Draft regulator for Buderus?

rsilvers

I started my Buderus G215-5 install and put in a tee on the flue for a draft regulator, but then was told it didn't need it due to the baffles. Should I remove the tee and put in straight pipe or put in the draft regulator anyway or return the draft regulator and get $40 back?

EBEBRATT-Ed

What does the install manual say about chimney size and venting?

In most cases you may not need the barometric unless the chimney draft is excessive (with a pressure fired boiler), and you may not know that until it is started and adjusted.

Also a barometric is not supposed to be installed in a tee. You supposed to use the flue collar that comes with the barometric. You may be required to have a spill switch wired to the barometric

Robert O'Brien

NFPA31 requires a draft regulator unless manufacturer specifies otherwise

rsilvers

Do you interpret the manual as them specifying otherwise? They say to only install one “if necessary,” which seems to mean they are not saying it’s a required part of the installation.  

With this boiler is it usually needed to get draft at the target level? Or do 90 percent of the installs that have them leave them closed?

DJD775

At this point you probably don't know if one "is necessary" without testing the draft after the burner has been operating for a while. I would just leave it in and adjust as necessary once the install is complete. Even if the draft is within spec now it could be out of spec once the colder weather arrives if not regulated. The worst thing that can happen if you have low draft is that the regulator will never open.

STEVEusaPA

I'd put one on...installed correctly...like @EBEBRATT-Ed mentioned.

DJD775

I've read in several places that you can't install the draft regulator in a prefab tee but can anyone explain why? I understand why it can't be installed in a bullhead tee as shown below but not as pictured in the original post. According to the Field Control manual for an RC regulator it is acceptable as long as a certain dimension is adhered to as specified in the Note below.

Steamhead

DJD775 said:

At this point you probably don't know if one "is necessary" without testing the draft after the burner has been operating for a while. I would just leave it in and adjust as necessary once the install is complete. Even if the draft is within spec now it could be out of spec once the colder weather arrives if not regulated. The worst thing that can happen if you have low draft is that the regulator will never open.

This.

EBEBRATT-Ed

@DJD775
I think it has to do with the flapper swinging into the flow of flue gas in the vent pipe. The vent collar is a different length than a tee

DJD775

@EBEBRATT-Ed
That makes sense and aligns with Field Controls specifying a minimum distance from the regulator to the base of the tee.

EdTheHeaterMan

rsilvers said:

Do you interpret the manual as them specifying otherwise? They say to only install one “if necessary,” which seems to mean they are not saying it’s a required part of the installation.  

With this boiler is it usually needed to get draft at the target level? Or do 90 percent of the installs that have them leave them closed?

That part of the manual you refer to does not say "Do NOT use a Barometric Draft Regulator," so I would install one. As far as using a Tee fitting to mount the control... Add a 3" extension to the tee and you will be just fine. Or just place the collar that came with the Barometric over the short tee siding to extend it to the manufacturers specification. @EBEBRATT-Ed has the correct answer as to why you don't use factory made tee. some of them come with a very short throat.

You can see in this altered diagram of a Barometric Draft Control, the upper right illustration will have the flow of flue gasses cause the damper to open more than needed to maintain the necessary Breaching Draft of .02"WC max.

rsilvers

Buderus tech support also said you can't know if it needs it or not without trying it, and it's a pain to try without it and add one later, so just put one in. And, as said here, also said with colder weather is may later be needed.

Thank you. I will use one and make sure the dimensions match the length requirements.

Bob Harper

I recommend performing combustion analysis first as a baseline then install the baro. and adjust the breech pressure to -0.02 wci and re-test. Not only will you see an improvement in the CA numbers, but you will suck less heat out of the heat exchanger and improve efficiency. Make sure the counterweight is on the vertical side before you set it. You should put it close to the boiler but 1.5-2 duct diameters from the appliance collar, elbows, or tees.

EBEBRATT-Ed

It's a pressure fire boiler as far as the combustion chamber is concerned.

As long as the vent is large enough (not too small) you don't need a barometric.

If you connect this pressure fired boiler to a high chimney and have excessive draft.........then you need the barometric to bring the overfire draft (pressure) into spec.

That is all Buderus is saying.

EdTheHeaterMan

EBEBRATT-Ed said:

It's a pressure fire boiler as far as the combustion chamber is concerned.

As long as the vent is large enough (not too small) you don't need a barometric.

If you connect this pressure fired boiler to a high chimney and have excessive draft.........then you need the barometric to bring the overfire draft (pressure) into spec.

That is all Buderus is saying.

I'm wondering who is going to observe the draft performance of that chimney over the operating season to be sure the OF Draft does not exceed the -.025"WC the manufacturer recommends>. Might @EBEBRATT-Ed be volunteering for that task, so that @rsilvers can save $58.13 on a Draft Control? What a nice guy Ed!

It's all in the way you read it Ed. I am playing with you!

captainco

I guess if the law of physics doesn't apply in your area you don't need a barometric. Also as long as the outside temperature and barometric pressure are always the same you don't need a barometric. If the wind never blows you don't need a barometric. If the baffles inside adjust to all of the above you don't need a barometric.

There is no requirement that requires us to use the Field Controls adapter to install the barometric. A tee is just fine. The damper blade is not allowed to swing into the flow of flue gases and I don't remember a standard tee that is too short or at least not in the last 40 years.

The "M" barometric is better than the "RC" but it will work. I would set the barometric for the higher draft -.02" and keep the positive pressure inside on the low side.