New Caddy Advanced owner

[brenndatomu]

Hopefully this works.

View attachment 334140

Not much to see I guess. You can see the flashing green light. Flames don't really look out of control, which I think makes sense because the air controls fully close. But the glass is loading with soot and there is a smokey smell. Draft is on the high end at 0.06-0.07" but not horrible.

From what I read in the manual, in "overtemp" it either kicks the blower to normal speed (if firebox is at max temperature) or blower to max speed (if plenum is at max temperature). It seems like blower is still in normal speed.

I can get a more detailed video, when it does it again. My wife just informed me that it did it again about an hour after loading it last night. I went to bed but she was up and saw it. She said that it exhibited the same characteristics.

Getting the draft down to -0.04" would help cool things down for sure. If the Caddy is the same as the Heat Commander you have a TC in the LR upper corner of the firebox, and one right above it, but above the rear baffle...which speaking of, I wonder if the baffle(s) could be out of place and the upper TC is being exposed to direct flame? The baffles should be centered and pushed clear back (again, assuming its the same as the HC)
I know they had some early HC's that had the TC's wired backwards, and that caused some major issues, but yours is basically working, so thats not what you have going on here.

 

[LogCabinFever]

Getting the draft down to -0.04" would help cool things down for sure. If the Caddy is the same as the Heat Commander you have a TC in the LR upper corner of the firebox, and one right above it, but above the rear baffle...which speaking of, I wonder if the baffle(s) could be out of place and the upper TC is being exposed to direct flame? The baffles should be centered and pushed clear back (again, assuming its the same as the HC)
I know they had some early HC's that had the TC's wired backwards, and that caused some major issues, but yours is basically working, so thats not what you have going on here.

I’ll look and see. I tried calling technical support today but it seems the offices are closed. I’ll try again tomorrow.

Also, when you say -0.04”, do you mean below zero? I thought I measure it between 0.04” and 0.06”. My gauge only goes to -0.05”. Unless it’ll read the opposite since high and low are swapped?

 

[brenndatomu]

I’ll look and see. I tried calling technical support today but it seems the offices are closed. I’ll try again tomorrow.

Also, when you say -0.04”, do you mean below zero? I thought I measure it between 0.04” and 0.06”. My gauge only goes to -0.05”. Unless it’ll read the opposite since high and low are swapped?

You are doing it correctly...we use the right side of the gauge because of its greater range, but yes, it is reading the negative pressure of the chimney.

 

[Citationls]

Most likely unrelated to your overtemp problem but how did you measure your static pressure? You should be measuring the difference in pressure between the filter and the blower motor, and the plenum itself. If you are only measuring the difference between the plenum and atmospheric pressure, you will have a lower reading.
Only reason I mention this is because if you measured correctly and your static pressure is .13 your blower may be moving too much air. Heat commander manual states static pressure should be at least .2. Not sure if your model has a spec. I believe moving more air means less time for the air to heat up, causing lower air temps at the registers. Higher blower speed also means more power consumption.
Aside from that, if your flue draft is under .06, your gaskets are all sealing properly, and your temp readings are in range, i would thing the thermostat inside the stove would be your issue as someone else already mentioned. Unless there is an issue with the control board. I only have magnetic thermometers (which aren't the most accurate) but mine are positioned on the burn tube access door and read as low as 150f when the furnace is idling with coals. During the active burn cycle they read as high as 300f.

 

[LogCabinFever]

Most likely unrelated to your overtemp problem but how did you measure your static pressure? You should be measuring the difference in pressure between the filter and the blower motor, and the plenum itself. If you are only measuring the difference between the plenum and atmospheric pressure, you will have a lower reading.
Only reason I mention this is because if you measured correctly and your static pressure is .13 your blower may be moving too much air. Heat commander manual states static pressure should be at least .2. Not sure if your model has a spec. I believe moving more air means less time for the air to heat up, causing lower air temps at the registers. Higher blower speed also means more power consumption.
Aside from that, if your flue draft is under .06, your gaskets are all sealing properly, and your temp readings are in range, i would thing the thermostat inside the stove would be your issue as someone else already mentioned. Unless there is an issue with the control board. I only have magnetic thermometers (which aren't the most accurate) but mine are positioned on the burn tube access door and read as low as 150f when the furnace is idling with coals. During the active burn cycle they read as high as 300f.

So I measured between blower and atmosphere, which is probably incorrect. I didn’t run the furnace today since it’s been mild in CT, but I’ll check tomorrow. Manual says between 0.2” and 0.5”. But the filter says to replace it if it gets to 0.5”.

