[stagetek]

On a related note; we've been having trouble with a flow-through humidifier connected to our furnace. RH varies from single digits through to about 27 % after meal preparation. The house is well insulated and the windows are double pane low E, installed 4 years ago. Attic insulation was boosted to R50 this past summer.

After more unsatisfactory service from the company that did the installation of all the HVAC related equipment, we called a second company for an assessment. They felt that as the humidifier appeared to be working the problem was with airflow.

The variable speed fan was set at it's highest speed for when there is a greater than 2 degree variance between setpoint and process variable, and a more moderate setting for continuous air movement through the L2B air purifier. All the filters were clean and did not need replacement. They feel that system sizing may be an issue.

The tech peeled back the insulation on the suction line and the following pictures show that the line from the outside unit is well under the specified 3/4 inch OD. This line comes in and then joins to a larger diameter pipe which in turn is joined to a still larger line at the duct work.





Size of line prior to 2nd expansion joint.



Second expansion joint.



Size of suction line coming in from outside unit.

[hvac1000]

Looks like 5/8 OD copper line to me. Could it be possible they used the old line set from your older unit over again on your new install? This does happen since the cost of copper is so high. The manufactures directions state what is the minimum size suction line that can be used for so many feet of travel. In many cases you actually need a line sized larger than the fitting on the coil and in some cases you can get by with a smaller size SO just looking at the size means nothing without checking the install manual for that exact unit. Measure the distance, then refer to the manual for the exact size that should have been installed.

[KISS]

I would agree. There is sometimes elevation involved with the charts too. If there was a change from R22 ro R410 and they didn't properly flush the line, this can cause issues too.

Measuring static pressure would confirm if it's an airflow issue or not. Static pressure can also be used to determine if a filter element is dirty.

What model thermostat was used. Is the AC multiple stage? Is the heating multiple stage?

Was a manual J done for the house. This sizes the AC and cooling loads.

Was a manual D done for the house. This sizes the ductwork.

Do you notice any icing on the coils anywhere?

The humidity problem perplexes me, You failed to mention if this is a heating season or cooling season problem. Typically humidifiers are used in the heating season only. AC removes lots of humidity.

I'd like to ask where is the humidity measured and where in the system is it controlled from? Does the thermostat try to do some humidity control too? They can try to do it indirectly by varying the temperature and the cycle rate with a capable stat.

[stagetek]

It's heating season here; due to the problems with the humidifier we finally brought in a second company. During the inspection the insulation was cut in order to measure the line.

Both heating and cooling are multi stage. Humidifer is mounted on the duct work going into the L2B unit, which feeds into the furnace. Specs are from the manufacturer's site.

[KISS]

That's what's odd. Take this example: http://www.skuttle.com/pdfs/airclean_owners_install.pdf

Sensing should be in the return air stream. Injection should be after the air cleaner. Humidistat should be after the humidifier.

In some cases, there should be a large distance. This mfr specifies 8 feet.

So, it's like humidistat, 8 feet, air cleaner, input air to furnace.

You have to get things in the right order. The separation distance enhances the effectiveness of the air cleaner and improves humidity control.

[stagetek]

That's considerably smaller than my L2B unit:



Their website (http://www.l2binc.com/products/1/residential) has an updated model; as the picture above shows, the HEPA and charcoal filters are in a housing between the furnace and main L2B unit in our system.

[hvac1000]

Looks like that baby will cut down on the air flow for sure.

[KISS]

I'm having a hard time interpreting the graphs. It seems as though they pulled the wool over ones eyes a bit by saying that the speeds have to be moved up a notch whatever this means. Usually it's not that simple unless the unit is a Carrier or the air handler motor was replaced with an Evergreen technology motor.

This just gives you an idea that there is some science involved. The Air Side of Air Conditioning - Checking Velocity - Static Pressures

Measuring Static pressure and CFM is a great way to determine overall health of the system. If the air filer gets stopped up, the static pressure increases. If the CFM/ton of AC isn't about 400, then there are other issues.

Carrier's Infinity systems and thermostats allow one to check the CFM and static pressure direct from the tstat using an installer menu. The furnace error history is displayed and their Patented filter sense technology runs the system at 1:00 PM everyday at high speed and effectively looks at the change in static pressure since the last filter change. In some systems the motor CFM is actively controlled indirectly through the motor interface.

[KISS]

Here are a bunch of Amana's manuals: Heat and AC (HVAC) Technical Documents - Kentucky | www.lexpromechanical.com | Pdf, Amana, Distinctions, Spec, Pdfamana