Heater is Keep Making a Ticking Sound (New GD 23BHE)

[Guest]

Makes sense.

Thank you.

Jim

[Running from Gnats]

Did you keep the wrong part? Can you get a letter verifying the wrong part was installed? The manufacture needs to reimburse you for ALL expenses if this is a new rig. You should not be paying for their mistake. PERIOD. Talk to GD and see if they will assist you in getting reimbursed. Failing getting a reimbursement, you should take this to small claims where you can ask for expenses.

[Scott'n'Wendy]

Wow. That would be a hard one to troubleshoot and fix. You would normally assume the unit has the correct original parts if it is new!
Hope you don't end up paying for the fix. At least you have a spare board and sail switch?

[elranas]

Hey everyone,


The problem persisted even after replacing the igniter. I sang victory too early! AirExcel sent us a new furnace and even then it kept happening. That eliminated being an issue with the furnace. Grand Design sent another mobile RV repair company for a second opinion. After almost three weeks of back and forth where everyone thinks and admits this is an issue, the tech and Grand Design decided that this is normal. They are saying that the furnace rests a couple of times until it reaches the desired thermostat temperature. Rests meaning that the furnace runs for about four minutes and then the flame goes off for about a minute. The hi-limit switch makes contact again, the igniter makes a ticking sound and the flame comes back ON (blower is ON the entire time). These stops of flame ON flame OFF will continue until the thermostat reaches the desired temperature.


I have multiple techs telling me that a furnace should continually run until the thermostat cuts it off.

Does anyone else with a Suburban SF 25Q furnace experience the same thing?

[howson]

Hey everyone,


The problem persisted even after replacing the igniter. I sang victory too early! AirExcel sent us a new furnace and even then it kept happening. That eliminated being an issue with the furnace. Grand Design sent another mobile RV repair company for a second opinion. After almost three weeks of back and forth where everyone thinks and admits this is an issue, the tech and Grand Design decided that this is normal. They are saying that the furnace rests a couple of times until it reaches the desired thermostat temperature. Rests meaning that the furnace runs for about four minutes and then the flame goes off for about a minute. The hi-limit switch makes contact again, the igniter makes a ticking sound and the flame comes back ON (blower is ON the entire time). These stops of flame ON flame OFF will continue until the thermostat reaches the desired temperature.

I have multiple techs telling me that a furnace should continually run until the thermostat cuts it off.

Does anyone else with a Suburban SF 25Q furnace experience the same thing?

If the Hi Limit Switch is opening it's due to an overheating fault. The Hi Limit switch is a safety device. To my knowledge it should not open unless there is a fault (overheating).

Your first post may have a clue (quote from post 1): ...and stops when reaching the desired temperature (which is almost never on cold night - I think this heater is not strong enough but this is a different topic)

IF the Hi Limit is opening (due to overheating) AND the trailer is not getting warm enough, perhaps the heater issue is a symptom and the problem is the ducting in the trailer. It could be crushed/blocked/disconnected in such a way that there's no path for the hot air to go out of the furnace. If the hot air can't leave the furnace, that causes the Hi Limit Switch to open. The thermostat is still calling for heat (since it hasn't reached the set temp yet in the trailer) so the cycle repeats until finally the trailer is warm enough.

This assumes the Hi Limit self-resets. I'm not 100% sure that's true. Hopefully colan or another furnace-smart person can confirm.

[Cate&Rob]

elranas howson

I don’t have a Suburban furnace, but I would agree with the technicians who are telling you that the furnace should run continuously until the thermostat set temperature is reached. This is the way that my Atwood furnace operates.

I think that Howard may be on to something here. If the airflow can’t remove the heat from the furnace, it will overheat and go through the reset cycle that you describe. I would be inclined to disconnect all ductwork from the furnace (to maximize air flow) and see if this will allow the burner to run constantly.

Rob

[elranas]

We took the unit outside the trailer and let it run and the same thing happened. Also, we added another two 4" ducts (utilizing all six openings now) and checked all the others and the same thing happened. We are confident that this is not an airflow issue because the unit overheats even on a bench test. The furnace gets too hot that's what I think the issue but I don't know what else it could be other than airflow.

[Guest]

We took the unit outside the trailer and let it run and the same thing happened. Also, we added another two 4" ducts (utilizing all six openings now) and checked all the others and the same thing happened. We are confident that this is not an airflow issue because the unit overheats even on a bench test. The furnace gets too hot that's what I think the issue but I don't know what else it could be other than airflow.

You may have a defective hi limit switch. Do not try to bypass it as the logic on startup most likely will not allow the burner to ignite. If the main fan is running unobstructed, the heat exchanger should not overheat. One more item you may want to check is the delivered propane pressure via the regulator.

Jim

[elranas]

The RV is 4 month old so the furnace was new but AirExcel sent us another one so two new furnaces doing the same thing and we replace the hi-limit switch once so we between the first unit, the second and the switch we replaced, we went through 3 hi-limit switches. We checked the gas pressure and it is at 11 water columns on both of the gas regulators we tested.

[howson]

elranas -- what evidence, beyond anecdotal, is there that proves the "furnace gets too hot"?