I have two ports. As shown in the attached photo, one is in the blower housing, and the other is just on the other side of the filter. If I checked it between those two ports that would measure the pressure differential before, and after the filter, correct? You mention putting a port in the Plenum, but I thought static pressure was always measured on the return line, unless I’m not correct about that?

Find it hard to believe that I’m moving too much air. There’s not much pressure coming out of the supply registers, particularly at the opposite end of the house about 30 feet away from the furnace. The supply duct measures 8”x16” with I think 8 - 6” branches coming off of that. I also don’t step down in trunk size like I should. So that might be part of the issue.


So I got around to installing the barometric damper. My draft is now pretty steady 0.04” to 0.05”. The furnace seems to like it better. I’ve only run it once with the barometric damper, but I did not go into overtemp mode. Might be a fluke, but I’ll run in a couple more times.

Having trouble getting a hold of SBI. They must be on vacation the whole week of Christmas and the whole week of New Year’s.

 

[LogCabinFever]

So I got around to measuring my pressure in the duct. High end of mano line on supply plenum and low end of mano line at blower housing. If I'm correct, my total static pressure is just over 1.3" w.c. That's not a typo. Seems like I'm choking the furnace.

Did some measuring and some calcs:

Return duct:
8"x12" + 8" round + 12" round = 259 sq in

Supply duct:
8"x16" = 128 sq in
ductwork guy added a supply to the basement but it comes off of the trunk so it doesn't seem like that helps. In the end, it reduces to a 8x16 at the supply plenum

So I have half as much supply as I do return. I wonder if the ductwork guy miscalculated. Maybe that's why I'm not getting much pressure from the vents at the far end of the home.

SBI got back to me and said that the loudness may be because of restrictive duct. I've been getting this sharp whistling, so I wonder if that's it.

Back to the drawing board. May have to call the duct guy back.

 

[brenndatomu]

One thing I noticed is that bigger filter you added is MERV 11...the one that came with the Caddy is more like 4...that adds restriction to flow too.
But yeah, (1) 8x16" duct is way too small, even on the Heat Commander minimum supply is something like 180 sq inches...and then general rule of thumb is the return should be 10% larger than supply

 

[LogCabinFever]

One thing I noticed is that bigger filter you added is MERV 11...the one that came with the Caddy is more like 4...that adds restriction to flow too.
But yeah, (1) 8x16" duct is way too small, even on the Heat Commander minimum supply is something like 180 sq inches...and then general rule of thumb is the return should be 10% larger than supply

I checked into the filter and actually the stock filter is more restrictive, believe it or not. The stock filter is a Maxi-Pleat 610 Merv 8 14x25x1, and according to the charts adds a bit above 0.22" wc as opposed to the 16x25x4 Merv 11 I put in which added roughly 0.16" wc

Pleated Filters

filtrationlab.com

That was one thing I was initially worried about, but I think the added surface area of the filter reduces the resistance. Seems like my main issue is supply.

Now I need to figure out what to do. I don't have much room to increase the trunk line size. I'd really hate to replace 30 ft of supply trunk line and rehook up everything. I wonder if I could leave it as is and then when we do the addition, more supply trunk line will go out in the opposite direction. The furnace would be at the stem of the T section. I could just increase size of the T stem portion. Think that excessive static pressure will be bad for the furnace/blower over a period of 2-3 yrs?

 

[brenndatomu]

Restriction actually puts less load on the blower, the only thing that really matters is the duct temp and if it is able to keep the furnace from getting too hot...well, that and how it heats the house.

 

[LogCabinFever]

Restriction actually puts less load on the blower, the only thing that really matters is the duct temp and if it is able to keep the furnace from getting too hot...well, that and how it heats the house.

That’s good to know I’m not putting stress on the system. But yes, I’d like to be able to effectively Heat the house. I guess there’s no sense in increasing blower speed to get more pressure at the vents since air velocity relates to static pressure. That would only make it worse. Might have to swap out the trunk line

 

[brenndatomu]

Any centrifugal pump (a furnace blower is just an air pump) will pull less amps when restricted, because it's doing less work. (moving less material)

 

[salecker]

I checked into the filter and actually the stock filter is more restrictive, believe it or not. The stock filter is a Maxi-Pleat 610 Merv 8 14x25x1, and according to the charts adds a bit above 0.22" wc as opposed to the 16x25x4 Merv 11 I put in which added roughly 0.16" wc

Pleated Filters

filtrationlab.com

That was one thing I was initially worried about, but I think the added surface area of the filter reduces the resistance. Seems like my main issue is supply.

Now I need to figure out what to do. I don't have much room to increase the trunk line size. I'd really hate to replace 30 ft of supply trunk line and rehook up everything. I wonder if I could leave it as is and then when we do the addition, more supply trunk line will go out in the opposite direction. The furnace would be at the stem of the T section. I could just increase size of the T stem portion. Think that excessive static pressure will be bad for the furnace/blower over a period of 2-3 yrs?

