Atmospheric barometric conversion

SWEI

A friend scored one (unused) at an auction. Regenerative blower, heavy cloth debris bag, 208/240 3Ø motor - something like 3.6 HP. Runs quieter than a typical shop vac but pulls like one of those PTO-driven truck-mounted carpet extractors.

I told him I want the next one that comes up on the block.

RobG

SWEI said:

A friend scored one (unused) at an auction. Regenerative blower, heavy cloth debris bag, 208/240 3Ø motor - something like 3.6 HP. Runs quieter than a typical shop vac but pulls like one of those PTO-driven truck-mounted carpet extractors.

I told him I want the next one that comes up on the block.

The difficulty looks to be in portability (not good as a job site vac). Can they be hooked up as a stationary shop vac and have PVC pipe run around the shop?

SWEI

RobG said:

The difficulty looks to be in portability (not good as a job site vac).

This is a fairly small wheeled one, and it probably weighs around 200 lbs. We are thinking of mounting either the one he got or some other regenerative blower in the step van we use for blowing cellulose insulation. It would allow us to bring the overspray back to the truck without trash cans and shovels.

Can they be hooked up as a stationary shop vac and have PVC pipe run around the shop?

Absolutely. They use very similar setups for dust collection in commercial spaces.

ChrisJ

Modification complete.


@Jstar is going to laugh at me because I taped all the joints and used refractory cement on the cover for the drafthood.

All I need to know is what size hole to drill for the probe and where the best place is.

vaporvac

Handsome. You've eliminated the envelope once again!

JStar

I'll drill the hole when I'm there.

And, yeah, that tape is going to be on the floor after the first week of operation.

vaporvac

I'm glad to hear that @JStar. I was starting to get worried cuz Ididn't use it.

ChrisJ

Oh cmon, it's rated for 600F and is 3M brand.

ChrisJ

vaporvac said:

I'm glad to hear that @JStar. I was starting to get worried cuz Ididn't use it.

If it falls off I'll pick it up and stick it back on using a little bead of high temp silicone. This way Jstar won't have to know about my failure.

ChrisJ

Robert O'Brien said:

ChrisJ said:

JStar said:

Control air - control efficiency.

One thing I'm not understanding is how the drafthood pulls a draft through the appliance? I'm sorry for the childish drawing, but it's the best I could do. Why would the flue ever pull air through the boiler rather than direct from the hood and room?

Venturi

Looking at what the EG-40 drafthood looks like I think you're right. Both the EG-40 and EG-45 are similar, except the 45 is a wide open box with the boiler venting right below the 6" opening for the pipe.

Not sure what that black is, but there's no black in the boiler,collector hood or anywhere else in the drafthood. My guess is it was something on the hood when I installed it back in January.

ChrisJ

Here's a picture of the top of the cast iron block under the collector hood.

Will this corrosion / rust be reduced at all with the barometric, or is this just the nature of the beast? I ask because I recall reading about fire side corrosion issues behind eliminated with a barometric.




Also took a short video of the damper this morning when firing the boiler. Was quite warm out today and I shut it down just as it started boiling.

https://youtu.be/Bf8xcqIfaqQ

Tim McElwain

What is the tape on the flue pipe for? That is not code and should be screwed together if single wall pipe. No concern for leakage as the system with proper draft runs at a negative pressure in the flue.

There is always some corrosion on any cast iron surface subjected to the flue gases which remember are hopefully in a vaporized state when exiting the boiler through the flue. The fixed draft hood has no way to eliminate some excessive wet time as it takes time for draft to be created sufficient along with temperature to allow for flue gas removal. The barometric is much better at resolving that issue as it adjusts for draft as needed.

ChrisJ

Tim McElwain said:

What is the tape on the flue pipe for? That is not code and should be screwed together if single wall pipe. No concern for leakage as the system with proper draft runs at a negative pressure in the flue.

There is always some corrosion on any cast iron surface subjected to the flue gases which remember are hopefully in a vaporized state when exiting the boiler through the flue. The fixed draft hood has no way to eliminate some excessive wet time as it takes time for draft to be created sufficient along with temperature to allow for flue gas removal. The barometric is much better at resolving that issue as it adjusts for draft as needed.

Hi Tim,
Thanks for responding.

Tape is (maybe was?) just cosmetic. All joints have 3 screws in them per code. I've seem them before with the foil tape and always liked the look.

ChrisJ

Ok so everyone guilted me into removing the tape.
Also took a good shot of the blocked off drafthood.

Bob Bona_4

Much better without the tape, someday that pipe's gotta come apart for service

jumper

Henry said:

Modifications to a certified gas apliance are not permited in Canada. Such a modification would need a field aproval. There is also the problem of liability in case of a problem with the apliance. I am sure that the insurance company would go after the outfit that modified the apliance even if the modification did not cause the problem.

