No heat from floor registers

[PeteK]

Recently used the furnace for the first time. It worked like a champ except I was getting no heat from the floor registers. The volume of air from vents mounted in the cabinets was great, no issues at all. I took the grill off under the fridge and did verify that all ductwork was connected to the furnace. I couldn't see anything wrong visually.

Can you get to floor ducts via the belly without taking the coroplast down? It's a rear kitchen so I'd have to get all they way to the rear. I am still under warranty, but really hesitant to take it tot he dealer as I want to use it this year.

May try to get a camera I can snake in there... Any other ideas?

Thanks

2021 29RKS

[chuckster57]

You won’t be able to get to the floor duct work without taking the coroplast down. Your furnace will have an opening that it sits on top of and you may want to check for heat loss at that gasket.

If your furnace is directly behind the return grill, take the grill off. Then turn the furnace on and feel around where the furnace rests for leaks.

[PeteK]

Originally Posted by chuckster57

You won’t be able to get to the floor duct work without taking the coroplast down. Your furnace will have an opening that it sits on top of and you may want to check for heat loss at that gasket.

If your furnace is directly behind the return grill, take the grill off. Then turn the furnace on and feel around where the furnace rests for leaks.

I had the grill off when it was running. Felt no unusual airflow. Could only get to 2ft or so of the flexible duct that went to the floor vents to feel for leaks.

Thanks.

[NH_Bulldog]

Pull a floor register off, remove two screws, lift the register and pull the tin boot up and check for a good connection to the duct.

Based on my experience, you will not get gale-force air flow out of any register especially if all of them are working correctly. I would be surprised if it could blow a candle out. If you are getting “great” flow from the cabinet vents, you are lucky.

Anyway, you can pull a register off, pull the boot up through the floor, release the band clamp the connects the duct, drop it back into the belly and then use a mirror/flashlight or a smartphone on video and shine it around down there and see if there is anything obvious. The ducts are just cheap mylar hoses that can get ripped, compressed, pinched, etc.

[PeteK]

Thats was going to be next. Thanks...

[jabba9]

Do you have gas and electric heat?

On my 2021 Alpine, the electric heat only vents from the ceiling and the gas heat only vents from the floor.

[chuckster57]

Originally Posted by jabba9

Do you have gas and electric heat?

On my 2021 Alpine, the electric heat only vents from the ceiling and the gas heat only vents from the floor.

OP states he using the furnace, so it would be gas heat.

[Life-in-Him]

Originally Posted by NH_Bulldog

Pull a floor register off, remove two screws, lift the register and pull the tin boot up and check for a good connection to the duct.

Based on my experience, you will not get gale-force air flow out of any register especially if all of them are working correctly. I would be surprised if it could blow a candle out. If you are getting “great” flow from the cabinet vents, you are lucky.

Anyway, you can pull a register off, pull the boot up through the floor, release the band clamp the connects the duct, drop it back into the belly and then use a mirror/flashlight or a smartphone on video and shine it around down there and see if there is anything obvious. The ducts are just cheap mylar hoses that can get ripped, compressed, pinched, etc.

Having similar issues as OP. Original airflow in bedroom (cougar 26rbswe) was ok. It moved the bottom of the bedspread.
But now, 36,000 miles later, a kleenex laying on the register won't move.
The hint of pulling the elbow out completely is great. I can run my boroscope down the duct & see what's going on.
I couldn't make the turn past the elbow before.
Thanks

[PeteK]

I think my issue is much closer to the furnace (rear of the 5'r). Like you, a Kleenex wouldn't move on any of the 3 floor vents. I haven't made it back over to storage yet to pull a register and see what if anything that reveals.

I'd be interested in what you find.

[Docedward]

I have a 2022 Cougar ½ Ton 29 MBS. It has three furnace wall vents that blow a hurricane as they are within 5 feet of furnace and two floor registers (like they married a 2015 model to a 2022) in the upstairs (bathroom and bedroom) and…not even warm and certainly no air movement. All the wood chips and metal screw shavings haven’t moved and inch.

[JRTJH]

Originally Posted by Docedward

I have a 2022 Cougar ½ Ton 29 MBS. It has three furnace wall vents that blow a hurricane as they are within 5 feet of furnace and two floor registers (like they married a 2015 model to a 2022) in the upstairs (bathroom and bedroom) and…not even warm and certainly no air movement. All the wood chips and metal screw shavings haven’t moved and inch.

My Cougar XLite 27RKS is the same. We have three heat vents in the bottom cabin that "blow hot air well"... Then we have the bathroom and bedroom floor vents that "won't lift a kleenex"...

Now, looking at the way Keystone built the HVAC ducting, it's easy to understand why it performs like it does...

First, there's a 4" mylar "dryer duct hose" that runs about 20' from the furnace (located under the refrigerator) forward, through the belly to the rear of the passthrough compartment. There it makes a vertical bend, is routed to a "metal duct run" that's screwed to the roof of the passthrough (which is the upper deck floor). That square aluminum duct is about 2" deep, 24" wide and 5' long. ALL the air supplied to that duct comes through that 4" round mylar dryer duct hose. I believe the intent is to use the radiant heat from that "big aluminum structure" to heat the passthrough. That's just my best guess as I can't prove the "engineer's intentions"...

