Houghton a/c youtube re: humidity issues

[Geronimo John]

Massive rewrite with GSMBear's eureka.

But the extra wire shown below would be an ideal splice point.  Then may be run the line via the abandoned drain line to a remote location as suggested.

A does not connect to B. 

GJ

 

[GSMBear]

17 hours ago, Geronimo John said:

But the extra wire shown below would be an ideal splice point.

Hi John -- that extra wire is the connector to the air distribution panel for the limited control functions offered there instead of from the remote.  None of those pins (4, I believe?) involve the thermistor.  That wiring clip appears unused in the picture because the air distribution panel has been removed to access the innards.  When it's all assembled, there is a corresponding end for that wiring harness on the air distribution panel side.  They get connected together upon assembly so that the display panel and controls will work.

The "hot poker stick through the Styrofoam" approach wasn't hard and it allows the factory thermistor to remain in place as a backup.  I'm going to test the auxiliary thermistor more on Saturday and report back here once that's done.  Fingers crossed!

[Geronimo John]

On 10/26/2023 at 4:02 AM, GSMBear said:

The "hot poker stick through the Styrofoam" approach wasn't hard and it allows the factory thermistor to remain in place as a backup.

GSMBear:

Thanks for the clarification.  Wishful thinking on my part I suspect.  I very much like the idea of keeping the factor thermistor in place as a back-up.  Please as time permits document the process and your relocation process.  With your work on this aspect, and the relay hack it will certainly improve the performance of the Houghton well beyond that of even the more recent "quite" A/C now showing up on the market.

I thank you for posting the DYI detailed how to for the "Wiring Modification for Interior Fan" for our A3400's.  Very helpful!

https://olivertraveltrailers.com/forums/applications/core/interface/file/attachment.php?id=28481&key=173b638cb772218f2b3b281fea586f0c

OEII Owners:  With my Ollie 3,878 miles east of Honolulu, I am wondering if any one knows if the Dometic drain line passes with in reach of the street side of our attic as I postulated this past summer?  If it does, this tube could be used to route the sensing end of the new thermistor to a location away from the air flow.

 

[GSMBear]

Good News!

I am happy to report that the auxiliary thermistor I bought from Amazon works as a replacement to the factory thermistor.

These two things are critical to the success:  locate the new thermistor away from the air distribution box and away from the airflow.  For me, this will be around the corner of a cabinet and likely in the same location as the original Dometic CCC2 thermostat that controlled the original Dometic AC and gas furnace.

I tried multiple experiments with the thermistor in the same area as the air distribution box with varying degrees of shielding from the airflow.  But it just wasn’t good enough to suit me.  This would have been the simpler solution and I wanted to rule it out before moving on to something more involved.  I think there’s just too much air movement everywhere around the distribution box and it tricks the thermistor into thinking it’s a different temperature than it really is.

The test that pleased me the most was when I stretched the cord out as long as it would go and I taped it in a location near where I hope to set it permanently.  The cord isn’t long enough to get me there right now.  But when taped to the wall around the corner from the airflow the AC set temperature of 70 was reached and three other temperature devices in the RV measured between 70 and 72 in different locations.  The on/off cycles were fairly short which concerns me a little bit and I’m hoping this will improve when I have the thermistor in the final location which will be more shielded from airflow and at a more reasonable vertical location.

In heat mode this morning, there was a greater difference between the set temperature of 66 and the actual temperature of 72.  Cycles were short and I think if I had let it continue the interior temperature would have gone higher than 72.  Perhaps this will also even out more once the thermistor is not as close to the ceiling.  I’m less concerned about an accurate reading with heat than I am with AC.  I use the RV more in the warmer seasons than I do in the cooler ones.

Also, when I turned on the heat this morning, there was a great deal of humidity pumped into the living space.  The windows fogged and the moisture on the interior aluminum skin (this is an Airstream instead of an Oliver) was visible.  I was surprised to see this and I wondered if it was due to residual moisture still on the evaporator fins from the prior day’s AC testing.

