Everything Drolet Tundra - Heatmax...

[brenndatomu]

Here is a picture of the video. This is back side of burn no strong flames, no more nice secondary burn going on. Mostly logs are about to brake up in larger coal chunks. The second picture of the top ( see red dot in middle ) is to show where i took the temp reading. Its 130*-135*.
View attachment 170828 View attachment 170829

I'm not quite as far along in the burn as you and I can only get 110* at the most reading in that same spot. Now I can get 130-140* reading around the front of the front duct connector, which is why I have that duct wide open and the back two throttled to .2 SP. Even with the top reading 130-140 around the connector, I still only have 110* internal duct air temps. If I throttle the front duct to .2, internal air temp goes up a bit, but CFM to the house drops and overall heat output drops.
Right now I am leaning toward making a whole new top for the furnace to put a plenum onto. I will bias the opening toward the front of the furnace since that is where the higher temps are.

 

[Builderml]

This morning I took readings around the two duct collars, the left side I was getting 170* around the right side I was 150+ and the front block off plate that you are now using I was at 200*.

 

[brenndatomu]

This morning I took readings around the two duct collars, the left side I was getting 170* around the right side I was 150+ and the front block off plate that you are now using I was at 200*.

This was damper closed on "cruise"? The only way I'd ever see (and probably not even then) would be a fresh load, damper open and flue temps soaring, basically running WOT

 

[laynes69]

Using the factory openings on the Tundra per spec, the 2-8" outlets are about 100 square inches. The Caddy however has a plenum opening of approximately 24" x 29" with almost 700 square inches. Factor in a take off of 8x20 or greater and a much higher volume of heat can be removed from the firebox. I think the false ceiling has to do with the potential hot spots from the lack of flow. If a thin layer of soot can slow the transfer of heat, a thin piece of steel can do it too. You can see in brenns pic of the firebox top, the extra piece up top is white, while the exposed top was darker. I doubt the Caddy had the false top.

 

[Builderml]

This was damper closed on "cruise"? The only way I'd ever see (and probably not even then) would be a fresh load, damper open and flue temps soaring, basically running WOT

The damper was closed at that point with real heavy secondary burns going on. I just don't know how long the damper had been closed to be honest my wife was the one that loaded it. That also was not a full load if wood.
Also Brenn, I notice I get the best heat out of the Tundra when my stack temp is at about 200* located about 30" above the T. That is surface temp via magnetic stove pipe thermometer.

 

[brenndatomu]

Using the factory openings on the Tundra per spec, the 2-8" outlets are about 100 square inches. The Caddy however has a plenum opening of approximately 24" x 29" with almost 700 square inches. Factor in a take off of 8x20 or greater and a much higher volume of heat can be removed from the firebox

I was originally gonna just plop a plenum on 'er and open the existing holes up. But now I have been debating if I want to go with a 24 x 24 hole, or a triangle shaped hole. The base of the triangle would be at the front of the furnace and the top (or tip) of the triangle would be toward the back in the center. My thinking is that would expose the most surface area in the place where the most heat seems to be. Also it would prevent airflow from the blower from short circuiting, never getting to the front, or not passing over the top of the firebox itself. The more I think about the triangle, the more I like it. That would give me 288" of area open, VS 151 that I am running right now

 

[laynes69]

Those 2 exchanger tubes will be at their hottest at the rear of the firebox. Where they combine up front, they will start to lose heat. I know the placement of the limit control is critical, due to the different paths of air thru the top of the furnace. A nice large plenum will allow for the mixing before it exits. The limit/control is located at the rear of the firebox where the heat exchanger attaches to the firebox.

 

[sloeffle]

Just tried loading a short video about 4 secs. and it said file to large.

It is best to upload the video to YouTube and then post a link here.

 

[brenndatomu]

Those 2 exchanger tubes will be at their hottest at the rear of the firebox. Where they combine up front, they will start to lose heat.

I hear ya, thats what I was thinkin too, but the hottest places on the top are at the front by far

 

[lexybird]

I like laynes idea of a bigger area and a large plenum for " mixing" to even things out and prevent the hotspots your getting . I would rather have good hot air ..then weaker air temps with high pressure

 

[Builderml]

OK guys I need help. Finally getting around to checking static pressure. So I have my piece of brake line bent at a 90deg angle , now do I point the tip down into the airstream so that the air blows into the tube? Or do I point the tip up so that the air passing acts as suction pulling? Or do I just place the tip so it is just inside the duct surface flush with the duct wall? I can tell you I don't have .2 static pressure any way I do it. Maybe why this thing is heating so well.lol

 

[maple1]

Think you want it stuck in so the air stream is crossing over the tip. Not blowing in or away.

