exhaust temperature

Wenn was unklar ist oder nicht so funktioniert wie ihr gern hättet.
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dgoodyear
Beiträge: 5
Registriert: 17. Nov 2020, 12:38
exhaust temperature

Beitrag von dgoodyear » 17. Nov 2020, 13:21

Hi, I am from Canada (Newfoundland) and I speak English but I am still hoping that with people on the forum may be able to help me. Luckily I have been using google translate to read the forum and have learned a lot of information. I can't remember how I came accross the forum but I am glad that I did. The forum and members share a great wealth of knowledge!

I installed a walltherm (Zebru I think) about 3 years ago. My thermal storage is a logix24 tank. I am using a k36e boiler charging set which is installed next to the tank about 15'-20' away from the walltherm. I usually burn every second day and get good charging in the logix24 but it did take some practice.

The boiler charging set has a built in mixing valve set to 60C and is using a grundfos alpha 2 pump. My chimney is greater than 20' as was required by the installation manual.

When originally installed, the boiler came with a dial thermostat installed at the heat exchanger. I was told by the distributor to set this to 70 C so thats what I did. I adjusted the pump speed so that temperature in the water jacket was constant. I noticed quickly that sometimes the pump would run all night after I fired the boiler. This would destratify the tank and the stove just became a radiator which bled the stored energy from the logix24 and deposit it back into the living room. I quickly realized that I needed a differential control so I installed a Steca 501. I set the minimum boiler temperature in the Steca controller to 70 C as was the setting on the old thermostat.

Because our house is a passive house (http://flatrockpassivehouse.blogspot.com/) I opted for the quick panel insulation to cut down on heat in the living room. Because of this, the supplied stove pipe thermometer was unable to be installed. I just installed it this past weekend. I tested the thermometer in ice water and in boiling water to verify accuracy before installation. The thermometer is installed about 6" above the location of the original flue gas thermometer. I lit the stove and went through a usual slow warm up (about 50 minutes) and then flipped the gasification flap. The flue gases started decreasing in temperature...but I expected them to go much lower. Instead of dropping to 150 C as expected, the gas temperature was about 230 C- 240 C. Following the troubleshooting section of the manual, I expected that the flap seals had to be replaced. I had not replaced them for 3 years. I inspected them and they looked a little compressed but not too bad. However, I decided to replace them anyways. I lit the stove again yesterday and expected to see an improvement....no improvement was made. I am now thinking it is not the flap seal. The seal looked fine before replacement and the new one looks even better. When I turn the flap, I can feel that it is sitting in the right position and hear a soft "thud" as it seals against the rope gaskets.

I clean the stove daily, weekly and monthly. Daily, I empty the ashes, clean the grates and the glass doors, monthly I remove the grates, the injector, the flame wall, and clean any debris. I clean the heat exchanger and the back bypass monthly, but there is only fine carbon soot stuck to the heat exchanger. The exchanger bypass at the back of the stove is set at it's lowest position.

I am now thinking I have something setup wrong during the commissioning of the stove and I am wasting alot of heat. Do any of you have any ideas about what I should check or what I may have set up wrong?

Thanks

DJG

dgoodyear
Beiträge: 5
Registriert: 17. Nov 2020, 12:38
Re: exhaust temperature

Beitrag von dgoodyear » 17. Nov 2020, 13:32

I will add that the pump does cycle on and off during the first 45 minutes after lighting the fire. I assume this is because of the volume of water in the heating circuit. but after the circuit is heated, the pump mostly stays on. the pump is on speed 2 and moves about 2-3 gallons per minute according to the pump display.

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JAU
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Re: exhaust temperature

Beitrag von JAU » 17. Nov 2020, 13:59

Welcome.

