Installig New Garn Controller

[bpirger]

Finally going to setup the new Garn controller. A few questions....

1. I assume my AC ground wire should go to the GROUND lug on the controller? Oddly enough, the little "manual" doesn't state this, nor that the power connection is under the black plastic shield. Obvious, I agree, but still....suprised.

2. Steve (heaterman) you mentioned in the past that Dectra was putting the temp sensor on the LWCO (low water cut off) shaft. Was that decision dropped? I have the LWCO I received with the Garn, and in the little manual, the sensor is placed in the well in the front of the unit. Now, my manual also says "backordered" digital units....so could it be that there is a different version with new shipping units with the temp sensor on the LWCO, located in the middle of the tank? Harry, was your sensor mounted to the LWCO or in the front? Quite certain I remember you had to drain a bit to get the new well in the front panel....?


There is quite a large difference between the sensors on the front of the Garn and the actual water temperature leaving the Garn....as has been discussed before in a few threads. Having a sensor in the middle, somewhat submerged I assume, would presumably be more accurate. I don't really care, it is just a calibration thing....I know that the front sensor will read quite a bit higher temp than the actual water supply....at least a few hours after the burn unti it starts to drop. In other words, temps agree after firing for awhile well, and then the divergence begins for many hours, and then finally once it gets down to 120 or so, they are close. I'm sure this is stratification happening, after the burn settles, and then finally it cools enough to agree again.

So, the question really about the sensor, could I get more heat into the storage if the sensor was placed in the middle and down a bit? Of course, becuase the temp there presumably would be a bit lower since it is deeper in the water...though while burning, stratification has to be somewhat minimal I'd think. I've been trying to hit the 190 target on the front sensor.

 

[Kemer]

Hey Bruce
My sensor is in the front.You will see a difference in your front sensor and your supply and return sensors.To tell the truth I try to hit 190* on the front sensor and it seems to work fine for gauging my heating needs.I rarely look at the other temps.You are going to love the new controller for the auto shut down but watch your water level because of the LWCO.I had a burn shut down on me once and it wasn't pretty.I have a site glass that gives me a good idea of my water level although it changes with expansion of the water.I want to know your flue temps when you get it hooked up for comparison.
Harry

 

[bpirger]

Hi Harry:

My first burn with the new controller seemed to be flawless. It auto shut off and what's left in the Garn is a little bed of charcoal for the next fire....I'd say right where I'd shut it off. Very happy with that.

My flue temps, for the hour I watched, seemed to climb up to about 450-500. 500 was the hottest I saw. Why it wiggles around like it does is interesting. What do you typically see?

I didn't hook up the other sensors....and I also must admit I jumpered over the LWCO sensor for the moment. I just filled her up, so I'm not concerned, and I remember well your experience with it shutting off in a burn. I guess I'd think it might be better if it had a two stage warning....a warning, then a shut off. After it shuts down, the timer fur the burn remains. That is a nice feature. What I'd like to see also would be a max temperature the tank achieved on the last burn, but I guess I don't really need to know that, but it would be nice!

Now comes the "tale of two sensors". The tank temperature on the controller is sitting at 176. The sensor I have been using in my a419, which is what my "switchover" to oil would use, and that I have been looking at for a year, is at 193. The sensors are both in immersion wells in the front, all of 3" away from each other, and yet they read 17 degrees apart! The a419 sensor is encapsulated in a metal "bulb", potted right in there if I recall. Looks like the new Dectra sensor is a "bare" transistor package, likely the Dallas digital sensor...exposed in the bare package. I put it all the way in, stuffed the little blue grommet to seal the hole, and replaced the fiberglass insulation back over all the wells. So which one to believe? How hot do I go?

I know when I get to 200 say on the a419, and shut off the fan, I hear the "simmering" of the water. No steam, but there is a clear distinct sound. I guess I could fire until the Garn sensor says 190, the a419 would be at 205+ I assume, and see what happens....but I guess I need not really test that. I could place the Dectra sensor in some thermal goup, though I worry a bit about the packaging of the sensor...not potted in a bulb. But 17 degrees?

If I hook up at supply and returns they will give me some additional insight I guess. I did turn on some of my temperature sensors sporadically, in a temporary setup, and I did seem to get some decent agreement between sensors on the supply line and front panel, just after firing....so that makes me think the Dectra sensor is low.

It really is nice to not have to shut off the fan! After a few days I'm sure I'll even trust it. But it would be nice to know the temp the tank arrived at.....

On a curious note, it does look like Dectra has some considerable plans for the future when looking at the PCB. There's a number of relay's on there, remote monitoring labels, a setpoint temperature, etc. I'm surprised they might be considering a variable burn rate, as the efficiency would presumably be reduced. Maybe something to control the air flow to optimize the exhaust temp? I'd think if I'm reading 450-500 on the stack sensor, there's more heat that could be taken from the flu gas than on that last run.

