Do I really need a flu damper?...

wcweaver3

Hi -
I recently purchased a 2,300 square foot, 2 story home built in 1940. It has a Burnham natural gas fired hot water system, Model 207NSL-TEI2 (Series 2, Model "B"). It is rated at 198,000 BTU and was built in September, 2000. The boiler serves 2 zones.

Recently, it was called to my attention that while I have a 7" flue damper motor (RVGP-KS-7BKF) hooked up by wires to the furnace, it's not attached to anything in the flu. There is supposed to be a spindle running from the motor to a flapper inside the flu - and there isn't one. The flu, however, has a very robust outside flu cap so I am not concerned about birds, etc. getting down into the flu.

My guess is that it failed prior to me purchasing the home and the previous owner, rather than paying for a replacement, just decided to open the flu permanently and be done with it.

As I look through various posts, it appears a flu damper can save between 0% and 10% of the fuel bill. A new one, installed, is lots of $$$. Seems like an awful lot to save some small % on the fuel bill - especially since what I've read suggests flu dampers last < 10 years and maybe is lasts < 3.

Am I being too stingy and just get it replaced? Is there some safety issue here that I've missed?

Thank you!

SlamDunk

At the very least, you should separate the duct to make sure damper has been removed and is not in a partially open or closed position. Personally, I'd get it replaced before next heating season. Dampers last long enough. Mine is 12 years old. Divide cost to replace by 12yrs and that is likely your fuel savings.

Jamie Hall

I'm split on the subject. On the one hand, they do possibly save -- I doubt that they would save 10% or anything close to it, but a little. On the other hand, they are one more pesky point of failure for a system -- and on the properties I manage which had them, every single one has failed at least once. Usually at oh dark hundred in a blizzard. If you're living in the place, that's probably not a big deal -- learn how to force it open manually, and then when you wake up freezing some morning, hustle down and do it. For me, it's a big deal. Phone rings, heat is off, get dressed, hop in truck, engage four wheel drive, get over there, fix it. Nope.

Steamhead

Definitely get that damper replaced.

Not only does it keep the boiler from cooling down between cycles, which requires more energy to overcome the next time it fires, but closing off the chimney between cycles reduces air infiltration into your house. So you save there too.

Also, with a current-model Field damper unit, if it stops working all you need to do is replace the motor assembly- NOT the whole damper unit. This saves on repair costs.

For me, it's a no-brainer.

Motorapido

Luckily for you, it's a very easy part to replace yourself. When I bought my house, the one already in place was broken, and set so that the damper stayed fully open. As I recall, it took me about 15 or 20 minutes to swap in a new motor assembly. And from that moment on, my cat never likes to leave the boiler room since the room stays much warmer with the damper keeping the heat from rushing up the chimney. By keeping that damper closed when the boiler isn't firing, the damper results in a much, much warmer boiler room. Cat tested and approved. If you're concerned about it failing when you're not home and somebody else will have to figure out why the boiler isn't firing, tape a little note card to the boiler jacket mentioning the on/off switch for the damper and which direction to turn the shaft if the motor fails with the damper in the closed position (when the damper is closed, the circuitry prevents the boiler from firing, but if you turn off the damper switch and manually rotate the shaft to open the damper, the boiler will fire, and everything will work fine until you get around to fixing the damper motor).

Solid_Fuel_Man

It is kind of like not having a damper in a fireplace flue. 

It would be interesting to see a real world study on the amount of heat they keep in the home vs convected up the chimney 24/7. As well as the cold air pulled into the home to replace that hot air. 

I'd wager it would be over 10%. But that is just a guess. 

Aluvaboy

I recently replaced a Honeywell Aquastat on a Crown boiler. The vent damper was connected to the old Aquastat in a funky way. The connector plug from the vent damper was cut and the wires connected straight into the Aquastat. The new replacement Aquastat had a molex plug which would accept the plug from the damper. Unfortunately the plug that was cut was never saved it was a PIA to trace the wires and finally have it working again!

EdTheHeaterMan

Aluvaboy said:

I recently replaced a Honeywell Aquastat on a Crown boiler. The vent damper was connected to the old Aquastat in a funky way. The connector plug from the vent damper was cut and the wires connected straight into the Aquastat. The new replacement Aquastat had a molex plug which would accept the plug from the damper. Unfortunately the plug that was cut was never saved it was a PIA to trace the wires and finally have it working again!