Whow. I didn't know they sell these stoves outside of Europe. :o
dgoodyear hat geschrieben:
17. Nov 2020, 13:21
I just installed it this past weekend.
Ok. Therefor you might have used your Walltherm the past 3 years with higher exhaust temperature then expected.
dgoodyear hat geschrieben:
17. Nov 2020, 13:21
Instead of dropping to 150 C as expected, the gas temperature was about 230 C- 240 C.
That's not just a little. :?
dgoodyear hat geschrieben:
17. Nov 2020, 13:21
Following the troubleshooting section of the manual, I expected that the flap seals had to be replaced. I had not replaced them for 3 years.
My father and I still have the first sealings installed. I also doubt they had anything to do with the problem.

Wallnöfer changed their design a bit over the years. To check which one you have there are some details i'd like to know:
When you lift the top front cover to access the gasification flap, does the heat exchanger have vertical rips or is it just one solid horizontal block?
Is under the top back cover an adjustable sheet metal installed? Is it fully closed (picture might be helpful)?
dgoodyear hat geschrieben:
17. Nov 2020, 13:32
I assume this is because of the volume of water in the heating circuit.
You assume correct and it's expected to do so.
What water temperature is stored in the tank? I guess 70°C.


greeting, JAU

dgoodyear
Beiträge: 5
Registriert: 17. Nov 2020, 12:38
Re: exhaust temperature

Beitrag von dgoodyear » 17. Nov 2020, 14:35

thanks for the quick reply! yes they did sell them here in canada and the usa. However owing to new US EPA standards for boilers, the north american dealer is no longer importing them, but apparently I can still get parts if needed!

My model has vertical ribs only. There is no horizontal heat exchanger as in the older models. The back top cover has a sheet of metal which hangs below into the vertical heat exchanger. Vanes slip in between the exchanger which increase resistance to flue gas draft.

sorry i can not figure out how to upload an image...but here is the manual link. Its a uk website but looks like the same user manual. page 50 shows the assembly under the back top cover. https://www.firepowerheating.co.uk/m/d/ ... manual.pdf

Agreed, the fume flap seals are not part of the issue anymore. something else is going on.

the top thermometer on the logix24 is around 50C, the bottom is about 25. I usually bring the tank up to a uniform 70 C + in about 3 hours from initial lighting but have a feeling it could be quicker based on the fact that my flue gas temperature is too high.

dgoodyear
Beiträge: 5
Registriert: 17. Nov 2020, 12:38
Re: exhaust temperature

Beitrag von dgoodyear » 17. Nov 2020, 14:37

I did notice that the handles on the model in the manual do not look like mine but the rest of the stove is basically the same from what I can tell. My handles are solid aluminum.

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JAU
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Re: exhaust temperature

Beitrag von JAU » 17. Nov 2020, 15:12

dgoodyear hat geschrieben:
17. Nov 2020, 14:35
sorry i can not figure out how to upload an image...
viewtopic.php?f=5&t=30#p252
dgoodyear hat geschrieben:
17. Nov 2020, 14:35
My model has vertical ribs only. There is no horizontal heat exchanger as in the older models.
Actually it has, but without smoke channels in it.
dgoodyear hat geschrieben:
17. Nov 2020, 14:35
Vanes slip in between the exchanger which increase resistance to flue gas draft.
They are adjustable, is the knob on the outside all the way down?
There should be another sheet inside. Is it present and still straight?

If everything seems ok, your chimney could be to powerful.
A user with an older model had the same problem (200°C). You might take a look at his solution: viewtopic.php?f=6&t=134&start=10#p1372

dgoodyear hat geschrieben:
17. Nov 2020, 14:35
I usually bring the tank up to a uniform 70 C + in about 3 hours
Volume 600l? Sounds quite right.


greetings JAU

dgoodyear
Beiträge: 5
Registriert: 17. Nov 2020, 12:38
Re: exhaust temperature

Beitrag von dgoodyear » 17. Nov 2020, 15:22

Right, I see what you are saying, the top of the heat exchanger is flat.

yes they are adjustable, and the knob is currently all the way down which I assume is maximum resistance to the draft.

the sheet has two metal posts, it is placed exactly according to the manual and straight.

the volume is 1000l. the loading is about 3 hours or so but the pump stays on for a while longer until the stove cools down, so maybe 5 hours total.

Thanks ill definitely have a look at that link, it may be helpful.


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