 

[Kemer]

Hey Bruce
You flue temps are the same as mine.I keep a log and the highest I have seen was 565* but for the most part 450*- 500* is the norm.The faster you get to the high temps the less smoke.If
I get a good fire it will stop smoking in less then 5 min.but if I get a lazy fire in might take 15 min.It's amazing to watch the readout and try to match the speed the temps rise to the kind of wood you have and the way you pack it in. As far as the lwco sw.I might disconnect mine as long as I can see my water level through the site glass.I have my a419 sensor and my controller sensor in the same port and they read the same.From what garn told me the air controller thing will be a flap that shuts after a burn as to not let any heat out of the flue.In my case with a vertical chim I think it's a good feature.
Harry

 

[BHetrick10]

I like the flap Idea. I talked to Garn about this over a year ago saying this was an area for improvement. Who wants air to thermal siphon your heat out of your Garn. I was told the exhaust and intake both slop down to act as a heat trap to prevent this, well I got out my level and checked. There's no sloped at all. I wish they was. This would help act as a trap and let moisture drain out if you get condensation from having a fire started with low water temp.

Anyways I am installing a dampener in my intake to do this. They open and close slow though. I am going to run a timed delay relay off the blower circuit. It will open the dampener then kick on the blower. Simple equipment that the heating supply shop has that I have used before should work good I hope. I didnt run my Gan yet to find out the air velocity. If its really high I will probably put it in the exhaust so I dont have to worry about it getting sucked shut. Those little actuators are pretty tough though.

 

[RowCropRenegade]

What type of wood are you guys burning to get 500+ temps on flue temperature. I been burning mostly maple and ash this season and hover inbetween 350-400 pretty consistently.

Probably going to finish the season the way my unit is set up now. But I'm interested in your auto shutdown feature bpirger and the flap/dampner idea of yours BHetrick10.

Keep them Garns chugging boys!

 

[TCaldwell]

Usally after i clean the hx tubes, about once a month, I notice a substaintal flue temp drop. i use a knotted wire wheel with drill extensions and a drill. This method seems to work well. As to flue temps, 400 is about norm for high burn with mixed moisture content wood. with dry high density, like oak 500+ is not uncommon. About the combustion air flap, keep in mind if the power goes out during a burn, that you want the flap to stay open!

 

[heaterman]

I like the flap Idea. I talked to Garn about this over a year ago saying this was an area for improvement. Who wants air to thermal siphon your heat out of your Garn. I was told the exhaust and intake both slop down to act as a heat trap to prevent this, well I got out my level and checked. There's no sloped at all. I wish they was. This would help act as a trap and let moisture drain out if you get condensation from having a fire started with low water temp.

Anyways I am installing a dampener in my intake to do this. They open and close slow though. I am going to run a timed delay relay off the blower circuit. It will open the dampener then kick on the blower. Simple equipment that the heating supply shop has that I have used before should work good I hope. I didnt run my Gan yet to find out the air velocity. If its really high I will probably put it in the exhaust so I dont have to worry about it getting sucked shut. Those little actuators are pretty tough though.

Heat loss from the flue is really a minimal issue, if an issue at all from what I have seen. You can measure temperature at the exhaust but there is very little air flow to bleed heat from the storage. The downward slope Garn is referring to is not the hx tubes themselves but rather the fact that between the firebox and the first flue tube there is a 2' drop which does indeed act as a "trap". The flue is very neutral from a gravity heat flow standpoint.
I would be very cautious with the use of a damper. All it would take is one failure to open and you could have a mess on your hands. (unless one installed a proximity switch of some kind that kept the blower from running if it stayed closed.) The airflow through the Garn is about 375-400cfm so velocity has to be nearly 900-1000fpm if I'm doing the calculation right in my head. Been a very long day with about 800 miles under my belt so take those numbers with a grain of salt. My bed is calling me............

 

[bpirger]

RowCrop....my Garn is the 1500....do you have the 2000? I wonder if that introduces a difference in the flue temps. I was burning cherry primarily on that load, split and stacked by April 2011, so not the driest, but not wet either.

The auto shutdown is just the new Garn controller....no more timer to guess the burn length. Today I started a fire and walked away....burned for 2 hours and 40 minutes the display is telling me....this was with a firebox about 5/8 filled with 23" splits.

 

[jebatty]

The Garn 3200, with clean hx tubes, also runs in the 400's to 500 range in high burn, lower after that.

 

[Sawyer]

Hey Bruce
My sensor is in the front.You will see a difference in your front sensor and your supply and return sensors.To tell the truth I try to hit 190* on the front sensor and it seems to work fine for gauging my heating needs.I rarely look at the other temps.You are going to love the new controller for the auto shut down but watch your water level because of the LWCO.I had a burn shut down on me once and it wasn't pretty.I have a site glass that gives me a good idea of my water level although it changes with expansion of the water.I want to know your flue temps when you get it hooked up for comparison.
Harry

After finding my water level significantly lowered I also installed a sight tube. I filled the Garn and ran the water temperature up to approaching boiling while the excess came out of the overflow. On my next burn my supply temps were 185 degrees. I put water level marks on the tube at these and a few other temperatures lower. I now know when my water volume is receding and I would have to add water by the sight glass. In the last two months it has not dropped enough to be worth the bother.