Now, realistically, the volume of air movement through a 4" corrugated tube is going to be "virtually non-existant 20 feet from the source. Then add the "explosive expansion of 4" of air into a 48 square inch box that's 5' long... What comes out of those two 3x10 floor vents is, IMO, understandably "non-existant".....

I'm not suggesting that it's "the right way to design a HVAC system, rather my point is that it's "the expected outcome from what's installed in the trailer"... Right or wrong, it's what we have to deal with.

[Docedward]

I absolutely agree with your conclusion. And why I suggested that this seems like a 2015 married to a 2022 model is this comes with their amazing “Blade” technology for the AC flow in the ceiling and yet… the furnace flow is very much “un” engineered.

[JRTJH]

Trust me when I say that the "amazing blade technology" was a feature intended to reduce warranty repairs from collapsed ducting that was expensive to repair... A "side benefit was improved airflow" which was not the purpose of the engineering changes ... LOL

If it doesn't benefit Keystone, doesn't improve their profit margin or doesn't sell more trailers than JAYCO, their engineers aren't pushing for changes....

No heat in the upper part of a fifth wheel??? Not Keystone's problem until it starts to affect sales and profits. (unfortunate, but....)

[jasin1]

Originally Posted by JRTJH

My Cougar XLite 27RKS is the same. We have three heat vents in the bottom cabin that "blow hot air well"... Then we have the bathroom and bedroom floor vents that "won't lift a kleenex"...

Now, looking at the way Keystone built the HVAC ducting, it's easy to understand why it performs like it does...

First, there's a 4" mylar "dryer duct hose" that runs about 20' from the furnace (located under the refrigerator) forward, through the belly to the rear of the passthrough compartment. There it makes a vertical bend, is routed to a "metal duct run" that's screwed to the roof of the passthrough (which is the upper deck floor). That square aluminum duct is about 2" deep, 24" wide and 5' long. ALL the air supplied to that duct comes through that 4" round mylar dryer duct hose. I believe the intent is to use the radiant heat from that "big aluminum structure" to heat the passthrough. That's just my best guess as I can't prove the "engineer's intentions"...

Now, realistically, the volume of air movement through a 4" corrugated tube is going to be "virtually non-existant 20 feet from the source. Then add the "explosive expansion of 4" of air into a 48 square inch box that's 5' long... What comes out of those two 3x10 floor vents is, IMO, understandably "non-existant".....

I'm not suggesting that it's "the right way to design a HVAC system, rather my point is that it's "the expected outcome from what's installed in the trailer"... Right or wrong, it's what we have to deal with.

John looking at a picture of the typical rv furnace from bustinbeards insurance salvage job….why can’t you use one of the other unused taps for the furnace and run a second 4” flex duct to that aluminum 2”X24” duct

That may give you the added cfms to make up for friction loss in the long flex as well as for drop in velocity going from a small duct feeding a larger duct.

Or maybe have a 4”round to 6”round reducer/increaser right at the furnace and do away with the 4” flex altogether…get uninsulated 6” flex and tap that into the duct. The increased volume of the 6” may may up for the friction loss.

In a residential system at around .82 inch of static pressure …a 6”round pipe delivers around 100 cfm of air while a 4” pipe is around 35 cfm

Last option just add another separate floor register in the bedroom and block off the 3x10 floor register existing in the bedroom…that will allow more air to the bathroom while still allowing the duct to radiate heat for the pass through


You will lose some airflow from the back half of the trailer but it might balance it a little better…it’s like dividing a pizza up into slices…you can put more slices in the front or the back but it’s still the same size pizza your working with…just dividing it more evenly

Just a thought but you probably know better about the logistics of getting that done

[JRTJH]

jasin,

There are a few "workaround" solutions that would likely improve airflow. At the factory, running a double 4" dryer duct from an existing unused air tap is a good choice to "double the air input to the passthrough box"... Once the trailer is delivered to the owner, that solution means removing the coroplast from the entire belly, finding a 20' section of 4" ducting (or making one out of the shorter lengths found at Lowe's or HD), routing that new hose through the cramped belly to get it to the passthrough and then modifying that box to accept a second duct connector.

That is probably something few owners would be willing to do just to gain a little heat in the bedroom. I know our trailer is not that cold or uncomfortable. Since heat rises, just turning up the thermostat a degree or two has been enough to get sufficient heat in the bedroom/bath area, just from air movement in the cabin. In other words, the benefit doesn't outweigh the work to achieve improved air flow, at least for us.

The question then becomes, Why doesn't Keystone fix this "known issue"???

I can't speak for the company, but I'd suspect that Keystone has not encountered any evidence that "limited airflow in the bedroom" has been the cause of decreased sales, increased cost of warranty work. I'd also suspect that if they have "studied a modification to improve air flow" that the conclusion was probably that the increased cost of production changes does not improve the sales of trailers or annual profit statistics..

