Can someone explain to me what the Honeywell UV100E Ultraviolet Systems really do and if they "actually" work? Also:
1. Will they keep the coils clean?
2. Where would I mount them on my furnace? I have a heat pump and my return air comes into the bottom of my furnace and the evaporator coil is on bottom. Would it go between my evaporator coils (in the "A" part of the coil) or would it mount above in my duct work? If it is mounted above wouldn't my coils still get dirty and therefore why would I need this? If I mount it below wouldn't the dangerous UV light shine through my return air vent?
3. Are there other brands on the market out there that are better?
4. Finally there are several different models, some with 2 bulbs, some that say surface treatment some that say air treatment, some that mount in the duct some that mount near coil, I am lost here PLEASE Help!

Thank You in Advance!

UV doesn't clean or filter the air; it disinfects it. You will still need an air filter on the system. Surface treatment is effective for surfaces where condensation is causing mold and/or mildew. Air treatment is aimed at killing airborn bacteria, viruses, and spores. I have a return-mounted Sanuvox purifier, and it has provided a noticeable improvement in allergen reduction. Your existing system design may dictate what type of lamps you can use.

Ultrviole Light used in these bulbs kill living organisms such as bacteria, viruses and molds.

Humidifier use may increase the popensity for mold to grow. If someone in your household is sensitive to mold then by all means this product is useful.

They don't keep your coil clean. Changing your furnace filter regularly keeps your coil clean.

The UV system is an expense. The bulbs need to be changed yearly and they are not cheap. Ease of changing the bulbs is what you really care about.

The best placement is at the "A-coil" because this area has the largest surface area that you need to protect. You want the air supplied to your house to be germ free.

See:
UV Light Filters IAQ HVAC air conditioning & heating (http://www.elwalters.com/business_025.htm)

UV doesn't clean or filter the air; it disinfects it. You will still need an air filter on the system. Surface treatment is effective for surfaces where condensation is causing mold and/or mildew. Air treatment is aimed at killing airborn bacteria, viruses, and spores. I have a return-mounted Sanuvox purifier, and it has provided a noticeable improvement in allergen reduction. Your existing system design may dictate what type of lamps you can use.

I know I will still need my air filter, I am not asking that. What I am asking is will it prevent the mold/fuzzy crap that builds up on my evaporator coil if I mount it below it? Or will I still have to clean the coil routinely? Would it shine through the return air vent if mounted below the coil therefore I would need to mount it above?

What I am asking is will it prevent the mold/fuzzy crap that builds up on my evaporator coil if I mount it below it?

It will help with the condition but will not cure it. The unit is to be mounted where the manufacturer says it is allowed to be mounted and not where you want to mount it.

Or will i still have to clean the coil routinely?

Unless you have some sort of super efficiency air cleaner/filter with no air that bypasses it you will more than likely have to clean the indoor coil at some point during its life. UV lights are not designed to keep all dirt off the coil. As previously mentioned depending upon your system a UV light might be beneficial but the only way to tell is by having a HVAC professional do an On Site Visit to your home and have them take samples of what is there now for analysis.

Would it shine through the return air vent if mounted below the coil therefore I would need to mount it above?

Who knows? It is all relevant to the duct work. Post a complete diagram of your system with return air locations/size etc and I am sure someone can figure that out but with out the drawing there can be no help on this issue. I will say this much that NO visible direct light is allowed since it can cause damage to your eye sight.

Do a Google for yourself and read up on all the different brands and what they do. This way you will be very well informed on the subject and when the HVAC professional comes to your home you will be prepared to ask your specific questions about your specific system since they will be there looking at it in person.