Efficiency gain with a vent damper

Unknown

I was going to post a question about my AC system , and ran across a thread about automatic vent dampers . One pro stated that there is an average of 15 percent gain in AFUE when a vent damper is used on a new gas boiler , as opposed to a new unit not having one . Do any manufacturers state in their literature what kind of numbers they get with and without a damper ?

Robert O'Connor

Ron

ask Firedragon . On oil I think he quotes less than 1.5%

Regards,

Robert

Unknown

15% is an

exagerration. It is more like 1.5% to maybe 2%. I was involved with tests that AGA ran and the most we ever saw was about 3% actual savings. That was based on degree day analysis and cubic foot usage over a period of two years of real world testing.

Most of the boiler manufacturers use a vent damper to insure they meet the minimum requirement for efficiency using a 24 volt standing pilot system. They would otherwise have to go to electric ignition.

Unknown

Thanks Tim

I knew you would have the right numbers . The question of efficiency when using them was always in the back of my mind . I sorta thought 15 percent was on the way high side , but was not sure .

Boilerpro_3

In the older Peerless literature I had

On thier residential boilers, the AFUE on the standing pilot, natural gas, non dampered boilers was about 68%. Adding the damper brought it up to 78% and electronic ignition about 80%. These boilers are very heavy, high water content, cast iron sectionals, so I'd suspect their off cycle losses would be very high in addition to the losses from the space due to heated air escaping up the chimney. I'd suspect copper tubes would have much lowere stand by losses since the is only a little heat left in the boiler after each cycle. I'm curious about the only 2 to 3 % real savings in the test. This would appear to make the AFUE numbers very incorrect.

Boilerpro

Unknown

Boilerpro

most of the AFUE tests or results are based on lab testing with a fixed draft condition with low boiler temps around 140 degrees (F).

The tests I was involved with on 26 actual boilers of all makes and models over an actual 4 year period. Two years with out a damper then two years with the damper. The real figures of actual savings came out to no more than 3%. Those were not however mid or hi efficiency boilers. They were all 24 volt standing pilot or powerpile systems on conventional mostly cast iron boilers. We did have a couple of Raypaks and one Teledyne Laars.

We also at that itme had converted several boilers from standing pilot to spark ignition the savings on thoses was 3 to 5%. The best savings of all was adding insulation 3 to 6" in the attic and blowing in insulation in the walls. The savings there was 12% average.

Boilerpro_3

It's interesting....

> most of the AFUE tests or results are based on

> lab testing with a fixed draft condition with low

> boiler temps around 140 degrees (F).

>

> The tests

> I was involved with on 26 actual boilers of all

> makes and models over an actual 4 year period.

> Two years with out a damper then two years with

> the damper. The real figures of actual savings

> came out to no more than 3%. Those were not

> however mid or hi efficiency boilers. They were

> all 24 volt standing pilot or powerpile systems

> on conventional mostly cast iron boilers. We did

> have a couple of Raypaks and one Teledyne

> Laars.

>

> We also at that itme had converted

> several boilers from standing pilot to spark

> ignition the savings on thoses was 3 to 5%. The

> best savings of all was adding insulation 3 to 6"

> in the attic and blowing in insulation in the

> walls. The savings there was 12% average.

Boilerpro_3

It's interesting....

that the AFUE numbers are so out of whack with real life on this topic. What I would like to see with the standing pilot vs. electronic ignition tests are long term comparisons that would take into account the extra rust build up on most cast iron boilers that occurs with electronic ignition boilers in humid summer months. I imagine that the savings numbers would reverse. The standing pilot boilers would probably need a stack damper to help lock in the heat to keep the boiler nice and hot. I usually see residential boilers staying at 100 to 120F with just the heat from the pilot.

Boilerpro

J.C.A.

Hey Boilerpro,

I wanted to send you something, but I got a reject message from your server. It's saved . Chris

Firedragon_4

Well, more or less!

About 0.5% with a state-of-the art burner and heat exchanger. The wider the passages in the burner and heat exchanger, the better they work. These things were designed for coal boilers with non-flame retention head burners. Obsolete, IMO!

Boilerpro_3

J.C. A. Did you use

boilerpros@cin.net ?

Biolerpro

Unknown

Long Term effect

I have some unofficial results long term of standing pilot vs electric ignition systems.

I converted about 10 boilers and furnaces over to spark ignition systems back in 1976. I used the Johnson Controls G-60 controls 6 boilers 4 furnaces. These were at the request of customers for a number of reasons.

The boilers covered the following company's:

Weil-McLain, Peerless, Utica, and H.B. Smith

The furnaces:

Janitrol, Johnson AirEase and Bryant.

The majority of these are in damp basements. It was last year that I took it upon myself to check on what the status of these jobs may be now. I was able to get into 6 of the original jobs. Here is the scary part, they have all been replaced for various reasons. The warm air furnaces had all been replaced (4)as they ranged in age from 15 to over 20 years old. Two had definite damage to heat exchangers. The two Bryants both had heat exchanger damage. I did some further research in that neighborhood which all had the same Bryant furnaces ( a plat development). I got into six house which still had the original furnaces with Bryant bi-metal pilot (standing pilots) two of them had actually had the pilots replaced. All six upon a visual inspection and combustion analysis, carbon monoxide test (that is how I got them to let me in)were in excellent condition.

