ICS Magazine

What is an LGR Dehumidifier? More Than What You May Think…

December 3, 2012
fisher lgr dry conditions meter reader
What is an LGR dehumidifier? What a silly question! What is a Low-Grain Refrigerant dehumidifier? Obviously, it is a dehumidifier that says “LGR” on the name plate…right? Either this is going to be the shortest article of all time, or there is more to the story.
 
As it turns out, there is a lot more to answering the question of what an LGR dehumidifier truly is. Unfortunately, the water restorer needs to beware of many products that are released under the “LGR” name, because there is only a loose definition of the term. Many dehumidifiers are low grain refrigerants in name only. In many cases, “LGR” is simply used by manufacturers as a marketing term.
 
The IICRC S500 2006 defines LGR as follows: “Low-Grain Refrigerants have an enhanced refrigeration system that allows the dehumidifier to dry a space to a much lower humidity than conventional refrigerant dehumidifiers. The enhancement consists of methods of pre-cooling the incoming air stream; e.g., heat pipe or air-to-air heat exchanger. While conventional refrigerants begin to lose efficiency after drying the air to approximately 55 GPP, an LGR may continue to effectively remove some moisture from the air stream to as low as 34 GPP or 38°F/3°C dew point. A low-grain refrigerant dehumidifier removes more water, continues to dry to lower humidity, and removes more water per kilowatt of electricity consumed than a similarly sized conventional refrigerant dehumidifier. (ANSI/IICRC S-500 2006, p. 148)”
 
This definition includes several key points:
  1. LGRs lower the humidity of the air better than conventional dehumidifiers.
  2. LGRs are more efficient than refrigerants.
  3. LGRs are enhanced by pre-cooling the airstream.
  4. LGRs can remove some moisture from air as dry as 34 GPP.

More Efficient?

You’ll see the problem with the first two points right away: “better” and “more efficient” are not defined. This provides manufacturers with a handy loophole. If a manufacturer is able to make a dehumidifier that pulls the slightest bit more water out of the air compared to a similarly-sized refrigerant dehu, then the manufacturer can feel free to label the unit “LGR.” But I don’t believe this approach to LGR dehumidification best serves the interests of the restoration industry.
Manufacturers are under immense pressure to develop LGR dehumidifiers for this industry. To my knowledge, not a single new conventional dehumidifier has been introduced to the restoration industry in North America in the last ten years. This is because virtually all restorers are demanding LGRs. Many insurance companies are willing to pay more for LGRs than conventional dehumidifiers. So, I can understand why manufacturers are eager to put the LGR label on their units. But just because I understand the reasons doesn’t mean it is the right thing for the restoration industry today. 
 

Specific Definition: Pre-Cooling

When the IICRC S500 2006 was published, there were two ways of pre-cooling the air entering a dehumidifier. One method was using a heat pipe system. It was an extra set of dehumidifier coils which stole cold air from behind the evaporator (cold) coils. The heat pipe then brought the coldness into the intake of the dehumidifier, and pre-cooled the air coming in.
 
The other way of pre-cooling the air in 2006 was to use an air-to-air heat exchange block made of plastic or aluminum. This system was very similar in principle to the heat pipe described above. Coldness from the back side of the evaporator (cold) coils was routed to the intake air of the dehumidifier, pre-cooling the air.
 
Both heat pipe and air-to-air heat exchange systems work effectively. However, both require extra space (and weight) as well as more materials. Some of these materials, such as copper and aluminum, are quite expensive. Continued development has some manufacturers looking at ways to eliminate this cost, and achieve LGR performance characteristics at a lower material cost. I look forward to seeing the results of new innovations for advancing LGR technology.
 
So, one way to verify whether your machine is truly an LGR dehu would be to open up the unit and verify the presence of a pre-cooling system. This would be evidence that the unit in your possession is really an LGR. However, several products have been released in the last few years which have pre-coolers but in fact do not achieve the final definition of LGR performance – performance below 34 GPP.
 

Best LGR Definition: Performance Below 34 GPP

The best performance definition for an LGR dehumidifier is that it should be able to remove some water in very dry conditions. Again, we have to be careful with this definition, because what is the definition of “some” water? Is that two drops? Two pints? Two gallons?
 
In my opinion, a true LGR should be able to remove at least as many pints per day as the number of amps it uses at these extremely dry conditions. For example, if a dehumidifier uses 10 amps of electricity at 115 volts, then we should see at least 10 pints of water in the bucket after 24 hours of dehumidification below 34 GPP. A 5-amp LGR would be expected to pull at least 5 pints in dry conditions. These seem like tiny numbers, but even a small amount of liquid water equates to a huge amount of water vapor. Remember, 10 evaporated pints of water would equate to over 116 grains of moisture in every pound of air in the average size structure.
 

Test Your Dehumidifiers – Or Not….

I wish it were possible to hook up a dehumidifier in the shop to test it at these conditions, but without a sealed and climate-controlled test chamber, this is a very difficult test to set up. If you live in a desert area, or it is the dead of winter, you may be able to replicate 34 GPP air for a 24-hour period. You might direct air from one dehumidifier into the LGR you want to test, but this isn’t a fair test, as the temperature of the air coming out of the dehu is elevated – typically 100° or more. In these conditions, even the best LGRs would show no performance. In these ultra-dry conditions, you can expect performance between 70° and 80°. Real LGRs are amazing machines, but even they have limits!
 

Ensuring LGR Performance

Even if you have a true LGR unit, it may not be performing as you expect. Why? Because the dehumidifier coils aren’t clean. 
 
Dehumidifier coils work on the principle of energy exchange. The copper tubes and aluminum fins exchange energy with the air flowing through the system. During the life of a dehumidifier it is exposed to large amounts of dust and other contaminants. If filters are not properly maintained, the amount of contamination deposited on the coils increases exponentially and the coils are soon covered with a thick layer of gunk. This gunk acts as an insulator between the air and the coils. It also restricts airflow through the coils. Both factors will considerably reduce the heat-transfer capabilities of the coils. 
 
Cleaning the coils of a dehumidifier is a simple process and should be performed regularly as specified by the manufacturer of the machine. Look in your user guide for directions.
 

LGR – Buyer Beware

Before making a large investment in any manufacturer’s products, you should be sure that the unit is going to meet your needs. Buy one or a few and test them in your operation. Get some feedback from your trusted technicians and project managers. Unfortunately, we often get busy and take too big a risk with a new brand or model and get burned. 
 
Also, if you are an “early-adopter,” be sure to keep in contact with the manufacturer of the product. Equipment manufacturers are often quite responsive to questions and concerns from customers. Speaking from experience, I know that manufacturers love specific feedback that can help make their product better. 
 
Ultimately, you need to be aware that just because a dehumidifier says LGR on the label, it doesn’t mean that the unit is truly an LGR. The proof will be in the amount of water your machine actually removes in low grain conditions.