Can you parallel the trunk with some round pipe ?

 

[Citationls]

Thats great that the baro helped! Looks like you measured static pressure right, that's nice that they give you test ports to measure with. I looked in the Caddy Advance manual and that looks to be the same, or at least similar, to the blower on the Heat Commander. Assuming everything is the same, you should have between 170 and 280 square inches of surface area of duct work coming off the supply plenum. I didn't need return ducts for my setup so I'm not sure about sizing for those.
How big will your addition be? If it will be adding over 1/3 of the size to your current house, you would need another 42 square inches of supply duct to heat the addition evenly. That would bring your total supply duct area to 170 square inches which would be within spec for that blower. In that case you could increase your supply plenum size for the first few feet until you reach the T where your existing ductwork goes one way and new ductwork for the addition splits off in the other direction. This is rough numbers and making quite a few assumptions but figured I'd throw it out there.

 

[LogCabinFever]

Can you parallel the trunk with some round pipe ?

Can't parallel any duct. The paired return and supply ducts are sandwiched between the chimney foundation on one side and the main carrying beam on the other. However, because there is a 8x12 return that runs vertical and a 8x16 supply that is horizontal, there is some room to expand the supply so that the bottom of it meets the bottom of the return, not sacrificing any headroom (see photo). This would make my supply trunk 12x16 = 192 sq in.

However, that still involves swapping out ~30ft of supply trunk line. Not my idea of a good time. Also, what would that do once I add the addition? Now I'd perhaps have too much return...?

Thats great that the baro helped! Looks like you measured static pressure right, that's nice that they give you test ports to measure with. I looked in the Caddy Advance manual and that looks to be the same, or at least similar, to the blower on the Heat Commander. Assuming everything is the same, you should have between 170 and 280 square inches of surface area of duct work coming off the supply plenum. I didn't need return ducts for my setup so I'm not sure about sizing for those.
How big will your addition be? If it will be adding over 1/3 of the size to your current house, you would need another 42 square inches of supply duct to heat the addition evenly. That would bring your total supply duct area to 170 square inches which would be within spec for that blower. In that case you could increase your supply plenum size for the first few feet until you reach the T where your existing ductwork goes one way and new ductwork for the addition splits off in the other direction. This is rough numbers and making quite a few assumptions but figured I'd throw it out there.

I like your thinking. The addition will be about 480 sqft of normal heated space, plus potentially 480sqft of heated basement. Not sure about the basement yet though. but that would add close to 1000sqft if we include the basement. So I could potentially remedy the situation when the addition comes, but I'd like to remedy it temporarily since the addition is 2-3yrs out.

If I increase the trunkline now, then add the addition, would I have too much supply at that point? I just don't want to get into a situation of having to add that much more return. There's only so much room in the furnace area.

I'm also considering this:

Really crude sketch, but basically coming right off the left side of the plenum with a round duct to make an upper supply register in the basement. The original 8x16 exits out of the rear of the plenum. The contractor added a supply line but it was like 15' down the trunk line, which doesn't seem to contribute to that SQ IN requirement. Would this work to open it up a bit, and get some air velocity going into the 8x16 line? This would be far cheaper than replacing the trunkline, I just don't know if it would accomplish the same thing.

The only potential issue is that this would put a top supply register within only 5-6ft of a bottom return register. Would that be too close?

 

[brenndatomu]

Really crude sketch, but basically coming right off the left side of the plenum with a round duct to make an upper supply register in the basement. The original 8x16 exits out of the rear of the plenum. The contractor added a supply line but it was like 15' down the trunk line, which doesn't seem to contribute to that SQ IN requirement. Would this work to open it up a bit, and get some air velocity going into the 8x16 line?

That would increase flow through the furnace, but not help you get more heat to the house (other than the basement)
What's right above that area? Can you put in a floor register right above your proposed 8" duct? That would help your situation...

 

[Citationls]

Looking back at your previous posts, you said you weren't impressed with the caddys ability to heat your 1600sq ft house in CT. I also live in CT and my heat commander is certainly overkill for the 1600ish sq ft of my house that I heat. You also said it doesn't seem like much air is coming out of the farthest vent. I would think even with the reduced duct sizing, the caddy should be able to heat your house pretty effortlessly. This is assuming it puts out similar heat to the heat commander. I normally have 190sq in of ductwork coming off my supply plenum. Static pressure is usually .3ish. I just reduced supply area to 110sq in and static pressure increased to .7ish. The air coming out of the supply registers that werent blocked off was enough to fly a kite over (Not really but it was a lot). If you have static pressure of over 1iwc with 128sq in of supply duct at the plenum and your filter isn't restrictive I would assume you have lots of bends in your supply and/or return. That would most likely be the reason for your lack of air flow. Considering you said the pressure in your supply plenum was .13iwc more than atmospheric pressure that would mean you would have -1.0iwc on your return side. That seems excessive to me. Can you easily disconnect your return plenum to see if supply side airflow drastically increases? Someone feel free to correct me if I'm wrong.

