Is it time for a breath of fresh air?
In recent years, many new options have arrived on the extraction system market. There are now choices of super-quiet or super-powerful duct fans, quieter and tougher ducting, and some advancements, such as increased bed-depth, in the options available for carbon filters.
Perhaps you have already been thinking of changing your extraction system. Maybe the one you have is getting a little old, or noisy, or maybe it just isn't keeping temperatures down enough when the summer weather kicks in.
The reasons you need an adequate extraction system
An adequate extraction system is a vital part of just about any successful indoor grow for the following reasons:
- In an indoor grow-space, grow-lights produce heat which would normally build up until it becomes too hot for the plants to grow anywhere near optimally.
- During photosynthesis, plants use CO2 which they obtain from the air in the grow-space. As the CO2 in the air gets used up, plant-growth speed will become more and more compromised until eventually it becomes quite a considerable bottle-neck.
- As plants transpire, they release water into the surrounding air which raises the relative humidity of the grow space. This can cause problems with the VPD (Vapour Pressure Deficit) and can also cause mould risk issues.
To maintain plant growth speed as close to optimal as possible, the hot, stale, CO2 depleted air needs to be replaced with fresh, cool air with normal levels of CO2 in it.
So, why would I want to upgrade my extraction?
Most growers question themselves as to whether their current extraction system needs updating for 3 main reasons:
- Firstly, would I benefit from a quieter system?
- Secondly, is it worth upgrading to one that is electrically more efficient?
- Lastly, is the one I already have powerful enough?
Silence is Golden
The first question is the easiest one to answer. Just ask yourself: "Is the sound of my extraction system noticeable to my neighbours or those who live in the same building as the grow-space, particularly at night?". To answer that question, all you need to do is wait until the wee small hours, turn off everything else like the television that makes any sound, have a wander around the building and have a good listen.
To answer the second question, if you're running a normal AC fan (non-EC type) and you are using a fan speed controller then the chances are that almost full power is being used even though the fan may only be working at, say, 50%. EC fans and the controllers that work with them use a proportional amount of power for their running speed. An EC fan and controller running at 50% only uses 50% of the power that it would at 100%. Of course, ultimately, the grower needs to calculate if the electricity savings of an EC system is worth the cost of the upgrade. However, the savings on your electricity bill is, in most cases, quite considerable.
Take for example a typical 10" box fan and a hybrid fan speed controller which runs at full-speed for 8 hours a day, ¾-speed for 4 hours a day, and at ½-speed for 12 hours a day. The typical cost of running this would be £330 per year.
A 10" Revolution Vector EC fan and controller is much more efficient. Particularly during the 16 hours per day when the fan is not running at full speed. In fact, the cost of running the EC fan + controller for a year on the same schedule is just £40.22.
This represents a very significant saving of nearly £290 in electricity costs per year! Although we have used a fairly large extraction system as an example, the savings are pretty considerable no matter what size of fan + controller that you compare.
Making sure the extraction rate is high enough
Getting to the third question, if your extraction system is not powerful enough then it may not be able to keep the temperature down during the heat of summer.
- This might be because it was not quite up to the job when you first started out.
- It might also be because your duct fan and filter combination is getting old and isn't shifting the same amount of air as it was when it was new.
- Perhaps you have increased the size of your grow-space / number of lights and your old extraction system is now inadequate for the job at hand.
- Or, perhaps your grow-space is in a loft or attic or along a south-facing wall and gets warmer than other parts of the building in the hot summer sun.
There are a couple of simple calculations to find out if your extraction system is adequate by using the guide below.
Calculating the size of extraction system you need
The rate of air movement that a duct fan can achieve can usually be found in its specifications. However, this spec is usually the rate of air-flow of the fan in free-air with nothing attached to it. Anything that is attached to it (like a carbon filter and ducting) will put a "load" on the fan and will therefore reduce its air-flow. As a result, the air-flow rating of the duct fan is only the starting point for calculating the rate of air flow for the whole extraction system which comprises of a duct fan, ducting and a carbon filter.
The exact mathematics of calculating the reduction in air flow due to ducting, carbon filters, bends in the ducting etc. can quickly become complicated. Fortunately, we can make an adequate guesstimate of how much they reduce the air flow and therefore simplify the calculation for a fairly average installation.
Here is the simple way of finding what the minimum rate of extraction is that you will need:
Find out the volume of your grow tent or grow space in cubic metres. This is worked out by multiplying the width by the depth by the height (W x D x H). For example, a 2.4m x 1.2m x 2m grow tent has a volume of: 2.4 x 1.2 x 2 = 5.76 m3.
Multiply the volume by 60 to find out how much air needs to be removed per hour. In this example: 5.76 x 60 = 345.6 m3/hr.
So, the duct fan in this extraction system should be rated at 345.6 m3/hr at the very least. This rate of extraction will be just about be adequate if the grow-space is not located where the sun will cause extra problems.
For locations like that it would be better to go for a system that has a greater extraction rate and to use a fan speed temperature controller along with it to reduce the extraction rate when operation at full-speed is not needed. We would probably advise increasing the extraction rate by anything up to an extra 50%.
This works out to be 345.6 x 1.5 = 518.4 m3/hr to make sure that there is some in reserve for the hottest times of the year. Partner that up with a decent fan-speed temperature controller and you have a system that will keep your grow-space at the right temperature and have plenty of head-room left over to cope with those summer days that turn out to be scorchers.
Are there any other reasons to replace my extraction system?
Another time to think about upgrading your extraction is when you have increased the size of your grow-space. You can use the calculations above to work out if your old extraction system can still do the business adequately. If not, then it would be very sensible to consider an upgrade to an extraction system that is going to cut the mustard, particularly during the summer.
If you have answered yes to any of the above questions, then why consider one of the many extraction kit options that we have on offer. All the parts are matched to work together perfectly, and there's money to be saved over buying the parts separately.
So, I've decided to upgrade my extraction system, what are my options?
1) Quiet Options
If a job's worth doing, it's worth doing well! Here are 2 of the quietest extraction kits that money can buy:
2) I Just Need More Power!
The extraction kits above are available in different sizes with air-flow ratings that will cover most eventualities. However, if you are just looking to upgrade the air-flow rating of your extraction kit and you aren't too concerned about noise or efficiency then the following options might be just right for you. They are all available in different sizes:
Choosing an extraction system can be a confusing affair as there is a large choice from different manufacturers. There are aspects to bear in mind, though, and they are both down to do with how different manufacturers portray what would seem to be comparable specifications. First of all, the free-air air-flow rating says nothing about how well a particular duct fan can maintain air-flow with a particular load. It is easy to presume that if a 5 metre length of ducting reduces the air flow by 10% for one fan that the same 5 metre length of ducting will reduce air-flow down by 10% for all duct fans. Unfortunately, this is not the case. Different fans have different abilities to maintain air pressure through a load. This is where the paradigm of "you get what you pay for" comes into play. Those products at the higher end of the market are almost certainly going to be able to maintain pressure under load than a cheaper model. Beware cheap duct fans, particularly if a carbon filter and ducting are going to be attached.
The other difficulty presented by manufacturers and their specifications is to do with the sound level rating. This rating, which is usually expressed in decibels (dB) can be measured a host of different ways. The figure quoted by a manufacturer can be affected by the following: How far away from the fan is the sound level being measured (1 metre? 3 metres?), has ducting/filter or other load been attached? It is well worth being aware that manufacturers do not all use the same methodology in their testing. However, if you go for a model made by a well-known manufacturer with a good reputation then you will almost certainly get a reliable, powerful fan with low noise levels.
