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HVAC Coil Cleaning #4782535
06/09/18 08:44 PM
06/09/18 08:44 PM
Joined: Feb 2010
Posts: 4,838
Central Texas
sleddriver Offline OP
sleddriver  Offline OP
Joined: Feb 2010
Posts: 4,838
Central Texas
My yearly ritual. Close neighbor's contractor generated lots of limestone dust & mortar mix that wafted over where the outside unit was located. Sprayed down outside coil with a whole can of TuffStuff. Next I sprayed the indoor A-frame coil, letting both soak while I went to purchase new 3M filters. Too bad Lowe's no longer sells these better quality filters in a single. Now have to buy two bundled together. I prefer 3M filters because their pressure drop is quite a bit lower than Purolator's equivalent filter.

Got back and used a pump up sprayer to rinse both coils with soft water. Outdoors, I prefer to borrow neighbors pressure washer + wide-fan-tip and backflush the coil. Unfortunately he was unreachable today, it rained 0.3" and now outdoor humidity is 100%.

Removed outer cover on evap. coil and rinsed it from the clean (downstream) side. There was quite a bit of "very fine" dirt. As the coil sweats, this fine dirt turns to mud and will remain in place until this cleaning treatment. Post rinse, the drip tray had lots of this dissolved mud. So I flushed it out from both furthest ends back towards the drain until it was gone.

Upon installation of both new filters, I noticed something very odd. The Air Flow indication arrow appeared to be backwards. Didn't make sense. I'll call 3M Monday. Given the poor fit though, I used some UL-181B/X metal foil tape to seal in both filters preventing air from sneaking around the perimeter.

Buttoned it all up. Indoor air temp had risen to 82F over several hours. Humidity was probably 42% or so. I set the t-stat to 75F and restarted. Indoors is now 76F and indoor humidity has dropped to 37%. Quite a shock as outdoors it's 78F, dew point is 77F, which means outdoor humidity = 99%. So air flow across the clean evap coil is good, it is cold and sweating, thus indoor humidity has quickly dropped since the restart.

I always notice this drop in indoor humidity after cleaning the evap coil. Before, indoor humidity would be around 41% with t-stat set @ 78F. In humid Cen. Tx., humidity removal (latent heat) is just as important as cooling air (sensible heat).

Very surprised by the rain today. Didn't see it in the forecast. Weather-babe blew it.


1998 Volvo V70 T5 228,880 mi. Original Owner.
M1 10W-30 HM
"It's never a mistake to buy tools, defined broadly. They're not a cost, they're an investment." - J.B. Peterson
Re: HVAC Coil Cleaning [Re: sleddriver] #4782705
06/10/18 03:19 AM
06/10/18 03:19 AM
Joined: Feb 2014
Posts: 2,285
Kansan,1911 45ACP fan
Marco620 Offline
Marco620  Offline
Joined: Feb 2014
Posts: 2,285
Kansan,1911 45ACP fan
I go to Home Depot. They sell a spray yhats is citrus based to help


15' Civic 179k.0w20 Redline/Archoil9100,Eibach,Yokohama/Borla Exhaust/Tein Suspension/Fu7317/Redline Si-1
Right to work state proud. Non union household
Re: HVAC Coil Cleaning [Re: sleddriver] #4782752
06/10/18 06:04 AM
06/10/18 06:04 AM
Joined: Dec 2009
Posts: 5,037
Tn.
CourierDriver Offline
CourierDriver  Offline
Joined: Dec 2009
Posts: 5,037
Tn.
Cleaning the coils is a good thing as heat transfer is important as the freon changes back and forth from a gas to a liquid. Also, clean your blower motor fan blades at your evaporator. If they have dirt on them which most do, your efficiency can go down about 15 percent/cfm. They are not always easy to get to...good luck. Youtube should a video on this..

If you want to, you can install an electronic return air filter grille system where your return air filter is located if you want to spend the money...no more filters to buy, just wash out the electric grille when it gets dirty..


About 610,000 people die of heart disease in the USA every year/that's 1 in every 4 deaths. Thats 1,670 a day,,did someone say guns are dangerous..right...
Re: HVAC Coil Cleaning [Re: sleddriver] #4782774
06/10/18 06:52 AM
06/10/18 06:52 AM
Joined: Mar 2015
Posts: 5,142
Glendale, Arizona
billt460 Offline
billt460  Offline
Joined: Mar 2015
Posts: 5,142
Glendale, Arizona
I clean my coils at the spring start up of my unit every year. Out here in Arizona it gets very dusty, and if you don't clean them, your coils can lose a great deal of heat transfer efficiency. But I don't use a pressure washer to do it. Just a garden hose at city pressure, and a good nozzle. A pressure washer can easily bend the very thin Aluminum metal used in the coil construction.