 

[LogCabinFever]

That would increase flow through the furnace, but not help you get more heat to the house (other than the basement)
What's right above that area? Can you put in a floor register right above your proposed 8" duct? That would help your situation...

If I put a floor register right above the proposed duct, it would land in the middle of the floor upstairs and within like 6' of a 12x12 return floor register. I guess my thought is that I need to bleed off some pressure from the supply plenum so air can flow more freely through the 8x16 supply trunk, but perhaps it doesn't work like that.

Looking back at your previous posts, you said you weren't impressed with the caddys ability to heat your 1600sq ft house in CT. I also live in CT and my heat commander is certainly overkill for the 1600ish sq ft of my house that I heat. You also said it doesn't seem like much air is coming out of the farthest vent. I would think even with the reduced duct sizing, the caddy should be able to heat your house pretty effortlessly. This is assuming it puts out similar heat to the heat commander. I normally have 190sq in of ductwork coming off my supply plenum. Static pressure is usually .3ish. I just reduced supply area to 110sq in and static pressure increased to .7ish. The air coming out of the supply registers that werent blocked off was enough to fly a kite over (Not really but it was a lot). If you have static pressure of over 1iwc with 128sq in of supply duct at the plenum and your filter isn't restrictive I would assume you have lots of bends in your supply and/or return. That would most likely be the reason for your lack of air flow. Considering you said the pressure in your supply plenum was .13iwc more than atmospheric pressure that would mean you would have -1.0iwc on your return side. That seems excessive to me. Can you easily disconnect your return plenum to see if supply side airflow drastically increases? Someone feel free to correct me if I'm wrong.

It's the opposite. the return side is showing -.13 and the supply is over 1.0, which makes sense, given the sizing of ductwork for each.

In looking at some of my supply branches, I don't see too many bends. The one at the opposite end of the house is the worst with bends totaling 360 degrees and a branch length of maybe 20 ft. I think it's 6" pipe but I'll measure it. I don't know what's normal but that doesn't seem too bad to me. It is definitely true that the closer branches with minimal bends have the greatest pressure, but I would still say it's not great pressure. If I put a piece of paper over the vent with the highest pressure, I doubt it would move much.

I guess my thought is this: I think of air as a fluid going through ductwork. Like a funnel, if the funnel narrows too much then it just doesn't flow well. I see the supply plenum as the opening of the funnel and the trunkline as the narrowing of it. If I punch a hole in the opening of the funnel for some of the fluid to escape (bleed off), wouldn't that enable the fluid to go through the narrowing a bit easier? Perhaps my analogy is incorrect though.

 

[brenndatomu]

I guess my thought is this: I think of air as a fluid going through ductwork. Like a funnel, if the funnel narrows too much then it just doesn't flow well. I see the supply plenum as the opening of the funnel and the trunkline as the narrowing of it. If I punch a hole in the opening of the funnel for some of the fluid to escape (bleed off), wouldn't that enable the fluid to go through the narrowing a bit easier? Perhaps my analogy is incorrect though.

That would not "enable the fluid to go through the narrowing a bit easier" but it would allow more flow through the furnace, therefore more BTU's can be stripped away. which will heat the house better, IF, you can put the air/heat in the right spot...dumping it into the basement wouldnt do much, other than make warmer floors maybe.
Bottom line is you need to upsize that trunk restriction. or partially bypass it somehow.

 

[Citationls]

Like brenddatomu is saying, giving the air a place to go outside of the funnel only let's more fluid flow out of the funnel into the wrong spot. You would be moving more fluid but to the wrong places. It won't effect the output at the end of the funnel. For ductwork, if the "hole" is upstream of the branch takeoffs you would actually be decreasing the pressure in the system, resulting in less air being forced down your existing takeoffs. Ive attached a picture of a duct sizing chart (I hope). If you have 8 6" ducts going to your register, each duct can flow 85cfm. Since you have 8, you would need a total of at least 650cfm at the start of your trunk line. This is without including friction loss due to air moving down the ductwork and around bends. Your 8x16 trunk line can only flow 580cfm. You need a trunk line more like 8×20 or 10x16. You're better off having it be too big than too small in the beginning. There is more to calculating the correct size ductwork than using this chart but it will get you ballpark where you need to be.