Overall, I’m pleased with the testing knowing that I can relocate the thermistor elsewhere and get reasonably good results.  If I have to adjust the settings to reflect the differences between set temperatures and actual temperatures I’ll learn that over time and adjust.

I feel like the two major wins in this obsession of mine are:  1) getting the additional relay installed to allow the interior fan to cycle with the compressor (solves humidity issue with AC), and 2) finding an easy path to get an auxiliary thermistor from the rooftop control board location to the interior sealed area without much effort.

For those interested, this is the thermistor I am using right now.  It has the two-pin connector on the end that fits the control board.  https://a.co/d/dV31de2

[Geronimo John]

What a wonderful effort!  Many many thanks.  I have some thoughts that may be worth a cup of coffee.....

 I am suggesting an "Old School" approach to short cycling that likely you have not seen done.  

13 hours ago, GSMBear said:

I tried multiple experiments with the thermistor in the same area as the air distribution box with varying degrees of shielding from the airflow.  ....   I think there’s just too much air movement everywhere around the distribution box and it tricks the thermistor into thinking it’s a different temperature than it really is.

In the olden days (IE. before transistors and electronic controls), if I had a T-stat sensing bulb that was in a difficult location (that we could not change), and the cold air was causing short cycling, we would first try shielding the sensor from the air flow. If that did not provide relief from short cycling,  then we would add thermal mass to the sensing bulb.  Thermal mass would work on a small thermistor as well I suspect.

Try putting the thermistor into a small plastic pill container with a hole in the lid for the cable.  Leave the lid hole sort of open, maybe even put a hole in the pill container bottom.  Then tape it to the wall and note what happens.  Then move it around the space. If the short cycling persists add thermal mass to the container with the thermistor and repeat.  Something like a few small glass beads.  Need more dampening, add more glass beads.  The increasing thermal mass of the weighted container will ameliorate the output of the thermistor.  That will delay temperature rise and fall as the unit cycles.  Thereby delaying both start and stop.  Basically extending the run times and off times as well.  

i am thinking that should the drain line approach be feasible (No answers to my question above about that yet.) then a thermal mass enabled thermistor in the attic with an air port via the smoke detector just may work.   

On the other hand there maybe a different thermistor that would do the same thing.  But first proof of concept would be the first logical step.

GJ

[Geronimo John]

14 hours ago, GSMBear said:

Also, when I turned on the heat this morning, there was a great deal of humidity pumped into the living space.  The windows fogged and the moisture on the interior aluminum skin (this is an Airstream instead of an Oliver) was visible.  I was surprised to see this and I wondered if it was due to residual moisture still on the evaporator fins from the prior day’s AC testing.

LOL.  I have done the same thing.  When the Owner of Houghton stated that their coils did not retain much moisture, I tested it by running the a/c wide open with the windows open on a humid day.  As soon as I had a flow of water going overboard, I knew I had a "Loaded Coil".  Then I closed the door and windows and switched the Houghton from cool to heat pump, it clearly demonstrated just how fast one could run out unwanted guests!

GJ

[GSMBear]

8 hours ago, Geronimo John said:

Try putting the thermistor into a small plastic pill container with a hole in the lid for the cable.  Leave the lid hole sort of open, maybe even put a hole in the pill container bottom.

Great minds think alike? 🤔

What I did ended up being similar to this.  The final location where I wanted the thermistor provided some good shielding from airflow.  It's also at a more reasonable vertical level.  My initial testing had the thermistor pretty close to the ceiling because that's as far as the original wire would reach and still get it around the corner of the cabinet.

I took a big gasp and snipped the end of the thermistor wire about 8 inches from the tip.  Then I added several feet of supplemental wire to extend the length so that it would reach where I wanted it to go.  I tucked it behind the cover of the ugly mechanical thermostat that now controls the gas furnace.  At first I had it poking out the other side so I wouldn't see it but that appeared to provide too much shielding.  I switched it to the side you see in the picture and it seems to have the perfect balance.

