You have two furnaces connected in the same flue as the water heater with the draft hood?

 

Yes. Should I not? Who the right person to call to address that? I only have one flue going up and out the roof. What are some typical ways to address this?

 

B-vent carries a 6" clearance to combustibles. Single walled unlisted connector is 6" as you stated. If mfrs. are to continue putting their condensate ports on the front corners of coils, a tech has two choices: he can rotate the coil facing another direction or he can use B-vent all the way. In this case, you could use a 4" draft hood connector attached to the appliance collar then increase to your larger diameter as the sizing charts allow and dictate. The B-vent should be supported every 5 LF of horizontal run and in two planes at each offset/ return.

The gas cock would be treated as noncombustible but the valve seat will probably see a shorter service life. No code on placement near hot things but best practices would probably say this was a poor choice.

There is no prohibition to manifolding multiple CAT I appliances. The code even tells you how and provides sizing charts. Is it a good idea connecting them with the draft hood-equipped water heater? Nope. Let's say something obstructs the vent termination. In my area, roofers think they make great barstools to sit on. The furnace and continue firing because the flue gases and heat will spill out the draft hood of the water heater into the CAZ without tripping the flame rollout switch, the vacuum switch or the high temperature limit switch in the furnace.

The vent connector on the WH is undersized. Note the 4" adapter on the draft hood. It's there because with less than 3 feet of vent rise at 40 MBH, you need to increase the size of the connector 1".

 

B-vent carries a 6" clearance to combustibles.

I thought it was 1" for B-vent. Is that a typo or did I misunderstand?

If mfrs. are to continue putting their condensate ports on the front corners of coils, a tech has two choices: he can rotate the coil facing another direction or he can use B-vent all the way. In this case, you could use a 4" draft hood connector attached to the appliance collar then increase to your larger diameter as the sizing charts allow and dictate. The B-vent should be supported every 5 LF of horizontal run and in two planes at each offset/ return.

So is the PVC nearly touching a problem then? This coil actually has ports at both front corners. They could have used the ones on the left instead of the ones on the right. There's gas supply over there, but seems like they could deal with that somehow.

The gas cock would be treated as noncombustible but the valve seat will probably see a shorter service life. No code on placement near hot things but best practices would probably say this was a poor choice.

I'll ask them about changing that too.

There is no prohibition to manifolding multiple CAT I appliances. The code even tells you how and provides sizing charts. Is it a good idea connecting them with the draft hood-equipped water heater? Nope. Let's say something obstructs the vent termination. In my area, roofers think they make great barstools to sit on. The furnace and continue firing because the flue gases and heat will spill out the draft hood of the water heater into the CAZ without tripping the flame rollout switch, the vacuum switch or the high temperature limit switch in the furnace.

The vent connector on the WH is undersized. Note the 4" adapter on the draft hood. It's there because with less than 3 feet of vent rise at 40 MBH, you need to increase the size of the connector 1".

Is there a trade that specializes in venting? Who should I call to address this? The WH was permitted and inspected, but inspectors aren't perfect. Is this something that potentially should've been caught on an inspection?

Thanks for the responses all. I really appreciate it. Sounds like there are are some concerns, but not necessarily the things I was concerned out.

Thanks!
Brett

 

B vent has a required clearance of 1 inch while single wall vent has a clearance of 6 inches from combustibles.

 

Yeah, that's not good.
I would never run pvc that close to single wall nor b-vent. I typically only run b-vent 1" clearance, but still install a metal shield if it's within 2".
I don't like the gas valve that close either.
The white tubing insulation will probably be fine, but I would still put a shield between it and the single wall.
The filter drier doesn't look like any concern to me, I don't consider that combustible material. You have to get that paint pretty hot for it to burn.
As for the venting, just have them perform a CA, and CAZ test.
Just a little common sense goes a long way.

So, yes your concerns are valid.

 

Typo- B-vent carries a 1" clearance to combustibles. Flying fingers typing.

Draft is simply the stack pressure differential With Respect To the CAZ air. Remember, "draft" is technically not mass flow of air. They are two totally separate things. Generally, vertical rise increases draft pressure while horizontal runs, elbows, tees, and rough linings add to friction loss. Draft creates the potential for "stuff" to move through a conduit. The diameter of the conduit minus the friction loss at a given draft pressure determines mass flow.

"combustion air" is technically only that minimum air for combustion. It does NOT provide the pressure gradient WRT the adjoining spaces to the CAZ. When you add in dilution and excess air you get "makeup air". The pressure differential of this MUA flowing into the CAZ is what determines the adequacy of air for combustion and venting along with the pressure gradient required. "Stuff" moving into a draft hood does not in and of itself guarantee successful venting. High draft pressure can result in excessive velocity (>1 m/s) with high mass flow resulting in a "curtain effect" where the combustion chamber, being blunted at the hood, vents out the base. You can detect this with an ambient O2 reading at floor level dropping.

If the CAZ maintains the minimum ventilation rate of 0.35 ACH50 per ASHRAE 62.2, and you have a draft pressure in the stack of -0.02wci/ 5 Pascals above the CAZ pressure gradient, you should achieve sufficient ventilation to meet the stated clearances to combustibles for the appliances and venting. Inadequate MUA invalidates clearances.

Example: you measure a stack draft of -0.02 wci. The CAZ is -3 Pa WRT to the adjoining space. Your net draft is -0.012 wci, which is insufficient draft pressure for proper combustion, venting, or clearances. The CAZ should be neutral or positive WRT the stack, which begs the question how does MUA enter a CAZ that is positive.
HTH