30 year old Slant fin cast iron still burning at 84%

Ken Field

If a boiler is sized correctly, the efficiency number you get from the analyzer will be more like what the boiler will do on its design temp day. Because all other losses are not working against you on that day. On a warmer day, the boiler is oversized and cycle loss will hurt it. On a summer day if it is running for domestic hot water, all losses will hurt it. Flame efficiency is good but bad info has been drummed into peoples heads by the misleading yellow tag that is stuck to a relatively inefficient boiler.

Ken

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Big Will

The guy put it in himself.

In my area their are very few hydronic contractors. I guess 30 years ago their was less than that. He said he couldn't even find anyone to do it. He had the house built but put the system in with slant fins help. I think they were using a Midwest design temp not a northern California design. I will run the number tomorrow but i he could run inside of condensing temps most of the year with the amount of base board he has. Kinda want him to leave the thing alone just to see how long it will go.

Home Depot Employee

Combustion/operating efficiencies versus annual AFUE are difficult to compare.

Combustion efficiencies of some of the oldest equipment will surprise you

Like your truck, you may get 20MPG on the highway driving 55, but realistically thats not what you should expect out of it at all times.

Unknown

Good, but not all that unusual

I think even back then gas-fired pkg boilers had to meet an 80% rating anyway.

Dave

Brad White_199

Burning, Man...

Combustion efficiency is largely affected by retention time of flue gasses in the passageways. Any old coal-fired pork chop boiler can get into the high 80's or more if under-fired. I have seen plenty of tags at 86 to 88 percent.

"That don't impress me much".

The stack temperature drops of course and combustion is more complete all other things being equal.

Naturally, to actually heat a building this way, so mis-matched it may be, that your startup and cycle losses quickly negate any combustion efficiency numbers. That is where you pay.

Big Will

The cycle rate is high. about ten to warm up and four on six off. The efficiency for the first 90sec was terrible before evening out. I had thought that the analyzer would give me a good number for afue. But after reading the comments it makes sense that it is only snapshot of a full heating cycle. It would be cool if the analyzer could track it like the delta track recorders for temp.