I still remember being told this in the seventies by Ontario official. Now after digesting it for forty years I agree with him.You can tune damper perfectly but then somebody will fool with it.

ChrisJ

No one here will be messing with it. Besides how is that any different from an oil burner?

Steamhead

It's not, really, except for the fuel.

Henry

ChrisJ said:

Henry said:

Modifications to a certified gas apliance are not permited in Canada. Such a modification would need a field aproval. There is also the problem of liability in case of a problem with the apliance. I am sure that the insurance company would go after the outfit that modified the apliance even if the modification did not cause the problem.

Hi Henry, thanks for responding.

Good thing I'm not in Canada and I'm the owner of the appliance eh?

NFPA 54 12.13.4

12.13.4* Additional Devices. Appliances (except incinerators)
requiring controlled chimney draft shall be permitted to be
equipped with listed double-acting barometric draft regulators
installed and adjusted in accordance with the manufacturers'instructions.

I am well aware of NFPA54, as we use it to compare to our code. This section is used for boilers that do not come with a draft control device such as a draft hood. The field conditions for such boilers would then require a barometric which MUST be double-acting. This section does not permit a modicfication of an aproved and certified apliance. The draft hood is an integral part of the apliance.

ChrisJ

I suppose that is your interpretation of it as I do not see that wording there. The only thing it excludes is incinerators. It does not say " (except incinerators, and boilers with integral drafthoods)"


Henry, honestly why are you even commenting on this? You know this isn't being done on a customer's appliance so what is your point? I'm confused?

vaporvac

Why aren't the dsbdrafts regularly used on the atmospherics? Is it just "tradition" or the money required to re=certify the design? Or is it the additional expense of the components and spill switch? It just seems much safer to this HO's eyes.

ChrisJ

vaporvac said:

Why aren't the dsbdrafts regularly used on the atmospherics? Is it just "tradition" or the money required to re=certify the design? Or is it the additional expense of the components and spill switch? It just seems much safer to this HO's eyes.

My opinion based on what I've read?

It's a complete guess on my part but I think manufacturer's didn't want to swap out a $1 sheet metal drafthood for a $70 damper. I guess another factor is the damper needs to be setup but for that matter is it actually that far off in it's default (no washers) setting vs a drafthood? I don't know.

Drafthoods require a spill switch now so it's not that.

Charlie from wmass

Henry do you see or know of a negative result from using a barometric damper for a draft hood. Codes are malleable as technology changes. We could petition to get all equipment to be required to not use draft hoods. I see more evidence to support that than to condemn Chris' modification.

SWEI

Good luck. GAMA has a lot of lawyers.

ChrisJ

General Aviation
Manufactures Association?

Steamhead

Gas Appliance Manufacturers' Association.

Charlie from wmass

I never said it was easy. Just need to get one manufacturer to go along to show they are cutting edge and above and beyond their competitors to do this. We don't need more lawyers, we need more customer demand. Dollars for CEO's is better incentive after all.

ChrisJ

It's a shame, we can't even get Burnham to allow a Megasteam to be used with gas.

ChrisJ

The other night Charlie mentioned that it was a bad idea to have the 24v damper mounted with the motor straight down. The instructions confirm this so I rotated the damper.

This meant I needed a longer cable. Luckily the actual wire was long enough but the jacket was too short so I carefully removed the pins from one of the plastic connectors, pulled the old jacket off and then snaked them through a longer jacket.

The jacket is from a piece of plenum rated fiber optic cable and is metal underneath the blue plastic covering.

Henry

We looked at various consequences of fiddling with an atmospheric boiler in a house that was constructed in the lab at NGTC. We tested depressurisation, venting, power venting etc. Draft hoods are across all the burners. Therefore there is an even draft across all the burners. By putting a box and then a circular pipe in the middle, there are possibilities of insuficient draft at the edges. If it is put one one side, then the other side can have less draft. The manufacturers in their labs have tested and fond the most reliable way for an atmospheric boiler to operate.

ChrisJ

Henry said:

We looked at various consequences of fiddling with an atmospheric boiler in a house that was constructed in the lab at NGTC. We tested depressurisation, venting, power venting etc. Draft hoods are across all the burners. Therefore there is an even draft across all the burners. By putting a box and then a circular pipe in the middle, there are possibilities of insuficient draft at the edges. If it is put one one side, then the other side can have less draft. The manufacturers in their labs have tested and fond the most reliable way for an atmospheric boiler to operate.

My setup is using the same exact collector (across all passages, or as you said, all burners) mounted on top of the block and same exact drafthood except enclosed (box), to pull into the same circular 6" pipe in the same position. Nothing was changed other than covering the bottom of the drafthood. The flow characteristics of the boiler do not change.

