EDIT: This turned out to be an air flow issue. The solution was quite simple. The furnace has three knockouts on the back when using flexible vent duct adapted to hard in-floor ducting. Crossroads has only used two of the three ducts, so I knocked the third one out, moved the lower two so they ducted in to the floor and ducted the top one so it ducted in to a 4" adjustable vent blowing directly in to the kitchen.Pictures:The stock furnace access panel/cold air return:Access panel removed:Duct disconnected from floor:This shows duct connected to new access panel/cold air return:Access panel sitting on floor:Access panel installed:All I have left to do is seal a couple spots a bit better with duct tape and stain the new access panel I built to match the interior of the TT.So, if you've got a Crossroads Zinger ZT33BH and are having furnace issues, this may solve them for you. Grand total for materials was $40 for the lumber, and my dealer provided all the ductwork and fittings for free (since it should have been a warranty issue, but I couldn't get them to do a service call to where my trailer is located).Brand new 2013 Zinger ZT33BH, and the furnace is misbehaving:1.) Thermostat calls for heat2.) Furnace fan starts3.) Burner ignites4.) Runs for ~2 minutes then stops, fan continues running5.) burner ignites again6.) Repeat steps 4 and 5 until:7.) thermostat is satisfied and furnace shuts down normallyMy only guess is a bad high limit or sail switch, but I'm not a furnace guy. Should still be covered by warranty, but I'd like it fixed in place instead of hauling it to dealer (I'm all set up for the season, don't really want to move).Anyone else have/have seen this issue?

Where is your heat VENT compared to the thermostat. If the vent blows heated air directly on or near the thermostat it could easily cause it to short cycle that way. I have one heat vent located just inside my bathroom door and the thermostat is located just OUTSIDE that door. If I leave the bathroom door open it will short cycle so we either partially close that vent or close the bathroom door.

here's a shot of where the registers are. I don't *think* the one in front of the island is blowing on the thermostat, but maybe it is. I'm not at the trailer again until the weekend, I'll stand next to it while it's in operation and see if I can feel it blowing there.EDIT: Maybe the one in the bathroom is heating up the paper-thin wall between the bathroom and thermostat and triggering it that way. I'll test for heat there as well. I'll grab a thermometer and stick it there and see what happens.

Besides heat blowing direct on the thermostat... also check for air flow restrictions that could trigger the high limit switch. Mine had collapsed and poorly aligned ducting when originally built and the burner would cycle every one to three minutes.

smkettner wrote:Besides heat blowing direct on the thermostat... also check for air flow restrictions that could trigger the high limit switch. Mine had collapsed and poorly aligned ducting when originally built and the burner would cycle every one to three minutes.I'll take a look. The furnace is under the pantry, and I'm not sure where the access is (I think there are four screws and that panel comes off, I'll have to see). The vents appear to have decent air flow out of them, but you never know.

This is May , you do not need any furnace !!

Furnace Cycling - SOLUTION w/ Pictures | Good Sam Community

44 Replies

bmupton
Explorer
Jun 14, 2013
Yeah, I sent them a note giving them the details of my problem and the actually had a few suggestions for a fix, but in the end none of them were feasible for me to implement myself. I'm going to follow up with them to outline the things that weren't done even close to correctly and hopefully they make adjustments to how they assemble this model (and other models like it).
JJBIRISH
Explorer
Jun 14, 2013
bmupton wrote:
JJBIRISH wrote:
read the same thing here several times about builders not following mfg. instructions for furnace installation causing air flow issues, mostly short cycling… not very uncommon…
I’m not completely sure the mfg.’s bother to read the instructions even, per my earlier post about air volume and number and location of ducts… it a good idea to keep the manuals handy…

I'm being lambasted over in the mods forum for not following manufacturers instructions as well...I mounted my supply duct closer than 2' to the cold air return.

A slightly modified design where the cold air return is on the left and duct is on the right should satisfy that requirement, but the way I set it up was to direct the air from that duct up and away so that it wouldn't draw it's own heated air back inside.

At the end of the day, the furnace is no longer short cycling, and I've followed almost all of the manufacturers instructions, minus the 2' rule. I may build a modified panel to address that yet.

