Author Topic: Venting clearances help! Furnace, Tankless, HRV  (Read 838 times)

Offline Viperi

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Venting clearances help! Furnace, Tankless, HRV
« on: October 24, 2016, 04:07:14 PM »
Hey guys im looking for some help for some venting clearances. im currently doing a town home and in the front there is about 12 feet with electrical meter on left side and gas meter on the right side ( facing the house). in the backyard there is a 3 foot wall with a dryer exhaust.

Im trying to get a hrv exhaust and intake, furnace intake and exhaust (60,000btu) and a navien (180,000btw) all to fit.

I can get the exhaust for the HRV in the back beside the dryer.

Im having trouble fitting the rest in the front and need a clearance refresher.

-furnace and water tank 3feet away from gas meter ( Clearance from electrical meter?) ( whats the clearance from each of the 2 appliances 3ft from each others intake and exhaust?)

-HRV intake has to be 10ft from gas meter and 6 feet from Appliance exhaust?)


thanks for any help!

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Re: Venting clearances help! Furnace, Tankless, HRV
« Reply #1 on: October 24, 2016, 05:27:26 PM »
Towns with HRV's are always a challenge.  Why is there 12' on the front wall and only 3' on the back wall?  Is there not a fireplace bump out you can vent out?  And how does the townhouse have a left and right side?  Isn't there another unit on one side or both?

You're dryer needs to be the priority as it can only be a maximum of 25' including elbows which count as 5'.  If the shortest distance is out the side then the dryer vent can be installed beside the hydro meter or 3' from the gas regulator outlet vent.  The only clearance pertaining to the hydro meter, is that the gas meter regulator outlet vent must have at least 39" clearance.  The dryer vent must also be kept at least 3' from the water heater or furnace intake, and the HRV manufacturer probably specifies 6' from dryer vent to the HRV intake.  You're correct, the HRV intake needs to be kept 10' from the gas meter regulator outlet vent.

The furnace is under 101,000 BTU's so the furnace exhaust vent would need to be kept 1' from the water heater intake and 6' from the HRV intake.  The water heater is above 100,000 BTU's so its exhaust must be kept 3' from the furnace intake and 6' from the HRV intake.

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Clause 8.14.9 - When more than one direct-vent appliance of the same make and model are installed, the clearances between the air-intake and exhaust vent terminals may be reduced from the clearances required by this Code, provided that they have been tested and certified for such reduced clearances. The manufacturer’s certified installation instructions shall specify and illustrate the reduced clearances.

In some cases water heater manufacturers allow for reduced clearances.  When the neighbor has the same model of water heater this can be very helpful when trying to layout the vent configuration on a block of towns.  Typically a tankless water heater is above 100,000 BTU's and the exhaust would need to be kept 3' from a neighboring intake of the same model.  The Rinnai RL75i allows this clearance to be reduced to 12" and the Rheem RTGH allows for 24" from the center to center of each concentric vent termination.  I don't think the Navien approves such reduced clearances, but they do allow very long vent runs in comparison.  Some manufactures allow the intake and exhaust to be installed in different pressure zones or on opposite sides of the house.

Sometimes the only option is to get the builder to box in the HRV intake and run it up and out of the main floor.  Install the furnace vents 3' from the gas meter regulator vent outlet and install the Navien vents beside the hydro meter, or vice versa.  I suspect it's best to let the Navien follow the longest vent run from the mechanical room.  The HRV exhaust can be installed out back beside the dryer or beside either the Navien or furnace exhaust vents, with no clearance requirements. 

BTW most people aren't aware that, depending on your region and winter design temperature, the HRV intake must be run in R8 flex, not the standard R4.2 flex, as per OBC 9.32.3.10(4) and Table 9.32.3.10.A.

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Article 9.32.3.10(4) - Where a duct carrying outdoor air that is not tempered or not mixed with indoor air passes through heated space, it shall be insulated to not less than RSI 0.5 except that, where such a duct is exposed in the heated space for more than 3 m of length in the heated space, it shall be insulated to not less than the values listed in Table 9.32.3.10.A.

In Ottawa, our January winter design temperature is -25 to -29C, so any intake flex longer than 3m from the exterior vent, must be R8 flex.

And don't forget to leave room for a future air conditioner.

Offline Viperi

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Re: Venting clearances help! Furnace, Tankless, HRV
« Reply #2 on: October 24, 2016, 06:25:41 PM »
thanks for the quick reply very helpful!  the townhouse im at is in the middle. when i say left and right, i meant on the front of the house . the back has a addition with a crawlspace thats why i have a small wall in the backyard.

Does the hrv exhaust have any clearances to the intake of the appliances? Technically what would a hrv be labelled as in the code book?

The a/c is going in the back where the dryer vent is

 i thought all exhaust vents had to be 3feet away from electrical source ( Air conditioners, receptacles) . didn't know a electrical meter doesn't fall under the electrical category . thanks again. this is going to be a tough one tomorrow morning!

