Varioheat Furnace Air Filter

[Rivernerd]

After reviewing some posts asking why RV furnaces have no air filters, I decided to add one to our Truma Varioheat furnace.  Home furnaces have filters to protect the motors and fans from dust accumulation, why not RV furnaces?

My filter consists of a piece of filter fabric cut to size and attached to the front of the cold air intake with "No Residue" duct tape.

See photo below.

Here is what the furnace looked like before installation of the filter:

I tested the furnace after installation, and noted no difference in its operation.  I will be interested to see, over time, if the filter collects a noticeable amount of dust.  I would rather have the dust collect in the filter than on the fan and motor!

The filter fabric is available here for seven bucks:

https://smile.amazon.com/dp/B077SP23FP?ref=ppx_yo2ov_dt_b_product_details&th=1

The 4'x1' piece I received includes enough for many years of filter changes.

I welcome any comments, in favor or against, the use of such a filter.

[John E Davies]

Neat idea! I love it.

The manufacturers do not put on filters (in this country) because most owners would: Not know it was there. Not care if it was. Never change it. Burn out the fan motor. Complain on the internet about it.

I hate dust. I wish there were ways to keep it out entirely….

https://urbancaravans.com.au/dust-suppression-system/

https://olivertraveltrailers.com/forums/topic/5790-how-to-window-dust-pollen-smoke-filter/

https://olivertraveltrailers.com/forums/topic/3291-honeywell-hpa-compact-air-filters-for-pollen-dust-and-smoke-particles/
 

This subject has been on mind a loooong time but I have never done anything about it:

https://olivertraveltrailers.com/forums/topic/2598-cabin-pressurization-system-to-prevent-dust-infiltration

If you will do the R &D and test it on some gnarly ranch roads, and post a report, I will follow your lead.

Did I mention that I hate dust?

John Davies

Spokane WA

 

[Patriot]

A very creative idea for sure and please post up on how it works out long term. The only initial concern I would have with this mod is does this invalidate a new Truma furnace warranty? For those out of the Truma warranty period certainly not a warranty claim concern any longer.

Interesting mod!👍🏻

here-

https://www.manualslib.com/manual/1357660/Truma-Varioheat-Eco-Au.html?page=12

Patriot🇺🇸

[johnwen]

I don't have the Truma, just the Dometic.  I am convinced the lack of a filter on the return grill opening contributes/causes the sail switch to gather lint and dust.  After the sail is gummed up with the contaminants, it ceases to allow ignition and I have to clean it.  Not a hard chore but sometimes inconvenient.

John

[Rivernerd]

8 hours ago, John E Davies said:

If you will do the R &D and test it on some gnarly ranch roads, and post a report, I will follow your lead.

Did I mention that I hate dust?

I apparently don't hate dust as much as you do.  I find the robust dust filtration system shown in your photos intriguing, but not enough to be worth a try.  We don't plan to take our Elite II on as many unpaved roads as you apparently do.

But, even on paved roads, I suspect our Elite II will get more dust infiltration than our home does.  Thus, the rudimentary furnace filter idea.

[Rivernerd]

3 hours ago, Patriot said:

The only initial concern I would have with this mod is does this invalidate a new Truma furnace warranty?

Time will tell. 

I registered all of our Truma products, to extend the warranty from one to two years.  Logically, a simple filter, using purpose-built filter fabric, should extend, not shorten furnace life.  But, after 35 years of litigation practice, it does not surprise me when companies latch on to any excuse to deny warranty coverage.   On balance, I would rather try to protect the furnace I have, and take the warranty denial risk, than leave it unprotected and rely on the warranty.  In any event, Murphy's Law suggests that the furnace will fail two years and one month after purchase!

[John and Debbie]

2 hours ago, Rivernerd said:

Time will tell. 

I registered all of our Truma products, to extend the warranty from one to two years.  Logically, a simple filter, using purpose-built filter fabric, should extend, not shorten furnace life.  But, after 35 years of litigation practice, it does not surprise me when companies latch on to any excuse to deny warranty coverage.   On balance, I would rather try to protect the furnace I have, and take the warranty denial risk, than leave it unprotected and rely on the warranty.  In any event, Murphy's Law suggests that the furnace will fail two years and one month after purchase!