As long as it’s working the way you did it, you did much better than they…
BUT it’s their responsibility to know and do these things right not just for your sake, but everyone with that model…
the heck of it is they do it without cabinets and other obstructions in the way that make it more difficult…

Good job… I would be carful and not go any smaller on the intake vent and restrict at the other end of the furnace…
bmupton
Explorer
Jun 13, 2013
JJBIRISH wrote:
read the same thing here several times about builders not following mfg. instructions for furnace installation causing air flow issues, mostly short cycling… not very uncommon…
I’m not completely sure the mfg.’s bother to read the instructions even, per my earlier post about air volume and number and location of ducts… it a good idea to keep the manuals handy…

I'm being lambasted over in the mods forum for not following manufacturers instructions as well...I mounted my supply duct closer than 2' to the cold air return.

A slightly modified design where the cold air return is on the left and duct is on the right should satisfy that requirement, but the way I set it up was to direct the air from that duct up and away so that it wouldn't draw it's own heated air back inside.

At the end of the day, the furnace is no longer short cycling, and I've followed almost all of the manufacturers instructions, minus the 2' rule. I may build a modified panel to address that yet.
JJBIRISH
Explorer
Jun 13, 2013
read the same thing here several times about builders not following mfg. instructions for furnace installation causing air flow issues, mostly short cycling… not very uncommon…
I’m not completely sure the mfg.’s bother to read the instructions even, per my earlier post about air volume and number and location of ducts… it a good idea to keep the manuals handy…
bmupton
Explorer
Jun 13, 2013
Marsland wrote:
Very interesting discussion. Thanks bmupton.

My pain is everyone else's gain. I'm glad I could provide a solution.

Marsland wrote:
I too have this cycling issue on my TT (2012). My first thought was restricted air flow as I'm getting, what I consider, low flow from my vents.

I had the same issue. The vent in the bunkhouse got 90% of the air, the other vents barely had any coming out. With the addition of the duct, I can completely close the bunkhouse vent and the rest of the trailer warms up rather well now.

Marsland wrote:
But this issue of the RV manufacturer not installing to heater specs is worth looking into. I have the "Thermal Package" and that includes a higher BTU furnace. Now if the builder didn't modify the non thermal package trailer duct system to compensate???????? I will definitely look at this aspect before dropping the Coroplast and having a look see.

Agreed. When I first started looking at this I didn't for a second believe they would have not followed the install instructions. They were also right on the line for the square inch requirement for supply ducting to allow the heat out of the ductwork. These things together caused the air flow restriction and overheating. The one thing they did have right was the cold air return...they more than met those requirements.

Marsland wrote:
Richard

Brent

Marsland wrote:
PS I do hate that flexible duct work. I know it's easier to install but it is so inefficient with regards to airflow.

Luckily in my case the ducting is straight in and doesn't have to take funny corners. They at least did that somewhat well.

Overall, not impressed with Crossroads attention to detail on the furnace installation. Still like the trailer overall, but they could have been a lot more careful with this item.
Marsland
Explorer
Jun 13, 2013
Very interesting discussion. Thanks bmupton.

I too have this cycling issue on my TT (2012). My first thought was restricted air flow as I'm getting, what I consider, low flow from my vents. But this issue of the RV manufacturer not installing to heater specs is worth looking into. I have the "Thermal Package" and that includes a higher BTU furnace. Now if the builder didn't modify the non thermal package trailer duct system to compensate???????? I will definitely look at this aspect before dropping the Coroplast and having a look see.

Richard

PS I do hate that flexible duct work. I know it's easier to install but it is so inefficient with regards to airflow.
bmupton
Explorer
Jun 13, 2013
smkettner wrote:
So you added the third duct as per the oem instructions and it works. :R
Imagine that :B

Now I must look at mine before winter comes again.

Whodda thunk it right? Never occurred to me that Crossroads would have completely ignored the installation instructions...
time2roll
Nomad
Jun 13, 2013
So you added the third duct as per the oem instructions and it works. :R
Imagine that :B

Now I must look at mine before winter comes again.
bmupton
Explorer
Jun 13, 2013
See post 1 for pics and actual solution to this problem!
bmupton
Explorer
Jun 11, 2013
I'm going to give one last thing a try. The manual for the furnace states that when installed the way mine is (With flexible ducts to a floor adapter plate, that all three ducts from the rear of the furnace need to be used.

So I'm going to take the bottom two in to the floor, and take that top one to my newly added round duct in my new access panel.

That should give me the air flow required to prevent cycling.

I'll report back when complete.

Forum Discussion

Furnace Cycling - SOLUTION w/ Pictures

44 Replies

About RV Tips & Tricks

Related Content

Best solutions for internet - REAL solutions please! :)

Storage Solutions

Toy Hauler Pictures

Splendide dryer solution?

Furnace problems - 3 lights, any solution?