I remember you. You did a great rewire of the near boiler wiring and zone valves. I believe I sent you a wiring diagram my 3 yo Grandson made on my phone. I hope it was helpful LOL

@wcweaver3, Your savings will vary based on your chimney, basement (or boiler room) temperature and how long the off-cycle is (along with other factors). And if you are at all handy, you can do it yourself for a lot less. Remember that your chimney is an exhaust pipe for bad fumes you don't want in your home. Once your heater stops making those exhaust gasses, the damper will automatically close and keey the vacuum cleaner (Called the chimney) closed.

Think of it like this. You are sitting in your easy chair reading a book and for some unknown reason there is a 7" hole in the wall to the outside right next to your chair (Like maybe an open window). At some point the mechanism that allows you to close the hole in the wall breaks. Since it is not a real issue today, you forget about getting it fixed. then December rolls around and the hole is letting hot air out and extremely cold air in... right next to you. It is uncomfortable to say the least, and those leaves and rain (that are no longer clogging your gutter since you purchased GutterGard) are making a mess too. I don't think you would be so unconcerned in this case. But the same energy is being lost up your chimney as it would be in your broken window.

Just a different perspective

Mr. Ed

https://www.supplyhouse.com/Field-Controls-GVD-7PL-7-Automatic-GVD-Vent-Damper-without-harness.

Add markup on parts and labor to install, and overhead for company doing the job, and also a portion for warranty in case you get a bad one and you want the company to fix it for free. Although we are not supposed to talk price (See the Site Rules) your estimated cost may be lower if you shop it around. You might want to edit your post to remove the price. You might say " it cost $$$ too much to justify the savings over the life expectancy of the part"

To answer your original question Do You Need It? NO... Obviously since you have not had one for so long. But there is no regulation that stated "You MUST fix the damper when it fails". The outside flue cap has nothing to do with the energy saving feature of the Auto Vent damper, and the auto vent damper has nothing to do with keeping birds and debris from reaching the boiler. It is only there to save energy.

Aluvaboy

Mr. Ed,

Finally I completed everything. I installed two isolation valves for the circulator. Removed some more of the exposed wiring etc. Here are the pictures! I followed the wiring diagram you send me to the T. It was extremely helpful. LOL


Note: Today the outside temperature by me was around sixty degrees. That is why the temperature is showing 75 degrees on the Hydrostat display. Also I got this month's gas bill after I installed the Hydrostat 3250Plus. This is a full months bill after it was installed. Comparing before and after gas bills, I think I had a saving of approximately $100.00 after factoring in the short February! So the effort was worthwhile in my opinion.

EdTheHeaterMan

Aluvaboy said:

Mr. Ed,

Finally I completed everything. I installed two isolation valves for the circulator. Removed some more of the exposed wiring etc..

Sorry for commandeering your discussion @wcweaver3, We will move this back to Aluvaboy's original post

wcweaver3

Mr Ed - thank you for a very clear, thoughful post. Sincerely appreciate it!

SteamingatMohawk

@EdTheHeaterMan I respectfully have the very different opinion regarding the vent damper.

1. I realize vent dampers were not usually installed when the industry started, Today, if they weren't required, why would the manufacturers include them in their package?

2. 2021 edition of NFPA54, 12.13.3, Draft Control Devices says, " Where a draft control device is part of the appliance or is supplied by the appliance manufacturer, it shall be installed in accordance with the manufacturers instructions." I am reasonably sure boiler installations include the vent damper (plus possibly additional protective devices).

3. My opinion is it is clear that requiring a vent damper to be installed requires it to work properly. Otherwise the requirement to install it makes no sense. Using your logic, one could assume the high limits, LWCO etc. don't have to work either. Nice try, but that dog don't hunt.

4. By having a damper, heat loss is reduced from the boiler vicinity through the chimney.

5. A permanently open flue/chimney provides a path for air flow, which in the event of a fire in the area could make matters worse.

I apologize for disagreeing with you, but I had to speak up.