In other words, even if Keystone considered changes to improve airflow, they probably found that it wouldn't benefit their profit margin but would cost them money to make the production changes. In other words, it would cost more than they see in profit increases. So, as a business, it would mean a loss not a gain. So, likely it was "rejected" before ever getting approval, even for a test run.....

I'd suspect that for the average owner, as well as for Keystone executives, the cost to modify their current trailer, as frustrating as two static vents can be, the effort just doesn't outweigh the added gain of a little airflow... In other words, for most owners, it's just not worth ripping everything apart to fix something that's not going to be worth the effort.....

In our trailer, even in 25-30F temps, we have never been "cold in the bedroom or bath" after the trailer warms up. The only "wish" would be to have the increased airflow when we set up and during that hour we leave our coats on while the trailer is warming up. After warm, we haven't needed to make any adjustments to how we use the trailer or heat the upper deck. So, for us, an irritant, not a problem.

Bottom line, could Keystone fix this issue? Yes, the certainly could.
Will Keystone fix it? Probably not, at least not until it starts to affect their bottom line income, and that's not likely to happen in today's RV market where they simply can't build them fast enough for dealers to sell them.

[jasin1]

Yep I see your point. I actually like the bedroom a little colder then the rest of the house/rv….
Years ago i hear people would sleep with their window cracked open in the bedroom for better health

[JRTJH]

Our house in Denver had crank out windows. The two at the head of our bed were cracked open about an inch all winter. In mid-February, when got really, REALLY cold and we couldn't close the windows, they were usually frozen in place...

So, yeah, people used to sleep with the windows open for whatever reasons. Our reason was we needed to keep our daughter's bedroom warm enough but it was too hot for us. I don't think "hardiness or health" ever entered the picture, at least for us... LOL

After Denver, we were assigned to Bitburg, Germany. The apartment we lived in had heat controlled by a timer. It turned on at 6AM and turned off at 10PM. Trust me when I say that EVERYONE was snuggled in bed by 11PM during the winter !!!!!

[slow]

Assuming there are no kinks or other obstructions in the flexible duct and you have access to below the register of concern, I recommend you install a 70 mm diameter 12Vdc computer fan below the register. Wire it to come on only when the furnace is on and it will “pull” some of the available hot air where you need it.

Here is the concept in a different application: https://www.jaycoowners.com/forums/f...unk-71288.html

Alternatively, you can use dampers at the furnace outlets to “balance” the air flow out of the registers. There was some debate in the past on this method. But if there is ample clearance around your furnace and you do not restrict the overall air flow but rather redirect it, it can be done safely. The furnace does not care which outlet the air goes into as long as the total air flow is the same.

This is what ours looked like with dampers: https://www.keystoneforums.com/forum...pictureid=3637

[jasin1]

Originally Posted by slow

Assuming there are no kinks or other obstructions in the flexible duct and you have access to below the register of concern, I recommend you install a 70 mm diameter 12Vdc computer fan below the register. Wire it to come on only when the furnace is on and it will “pull” some of the available hot air where you need it.

Here is the concept in a different application: https://www.jaycoowners.com/forums/f...unk-71288.html

Alternatively, you can use dampers at the furnace outlets to “balance” the air flow out of the registers. There was some debate in the past on this method. But if there is ample clearance around your furnace and you do not restrict the overall air flow but rather redirect it, it can be done safely. The furnace does not care which outlet the air goes into as long as the total air flow is the same.

This is what ours looked like with dampers: https://www.keystoneforums.com/forum...pictureid=3637

Dampers can be quite useful on many different duct systems ….the problem lies in accessibility …dampers have a way of blowing into the closed position if they are not permanently secured in the final balanced position….I noticed at least two of your dampers were completely closed. I often go into homes where people mistakenly shut off more then a few of there registers in the house thinking it will redirect the air…while it will send more air to other places it can also cause the furnace to overheat…you need to take the temperature rise of the furnace and if your going to start restricting ducts then you need to have the duct capacity to handle the rerouted air..
You can only push so much air thru a 4 “ pipe with a fixed blower speed motor…yes you will get more velocity but it’s still a restriction and you may find yourself cycling on high limit or end up with a cracked heat exchanger.

It’s tempting to think that 400 cfms will come out of one 4 “ pipe but that’s not the case with the same small furnace blower

Or let me rephrase that…you could get 400 cfms out of one 4” pipe but it would not run long that way as it would quickly overheat and put a strain on the blower motor…restricting the ducts has the same effect

The fan idea may help…I stay away from them on residential systems as I usually try and correct the existing duct problem

[flybouy]

I think in the RV industry the HVAC systems are almost an afterthought. In commercial and new residential construction the systems are designed/engineered to meet standards and codes. In RV's I think vit's a matter of "stick in where it fits" and try to get a flex duct from point A to point B and if that means crushing the flex duct or adding sharp bends and long runs so be it, at long as the pretty blue lights under the cabinets still work.