Let Your Generator Set Breathe with a Remote Cooling System

by Visitor Pawelski on ‎05-19-2014 09:36 AM - last edited on ‎06-05-2014 11:52 AM by Administrator

Paul Pawelski Caterpillar Blog.jpg



Most standby diesel and gas generator sets are equipped with radiators to regulate temperature. However, there are times when it is better to use a remote cooling system for temperature control. In urban installations where the generator set is in a basement or on the ground floor of a building, it is often impractical to use a large air inlet on one side of the building and a large air exhaust on the other side. Implementing a remote radiator behind the building can be a much better option, because all the cooling noise is on one side of the building and most of the mechanical noise from the engine can be contained inside the power room. 


Just because there is no radiator in the power room, it doesn’t mean that the room can be completely sealed. Not only does the engine need combustion air, but both the engine and the generator need a constant source of cool air to keep from overheating. Approximately seven percent of the heat from the fuel burned in a generator set is radiated into the power room by either the engine or the generator. For example, a generator set producing 2MW will give off almost 148 kW (50,000 BTUs) of heat in the power room. Unless there is constant airflow through the room, the temperature will keep getting hotter. Under these conditions, the insulation on the generator windings, the torsional damper on the front of the engine, and the electronic components will eventually begin to fail.


The damper at the front of the engine and the generator insulation are the two components most at risk from overheating. The damper requires moving air at temperatures below 50 °C (122 °F), and the generator’s entry air needs to be as far below 40 °C (104 °F) as possible. This can be best achieved by either routing the inlet air so it enters the room low to the ground by the back of the generator, or by installing a forced air duct system, or air curtain, to push cool air out of floor vents around the generator set with a room exhaust opening above the generator set. Both of these strategies optimize cool airflow.

Routing the air close to the ground is easier to do, but close attention to the airflow around the damper is required to make sure a recirculating vortex doesn’t trap hot air. Creating an air curtain has the added benefit of collecting the heat in a column above the generator set, keeping the rest of the room cooler. Other combinations of air inlet and outlet locations do not provide enough cool air near the damper and generator, so they require additional airflow strategies to keep the room cool.  


Designing power rooms for optimized airflow requires a bit of planning. We recommend using the equation below to figure out exactly how much airflow is needed to keep a steady temperature:


  • Q = needed airflow in cubic meters per minute
  • H = the heat being put into the room in kW
  • D = the density of air (about 1.099 kg per cubic meter)
  • Cp = the specific heat of air (about 0.017 kW minute per kg per degree in Celsius)
  • dT = the amount of heat that can go above the outside ambient temperature in Celsius

Let’s run through it together. If the outside air temperature stays below 30 °C, (86 °F) and you want to keep the room air temperature below 40 °C (104 °F), then the dT equals 10 °C (18°F). Now, let’s apply that to a two-megawatt engine that radiates 147 kW of power into the room:


Q=786.8 cubic meters per minute (27,786 cubic feet per minute)

Note: The final number only represents the value needed to cool the generator set. If the engine does not have outdoor ducting connected its air filters, then the amount of air used for combustion needs to be added to get the total amount of air that needs to enter the room.


For more information on how to design an optimized power room and get the most from your generator set, please contact your local Cat® dealer. You can also download our Application and Installation Guide for Engine Room Ventilation here.


We’d like to hear more about your experiences with power room setup and generator set airflow optimization.

  • How would you solve airflow issues in urban settings?
  • What does this equation tell you about your own power room setup?
  • What can Caterpillar do to help you get more from your generator set?

by Visitor powergear726
on ‎06-05-2014 06:53 PM

aft series radiator.jpga

by Visitor powergear726
on ‎06-05-2014 07:12 PM

as per attached example of a remote radiator, 2 parisitic load is involved, one-the fan motor, 2-the water pump.

how is 2- parasitic loads, the total hp/kw rating of the said remote design, as you advocate,

1. compared to the engine mounted radiator ?

and additional load of force-draft and exhaust fans ?  

while i admit that having a remote cooling system reduce working noise level

in the power house, but aesthetically negative to the architech or owners.

