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# Lennox system not removing enough humidity

#41
08-12-12, 10:30 AM
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FYI, yes both black and white wire are HOT. If you put your meter leads across the 2 wires then it will read 240V. The proper way to check a 2 pole circuit is to put your meter leads across both hot wires, not 1 wire to ground.

#42
08-12-12, 10:51 AM
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OK, in that case I have 243.4 VAC.

Here is where I clamped the strips, I measured all 4 wires.

#43
08-15-12, 04:41 PM
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What was the return air temperature when you checked the split in heating mode?

#44
08-15-12, 04:47 PM
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In residential, three conductors come into the panel (ground aside); two hots and a neutral.

Hot + hot is always 240v.

Hot + neutral is 120v.

In the electrical panel, the breakers alternate between both hots (going down), so any appliance circuit that's supplied by two breakers linked together is 240 volt.

With one hot disconnected, a 240 volt circuit can still give a 120 volt shock if you're touching something which is grounded.

A separate bus bar is used for neutrals.

#45
08-16-12, 06:44 PM
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18.7 x 2 x 243 = 9088 watts = 30899 BTUs

CFM = 30899/ (1.09 x 25f delta-t) = 1134 cfm

That's not plausible on low or medium speed - See page 12, table 6 of http://webmanuals.lennoxeurope.com/O...%20install.pdf

The temperature reading needs to be taken as close to the air handler as possible, but not close enough to pick up radiant heat.

See HVAC: FURNACE TEMPERATURE RISE TEST - YouTube starting at 2:20

Last edited by user 10; 08-16-12 at 07:41 PM.
#46
08-16-12, 08:08 PM
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Temp inside the return just before last bend turning upwards to the coils was 76 deg. The temp measured on the discharge was after a 45 deg bend then the supply duct goes left for about 6' to the register. I can place the probe in the supply line in the bend which will not have direct radiant heat.

If the temp rises 5 deg how much will it change the CFM numbers?

With the fan on low, the ducting pops back out when the fan turns off. When the fan is on high, the ducting pops and bangs a few times and is fairly loud.

Perhaps it's the incorrect fan for the house? Just to bring up some older notes, the last tech said the inside unit doesn't normally match to the outside unit but does on paper. Where should I look for a fan model #? Should I get some voltage/current readings at the fan?

That CFM definately isn't plausable I agree, but do those CFM numbers coincide with what's happening and why I have oor moisture control?

#47
08-17-12, 12:04 PM
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On high or medium, the fan could be moving over 800 cfm. (can't tell without taking measurements)

Problems not related to airflow can cause poor dehumidification - leaky ducts if in the attic, unit oversized, not properly charged.

---------------------------------------------------------

30F rise = 944 cfm - still not realistic on low.

The speed that gives a 35F rise give or take a little bit is correct for your 2 ton system.

Are you sure the lowest speed is being energized in emergency heat mode?

#48
08-17-12, 01:51 PM
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I energized the bottom tab, farthest from common..4th slot.

#49
08-17-12, 04:59 PM
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The 4th slot is the lowest - yellow wire is used for emergency heat, black for cooling and normal heat. (heatpump on, strips cycle as require)

You can verify that the yellow wire is being energized in emergency heat mode with an ammeter.

It sounds like the temperature reading is a few degrees off.

But the bottom line is you have a 2.5 ton air handler (1000 cfm give or take 100), so the blower should be set to medium or low speed (2 tons = 800 cfm give or take 100) for cooling unless your air ducts are undersized. If the split in cooling mode is consistently less than 15 degrees with the blower on medium or low speed, the refrigerant charge needs to be checked.