First I soak the coils as much as possible with Simple Green straight from the bottle. I then immediately spray from both directions top to bottom. And you wouldn't believe how much dirt gets washed out. After I'm finished, I immediately start the unit, and let it run for a good half hour to dry it out completely.

Re: HVAC Coil Cleaning [Re: sleddriver] #4782783
06/10/18 07:10 AM
06/10/18 07:10 AM
Joined: Dec 2007
Posts: 566
Madison, Wisconsin
TWG1572 Offline
TWG1572  Offline
Joined: Dec 2007
Posts: 566
Madison, Wisconsin
This is a good reminder thread. I used your thread from last year as a motivation to start cleaning my A frame coil. Lots of nasties, so much that I ended up plugging my drain line. It was a cobbled up affair made of 3/8 rubber hose that the prior owner installed, so I ended up installing a proper PVC drain with traps and cleanouts.

My only frustration is I can't ever seem to get my humidity down below 45, regardless of temp. I have no idea why that is.

Re: HVAC Coil Cleaning [Re: sleddriver] #4782796
06/10/18 07:36 AM
06/10/18 07:36 AM
Joined: Jun 2002
Posts: 12,518
The Motor City
Kestas Offline
Kestas  Offline
Joined: Jun 2002
Posts: 12,518
The Motor City
Are you talking about a dew point of 45? I don't think you can get much lower without running the risk of icing over the evaporator coils.

Re: HVAC Coil Cleaning [Re: sleddriver] #4782799
06/10/18 07:42 AM
06/10/18 07:42 AM
Joined: Dec 2016
Posts: 6,226
Waco, TX
Linctex Offline
Linctex  Offline
Joined: Dec 2016
Posts: 6,226
Waco, TX


Yep did all mine three weeks ago - pretty much same procedure you described.

Originally Posted By: sleddriver

Upon installation of both new filters, I noticed something very odd. The Air Flow indication arrow appeared to be backwards. Didn't make sense. I'll call 3M Monday.


Me too....... 3M "Filtrete"... correct?

I followed the flow arrow....It sure looks like it's in backwards to me, too.


"The evidence demands a verdict".
(Re:VOA)"it's nearly impossible to actually know the particular additives that are in there at what concentrations."
Re: HVAC Coil Cleaning [Re: TWG1572] #4782801
06/10/18 07:43 AM
06/10/18 07:43 AM
Joined: Dec 2016
Posts: 6,226
Waco, TX
Linctex Offline
Linctex  Offline
Joined: Dec 2016
Posts: 6,226
Waco, TX
Originally Posted By: TWG1572


My only frustration is I can't ever seem to get my humidity down below 45, regardless of temp. I have no idea why that is.


It might not be healthy to live in an environment that dry.


"The evidence demands a verdict".
(Re:VOA)"it's nearly impossible to actually know the particular additives that are in there at what concentrations."
Re: HVAC Coil Cleaning [Re: sleddriver] #4782804
06/10/18 07:49 AM
06/10/18 07:49 AM
Joined: Sep 2004
Posts: 21,629
Orlando, FL
Mr Nice Offline
Mr Nice  Offline
Joined: Sep 2004
Posts: 21,629
Orlando, FL
I need to start cleaning my A/C coils.

Re: HVAC Coil Cleaning [Re: Kestas] #4782809
06/10/18 07:56 AM
06/10/18 07:56 AM
Joined: Dec 2007
Posts: 566
Madison, Wisconsin
TWG1572 Offline
TWG1572  Offline
Joined: Dec 2007
Posts: 566
Madison, Wisconsin
Originally Posted By: Kestas
Are you talking about a dew point of 45? I don't think you can get much lower without running the risk of icing over the evaporator coils.


No - I was talking relative humidity. Sorry about being unclear. It seems to be in the "acceptable" range, but the air can feel a bit muggy in the house at times. I see Sleddriver reporting humidity levels in the high 30's and wonder if I could do something to get mine lower. It's probably not going to happen though.


Last edited by TWG1572; 06/10/18 07:57 AM.
Re: HVAC Coil Cleaning [Re: Linctex] #4782820
06/10/18 08:09 AM
06/10/18 08:09 AM
Joined: Mar 2015
Posts: 5,142
Glendale, Arizona
billt460 Offline
billt460  Offline
Joined: Mar 2015
Posts: 5,142
Glendale, Arizona
Originally Posted By: Linctex
Originally Posted By: TWG1572


My only frustration is I can't ever seem to get my humidity down below 45, regardless of temp. I have no idea why that is.