The short cycling stopped.  I didn't time it but I'd say the on cycle was about 10 minutes and felt very comparable to the original Dometic unit.  The off cycle was a little longer.  Two wifi-enabled temperature sensors provided temperatures of 68.5 at the front by the panoramic windows (in the airflow path) and 70 directly on top of the mechanical thermostat where the sensor is (shielded).  I probably had this kind of temperature difference with the original AC but I never measured it.  It was too warm to test the heat but I'll get that done later.  (If our theories are correct, those fins still would have had a lot of moisture on them.)

Pictures below show the path the thermistor wire took:  1) from a factory wire access hole to a nearby ceiling puck light, then 2) across to the top of the interior of the microwave cabinet, then 3) down the side of a closet and under a shelf and through an existing wire access hole for closet lighting to 4) the ridiculously large and off-center hole from the Dometic CCC2 to 5) the final location!

In the first picture you can see the snipped drain tube from the Dometic in the top left corner.  In my Airstream, this runs directly down the side of the wall and it exits in the street-side wheel well.  Would have been nice to integrate this somehow with the Houghton.  I'm not sure how this is different in an Oliver RV so I've not commented on your question about this.  I'm not understanding how this might provide a path for the wire but I'm sure it's because of my lack of familiarity with your setup.

 

[GSMBear]

John -- having another thought. . . 

Your Houghton is a replacement to an original Dometic, right?  Is there still an RJ-45 cable that runs from the air distribution box location to the location of your original thermostat?  If so, might that wire be the ticket to relocating the thermistor?

If I recall correctly, that's not exactly a phone wire.  Can't recall where I read it but I think the gist of the message was that two of the wires have their positions swapped from one end to the other which makes it different from a phone wire.  The wires are color coded so that should be enough to identify which ones (there are 4, I believe?) are being used to extend the thermistor.  And I don't think the concept of polarity is involved -- meaning, I don't think it matters which wire gets connected to the two on the other end.

[Geronimo John]

5 hours ago, GSMBear said:

Your Houghton is a replacement to an original Dometic, right?  Is there still an RJ-45 cable that runs from the air distribution box location to the location of your original thermostat?  If so, might that wire be the ticket to relocating the thermistor?

Yes, but...

Our data cable that runs from the Dometic to the multi function digital T-stat is very small wire.  As such, several of our OEII owners, myself included, have reused that four wire cable to extend the furnace cable over to the old T-stat location.

To do so we needed more current carrying capability for a new simple T-stat just for the furnace.  So, we tied together two of the wires on each end to double the copper size for higher current flow.  Since our Suburban furnace control is OEM run from the furnace to the Dometic A/C communications box, we connected the two "double cables" as a jumper from the now Houghton under belly to a dedicated single use thermostat that just runs the furnace.   This works very well for the furnace.

The Oliver double fiberglass hull is insulated and I suspect it would be very difficult to find another path  to the former Dometic thermostat (Now new T-stat for heat).  But if we can, that would be the cat's meow. 

Because of my preconceived concerns with the level of difficulty to do so would be a PITA.  This is the reason that I was looking at possible other options to extend the thermistor cable.  In that quest I took stock of the installed drain tube.  On the OEII, it appears to run to the area behind the street side tires.  My hope is that the path may take it to within reach of our rear attic area.  Hence my question above (Saturday).  But no responses so far to that question (Last Saturday, above in this thread.)

But now, with your efforts in mind, I am thinking if the OEII drain tube could be intercepted in the basement space under the rear bunk.  We OEII Houghton owners could use the drain tube to convey an extended thermistor wire over and down to the street side under bed area, and then over and up into the old Dometic thermostat location where we have the new single use T-stat.  Once there we could poke it out as you did on your AS.   

That would then pretty much solve the Houghton's issues for the OEII's as well.  

OEII OWNERS:  Anybody know if it is reasonable to intercept the drain tube inside the street side bed basement area?  

 

GJ

[GSMBear]

Ah, I see.  Very clever how the former wires were put to good use.  But as a former co-worker used to say:  "Your problem is very clear to me."