 

[Builderml]

Sorry for the long post but i figured this might help some people. Pretty cut and dry.

Static Pressure Testing, Step By Step
It typically should take less than five minutes to measure a system’s static pressure. Here are sample instructions for a furnace and a remote coil:

STEP 1: Locate the appropriate places to drill the test holes on the supply side (+) between the furnace and the coil, and on the return side (-) between the filter and the furnace. Center the holes for neat appearance. Stay away from any coils, cap tubes, condensate pans, or circuit boards to avoid damage. Always look before you drill.

STEP 2: Drill test holes using a 3/8-in. drill bit with a metal piercing tip. A bullet tip drill makes a clean round hole. Make sure to use your drill bit sheath (Described above) to prevent from drilling into the coil. If there’s duct liner inside, be sure to penetrate it to assure a good reading.

STEP 3: Push one end of the tubing onto the static pressure tip. Place the other end of the hose on the HIGH (+) pressure port of the gauge. If required, make sure the gauge is level and zero the gauge by adjusting the screw on the face with the small screwdriver. (Digital gauges each zero differently, so check owner’s manual.)

STEP 4: Read the supply or positive (+) static pressure by inserting the static pressure tip in the test hole into the air stream with the tip facing into the airflow. The magnet on the tip will hold it in place while the value is read and recorded. This measurement is the pressure the fan is "seeing" on the supply side of the system.

STEP 5: Read the return or negative (-) static pressure by moving the tube from the HIGH to the LOW-pressure port on the gauge. Insert the static pressure tip in the test hole on the return side with the tip facing the airflow. Read and record the negative static pressure. Don’t forget to insert hole plugs in the test holes when you’re done testing.

STEP 6: Calculate the system’s Total External Static Pressure by adding the two values. Since the negative and positive signs identify the type of pressure measured, you can ignore them when adding the two values together.

For example:
The supply static pressure reading is (+) .26 w.c.
The return static pressure reading is (-) .21” w.c.
The total system static pressure is .47” w.c.

.26” + .21” = .47” w.c.

 

[Builderml]

Here is what i came up with. SBI really only cares what the static pressure is for the furnace only. So with that in mind i drilled 1 hole in each 8" duct about 4" up from the furnace, (see picture the larger hex head was my test spot) i took my test tip "( brake line bent 90*) and pointed it down towards the furnace. Which from the reading above they call it "supply static pressure" i come up with .25-.27 for both ducts. I did bump up my fan speed to #3 just prior to testing. The whole time before today i was on factory setting #2. While the supply static pressure may be a little high i don't think that it will hurt the furnace, help run cooler if anything. Let me know if you think i am wrong. But with testing this way it tells me what the air that is moving across the furnace is which is what i think SBI really cares about. All the other testing will tell you static pressure in ductwork, which i don't think sbi cares about, also pressures that the fan is seeing.

Edit- well after doing some more searching looks like I need to get an a-303 static pressure tip, doesn't look like my redneck brakeline is the way to go. Once I get the tip I should be able to get accurate readings

 

[Highbeam]

While the supply static pressure may be a little high i don't think that it will hurt the furnace, help run cooler if anything. Let me know if you think i am wrong.

Seems to me that higher pressure means that less air is moving. For instance, if you plug up the ducts your pressure will build high. A low duct pressure reading means that the fan is able to move more air and more air means more cooling of the furnace which means more heat to your home.

 

[Builderml]

I will say that bumping up the fan speed the furnace seems to cycle more now that I am in the coal stage of the burn. Might make it harder for me to bounce off the high limit.

 

[Builderml]

Seems to me that higher pressure means that less air is moving. For instance, if you plug up the ducts your pressure will build high. A low duct pressure reading means that the fan is able to move more air and more air means more cooling of the furnace which means more heat to your home.

Not so sure about that, I am noticing that it is cycling more during coal stage telling me that it is cooling the furnace off faster. I should have taken a reading prior to bumping up fan speed, maybe I will in the near future. The cooling off may just be due to the 200 cfm increase and not so much the static pressure change if I did in fact change the static pressure.

 

[Highbeam]

Not so sure about that, I am noticing that it is cycling more during coal stage telling me that it is cooling the furnace off faster. I should have taken a reading prior to bumping up fan speed, maybe I will in the near future. The cooling off may just be due to the 200 cfm increase and not so much the static pressure change if I did in fact change the static pressure.