 

[bpirger]

My assumption is that water can likely be added twice a year, assuming one burns all year, or so. Has anyone seen anything different? I would think that low water could result in a few issues:

1. Less storage capacity.
2. If it gets below the outfeed line, one could suck air into the plumbing, not good.
3. If it gets below the firechamber, then cooling of the steel could become a real issue...and this is certainly not good.


It seems one would have to boil off a lot of water to reach either #2 or #3, and while I'm sure it is possible, especially if firing to 200 all the time repeatedly or so, I'd think the loss is minimal. Next time I drain the beast, I think I should add a sight glass to the unused well on the front as well. For now I guess it is the occasional look inside the manhole. But to be honest, my guess would be the next time I do this is in May with the next water sample.

Does this sound inconsistent with anyone's finding? Do you find yourselves adding water more frequently?

 

[Kemer]

I had to add water two times this year.Ist. time I filled it to the recommended level at 140* as per Manual the marked my site glass. The trouble is with the different water temps the level changes.The odd thing is I get two different levels at the same temp.I think it has some thing to do with the shape of the garn.The higher you keep the water the more it expands and shows a different location on the site glass.So I adjusted my site glass so if I see water in it I know I'm in a safe range.Hope this makes sense

 

[BHetrick10]

Question for you guys with the site glasses. Are you constructing them out of white 1" pex? I seen it done somewhere with a fishing bobber in the pex to see the level.

Sorry for high jacking the thread. I only asked it in here because it keeps getting mentioned.

 

[DaBackBurner]

RowCrop... you may want to check the calibration on your flue thermometer if your getting abnormal temps. I was getting your temps at the beginning of this year and scratched my head for awhile thinking I had less than desirable wood, cfm, dirty hx tubes etc. The easiest thing to check always is the last for me...go figure. I finally decided to check my flue thermostat and found it was approx. 50-60 deg low which was verified with a new thermometer as well. I just boiled a pot of water to calibrate it...not the best method I'm sure but I wasn't looking for ultra precise. My high-burn is in the 450-500 deg range like last year now (It always was but my thermometer didn't indicate that).

 

[Sawyer]

Question for you guys with the site glasses. Are you constructing them out of white 1" pex? I seen it done somewhere with a fishing bobber in the pex to see the level.

Sorry for high jacking the thread. I only asked it in here because it keeps getting mentioned.

I used 3/4" Wirsbo Hepex. I used a pink floating ball for an indicator.

 

[Sawyer]

Next time I drain the beast, I think I should add a sight glass to the unused well on the front as well.

Bruce, I installed mine with a full tank. I was worried, put plastic sheeting on all the walls and dressed in a rain suit. I took off the cap of the nipple on the spare bung and with the VALVE OPEN there is not any pressure to spray and it was easy to start the valve threading and close the valve as soon as it started to thread. There was hardly a cup of water on the floor and I was ready to install the street elbow, pex fitting, and the tube.

 

[Kemer]

George
How long is your site glass? Mine is about 12".I added a shut off and had to try a few different nipples to get the right range for expansion.
Harry

Sorry I missed your other post.

 

[Sawyer]

George
How long is your site glass? Mine is about 12".I added a shut off and had to try a few different nipples to get the right range for expansion.
Harry Sorry I missed your other post.

Harry,
I just measured and my highest water mark (above the boil mark in the photo) is 16" above the bottom of the street elbow or nipple. This level was reached after I topped off my tank which was about 7"-8" low and then brought it up to boiling sounds and reading 205 degrees at the supply pump. After this time, and carrying a few buckets of water outside from the overflow tube, the near boil point is as indicated with Boil in the photo and is 2" below the previous mark or 14" above the bottom of the nipple/street elbow. I innitially ran the tube above the top as I had that for a piece of scrap.......guess it will never overflow!

my water level was down to leakage around my manhole cover for almost a year. I corrected it with 5/8" backer rod (suggested by Tom Caldwell) applied to the manhole ring which allowed a more flexible seal to accommodate an imperfect surface below the cover.

 

[bpirger]

Do you know where the LWCO sensor would kick "on" on your tube George? Is it 2" below the pink float, 3", etc?

 

[Sawyer]

I do not know Bruce, the bottom line is a 115 degree mark. If the water kept contracting and the temperature dropped to 40 degrees in the tank, I would assume the water level would drop at least an additional 2"-3" and these marks are with a newly filled tank. My garden hose ran for quite a while when I refilled this fall. When I looked in the tank to draw my water sample and inspect my anodes I was surprised how low the water was. I was worried the exposed steel above the water level would not receive the chemicals and I was not going to let that happen again. Garn said the chemicals will protect from the water vapors. Your question makes me wonder how much water loss Garn allowed for before the LWCO functions.