Point I believe the pilot burning 24/7 helps to keep down moisture damage to heat exchangers. Keep in mind this is not a scientific study and I am sure Jim Davis and his folks have much better scientific results on the extensive studies they do on this subject.

The six boilers only got in and look at two boilers still in operation. One had replaced the Johnson system with Honeywell S8610U Universal replacement module. Both in excellent condition. The other four told me they had moved into the house since I did the original change but that the boilers had not been replaced. There are a number of other houses in both of these areas that have standing pilots. I talked to five who still also have the original boilers.

Point and remember this is not scientific boilers electric ignition or standing pilot really no difference.

There are a lot of things that come into the mix on this subject such as the environment the systems operate in and the overall maintenance to equipment.

In the thousands of sysems I have seen I do not feel it makes that much of a difference. Me I just prefer the standing pilot as it has kept my old GE furnace running for over 50 years with out any real problems. Spring test of heat exchanger just recently still in good shape.

Boilerpro_3

Timmie, did the boilers have stack dampers?...

I found with my own 1962 270 mbh in American standard atmospheric cast iron sectional G series? that the pilot light did not keep the boiler very warm by itself. I installed a Lau thermal actuated vent damper (not very tight closing to say the least) and the boiler now stays about 100 to 110 in my 50 F basement.
Admittedly those old pilots burned pretty big though.

Boilerpro

Unknown

None of those boilers had

dampers. I have used Ameri-therm thermal dampers in the past and they worked great. They stopped making them howver. There were also some areas you could not use them. I have had one on my water heater and furnace for over 20 years. They work great.

I tested all of the thermal dampers and Ameri-therm opened the quickest and closed the fastest so I felt it was the best way to go. It is also a four quadrant bi-metal damper so if any one failed it would have three other quadrants to open. There has not been one bit of corrosion on either one of the dampers. I have a very damp basement and run a dehumidifier all the time to keep it dry so the system works great.

I know the dampers do not really save that much but every little bit counts.

Steamhead

BP

can you still get those Lau dampers?

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

Dale

Vent dampers

We installed hundreds of them, mostly ameritherm bimetal and effical for electric version. I had one on my 30 year old water heater and with it the pilot, true bigger than todays version, kept the heater at 120 degrees in the winter with a tight basement and add on blanket. I think the savings were dependent on the operating environment, if there was a leaky basement and the big dilution air opening was blocked during the off cycle the lack of draft and increased comfort was notable. Every year we remove old electronic dampers from still functioning furnaces and boilers, replacement cost just too high. I too liked the ameritherm except on the old honeywell spin valves like the 8139 where we remove either the valve or the damper.

Unknown

Funny thing, this AFUE

Vent Dampers and the efficiency attributed to them are a tough thing to nail down.

A running boiler has the exact same combustion efficiency with or without a damper. The only time a damper saves money is while the boiler is off.

AFUE calculations make some assumptions about off time, and about sizing. For example, let's assume a heat loss of 72,000 BTUH. IBR assumes that you will require a boiler with an output of 83,000 to get an output of 72,000 to your radiation. From the room where the boiler is, to the rooms where the heat is needed, 11,000 BTUH will disappear from the structure.

To get 83,000 BTUH out, a boiler (at 83%) would be 100,000 input. Here's the funny part. AFUE testers assume that all boilers are 70% oversized. Now we have a boiler that is fired at 170,000 to feed a load that is actually 72,000 BTUH (output).

Let's test THIS set-up, to see if a vent damper will save money. My guess, it will.

Does this number relate to your customer? The more a boiler runs, the less the damper saves. The closer the boiler is sized to the load, the less the DAMPER saves and the MORE the boiler saves.

But then there is the spring and fall. Dampers really shine, then. They DO have value. Frank "Steamhead" Wilsey can tell you about savings on old coal chimneys matched to modern boilers. They have a place. The numbers vary, though.

Noel

Boilerpro_3

Haven't looked for a long time, Steamhead

The one I put one my boiler has been there about 10years and I bought it a few years before that. I have an Ameritherm on my water heater.... found it on a shelf of a local lumberyard and they almost gave it to me....it had been sitting there so long. I can check around for then Laus' if you like.

As a side note, another reason I like vent dampers is that they help prevent boiler room freeze ups when you have a huge intake grill. In one of our family's apartments buildings we had a boiler room that nearly froze up when it was severely cold. Installed a 12inch vent damper on the boiler (bare burner atmospheric) and the boiler room then was usually over 100F in the coldest weather.

Boilerpro

Boilerpro_3

Very interesting, Noel.....

I need to sit down and read that description of how AFUE is calculated.


Boilerpro

Unknown

I have it at work.

I'll fax it to you if you e-mail me a number to fax to.

Noel