Understanding UV watts

[MrsBugmaster]

Please help me understand wattage in uv sterilizers.
UV Sterilizer : I have two of them. A 120 watt Aqua UV. It has 3 - 40 watt bulbs. It’s big and takes up a lot of space. Also have an Ice Cap UV with 1- 90 watt bulb. My question is which one is really better? Wouldn’t a single 90 watt bulb be more powerful than 3 40watts? Yes 3 X 40 is 120watts but I mean the water is still just going thru 40watts but 3 times so is it really 120 watts strength bulb vs one 90 watt bulb? Will be going on my new 270 gallon tank.

 

[MarineandReef Jaron]

I think the best way to explain is based on the chart below from the aqua ultraviolet instruction manual. Basically, there are 2 factors concerning UV performance.
1. UV Exposure
2. Flow Rate

In other words how much UV is applied to the water and how much water can you process? If you can use a lot of UV but not process much water and you won't get a big effect. Likewise, you can pump a lot of water through your sterilizer but if UV exposure is low you won't get much effect. The way the amount of UV is measured is micromoles per centimeter squared. In other words how much UV light energy is applied for each square centimeter of water that passes through the unit. You can increase the UV exposure 3 ways.

1. Using a more powerful lamp
2. Slowing the water flow through the unit.
3. Using a longer lamp so that the water passes over the UV lamp for longer without decreasing the flow rate.

Once you have the uv exposure correct then the question is can you process enough water to get effective results given your system volume? This is what the chart explains.

So why is a 3 lamp 120 watt unit rated higher than a single lamp 90 watt unit? The 120 watt unit can allow higher flow rates at the same level of UV exposure. The UV exposure is high not because the unit uses a more powerful lamp but because the water has to pass over nearly 9 feet of UV lamp. Even though the lamps aren't as intense the effect is that the amount of micromoles of UV light the water is exposed to in the 120 watt unit is greater than the 90 watt unit when the flow rates are the same. More importantly, you can match the UV exposure but process more water through the 120 watt unit so you can use the 120 watt unit for a larger aquarium or pond.

 

[MrsBugmaster]

I think the best way to explain is based on the chart below from the aqua ultraviolet instruction manual. Basically, there are 2 factors concerning UV performance.
1. UV Exposure
2. Flow Rate

In other words how much UV is applied to the water and how much water can you process? If you can use a lot of UV but not process much water and you won't get a big effect. Likewise, you can pump a lot of water through your sterilizer but if UV exposure is low you won't get much effect. The way the amount of UV is measured is micromoles per centimeter squared. In other words how much UV light energy is applied for each square centimeter of water that passes through the unit. You can increase the UV exposure 3 ways.

1. Using a more powerful lamp
2. Slowing the water flow through the unit.
3. Using a longer lamp so that the water passes over the UV lamp for longer without decreasing the flow rate.

Once you have the uv exposure correct then the question is can you process enough water to get effective results given your system volume? This is what the chart explains.

So why is a 3 lamp 120 watt unit rated higher than a single lamp 90 watt unit? The 120 watt unit can allow higher flow rates at the same level of UV exposure. The UV exposure is high not because the unit uses a more powerful lamp but because the water has to pass over nearly 9 feet of UV lamp. Even though the lamps aren't as intense the effect is that the amount of micromoles of UV light the water is exposed to in the 120 watt unit is greater than the 90 watt unit when the flow rates are the same. More importantly, you can match the UV exposure but process more water through the 120 watt unit so you can use the 120 watt unit for a larger aquarium or pond.

WOW, thanks for the detailed info! That helped a lot