Thermo Damper ?

rlaggren

Not a pro in the heating biz - just a lowly plumber. I found this while cleaning a '60s WM boiler feeding an old gravity system at my sister's house. It's in the horizontal flue above the boiler and probably has been there since the conversion. See attached pics.



I haven't seen any reference to anything like this in lots of reading here, nor anywhere else on the net. Anybody familiar with it at all? It seems to have worked OK for 40+ years and I'm wondering if something like it is still available. It uses some kind of thermal element - no electrical to it at all.



The pic is looking into the elbow above the draft hood on top of the boiler. I don't know if you can enlarge these easily so I'll try to include a link to some online pics.   Hmmm. only have one up yet...



<a href="http://www.flickr.com/photos/rlaggren/5053113044/">http://www.flickr.com/photos/rlaggren/5053113044/</a>



And that label shows upside down in the preview but  I swear it's right side up in my photo on my machine...





Regards, Rufus

Mike Kusiak_2

Ameri-therm

That's an Ameri-therm thermal vent damper. The metal fingers are made of bi-metallic material and open when exposed to the heat of combustion gasses. These were popular in the late 70's and early 80's during the last energy crisis. They are no longer made but many are still in service.



At that time many other companies made them, but there were concerns about flue gas spillage if the fingers failed to open. The Ameri-therm was probably the best and most reliable of them all, but thermal dampers have now been replaced with electrically actuated ones which have an interlock which prevent the burner from firing unless the damper is proved open.

rlaggren

Germans still make them

Mike



Thanks for your reply. I spent an hour looking and apparently one German company, Kutzner + Weber,  includes thermal dampers as part of their current line.



http://www.kutzner-weber.de/gb/products/flue-gas-dampers.html



Just to clarify where I come from. The thermal damper has apparently worked well in my sister's house. We own another house with a 225,000 Burkay boiler feeding an old gravity system. It too has and continues to run happily (cross fingers) for 40+ years but a lot of heat goes up the flue between firing's. There are many and various things to improve that system but until a new MC type boiler, it'd be nice to plug the flue cheaply and reliably between firings. After reading boilerpro's lament about flue dampers, I had hopes that

the thermal dampers would sidestep the reliability problem and be

cheaper and easier to install. But I guess our market has moved on to electronic controls exclusively. Oh well.



Rufus

Ironman

Would Highly Recommend...

That you install a draft spillage switch with these.

Mike Kusiak_2

Ameri-therm availability

There are usually quite a few new old stock Ameri-therm dampers still available for sale on Ebay. I have seen them there in various flue pipe sizes.



Keep in mind that these do not meet the requirements of the latest fuel gas codes because they have no safety interlock.



Yes, the thermal dampers are still used in Europe, especially for vented gas heaters which require no electricity. If you look at the photos in the Kutzner Weber catalog you can see a damper identical in design to the Ameri-therm still being made.

 

Brad White

Spill Switch

Ironman's point is well-taken. I would add that with the spill switch you will get nuisance tripping in those 15 seconds it takes to have the damper leaves open, if the damper is installed too close to the draft diverter hood. When installed within a good rise off the heater, this tends not to happen.



I love what these dampers do in principle but just do not trust them, for the reason of momentary spillage potential.

Tim McElwain

Take it from an old gas man

the unit you have was tested by our lab at the gas company many years ago and it was the only thermal damper we would allow. Its opening and closing times are well within safe perimeters for proper venting. I personally have two of them on my heating and water heating equipment. They were installed in 1976 and I check them twice annually and they still work fine. It is a good idea to install them as close to the chimney as possible and include a blocked vent switch tied into your primary voltage feed or your thermocouple circuit on the water heater.



There were some incidents from thermal dampers which caused all of them to be condemned from further sale. They are no longer approved by code so new ones are not an option.

LarryC

Would it be OK to install one?

Wallies, would it be appropriate to install one of these under the following conditions?

 

1) Leaky old farm house 1900's vintage.  Stacked stone, hand dug basement.

2) Peerless EC-05 Boiler feeding HW base board.

3) Fuel is #2 oil.  Nozzle is 1.5, pump pressure is 120 psi.  Beckett gun.

3) 8 inch flue with barometric damper feeding ~40 foot unlined chimney.

4) Flue pipe about 40 inch length that includes an ell and baro damper with a total of a 6 inch rise from the top of the funance to the bottom of the thimble.