Unfortunately, I'm coming up short on solutions.  But tinkering and just sitting in the space and thoughtfully observing - and then repeating as necessary - is likely what lead me to find a solution that worked my situation.

When you ask about intercepting the drain tube in the basement area, are you saying this would require cutting out a section of the fiberglass skin to (hopefully) find the tube located behind it?  Akin to cutting away drywall to find a pipe or wire inside the wall?  I can understand your concern about that, if so.

[Geronimo John]

17 minutes ago, GSMBear said:

When you ask about intercepting the drain tube in the basement area, are you saying this would require cutting out a section of the fiberglass skin to (hopefully) find the tube located behind it?  Akin to cutting away drywall to find a pipe or wire inside the wall?  I can understand your concern about that, if so.

Being in HI and Ollie in OK, I'm at a disadvantage in long range planning.  The drain tube runs between our outer and inner fiberglass hulls from the Houghton across the roof and then down the wall to below the windows and belly band.  It then passes through the belly band area and down another foot or so past the twin bed mattress.  The inner hull there separates from the outer hull to make a cavity for utilities.  At that point I think it is only covered by the Rejex insulation. 

If that is the case then it would only be a matter of knowing where to look.  

OTT OWNERS:  Please jump in if you have any thoughts on this possible route of our A/C drain tube.

Thanks

GJ

[GSMBear]

I was browsing the RecPro website the other day and noticed a new addition to their Quiet AC lineup.  They now have an AC/Heat pump model with a condensate pump for retrofit installations that have existing drain management to whisk away the condensation.

Unfortunately for Oliver owners, the 15K size of the unit is probably too much for the space.  It is also their higher profile unit which might not be appealing to some.  Perhaps it will be an expanded offering someday in their low profile units.

[Geronimo John]

On 8/21/2023 at 11:07 AM, GSMBear said:

Hi John -- yes, the thermistor wires end up on a 2-pin connector on the control board on the curb side of the rooftop unit.

Can you please ID that thermistor for us?  Maybe an Amazon picture.  

I have a service ticket with Mike and we are working the routing to get a path using your "Hot Poker" and JD's "Wire Extender" concepts.  Mike and I are in Round 3 and he has the ball.  I'll keep all posted soonest.  With this last element we will have fully solved the Houghton's shortcomings.  

GJ

[GSMBear]

9 hours ago, Geronimo John said:

Can you please ID that thermistor for us?  Maybe an Amazon picture.  

I have a service ticket with Mike and we are working the routing to get a path using your "Hot Poker" and JD's "Wire Extender" concepts.  Mike and I are in Round 3 and he has the ball.  I'll keep all posted soonest.  With this last element we will have fully solved the Houghton's shortcomings.  

GJ

This is the one that I used:  https://a.co/d/ceHt1sT.

That's a suspicious looking link but I guess that's how Amazon creates them so that they're short.  I followed the link and it does go to the correct place.  Or search for this item in the picture.

[GSMBear]

On 7/30/2023 at 8:18 AM, GSMBear said:

RecPro Houghton Interior Fan Mod.pdf 1.33 MB · 26 downloads

I finally had a chance to document the steps for modifying the factory wiring for the Houghton/RecPro A3400 air conditioner to prevent the interior fan from running continuously.

The instructions are in the attached PDF document for anyone interested.

I kind soul over on the AirForums has brought to my attention a discrepancy in the original PDF document I shared about the fan mod that I did on the RecPro/Houghton AC unit.  Steps 5 & 6 are correct when viewing the pictures but the narrative I added was incorrect.  I've updated the narrative and I will try to post the v2 document here.

RecPro Houghton Interior Fan Mod v2.pdf

[Geronimo John]

On 4/6/2023 at 3:07 AM, Tummy said:

There are multiple ways and connectors you can use to do it, but I used Wago three wire connector to connect the wire marked COMP to one side of the coil.  Then another connector to add the N1 wire to the other coil terminal.  Then connected the Fan low wire on the normally open terminal.

Tummy:

I, and several others would surely appreciate some pictures of your WAGO solution to the continuous fan run.  It appears to be vastly simpler than what we have been pouring over.