also to neighboring bldgs. 

given the above what is the best selling point for the said installation options,

to be accepted ?

i am in the supply and installation of gensets, and also of those above i attached pictures,

i supply also.

by Visitor Pawelski
on ‎06-23-2014 07:52 AM

If a genset is used that requires 100 break kW to run the fan of an installed radiator, you will need about 110.8 break kW of power to run the electric fan on a remote radiator. Here is why: A typical generator on a Cat genset is 95% efficient. Likewise, the typical electric drive fan motor is also 95% efficient. If the fan on the remote radiator takes the same amount of power to turn, it needs 100 kW mechanical power so 100/0.95=105.26 ekW coming into the electric motor. To make 105.26 ekW, the generator needs 105.25/0.95=110.8 bkW from the engine.


In a real world application, you will actually use a little bit less. That is because the fan on an installed radiator is trying to move air against an external restriction caused by the air flowing through the power room and duct work. An externally mounted radiator usually has no duct work so the fan is moving air against less restriction. However, as powergrear726 pointed out, there is a small amount of additional power required for the engine installed water pump (assuming that the external radiator is close enough that a second, electric drive pump is not needed). This additional power takes up about the same amount of power as is saved by the decrease in fan restriction so you still end up requiring about the same increase in bkW.


This can be decreased some by proper selection of radiator fans and motors. Some suppliers also offer variable speed fans so that the amount of power needed to run at the typical 70% load is less even though that system can still provide sufficient cooling at rated load. However, it is important that you understand the cooling system controls on a genset before selecting a radiator with an intelligent fan control to make sure that the two control systems don't negatively interact.


The amount of additional power required by forced air inlet or exhaust fans for the power room will depend a lot on the design of the ducting and exhaust locations. You can get into situations where the power room fan can take as much power as the radiator fans. In other cases where the power room airflow is well thought out and integrated into the total building air circulation plan, you can get to where the power draw is less then 10% of the radiator fan power. These are both extremes with most real world applications falling somewhere in between.


For standby applications, this power increase has little affect on the life cycle cost of the package since the amount of time that the genset runs is so small. The bigger issue is how to sell the higher initial installation cost,


Aesthetics can actually be a positive selling point. While large gensets can be placed on nearly any floor of a building, they are usually located on the ground floor or the basement to simplify building structural design. This results in large air inlets and exits needing to be located at traffic level. These openings can not be on the same side of the building and ideally should be on opposite sides to prevent hot air recirculation. That takes up prime presentation surface in addition to creating more street level noise when the gensets run. Usually, there is at least one non-presentation face to a building. This is typically the side on which the remote radiator is placed. You still need openings to allow air flow to be ducted into and out of the power room, but they can usually be somewhat smaller and since the total heat rise is less there is less risk from air recirculation so placing them on perpendicular building walls instead of opposite walls is less of a risk.


Radiators installed on the genset offer the simplest solution to add standby power. They use less power and all the designer has to do is cut big enough holes in opposite sides of the building to allow the needed airflow with out too much restriction. However, that simplicity comes at the cost of increased noise and loss of building presentation surface. Remote radiators offer more flexibility in the location of openings and reduce outside noise, but take more power and more care to effectively integrate them into the building design. As a supplier, you have to understand the customer's needs and the building designer's capability when you help them pick between the available options.


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on ‎08-01-2014 03:24 PM

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by Salauddin Rabby
on ‎08-01-2014 08:07 PM

We want to buy 1000KVA to 3000KVA used CAT generator.


by antonio alzona
on ‎08-03-2014 12:29 AM

I see that besides the installation cost of a separate radiator system, another problem that can occur is the leakage of heat and fumes along the piping system from the point of generation up to the radiator system. I feel that there is a need to weigh the cost of separating the radiator system versus benefit of total noise reduction, decreased  energy efficiency and  increase of total space allocation (radiator + generator). So, my question is in what condition is this separate radiator system really essential? or to rephrase it - when should we consider separating the radiator system from the generator?



by Visitor Pawelski
on ‎08-04-2014 06:56 AM


Installed radiators are in most cases the preferred solution. As long as you can flow air through the building with large enough openings and flow paths to keep the restriction low, installed radiators should be your first choice.