Yes, you're talking about two things. Low static vs. high static and then low speed blower vs. a high speed blower.

 

[brenndatomu]

Think you want it stuck in so the air stream is crossing over the tip. Not blowing in or away.

That is my understanding too. Tip of the sample tube 90* to the airflow (or duct) , could be wrong though?

i took my test tip "( brake line bent 90*) and pointed it down towards the furnace.

? So it was facing down, into the airflow? Doesn't sound right to me. You will have higher (false) pressure readings doing this I believe.

For example:
The supply static pressure reading is (+) .26 w.c.
The return static pressure reading is (-) .21” w.c.
The total system static pressure is .47” w.c.

.26” + .21” = .47” w.c.

So are we supposed to be setting the Total SP, or just the supply SP? Did you just drill a hole in the blower box to take the Return SP reading?
If SBI is calling for total SP, then we should be shooting for +.1 SSPR and -.1 RSPR? If that is the case then I have my SSP too high (.2). Haven't checked the RSP...
And the return static pressure would change according to how dirty your filter is at the moment, so do you set it based on a clean filter...a little dirty...a lot dirty?

 

[DoubleB]

I don't remember if it was this thread or another, but when this static pressure thing has come up before, it seems that the 0.2" is just for the supply side only. A few reasons this appears to be the case:

-The manual only talks about supply static pressure, and makes no mention of differential between supply and return. The manual suggests the reason for 0.2" SP is even air distribution amongst the hot air registers. This seems to be somewhat of a rule of thumb for a lot of HVAC equipment, but someone more qualified than I can comment on that.

-My unit came with a pleated filter. On a fan speed of 1 (low), I had -0.07" pressure in my return plenum, 0.37" pressure drop through the filter, and 0.07" static pressure in my supply plenum. I didn't even bother cranking up the fan speed for that purpose. If the pressure drop through the OEM filter is 5x my supply plenum SP, then the purpose of 0.2" SP has little to do with limiting the amount of pressure drop the blower has to overcome.

-I think the blower is rated for far more than 0.2" SP, again suggesting the manual guidance is more about even air distribution through the supply registers.

All that said I'd much prefer a spec for the total pressure drop against the blower, since that is what determines how much air the blower is pushing to cool the furnace.

 

[Builderml]

I think you guys are correct about the fact I shouldn't be pointing the brake line tip down into the air flow but that's the only way I could get up to .2 static pressure. Will allow me to sleep better at night.
Joking aside you think sbi could clearly state what static pressure they are talking about after all these are marketed to diy's.
Once I get the actual static pressure tip for my manometer at that point I'll worry about it until then its getting down close to zero tonight so I'll have fun feeding the tundra to see if she can handle it.

 

[Builderml]

Brenn, I did not take a reading on the return side. I only worked in the supply side.
I agree with DoubleB I think they are referring to the supply side static pressure but I guess we really don't know.

 

[brenndatomu]

Brenn, I did not take a reading on the return side. I only worked in the supply side.
I agree with DoubleB I think they are referring to the supply side static pressure but I guess we really don't know.

Well, you got my wheels turning anyways...I checked the static pressure on my blower cabinet...it was -.3" so I slide a new filter in, it dropped SP to -.15". Surprised me because the filter doesn't look that dirty

 

[DoubleB]

I'm less interested in supply static pressure, and more interested in total airflow. But it's hard to compare our systems since our ductwork layouts are so different. A suitable comparison might be blower power.

Who has a kill-a-watt or similar? How many Watts and/or amps are you pulling (damper closed)? And what fan speed are you on?

When I was on fan speed 1, I drew about 200 Watts.
When I am on fan speed 2, I draw about 220 Watts.

+/- 5 Watts for filter condition, voltage variation, etc.

I seem to get adequate airflow. My air discharge temps are about 115-125F cruising with the damper closed, depending upon the point in the burn cycle.

 

[brenndatomu]

When I was on fan speed 1, I drew about 200 Watts.
When I am on fan speed 2, I draw about 220 Watts.

+/- 5 Watts for filter condition, voltage variation, etc.

Yeah, I was gonna say...depends if you voltage is 110 or 125...

My air discharge temps are about 115-125F cruising with the damper closed, depending upon the point in the burn cycle.

Discharge temps at the register? Impressive...I'd roast outta here if I could pull those temps off