The second part of this sheet specifies what the supply air temperature should be (give or take a couple of degrees) at various wet/drybulb return air temperatures ->Efficient Indoor Comfort

#50
07-13-13, 08:46 AM
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Instead of starting a new thread I wanted to revisit this one. I have a set of gauges on the outside unit and the temp and pressures are as follows, all in degrees F

Outside air 77 F, WB 72.3 F
Inside air before coil 71.3F WB 60.5F

Discharge temp 12' from coil 59 F WB 51 F

Indoor humidity 58-61%

Fan speed on low

Last edited by hvactechfw; 07-14-13 at 06:49 PM. Reason: REMOVED REFRIGERANT PRESSURE INFO.... NOT ALLOWED PER FORUM RULES!
#51
07-13-13, 08:54 AM
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Model # is 26-024

Last edited by hvactechfw; 07-14-13 at 06:49 PM.
#52
07-13-13, 09:28 AM
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I went and re-measured as accurately as possibly my interior space. Inside walls are 27' wide and 44' long. This is a rambler with basement and half of foundation wall is below ground.

This comes out to 2376 sq ft.

I did not exclude wall thickness but since this house has the most avail space used, there isn't much to subtract....maybe 5%.

#53
07-13-13, 10:53 AM
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I know I had stated previously I have a 20x20 return upstairs and a 12x12 opening in the basement....the entire return duct from upstairs to basement is only 20"x8", entering the 15"x20" base of the air handler.

Upstairs opening is 20x20 but quickly reduces to 20x8.

I can tell the attic heat seeps into the duct, I have let the ac run for awhile while I was testing and at the upstairs return, I have 69 deg on the room side and 72.5 deg on the duct side behind the return filter.

#54
07-13-13, 11:08 AM
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Here's a rough sketch of the air handler and return ducting. Are we looking at a grossly undersized unit?

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#55
07-14-13, 02:32 PM
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Update:

After checking the pressures yesterday, I was convinced it was an airflow issue with the evap coil. Whether or not it was dirty or the fan was too high but since I haven't had this humidity problem as bad as this, so I cut the PVC drain and pulled the A-coil.

I wasn't able to see to the peak of the coils before but once I pulled it the evidence was clear, it was crazy dirty from mid-point on up, the flash hides the dirt unfortunately.

After about an hour of spraying, rinsing, scrubbing, spraying, rinsing...it came out fairly clean. The amount of water draining now is a steady stream, no drips.

I went ahead and blocked off about 25% of the duct after the air handler to slow the air down a little. I will re-check pressures and temps but all is stable now and I now have 15-16 deg drop across the coils.

There was a lot of fiber strands from the cheap filters I'm assuming, at the peak of the coils.

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#56
07-14-13, 06:52 PM
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MODERATOR NOTE

If you post any refrigerant pressures or anything to do with sealed system repair the info will be removed and your thread will be CLOSED! Please read the following sticky: http://www.doityourself.com/forum/ai...ng-your-c.html

#57
07-21-13, 07:38 PM
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Whoops....my bad. I didn't see that part of the rules.

Update after a week of a clean indoor coil, RH is holding between 40-45% and since I leave the air handler fan run continuously, the RH peaks around 55% overnight but is quickly reduced when the A/C kicks back on.

I still needed to block off about 30% of the supply line to slow the airflow and everything is in check. House is very comfortable at 73 deg and it appears that my 2-ton unit is slightly oversized for this house but now is working better than it has since we moved in.

I have cleaned the coil twice since we have been in the house, looked up through the filter opening and it appeared to be clean. But when I checked everything I could I ended up puling it and what I couldn't see was the dirt near the peak of the coils and still the entire coil needed light scrubbing. After that it made all the difference, now it's shiny clean and really sucking the moisture out.

#58
07-22-13, 09:16 AM
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Concerning Return air filter areas; 325-sq.ins., per ton gets the velocity through the filter(s) at 300-fpm or less which is Manual D required for low pres.-drop filters.

Do NOT use 1" deep pleated filters; too much pres.-drop!

Yours has 544-sq.ins., which is not too bad; 325 * 2-ton is 650-sq.ins.
However, it should not be bowing the filters in, to much!

The more filter area the better, & a lower Return air resistance will improve efficiency of airflow & increase CFM volume of airflow.

There could be other areas of resistance in the Return airflow.

#59
07-22-13, 10:09 AM
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1" pleated filters might be okay in some systems but not others; with a 16F drop, it's unlikely that low airflow is an issue.

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