Thanks

Geronimo John

Edited March 13 by Geronimo John

[Geronimo John]

On 10/29/2023 at 2:53 AM, GSMBear said:

I feel like the two major wins in this obsession of mine are:  1) getting the additional relay installed to allow the interior fan to cycle with the compressor (solves humidity issue with AC), and 2) finding an easy path to get an auxiliary thermistor from the rooftop control board location to the interior sealed area without much effort.

NEW OPTION TO RELO OE2 THERMISTOR:

I ran to ground with OTT that the Dometic drain line is accessible in the lower bunk area (Street side, Aft). We would need to cut into the Rejex insulation.   So a possible route is to go thru the styrofoam to the drain line, then in the drain line run the LONG thermistor wire back towards the rear street-side.  Target should be in line with the exposed drain tube aft of the left rear tire.  By cutting the drain line in the under bunk area, we could run the thermistor over to the location near the old thermostat. 

Last unknown is where to penetrate the styrofoam cover up top to find a specific routing of a new longer thermistor to be routed without soldering.  Ideally one that could be duplicated by others which would not require removal of this cover.     

With this in mind, we could leave the John D. mechanical furnace replacement thermostat in play with the two old Dometic small diameter wires spliced together to do so.

[Geronimo John]

2 hours ago, Geronimo John said:

Tummy:

I, and several others would surely appreciate some pictures of your WAGO solution to the continuous fan run.  It appears to be vastly simpler that what we have been pouring over.

Thanks

Geronimo John

Ok, maybe vastly is an overreach.   😞

GJ

[GSMBear]

Yesterday, I installed a Spartan Power Soft Start in my RecPro/Houghton A3400 air conditioner. It's identical to the one RecPro sells and is $100 cheaper on Amazon at https://a.co/d/cvYZV39.

The wiring method on this one is different from other popular models.  I've done both now and this one is much simpler.  I removed the fan and found a place mostly out of the way underneath it on a flat surface.

All you have to do is use your finger to trace the wrapped set of wires coming out of the compressor to a point where you can cut them.  There will be 3 wires: red, white, brown.

After snipping the wires, the 3 that are still connected to the compressor get connected to the "compressor" side of the Soft Start.  The 3 remaining wires on the other side of the snip location get wired to the "supply" side of the Soft Start.

Red-to-Red, Blue-to-White, and Black-to-Brown.  Button it up and let it run for 30 minutes with the temperature set close to the interior temp so that it will cycle on/off a few times.  Then good to go!

I had no trouble when mine cycled on while the microwave was running.  The combination of these two puts me near my limit of 30 amps so it will depend on what else might be running.  The refrigerator was off and if it had been running, that might have put me over the limit.  It's a balancing act, for sure.

The picture with my fingers shows the snipped wires that lead back to the compressor.  The other end of the same snipped wires represent the "supply" side.  The other picture shows the mounting location which is accessed by removing the 4 nuts that secure the large black fan.  Clean the surface with some rubbing alcohol first then peel the double stick tape and press it down. 

[mtt]

Hello Everyone,

I do not own an Oliver, however, I have developed a novel solution to the Houghton humidity issue that I would like to pass on. My solution builds on the compressor relay idea that was posted by GSMBear. My Design also interrupts the low-speed fan power so it will run when the compressor is on, however, it adds a timer control to start the fan every six minutes to sample the RV temperature.  I live in Oregon so it is not as humid here as it is in the south, however, this mod produces dehydrated air in the RV and the air conditioner discharges a lot of water it has pulled out of the RV,

The timing cycle works like this:

When the AC brings the RV to the target temperature and the compressor shuts down the timer will run the fan for 52 seconds to purge the remaining cold air. (Purging the remaining cold air improves efficiency.)

Then the timer will shut down the fan and wait for six minutes.

 

The timer will then run the fan for 52 seconds to sample the air in the RV.  If the AC detects a temperature rise it will start up, else the cycle will repeat by waiting for six minutes.

