My \"Still\" ........Boilerpro

Boilerpro_3

Making lots of clear liquid. Finally got my combustion analyzer and here are some numbers at 140F supply (about 125F return). Intake air was about 45F.

Stack temp: 116
Eff.: 92.2 %
co2: 8.6%
Excess air: 32.6%
co : 51 PPM
o2: 5.6%

These readings were taken just outside the Boiler. At the exhaust outside, the stack temp dropped to 108F and eff went up to 94.3%

Boilerpro_3

Lots of condensate........

It totaled up to almost 7 cups for one hour of running. Another interesting thing of note is that my once converted gravity system of about 470 EDR standing iron with all new 3/4 and 1/2 inch copper supplies took about 1 hour and 15 minutes to reach 140F supply. Why some manufacturers are recommending against the use of condensing boilers in gravity conversions is beyond me? BTW, the original installed radiation in the home was about 900 EDR, so the supply temp would have been even lower on an unchanged system. That's about 3,800 btu/hr sitting atop the boiler.

I checked the analyzer at 180F supply and was still about 88.5 %, I haven't measured condensate flow at that temp, but will run another test when I get a chance.

BP

Boilerpro_3

Oh, and with the condensate

it brings the efficiency to about 97.8%.... If I crunched my numbers right.

BP

Floyd_5

Okay.....

so how do you get exhaust temps. so much lower than the return water temps.
Do you know what the exact return water temps. are????
I know what I think and have observed... wondering as to your explaination.

I too, have wondered what the beef is about converted gravity or even straight cast like I have.....
Tonight @ 24* outdoor I'm chugging along @ 142 supply 134 return and making lots of liquid.....

Ultra high eff. equipment is here to stay.....

Boilerpro_3

The QL has a secondary heat exchanger.

The primary heat exchanger is an aluminum block condensing heat exchanger just like the Dunkirk Q90 series, WM ULtra etc. The secondary heat exchangers use the condensate water as a heat transfer fluid. A pumped coil in the exhaust stream (tower on back right) pulls additional heat from from the condensing heat exchanger exhaust which is then sprayed into the incoming air stream in the front tower, preheating the combustion air. Since condensate is used as the heat transfer medium, any hot condensate coming off the primary heat exchanger, vent piping, etc. is also cooled, extracting more heat.


I expect this setup works real nice at higher system temps (Dunkirk claims the unit will continue to condense with returns up to 180F). If the boiler is in a single zone high mass system or one with outdoor reset, the boiler will only be operating at high temps when the intake air is very cold. The high temp difference between the cold intake air and the condensing heat exchanger exhaust should keep the unit condensing in the secondary heat exchangers even when it is not in the primary heat exchanger.

I had a few minor problems with the unit,like short cycling on morning recovery of a single zone because a fixed 10 diff aquastat was supplied, condensate was getting into one of the pressure switches, the heat exchanger cover plate screws were loose, and, also related, the burner needed some adjustment to get rid of a vibration causing harmonic. The first three problems have been fixed, with the help of Mark at Dunkirk tech, and I believe addressed on newer models and the burner tuned in to eliminate the harmonics.

The only complaint I have is exhaust fan is noisy, your classic high pitched whine. I am working on this one and maybe will try one of the mufflers used on the Hydrotherm pulse boilers or the lennox pulse furnaces. On the 100,000 input Hydrotherm I installed about 5 years ago, the exhaust is nearly dead silent with the mufflers in place.

Boilerpro