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Re: Venting clearances help! Furnace, Tankless, HRV
« Reply #3 on: October 24, 2016, 09:21:38 PM »
The HRV exhaust can be installed anywhere except the HRV manufacturer probably wants a 6' clearance to the HRV intake vent.  Treat the HRV exhaust the way you would a bath fan exhaust or kitchen range hood exhaust.  They are not considered building openings and can be installed beside a gas exhaust vent, and they're not discharging anything harmful, so they can be installed beside any intake vent.  Clause 8.14.8(c) references a mechanical air-supply and requires 6' from a gas exhaust vent and Table 5.2 references a mechanical air intake and requires 10' from a regulator vent outlet.

Table 5.2 of the Gas Code requires a 1m clearance from a regulator vent outlet to any source of ignition.  (Air conditioners, receptacles, hydro meter)

According to the Gas Code you can't install a regulator vent outlet within 39" of the hydro meter, but there's nothing in the Gas Code preventing a gas exhaust vent from being installed beside a hydro meter.  Be aware the ESA may also require a secure footing around their hydro meter.  They usually want 1 meter of accessible space.  You wouldn't want to place a protruding exhaust vent somewhere that could create a tripping hazard around the hydro meter.

Offline slo-115

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Re: Venting clearances help! Furnace, Tankless, HRV
« Reply #4 on: October 26, 2016, 04:07:47 PM »
I was under the opinion that these new smart hydro meters are considered explosion proof. Therefore a regular can be vented within 1m of the hydro meter.  As per Esa Bulletin 2-10-9

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Re: Venting clearances help! Furnace, Tankless, HRV
« Reply #5 on: October 26, 2016, 05:13:37 PM »
You're right, a regulator vent outlet can be installed within 1m of a Smart hydro meter, as per ESA Bulletin 2-10-9.

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Permanently installed electric metering equipment including Standard “Smart Meters” are typically not arc producing, and are permitted to be located within 1 metre of the combustible gas relief vent.

Unfortunately Enbridge will never allow that to happen, as per the Enbridge Relief Vent Clearance to Electrical Equipment Bulletin.

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However, the ESA has informed Enbridge that since the electricity distributor reserves the right to install arc-producing metering devices at any time they choose, each distributor may also choose to enforce this rule even if the installation presently complies with the Electrical Safety Code.

Download the Enbridge Relief Vent Clearances to Electrical Equipment Bulletin - Here

Download the ESA Bulletin 2-10-9 Electrical equipment near combustible gas equipment - Here

Offline slo-115

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Re: Venting clearances help! Furnace, Tankless, HRV
« Reply #6 on: October 29, 2016, 10:08:43 AM »
That's interesting, I mostly do propane work and have never had a supplier with an issue. Propane is the 10ft rule so it can be difficult even with large country homes

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Re: Venting clearances help! Furnace, Tankless, HRV
« Reply #7 on: October 29, 2016, 10:55:25 AM »
When my second stage regulator, at the house, doesn't have 10 foot clearance to a source of ignition I will pipe the reg underground back towards the tanks.  Just remember not to use 3/4" copper.  We need to use 7/8" copper or 3/4" Gastite CSST to ensure our pipe size is equal to the relief outlet size.

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Re: Venting clearances help! Furnace, Tankless, HRV
« Reply #8 on: October 29, 2016, 10:59:32 AM »
By the way since you do a lot of propane work, I have had some propane distributers tell me I need to install my underground copper inside a conduit.   I always challenge the inspector to provide me with a code that says my underground copper must be installed in a conduit and never get an adequate response,  only that they make the rules.  In my opinion as long as the copper is coated it can be installed directly underground.

Do you have to deal with this issue?

Offline spencermoseley

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Re: Venting clearances help! Furnace, Tankless, HRV
« Reply #9 on: November 17, 2016, 12:35:33 AM »
I also faced this problem.

Offline Hgye

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Re: Venting clearances help! Furnace, Tankless, HRV
« Reply #10 on: November 20, 2016, 09:09:38 AM »
When my second stage regulator, at the house, doesn't have 10 foot clearance to a source of ignition I will pipe the reg underground back towards the tanks.  Just remember not to use 3/4" copper.  We need to use 7/8" copper or 3/4" Gastite CSST to ensure our pipe size is equal to the relief outlet size.

We can use csst or copper for vent piping?

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Re: Venting clearances help! Furnace, Tankless, HRV
« Reply #11 on: November 20, 2016, 09:30:24 AM »
It seems to be accepted by all the propane distributors in Ottawa, as long as the inside diameter of the CSST or copper tubing is at least the same size as the regulator relief vent opening.

CSST and copper tubing are mentioned in Clause 5.5.4(b),

Quote
5.5.4 - Except as specified in Clause 5.5.5, when a pressure regulator with internal relief or a gas overpressure relief valve is installed, it shall be vented separately to a safe location outdoors by a vent line
(a) of steel pipe, or of seamless steel tubing or copper tubing that complies with Clause 6.2; and
(b) of a size
(i) at least equal to the nominal pipe size of the vent outlet of the valve or regulator increased as specified by the manufacturer’s instructions; or
(ii) in the absence of manufacturer’s instructions, increased by one pipe size diameter for every 50 ft
(15 m) or part thereof that the vent line extends beyond the initial 50 ft (15 m). This increase shall be made at the connection on the device.

If you bury CSST it has to be installed inside a conduit.