The net result is only 1/8 as much time is spent blowing air over the wet coils, dramatically reducing the water return to the cabin and giving the water more time to drip off the coils.  It would be easy for the manufacturer to implement this solution in firmware and it is very frustrating that the manufacturer has not done so.

 

On a side note, I would not be in favor of relocating the plenum thermistor as it may be used for other purposes like detecting a coil freeze-up.

 

I installed the timer and relay into a plastic spacer that sits on top of the control box of my AC2801. The links below are for photos of the moded spacer before and after the installation. If anyone would like more details about my solution I would be happy to share.

 

https://trontamer.com/dl/mod1.jpg

https://trontamer.com/dl/mod2.jpg
 

[CRM]

4 hours ago, mtt said:

The timing cycle works like this:

When the AC brings the RV to the target temperature and the compressor shuts down the timer will run the fan for 52 seconds to purge the remaining cold air. (Purging the remaining cold air improves efficiency.)

 

 

 

Running the blower for 52 seconds right after shut down would defeat the purpose, I think... In my expedience, humidity starts rising immediately after the compressor shuts down if the fan continues to run. I wouldn't be worrying about a slight improvement in efficiency if I were trying to keep the humidity as low as possible.

Edited June 22 by CRM

[mtt]

On 6/22/2024 at 5:02 AM, CRM said:

Running the blower for 52 seconds right after shut down would defeat the purpose, I think... In my expedience, humidity starts rising immediately after the compressor shuts down if the fan continues to run. I wouldn't be worrying about a slight improvement in efficiency if I were trying to keep the humidity as low as possible.

Almost all modern home and commercial air conditioning systems are designed to purge the remaining cold air after the compressor shuts down and their ability to dehumidify is not compromised. With my application, the air in my rig is dryer than it has ever been.

That said, with a simple change to timer settings, the initial purge could be eliminated.

[CRM]

2 hours ago, mtt said:

Almost all modern home and commercial air conditioning systems are designed to purge the remaining cold air after the compressor shuts down and their ability to dehumidify is not compromised. With my application, the air in my rig is dryer than it has ever been.

That said, with a simple change to timer settings, the initial purge could be eliminated.

In homes and commercial buildings you're dealing a much higher ratio of evaporator surface area to conditioned space so humidity rise will be much smaller, but it will still be there whenever you blow air over evaporator coils with condensation on them. 

And I'm not doubting your findings under your test conditions, I just know when I tested running the fan after shutdown here in Florida with +90% outside RH that the humidity began to rise immediately. I do see how skipping that first 52 seconds and then running the fan occasionally to sample the air over the thermistor might keep from having to relocate it and not release as much humidity into the cabin, though..

[GSMBear]

On 6/22/2024 at 3:37 AM, mtt said:

On a side note, I would not be in favor of relocating the plenum thermistor as it may be used for other purposes like detecting a coil freeze-up.

The A3400 has separate sensors for the room temperature (the one I relocated), indoor coil, and outdoor coil. The room sensor is not used for detecting coil freeze-up.

In my particular application, it was easy to disconnect the factory sensor from the main board and attach an auxiliary sensor with a much longer cable and route it to the location of the RV's original thermostat.  This won't be the case in every application and I think your timer solution is a very valuable addition to the knowledge base with the non-desert applications of this otherwise fantastic AC unit.

It's been in the upper 80's and low 90's in East Tennessee this week and I've been running the AC with a setting of 74 degrees.  I keep the RV stored on my property where it is connected to power and internet.  I've been monitoring the temperatures in the front and rear sections and it remains within less than a degree of the set point.  My RV is 23' with no slides and was originally equipped with a 13.5K unit -- it is not an Oliver RV.

EDIT: please ignore the wire color descriptions in the schematic below. The schematic is attached to show the connection points for the coil sensors.

Edited June 26 by GSMBear

[hobojoe]

Have a question concerning low speed fan wire in the above diagram going to NO of the relay and a new wire from COM to where wire was removed on circuit board. An earlier post with attachment v2 shows thin white wire removed and attached to COM port, then new wire from NO to where wire was removed from circuit board. Am curious which is correct or will either one work?