5) Inspection tag data: 400 F net, Draft -.04, Draft O.F. -.02

 

Assuming it would be OK, would the installation of the thermo damper require retuning of the funance?  Would it significantly alter draft conditions?

Thanks.

Ironman

A Big No No

These were made for gas, not oil.

Tim McElwain

Field (Effikal)

does now make an electric vent damper for oil.

LarryC

Just Curious. Why not for Oil?

Why not for oil burners?  I am not protesting, I just want to know why.

Thanks.

Tim McElwain

I do not know why

they are not approved for oil. It is just that the instructions they had in the past for those dampers they were for gas only. They are not approved for any heating or water heating of any kind now.



You might go to www.oiltechtalk.com and ask the oil guys there they may have an answer.

Ironman

NOT FOR OIL

I can't tell you all the reasons, but a couple would be:



1. An oil burner needs to pre- purge and ignite with an un-obstructed flue. This type of damper's fingers don't open until well heated - probably 15 to 30 seconds after the burner ignites.

2. The fingers in the damper are an obvious soot catcher and would soon foul and restrict the flue.



A third reason would be that the damper's construction may not be able to handle the elevated temps from an oil burner.

rlaggren

Spill switch

Aha. Much info here. Thanks to all.



Am I correct that this is a cut-out switch with a sensor in the flue to flag an obstructed flue? Sounds like an excellent idea.



If so, what is the install format of such a thing? Does it have it's own short section of flue pipe or is it a small, eg. 1/2in, hole in the existing pipe for a probe?



What brands, numbers are out there or where should I go looking for such?



Thanks, Rufus

Ironman

The Spillage Swith...

Is just a small disc type limit that attaches to the air inlet of the draft hood. It should be wired in parallel to the gas valve coil or to the provided terminals on the ignition control.

Mark Eatherton

Series not parallel...

All safety components in a safety string must be wired in SERIES. If any one component is unable to satisfy, the burner doesn't get power.



Comfort calls are in parallel.



I'm thinking that is what your brain meant to tell you to say :-)



ME

Tim McElwain

Spill switch or another name for it is a

"blocked vent switch", a lot of new gas equipment comes with both spill switches and roll out switches as part of the design package. Both can however be retrofitted to existing equipment for increased safety. A warning however they are location sensitive and can cause nuisance shut downs if not applied correctly. The tech applying them should have a very good understanding of combustion principles and vent pipe activity.

Ironman

Thanks Mark...

I think that I've got half-himers. This is about the 4th or 5th time that I've done that this week. I had it right in my mind and would have wired it right, but keep stating it backwards.



Of all the things I've lost, I miss my mind the most!

rlaggren

FYI - Study of water heater "thermal" damper

http://www.osti.gov/bridge/servlets/purl/961526-xNQxIi/961526.pdf



PG&E (California) did the study in hopes of finding cheap easy ways to reduce energy costs. In this case the results were not nearly as good as expected. The net savings appear to be only 2-5% in the real world.



The damper appears to be a prototype of something ACT Metlund has patents on; at a guess it's not in production. I'm not sure it's actually a thermal damper - it seems to be actuated by pressure differential - but it's supposed to function similarly. The reduction in air flow closed vs. open appear quite small bordering on insignificant; however, the methodology may leave something to be desired.



The ACT website:

http://www.gothotwater.com/Company/default.asp



Rufus

Tim McElwain

There have been three

kinds of vent dampers over the past 30 years or so. None of them exceeded savings more the 2 to 3%.



The electric vent dampers we have on some boilers with standing pilots are there only so the standing pilot version boiler can still be sold. The vent damper keeps AFUE within DOE requirements



Thermal dampers came on strong in the 70's but several Carbon Monoxide issues caused them to be removed from approval.



There were also some mechanical dampers which operated on pressure differential, those never really worked and caused all kinds of problems.



All of this came about during the times of heat re-claimers and other supposed cost saving devices which actually sooted up most gas equipment they were tried on.



The damper originally discussed here the AmeriTherm was the only thermal damper which operated within safe opening and closing times and still saved energy again about 2 to 3% was the most ever seen.



Studies done back then by the American Gas Association in conjunction with a number of manufacturers concluded that derating, vent dampers, conversion from standing pilot to spark ignition etc did not match the energy savings from adding insulation and replacing windows. The AGA % savings on insulation was around 11% and windows was 5 to 7%. A combination of the two on actual tests AGA released a conservative figure of savings between 12 to 15% total.