EKO 40 Efficiency and Flue Temps

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Blennophobic

Member
Jan 31, 2008
20
Eastern Ontario
This is my first year running the EKO, so it's still basically brand new. For some reason my pressure relief valve opened a couple of weeks ago when I was away. My wife was operating it and so I have no idea what happened. All I was told was the controller had the error code on it for over-temp. She put the fire out right away when she heard the hissing and waited until I returned. I refilled it with water and all seemed OK.

Right away on the subsequent burn I noticed that my storage temp didn't seem to be climbing as quickly as usual. I also noticed the boiler temp on the controller did not seem to be as high as usual. After it cooled off I opened up the rear and cleaned the smoke tubes with the included round tool. There was a bit of brown ash built up everywhere in the unit, including the bottom chamber, so I scraped it all off and figured that was the problem. On the next burn there didn't seem to be any change. I got hold of a thermometer that goes to 600degF (Eastman Outdoors deep fry thermometer) to check flue temps, and it was indicating 500 - 600F range when up to temp and gasifying well. This bothers me because the efficiency can't be anywhere near advertised with this much heat going up the flue. Watching it run today, the boiler was having trouble getting over 70degC output when the flue temps were indicating about 600F. That does not sound right to me!!

My pump is the Taco 3-speed that when on high, is calculated to flow the correct amount to take away 140kbtu at my system head and typical deltaT... I have a Danfoss 60C thermostatic recirc valve.

Any ideas folks? Has anybody used a similar thermometer to measure flue temps? I know this sounds crazy, but could it be something to do with the water having overheated and not picking up heat as well now? This is really starting to bother me so any suggestions are welcome.

Thanks,

B.
 
nofossil said:
Water is water - you can't damage it. Those flue temps do seem a bit high, but not astronomically so. Are you getting the desired delta T going through the boiler?

My boiler set temp is 80C. The highest I've seen the supply temp lately is 75C, so the delta T is 15C above the thermostatic valve (60C). Supply temp previously hit 80C all the time and went into idle periodically. What can be different now?

B.
 
Shortly after startup my flue temps will peak at 550-600F. This is with my fan speed at 80%. Once I have a good coal bed established I'll trim the fan speed down to 50% and my flue temps will settle to 350-400 and stay there. During normal operation my flue temps rarely drop below 350ish.

For what it's worth my boiler setup seems to work best and work most consistently at a 20-25 degree F delta T running through the boiler. So if my input is 140 (storage may be lower with Danfoss) my output is usually 160-165. Sometimes it'll hit 170, but not often. Once all of my storage starts to exceed 140 I will start to see higher temps on the boiler, but not before. I never see 175-180+ until my storage is really cranking and in the 160 ball park.
 
Is your bypass damper closing complety??????????? It sounds to me like you are getting some bypass. That will give you high flue temps and also could be why you had an over heat. Take off the cover over the hx and make sure the bypass is closing tight.
leaddog
 
So Stee, your operating parameters don't sound much different from what I've described. Maybe the issue is all in my head.

leaddog, that thought had crossed my mind too. I'm going to check it out tomorrow when I clean it again.

thanks for the replies guys.

B.
 
You might also want to do a check to see if you might have any air trapped in the system that could be restricting your flow...

Gooserider
 
Gooserider said:
You might also want to do a check to see if you might have any air trapped in the system that could be restricting your flow...

Gooserider

I wondered if the pump got airlocked when it first boiled over... I don't think I'll ever know.

Checked the back flap and it seems to be closing fine.

I've resigned myself to the conclusion of user error. Maybe the wood was a little too moist, not sure. I tried some double-seasoned wood and that seems to be better. I guess the flue temps just need to be that high to get the heat exchange.

B.
 
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