Please explain how this can result in insufficient draft at the edges?

Do you have data from NGTC that you can share? What were their findings and under what conditions?

SWEI

Charlie from wmass said:

Just need to get one manufacturer to go along to show they are cutting edge and above and beyond their competitors to do this.

I keep hoping...

Charlie from wmass

I am having trouble understanding how you would have had that result Henry. The draft is provided by the flue and tempered by the hood. Some modular boilers use the mushroom style draft hood. Why don't they have uneven draft issues?

Bob Bona_4

The damper didn't look right in that position to me but I couldn't find the link to show. Just a pinging in my memories from past installs. Something about end play wear and increased notch interference when the shaft's vertical. Nice on the correction Chris!

I get what Henry is saying, a box is the worst for flow, stray draft eddies in the corners, inconsistency in pressures. Personally I would never modify a factory setup like this but that's me.

ChrisJ

Bob Bona said:

The damper didn't look right in that position to me but I couldn't find the link to show. Just a pinging in my memories from past installs. Something about end play wear and increased notch interference when the shaft's vertical. Nice on the correction Chris!



I get what Henry is saying, a box is the worst for flow, stray draft eddies in the corners, inconsistency in pressures. Personally I would never modify a factory setup like this but that's me.

But the box is what came from the factory? That's how they designed it. Should I modify that too?

Charlie's opinion is the damper can't be mounted motor down as water can drip down the shaft and that would shorten it's life.

ChrisJ

Here's the "box" Henry is concerned about.

captainco

Chris, I just noticed something. I hope the screw from the safety spill switch doesn't keep the barometric from swinging out.

Drafthood: Isolates the appliance from all venting disturbances such as updrafts and downdrafts and also allows the appliance to operate with a block flue.
Not sure what the definition of isolate is in Canada but in America is means: disconnect, prevent, interfere.

Draft is the main force that draws combustion air into the equipment. Otherwise it is random selection and no control.

Any lab that tested a drafthood appliance and found it safe fudged their results or didn't have a clue what they were doing.

In 1979 I started to teach contractors how to block off drafthoods and replace them with barometrics because we were putting hot water coils in the flue for energy purposes. What I didn't realize immediately is how much safer it made equipment.
Once I learned how to test the right way (which is still not done by any lab etc) I discovered just how dangerous drafthoods really were. I was told later by an authority that drafthoods were the most dangerous device ever invented. It was so bad that after a week long field test this authority decided to let someone else certify this equipment and left town.

A barometric stuck open is a drafthood almost but still better. If it is stuck closed there will be a loss of efficiency but never a safety issue. I wish there were more contractors as smart as Chris. There are certainly some on here but not everyone.

ChrisJ

captainco said:

Chris, I just noticed something. I hope the screw from the safety spill switch doesn't keep the barometric from swinging out.

Drafthood: Isolates the appliance from all venting disturbances such as updrafts and downdrafts and also allows the appliance to operate with a block flue.
Not sure what the definition of isolate is in Canada but in America is means: disconnect, prevent, interfere.

Draft is the main force that draws combustion air into the equipment. Otherwise it is random selection and no control.

Any lab that tested a drafthood appliance and found it safe fudged their results or didn't have a clue what they were doing.

In 1979 I started to teach contractors how to block off drafthoods and replace them with barometrics because we were putting hot water coils in the flue for energy purposes. What I didn't realize immediately is how much safer it made equipment.
Once I learned how to test the right way (which is still not done by any lab etc) I discovered just how dangerous drafthoods really were. I was told later by an authority that drafthoods were the most dangerous device ever invented. It was so bad that after a week long field test this authority decided to let someone else certify this equipment and left town.

A barometric stuck open is a drafthood almost but still better. If it is stuck closed there will be a loss of efficiency but never a safety issue. I wish there were more contractors as smart as Chris. There are certainly some on here but not everyone.

Hi Jim,

Thank you for commenting.

The damper clears with plenty of room. The first thing Jstar told me was to make sure the damper clears the screw for the spill switch.

captainco

My favorite part of NFPA 54 is the disclaimer of liability:
None of the information contained in the codes or standards have been tested, evaluated, or verified for accuracy or soundness of judgement.

Anyone using this document should rely on his or her own independent judgement or seek the advice of a competent professional.

If a contractor is not considered a competent professional then who is??

vaporvac

When my spill switches were installed it the screws did prevent an outward swing....it was done the the bottom. I felt intuitively that wasn't right (double-swing means opening in BOTH directions) and spent the time fiddling to get the screws in the other direction. That was a time-consuming pain which explained why it was probably wrong in the first place. Thanks for the clarification.