Potential Savings of vent damper

Eric B. Stauffer

I have an older (1982) Burnham boiler for steam. I am contemplating having a vent damper installed this fall. The cost from a local (Indianapolis) shop Appel Heating is about $500 installed, which includes a new gas valve since the specs call for a redundant model.

Am I likely to recoup the cost over the life of the boiler? It is a standing pilot so I believe there is a knockout that must be removed. How much can I expect my boiler heatup time to decrease?

Thanks in advance.

Duncan_2

Residential damper savings.

I've heard vent dampers save between 3% and 5% per year on residential sized boilers. That's adds up if you have a $1,000.00 a month fuel bill, but not much savings if your bill is more like $100.00 a month. In that case, the damper may die and cost you the price of a service call before it pays for itself. Sad, but true.

The problem is, the darned things don't usually last long enough to pay for themselves.

I think the manufacturers put dampers on residential boilers to meet efficiency standards more than anything else (but I sure could be wrong). Kind of an easy add-on to get that last couple percent efficiency for DOE standards.

That 3% to 5% figure comes from the fuzzy archives of my memory... If anyone can come up with a more reputable source than that, please do! I'd love to see the source, and how they got the numbers. It's gotta be somewhere between the gross efficiency and DOE, right?

Unknown

I can help a little

To be sure of what the savings would be depend on how it is used.

Think about this....A vent damper only saves energy when the boiler is off. When it is running, the damper is wide open.

How much off time will you have in a year? The more accurately you size the boiler, the less it is off. The less it is off translates to less savings by vent damper and more savings by proper sizing.

The same can be said of intermittant ignition.

How much does the testing figure you would save? Compare running efficiency to AFUE ratings to find out.

http://www.slantfin.com/spec-galaxygg.html

A GG 75 HD and a GG 75 HED are standing pilot and electronic ignition models of the same dampered boiler. At 75,000 input and 64,000 output, the thing runs at 85.33%

With a standing pilot, the stand-by losses drop it to 82.53%; and with int. ign. it is rated at 84.78%.

Looks like they figure the damper saves maybe a 1/2% over running at steady state.

For what it's worth.

Noel

Steamhead

Another thing to consider, Eric

you have a house built during the Coal Era, which meant the chimney was designed to pull air thru a bed of coal. The draft it produces now is much more than that gas boiler needs. The draft hood mostly takes care of this when the burner is running- but when the burner stops, the chimney keeps on pulling, which cools down the boiler very quickly. There is almost no resistance thru the passages of an atmospheric gas boiler.

There's a 3-story house near me that has such a strong chimney it actually pulled my hair toward the inlet when I had the smoke pipe off.

The solution here is a vent damper. I agree some of the early models weren't that reliable but we don't have trouble with the more recent ones. I have a damper on my boiler and it will stay warm all day when there's no call for heat.

I'll be installing dampers on some gas boilers near me soon that are connected to these Coal Era chimneys, and monitoring the results. I'll let you know how it turns out.

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Unknown

Vent Dampers

I agree with most everything the others posted. When I was with the gas company the American Gas Association ran a two year test on many energy saving devices. My company was one of the particpants. The findings after two years on vent dampers ranged from 2% down to no savings at all. We did have a couple of olders chimneys that we put dampers on the boilers and thermal dampers on the water heaters. The savings with both was 5%. The average was about 3 to 4 % savings.

Most boilers that have dampers on them today the purpose is to get the AFUE up to meet standards with a 24 volt system with a thermocouple.

The thing I always tell people is look at the return on your investment. Parts plus labor over $500 usually with a dual seated valve it will take some time to recoup that amount of money. If you want to also upgrade to intermittent pilot the retrofit kits minus a damper is $500 dollars alone not including labor (I am not a big fan however of doing that) I actually like to have a pilot burning in a furnace or boiler year round, especially in damp environments.

By the way the number one energy saving action from that AGA test was to install insulation in the walls and add insulation in the attic - the savings after two years was 12.5%.

Edward A. Carey

Vent Damper

One more thing to consider. If your chimney is oversized or an exterior chimney, you present heat loss from the boiler may be the only thing preventing condensation from forming in the chimney when the boiler is off.

By installing a vent damper on the boiler you prevent the standby loss while the boiler is off, and the chimney will no longer have a constant heat source. On an exterior chimney you could experience condensation, that could damage or even destroy the chimney.

I have seen chimneys that were thought to be sound, destroyed by the installation of higher efficiency boilers, that allow the condensation to form. By installing the damper you will be reducing the standby heat loss from the boiler into the chimney, resulting in a (very) slightly higher efficiency.

It can happen on oil as well as gas. You must look at the chimney and the boiler as a system, and run the calculations using the chimney tables for your chimney and boiler, relative to the potential of condensation forming in the chimney.

BTW, I have never been a big fan of chimney dampers. I have replaced enough of them that failed prematurely, and had not paid for themselves in savings.

Regards,
Edward A. Carey

Mike T., Swampeast MO

[draft so strong it pulled my hair]

Someone once called it, "bodacious draft scrubbing the heat off the boiler."

Dampers were my first question here because of that big draft and I was convinced that my money could be spent on better things.

I still wonder if it might help [Coal-Era chimneys].

Please do let us know Steamhead

Boilerpro

Another voice heard from

I remember seeing on some old Peerless "glossy" literature the AFUE numbers for thier residential cast iron boilers with and without dampers (was optional at that time). It showed roughly a 10% difference in efficiency. Stack dampers not only prevent heat loss from the boiler, but also the space they are located in. Most residential gas boilers are located in heated or semi heated spaces, so there is wasted heat also from the space. I would imagine the effect of dampers on the Peerless cast iron boilers is higher than many other boilers because they appear to have alot more cast iron and water content that can cool down during off cycles....meaning greater btu loss to the chimney. I know on my own 1962 American standard boiler used to drop to the temp of my basement (45 to 55F) and now it stays at 120F with just a leaky themally actuated unit. starting with a warm boiler on fireup I bet helps reduce condenstaion issues and improves startup firing efficiency. They do an excellent job of keeping boiler rooms from getting too cold,

Boilerpro

Duncan_2

Your mileage may vary.

Good info, Eric... Ya gotta love it. Amazing how many considerations come out when ten people look at the same thing.

I guess the answer is it all depends on: boiler off time, boiler size, boiler construction, boiler location, local draft conditions, chimney construction, condensation issues, your install costs vs. fuel costs, and damper lifetime to name some.

So asking how much your boiler heat-up time will be reduced is like asking how much installing that Weber carburetor on my Jeep will increase power or mpg. What kind of engine, How fast do I drive, What kind of roads, hills, traffic? - you get the idea...

Re-reading your post, you have a twenty year old boiler, which kinda works both for you and against you. It's age means its likely to be inefficient, so the potential for savings is there (depending on boiler size). But it may have only ten good years left. Then again, it could easily have thirty good years left, depending on its condition, so there's wiggle room there.

Clear as mud, eh?