Unrelated observation, I think laundry chutes are no longer allowed in residences so that the chase does not become a chimney of sorts.

EdTheHeaterMan

SteamingatMohawk said:

@EdTheHeaterMan I respectfully have the very different opinion regarding the vent damper.

I agree with your point of view. My answer is strictly a mechanical perspective. Once the manufacturer gets his appliance approved for sale based on the minimum efficiency required by regulations of any governing body, then a consumer can purchase it. Once a consumer has it in their possession, the regulation process that a manufacturer must pass has no jurisdiction. You don't need it to heat your home is a fact proven by this particular instance.

That said, I'm all for getting it working IF it is actually going to save the cost of the repair. I'm against the cost (retail cost for those who are not the DIY type) if for example a $1000.00 repair will only save $50.00 a year if that! (I'm not saying that repair should cost that much... just using it as an example). on the other hand if a $200.00 repair saves $100.00 per year then why isn't it already done?

Thanks @SteamingatMohawk ... I welcome opposing opinions (except when I'm right like now). LOL

Jamie Hall

I agree with you too, @SteamingatMohawk -- and with @EdTheHeaterMan , but with a minor caveat: in this wonderful modern day of lawyers everywhere, the regulations are not so important -- but if the idiot defeats the damper, and then finds that his efficiency doesn't match the manufacturer's numbers, at least some folks are going to blame the manufacturer...

EdTheHeaterMan

Jamie Hall said:

I agree with you too, @SteamingatMohawk -- and with @EdTheHeaterMan , but with a minor caveat: in this wonderful modern day of lawyers everywhere, the regulations are not so important -- but if the idiot defeats the damper, and then finds that his efficiency doesn't match the manufacturer's numbers, at least some folks are going to blame the manufacturer...

As it should be. LOL

The Manufacturer has enough money to pay for my stupidity, whether it be on purpose or not! That is why God made Lawyers

Hap_Hazzard

This is a very easy DIY project, and that will cut the cost considerably. I installed my own flue damper and didn't find it all that difficult, but for you it will be even easier. Just buy the same model and you can unplug the old one and plug in the new one. You won't need to worry about the wiring, which is not all that difficult anyway.

BTW, your motor looks just like the one I installed. I think I got it from SupplyHouse.

Oh, and hang on to that motor in case you need it someday. Usually it's the motor that goes bad first.

SteamingatMohawk

The regulations do not cease to exist once the equipment has been put into use.

There are too many “knuckleheads” out there doing whatever they darn well please. HH needs to at least try to rein them in, not encourage them.

Paul Pollets

Flue dampers are required in the boiler code or mechanical code in most states on cast iron boilers. The intent was to hold the heat in the casting after the boiler fires. You could install a mod-con, and avoid the part or repair. As well as a chimney liner.

EdTheHeaterMan

SteamingatMohawk said:

The regulations do not cease to exist once the equipment has been put into use.

There are too many “knuckleheads” out there doing whatever they darn well please. HH needs to at least try to rein them in, not encourage them.

Agree with @SteamingatMohawk on the regulations. they exist but do they apply? And there should be more legislation to create energy police to enforce those rules. (sarcasm)

Auto manufacturers also have regulations. But that never stopped me from supercharging my flat head Ford back in 1974. And it has not stopped my son from adjusting the computer on his Subaru for maximum horse power. Both of those examples are fuel wasting, non OEM hacks that still pass state inspection so I can drive it on the road. But many will disagree with this type of behavior from those juvenile delinquent, leather jack wearing, boom box playing, teenagers.

Kids thees days...

Solid_Fuel_Man

Boombox? Yeah, those used to eat a lot of D batteries when you held them up on your shoulder all day! 

The Steam Whisperer

My observation: My parents owned a 3 story apt building with about a 1,000,000 btu input draft hood equipped hot water boiler. Standard open grate for combustion air. In really cold weather ( below 0F) outdoors, there was concern about freezing pipes in the boiler room. After installing a blast gate to cut down excessive draft and installing a thermal vent damper ( very leaky) the boiler room was well over 100F in cold weather. I would say stack dampers are worthwhile, especially on typical oversized boilers. Also, looking at old AFUE data when damper were optional, The stack damper models were usually about 6 to7% more efficient.