #24 (http://hearthnhome.com/downloads/ins...ls/386_901.pdf), the minimum clearance above grade level for this vent hood is 12". Is that 12" at the bottom of the vent hood or top? The bottom was only about 3 inches above grade.

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**Rick Cantrell** · 03-30-2013, 11:49 AM

As pictured, that is improperly installed

Clearance cannot be to the top, vent is 15" tall.
Hearth and Home Technologies Crescent II Owner's Manual (Page 46 of 51)

**Nick Ostrowski** · 03-30-2013, 11:59 AM

Thanks Rick. Makes sense. I also thought about snow cover and the vent hood being buried under heavy snow.

**Rick Cantrell** · 03-30-2013, 12:19 PM

What I meant to say was;
I wouldn't say anything about it- unless you see brown crusty stuff underneath it.

**Bob Harper** · 03-30-2013, 06:24 PM

Clearance is to the bottom of the trapezoid portion of the termination. This termination was installed after the stucco was completed. While allowed, it has the propensity for water infiltration. That 'U' channel at the top was designed as a gutter/ flashing but cannot be retro-fitted so you must rely on caulking.

Yes, is this is in a snow region, this termination would need to be even taller. Most HHT units are approved for use with a snorkel termination but not all so check the listed instructions. A snorkel gets it up a little bit from the same penetration in the wall.

The exhaust is in the outer portion of the trapezoid from that funny bent flange-out while the air intake is from below and above in the screened section closer to the wall plate.

**Tom Parks** · 04-30-2014, 02:31 PM

This comment is much too late to be pertinent to this job, but the actual drawing in the manual plays a role here:

vent diagram.JPG

Since the extension line for the dimension comes off the bottom of the little square marked "V", then the dimension is to the bottom of the termination. Occasionally you might see a dimension in the manual coming from the centerline of a vent instead (particularly if there are several approved termination caps), so it is important to notice the difference.

Cheers.

**Tom Parks** · 05-01-2014, 05:32 AM

Originally Posted by Kevin Wood

Here on most units it is above the anticipated snow load.

Agreed, Ken.

Strangely, this particular installation manual does not mention snow, and these guys are from Minnesota!

**Tom Parks** · 05-01-2014, 06:24 AM

Originally Posted by Jim Abram

I know that reading the directions is cheating but,.... see link.

A. Vent Termination Minimum Clearances - Heat & Glo CRESCENT II CRESCENT II Owner's Manual [Page 11]

Clearance is to TOP per directions

Well, Jim, specifically, the clearance is measured from that point to things above the termination, but the language only says "vertical", so I would agree that the figure is somewhat ambiguous.

But your point reminds us why you have to read the directions for the exact model you are installing. Even the exact version, as sometimes there is a revision from version A to B, C or D.

We have run into a number of times when we downloaded the manual for planning, and the manual that came in with the unit was different. Tricky.

The original instructions referenced in this thread are for an HNG 6000TRXI-IPI, and the dimension (shown in the clip above) is shown to the bottom of the vent termination in that manual. That installation manual does not have the figure on p. 11 that you reference in the CRESCENT-II manual showing clearances measured from the top screen on the exhaust.

**Tom Parks** · 05-01-2014, 09:02 AM

Jim, I say that it is for the clearance above because I am familiar with the intent of the document.

It's obviously ambiguous because you are under the impression it could be either way. This is why manuals get revised - we should not be able to come to two different conclusions.

I've had the discussion many times with technical writers about the need to be explicit enough that an installer and an inspector will both always read the requirements the way that the engineers (and lawyers) intended.

**Bob Harper** · 05-07-2014, 04:37 PM

ALL mechanical vent openings into buildings must maintain a minimum of 12" from grade. If snow is a problem, the 12" must be maintained above the anticipated snow/ mulch line. If you look at 'A' in the diagram, it clearly references the bottom of the cap as it does in 'J' for the 7 foot clearance to the bottom of the cap. If you measured that 7' to the top of the cap, someone could smash their face into it on a public walkway. The overhead clearances such as soffits are measured from the top of the trap.

If you block the lower intake it may still work but usually it will soot, possibly suffer from deoxygenation/ ghosting, and even suffer a delayed ignition. Earlier manuals cleared up this confusion. Then they let everyone go and these new kids have been screwing up their manuals ever since. BTW, if you obstruct the bottom openings in this cap, you will increase the wall penetration temps. and possibly the firebox temps. It must breathe from below.

Yes, you must always refer to the manual for that specific model fireplace including the correct year/ revision. FYI, the Crescent I is a power vented unit with radically different venting requirements from the HG direct vents including the Crescent II.

I used to work for HG as a quality assurance manager including working in the R&D test lab. You can take my word for it or ignore me. I don't care but I'm trying to help here. Suite yourselves.