What does Truma say?  I would check if they have some sort of filter product for the Varioheat.  Maybe you already did that and hence your filter.  What if you put some filter material on the air grill on the trailer on the inside since that's where most of the dust will come from.  Just thinking of possibilities since we have the same furnace.

John

[Golfnut]

I only have an Elite I , but I might add filter on return air grill..  when I got the Oliver in July 2022. Wife and I wiped the whole inside down, vacuumed inside where the furnace was ( was really dusty).   Have not a problem with the furnace yet…. Going out middle of march to  outside Asheville N C.  It will probably get a workout..

[Rivernerd]

This is an update based on data gathered over the past 6 days using the Varioheat furnace during cool weather on the Oregon Coast.  We kept getting an error code on the CP Plus wall control unit advising that either the supply ducts or the return air vents were obstructed.  It would shut down, then re-ignite.  We ensured there was nothing under the bed on our standard floor plan Hull #1291, but the error codes persisted.  So, I removed the air filter I installed as described in my original post on this thread.  VOILA!  No more error messages.

I have concluded that the Varioheat furnace is calibrated to function without a filter, and that my addition of a filter set off an airflow sensor causing it to shut down.  So, my experiment with a homemade add-on filter created an unintended failure. 

I plan to leave the filter off of my Varioheat.  I recommend you do the same.

[Geronimo John]

On 4/15/2023 at 8:27 AM, Rivernerd said:

I have concluded that the Varioheat furnace is calibrated to function without a filter

If it is calibrated, then generally that means it can be recalibrated.  May be worth a call to the Varioheat MFG.

GJ

[Jason Foster]

On 4/15/2023 at 1:27 PM, Rivernerd said:

This is an update based on data gathered over the past 6 days using the Varioheat furnace during cool weather on the Oregon Coast.  We kept getting an error code on the CP Plus wall control unit advising that either the supply ducts or the return air vents were obstructed.  It would shut down, then re-ignite.  We ensured there was nothing under the bed on our standard floor plan Hull #1291, but the error codes persisted.  So, I removed the air filter I installed as described in my original post on this thread.  VOILA!  No more error messages.

I have concluded that the Varioheat furnace is calibrated to function without a filter, and that my addition of a filter set off an airflow sensor causing it to shut down.  So, my experiment with a homemade add-on filter created an unintended failure. 

I plan to leave the filter off of my Varioheat.  I recommend you do the same.

I asked Oliver why it didn't have a filter.  They didn't have an answer, and I'm still confused about this.  Your filter idea is exactly what I was thinking about doing, and even though you encountered the error message, I am assuming it is because you needed to INCREASE the filter surface area to improve airflow.  My idea included using a HEPA filter since I have horrible dust and mold allergies.  With your test, I will have to create a larger box to allow for more airflow.  Hopefully, this will be enough to not cause the error.

[Jason Foster]

On 1/27/2023 at 10:32 AM, Rivernerd said:

Time will tell. 

I registered all of our Truma products, to extend the warranty from one to two years.  Logically, a simple filter, using purpose-built filter fabric, should extend, not shorten furnace life.  But, after 35 years of litigation practice, it does not surprise me when companies latch on to any excuse to deny warranty coverage.   On balance, I would rather try to protect the furnace I have, and take the warranty denial risk, than leave it unprotected and rely on the warranty.  In any event, Murphy's Law suggests that the furnace will fail two years and one month after purchase!

This sounds like me.  I never buy extended warranties.  Not worth the paper they are likely not printed on.  Murphy's Law is almost always right.  My philosophy is just save the money for a new one or learn to fix the old one.  I know Truma offers a free extended warranty by registering, so I will get that but anything past two years is just bonus.  

[Geronimo John]

On 1/3/2024 at 9:54 PM, Jason Foster said:

With your test, I will have to create a larger box to allow for more airflow.  Hopefully, this will be enough to not cause the error.

The CFM through the furnace is not really that much.  A fan powered induction box could be tied into the Truma fan intake so as to "Pressurize" the inlet of the Truma thereby avoiding the low pressure warning.

GJ