It might not be healthy to live in an environment that dry.


My indoor humidity was 18% yesterday.

Re: HVAC Coil Cleaning [Re: sleddriver] #4782838
06/10/18 08:21 AM
06/10/18 08:21 AM
Joined: Nov 2011
Posts: 1,053
Lyndhurst NJ
Audios Offline
Audios  Offline
Joined: Nov 2011
Posts: 1,053
Lyndhurst NJ
I was up in my crawl space attempting to clean the evap coils and fan, but my unit is nearly 25 years old so i need to remove the whole case on the unit to access the blower. Its a York, I couldnt find any access points to just clean the coils and fan. The AC is pretty good, however on 90 plus days it struggles a bit to keep the house at 75. Is that typical? No access points at the evaporator?


2002 VW Golf TDI-Mobil 1 5/40 TDT
2007 Mercedes GL320 CDI Fuchs 5/40 GT Pro XTL
2005 BMW M3 BMW Twin Power 10/60
2003 BMW M5-Fuchs 5/40
1998 BMW M3/4/5 Fuchs 5/40
Re: HVAC Coil Cleaning [Re: TWG1572] #4782872
06/10/18 08:54 AM
06/10/18 08:54 AM
Joined: Dec 2016
Posts: 189
Wisconsin
emmett442 Offline
emmett442  Offline
Joined: Dec 2016
Posts: 189
Wisconsin
Originally Posted By: TWG1572
Originally Posted By: Kestas
Are you talking about a dew point of 45? I don't think you can get much lower without running the risk of icing over the evaporator coils.


No - I was talking relative humidity. Sorry about being unclear. It seems to be in the "acceptable" range, but the air can feel a bit muggy in the house at times. I see Sleddriver reporting humidity levels in the high 30's and wonder if I could do something to get mine lower. It's probably not going to happen though.



Blower speed has a big impact on humidity. The blower speed needs to be fast enough to provide adequate airflow to cool the house and prevent the evaporator from icing, but it has to be slow enough that the moisture has enough time to condense and run off the evaporator.

It's my experience that most systems are set up with the cooling blower speed too high. Cools the house just fine, but doesn't dehumidify well at all.

Blower cfm should be about 350 per ton. So if you have a 2 ton AC unit, set the blower speed close to 700cfm. There should be a blower perfromance chart somewhere in/on the furnace.


2011 Ford Crown Victoria LX 4.6L V8 auto
2009 Chevrolet Malibu LT 2.4L I4 auto
1974 Dodge D200 360 V8 4 speed manual
Re: HVAC Coil Cleaning [Re: sleddriver] #4782877
06/10/18 08:58 AM
06/10/18 08:58 AM
Joined: Sep 2012
Posts: 5,381
DFW
DBMaster Offline
DBMaster  Offline
Joined: Sep 2012
Posts: 5,381
DFW
I use pleated MERV8 filters sealed into the filter grills with foam weatherstripping. I clean the condenser coil annually, but previous checks of the evaporator revealed it to be very clean. I had to cut a "hatch" into my transition with tin snips to access it. I may check it again before the real heat kicks in, but filtration and sealing leaks around the filter housings will keep your evaporator very clean.

I do run my blower continuously which, as Sleddriver has pointed out in the past, does increase indoor humidity. I like the constant air movement and reduced dust. I replaced the blower motor in my unit two years ago. It was twenty years old at the time. Since I work for Lennox I got the motor and capacitor just above cost so it was a cheap fix. I noticed no real change in my electric bill when switching to continuous blower use.

Re: HVAC Coil Cleaning [Re: emmett442] #4782880
06/10/18 09:10 AM
06/10/18 09:10 AM
Joined: Mar 2015
Posts: 5,142
Glendale, Arizona
billt460 Offline
billt460  Offline
Joined: Mar 2015
Posts: 5,142
Glendale, Arizona
Originally Posted By: emmett442
Blower speed has a big impact on humidity. The blower speed needs to be fast enough to provide adequate airflow to cool the house and prevent the evaporator from icing, but it has to be slow enough that the moisture has enough time to condense and run off the evaporator.

It's my experience that most systems are set up with the cooling blower speed too high. Cools the house just fine, but doesn't dehumidify well at all.

Blower cfm should be about 350 per ton. So if you have a 2 ton AC unit, set the blower speed close to 700cfm. There should be a blower perfromance chart somewhere in/on the furnace.


This is a good point, and not something I've heard discussed before.

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