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Old 05-03-2020, 11:19 AM   #1
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1972 31' Sovereign
1975 31' Excella 500
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Benton , Arkansas
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Noisy Air Conditioner, fixed.....

For most of my trailers use I used my ancient Armstrong unit.

Last summer it broke down in the middle of Texas so I had to replace it the same day.

I bought a Coleman Mach III, and while I'm satisfied with its performance, I wasn't satisfied with the noise it produced.

What I noticed is that with the interior shroud taken off it is much quieter.

So I concluded that it must be the turbulence that the shroud induces that makes the unit noisy.

I thought about it for a while, and thought maybe if I put a thin layer of insulation in the bottom of the plenum it would quiet the torrent of air.

Yesterday I went and bought a residential air filter and commenced to cutting it up. I chose a thicker one, about a half an inch thick, and put one of the pieces I cut into the bottom of the plenum, and another smaller piece was cut to fit over the vent that points toward the back of the trailer.

The result?

The noise the unit makes was cut DRAMATICALLY. Very comparable to my other trailer that has ducted air.

This is a very simple and inexpensive fix that made a huge difference, my real question is, why did Coleman miss such a simple, cheap, and effective fix? Click image for larger version

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ID:	367094Attachment 1
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Old 05-03-2020, 11:22 AM   #2
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1972 31' Sovereign
1975 31' Excella 500
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Benton , Arkansas
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Noisy Air Conditioner, fixed.....

Quote:
Originally Posted by J. Morgan View Post
For most of my trailers use I used my ancient Armstrong unit.

Last summer it broke down in the middle of Texas so I had to replace it the same day.

I bought a Coleman Mach III, and while I'm satisfied with its performance, I wasn't satisfied with the noise it produced.

What I noticed is that with the interior shroud taken off it is much quieter.

So I concluded that it must be the turbulence that the shroud induces that makes the unit noisy.

I thought about it for a while, and thought maybe if I put a thin layer of insulation in the bottom of the plenum it would quiet the torrent of air.

Yesterday I went and bought a residential air filter and commenced to cutting it up. I chose a thicker one, about a half an inch thick, and put one of the pieces I cut into the bottom of the plenum, and another smaller piece was cut to fit over the vent that points toward the back of the trailer.

The result?

The noise the unit makes was cut DRAMATICALLY. Very comparable to my other trailer that has ducted air.

This is a very simple and inexpensive fix that made a huge difference, my real question is, why did Coleman miss such a simple, cheap, and effective fix? Attachment 367094Attachment 1


Here is the other picture that didn't post...Click image for larger version

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ID:	367095
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Old 05-03-2020, 12:31 PM   #3
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Interesting,

So you are basically just filtering the air as it is blown back out and that cut the noise?
How much restriction do you think this added and what if anything do you think that will do to the performance and longevity of the unit?
Finally, where exactly did you put the material in the bottom of the plenum? Laid in a layer under the handler?

This could be a KISS solution, awesome.

Thanks,
Ian
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Old 05-03-2020, 01:16 PM   #4
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2018 27' Globetrotter
Hanover , Pennsylvania
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Great idea for a fix!

As to why did Coleman miss such a simple fix I would say they didn't miss it but chose not to add it for economic reasons. I'm not sure how many A/C's Coleman makes but let's assume it's a 1000 per week (not that many when you consider Ford makes 4000+ F-150's per day). If it cost's $1 for the filter material and labor to install it that's a savings of $50k per year.

So they decided to save a little money and most people will live with the noise (not realizing there are creative people who will make improvements).

Regardless, it's quieter now!
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Old 05-03-2020, 01:26 PM   #5
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1972 31' Sovereign
1975 31' Excella 500
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Benton , Arkansas
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Noisy Air Conditioner, fixed.....

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Originally Posted by Iansk View Post
Interesting,

So you are basically just filtering the air as it is blown back out and that cut the noise?
How much restriction do you think this added and what if anything do you think that will do to the performance and longevity of the unit?
Finally, where exactly did you put the material in the bottom of the plenum? Laid in a layer under the handler?

This could be a KISS solution, awesome.

Thanks,
Ian


Yes but no.

I placed the filter over the register to the rear of the trailer because I didn't need so much air back there anyway, but the front register isn't blocked, except where I placed the filter material on the floor of the interior shroud.

The unit still moves plenty of air forward, and a surprising albeit a reduced amount of air rearward even through the filter.

The unit itself discharges very close to the rear register, so I'm thinking that my covering this has adds to the quietness quite a bit, but fortunately for my trailer reducing the flow backward a bit actually helps.

The performance so far seems unaffected, I don't think that the longevity will be affected, if the unit were to tend to freeze up in use I might reevaluate, but in the near 24 hours it's been in place there is no indication of a freeze up at all.

I put the filter material along the entire discharge section of the interior shroud up to about 2" from the discharge vents.

Right now it's 96 outside and 72 inside...

I'll update this as the day progresses.

Being able to hold normal conversations from any point within the trailer is pretty dang cool.

(Edit. I should have mentioned that I used a separate piece of filter material to cover the rear discharge vent, I can reach my fingers through the vent slots to change the amount of the vent that's restricted).
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Old 05-04-2020, 07:06 AM   #6
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Thank you for the reply and further details. I’ll try this this week.

Ian
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Old 05-04-2020, 07:20 AM   #7
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I read this yesterday and I am not sure I understand. Aren't you just reducing the amount of airflow over the coils and into the trailer? Are there any long term consequences of running your AC with less airflow than designed? It won't hurt the fan since that is just a centrifugal blower, but surely you have changed the delta T across the coil?
Larry
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Old 05-04-2020, 08:17 AM   #8
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1972 31' Sovereign
1975 31' Excella 500
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Benton , Arkansas
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Originally Posted by lsbrodsky View Post
I read this yesterday and I am not sure I understand. Aren't you just reducing the amount of airflow over the coils and into the trailer? Are there any long term consequences of running your AC with less airflow than designed? It won't hurt the fan since that is just a centrifugal blower, but surely you have changed the delta T across the coil?

Larry


Not really.

What's happening here is the filter media is calming the turbulence that normally occurs when the air discharged by the unit impacts the floor of the interior shroud.

While it probably does restrict the air to a slight degree, it's not noticeable in its operation.

Could it somehow shorten the lifespan of the unit? Maybe, but I doubt that it restricts the air as much as ducting would so I doubt there will be any measurable consequence. But even if there is, being able to talk in normal tones makes it worth it to me.

If the fix causes the evaporator to freeze up, that would indicate an issue, but that hasn't happened yet.

If it does happen when it gets more humid I'll post up here, but it's not going to happen, the unit still moves a LOT of air.
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