Given the information in this thread, the problem is unlikely to be in the furnace itself. In post #6 all the usual individual components that fail were replaced without remedy. In post #19 a new furnace was tried, also without remedy.

There are only four other possibilities that I can think of:

1) Airflow. Restriction in the return air system or outflow through the ducts can cause a problem. Post 22 suggests neither of these are an issue.

2) Propane. I am not knowledgeable on this topic, but have read enough that a qualified RV mechanic should be able to measure the pressure / volume of propane being delivered to the furnace. Perhaps the regulator is bad on your trailer which in turn is messing with the flame sensor's output? (If the board doesn't get a specified electrical output from the flame sensor it will turn off the propane.) Perhaps there's debris in the propane line where it connects to the furnace "disrupting" the smooth flow of propane?

3) Electrical: An intermittent, very short-term open in the wiring could be almost undetectable but might result in the symptoms you're experiencing. (I am guessing at this point based on system knowledge--it's how I'd troubleshoot the problem.) Only way to know for sure is using a meter with a very fast response time (an older "needle" voltmeter or an oscilloscope). An inexpensive digital meter may not react fast enough to short-term transients. I think this is unlikely...but possible.

4) What you're witnessiing really is "normal". I'd have to prove this to myself (if I was in your position) by finding another trailer equipped with an SF-25Q and monitoring it's behavior while it is operating.

If you can you take a video of the problem and post a link to it on the forum (you can't upload a video, only link to one) it would be very interesting to actually witness the issue.

Howard

[elranas]

elranas -- what evidence, beyond anecdotal, is there that proves the "furnace gets too hot"?

Given the information in this thread, the problem is unlikely to be in the furnace itself. In post #6 all the usual individual components that fail were replaced without remedy. In post #19 a new furnace was tried, also without remedy.

There are only four other possibilities that I can think of:

1) Airflow. Restriction in the return air system or outflow through the ducts can cause a problem. Post 22 suggests neither of these are an issue.

2) Propane. I am not knowledgeable on this topic, but have read enough that a qualified RV mechanic should be able to measure the pressure / volume of propane being delivered to the furnace. Perhaps the regulator is bad on your trailer which in turn is messing with the flame sensor's output? (If the board doesn't get a specified electrical output from the flame sensor it will turn off the propane.) Perhaps there's debris in the propane line where it connects to the furnace "disrupting" the smooth flow of propane?

3) Electrical: An intermittent, very short-term open in the wiring could be almost undetectable but might result in the symptoms you're experiencing. (I am guessing at this point based on system knowledge--it's how I'd troubleshoot the problem.) Only way to know for sure is using a meter with a very fast response time (an older "needle" voltmeter or an oscilloscope). An inexpensive digital meter may not react fast enough to short-term transients. I think this is unlikely...but possible.

4) What you're witnessiing really is "normal". I'd have to prove this to myself (if I was in your position) by finding another trailer equipped with an SF-25Q and monitoring it's behavior while it is operating.

If you can you take a video of the problem and post a link to it on the forum (you can't upload a video, only link to one) it would be very interesting to actually witness the issue.

Howard

I agree with everything you said but nothing we did solved the problem. Yes, I'm trying to find Imagine 23BHE / 21BHE owners who are willing to run their furnace for 10 minute for testing. At the end of the day allowing the hi-limit switch to trip over and over again is merely abusing a safety mechanism and my fear that it won't function when it's really needed.

We tested propane presurce and we are at 11 water column.

Here is a video:
https://www.dropbox.com/s/x29k4qsypf...issue.mp4?dl=0

[howson]

We tested propane presurce and we are at 11 water column.

Here is a video:
https://www.dropbox.com/s/x29k4qsypf...issue.mp4?dl=0

I'll have to do some reading on what "11 water column" means. Propane is not an area where I'm very knowledgeable.

For the video, work computer won't connect to Dropbox so I'll have to check it later tonight from home. Hopefully others here will review it and chime in so I can read their perspective on the issue.

[TucsonJim]

I'll have to do some reading on what "11 water column" means. Propane is not an area where I'm very knowledgeable.

For the video, work computer won't connect to Dropbox so I'll have to check it later tonight from home. Hopefully others here will review it and chime in so I can read their perspective on the issue.

Propane is measured in inches of water column by using a manometer. 11" of water column is the correct propane measurement. Since this is correct, it eliminates propane as the source.

Elranas. It sounds like you've done a very in depth trouble-shooting. The bench test proved it wasn't an issue with the vents. You've measured the propane. You've replaced the furnace, etc.

I'm totally guessing here. But was the thermostat replaced when you replaced the furnace? It seems like about the only component that hasn't been thoroughly evaluated.

Jim

[Guest]

If both furnaces have been tested on a bench outside the camper and the issue is with both furnaces, air/fuel ratio (propane pressure or line restriction) is the only thing outside of the 12V power feed or the thermostat. A lean condition could raise combustion temperatures. Also for the thermostat, is there an anticipator setting?

Propane static pressure and flow would be two important requirements.

Jim

[Cate&Rob]

Would it be possible to send the original furnace back to Suburban with a "Can you guys figure this out?" document of what is going on and what you have tried?

Rob