Remote radiators are for occasions where other design restraints prevent you from being able to implement this simple situation. Some examples are:

  • The power room has only one outside wall.
  • The power room is in the basement and the ducting of enough air in and out for the cooling system will result in more than 3/4 inch of water (0.18 kPa) restriction.
  • The gensets chosen require radiators larger than what can fit in the room or larger than can be supported on the genset rails (ex Cat C175-20).
  • Building security prevents the placement of openings only secured by grates or louvers that are large enough for a person to enter.
  • The genset is being used in Prime or Continuous mode with a heat recapture system to increase the efficiency.


by Visitor Pawelski
on ‎08-04-2014 07:01 AM

Symoon & Salauddin,


Please go to www.cat.com.  Under the "support" tab, select "find your dealer".  Your local dealer is the best starting point for finding new and used gensets and equipment.


by David Hurtado
on ‎10-14-2014 10:23 AM
I find that many facility designers are not familiar with the various options for remote-cooling of engine-generators. One specific application that raises a lot of questions is how to cool an engine equipped with an air-to-air charge-air -cooled system. I wrote an article on this subject (you can find it here: http://www.onsitepoweradvisor.com/2012/08/02/turbo-cool/) and welcome your comments on this solution.
by Visitor Pawelski
on ‎10-14-2014 12:08 PM

David, that is a very good summary of the issues. There are several charge air coolers on the market now from well established radiator and heat exchanger suppliers who know how to size them for the engines sold by major manufacturers. In the US, the important consideration is that the engine inlet manifold temperature, pressure, and flow match what was used for EPA validation - with correction factors for altitude and ambient temperature. While a floor mounted charge air cooler does increase your footprint, it minimizes pipe runs making it easier to match the inlet manifold conditions. It also makes it easier to maintain. Charge air coolers are exposed to high pressures and temperatures. Being able to visually inspect a charge air cooler for damage can be the difference between catching a small leak and having a major failure during operation that shuts down the genset.


by Victor Aliu
on ‎12-04-2014 04:24 AM

Dear All,


Can anyone help with an Installation Guide for the Remote Radiators and distance to a set of G3516LE Caterpillar Gensets>

by Visitor Pawelski
on ‎12-04-2014 07:21 AM




Talk to your local Caterpillar dealer. The dealer has access to Caterpillar PowerNet and our internal TMI data system and can provide you the cooling system A&I guide and data related to your specific make and model as well as expert advice.


The actual horizontal distance you can have to a remote radiator depends on the line resistance for the cooling circuits. The dealer can pull the pump performance curves for the G3516LE. The curves will show the range of allowed flows and how much line and radiator restriction results in those flows. Your radiator supplier will have something similar showing the radiator restriction at various flow rates. You can then use the equivalent line length method to determine how much restriction your intended pipe sizing and routing will cause. If your lines routing has very few elbows or valves in it, distances of 50 feet or more are often obtained. The third party site, Engineering Toolbox has a fairly good step by step instruction on how to do the length analysis at: http://www.engineeringtoolbox.com/equivalent-pipe-length-method-d_804.html . Please note that Caterpillar has not verified the suitability of the data shown on this site or any other third party site for doing cooling system calculations. Your installation designer will have to use his or her engineering judgment to determine the final routing.

by New member Sos3
on ‎12-09-2014 01:52 PM

Is it safe to perform a load bank n the rain?

by New member Sos3
on ‎12-09-2014 01:54 PM

Is there a manual outlining procedures for load bankng

by Visitor Pawelski
on ‎12-11-2014 07:36 AM




The answer to both your questions need to come from the load bank provider. The load bank will have a manual with it. If you are renting the load bank, insist on getting the manual with the load bank and READ IT. The load bank will have an IP rating. The IP rating describes how secure the device is against physical ingress (can you get your fingers on a charged component) and water ingress (can water get to components it can harm)? Ratings vary from IP22 (finger size objects can't reach dangerous components & vertical rainfall can not reach dangerous components) to IP55 (totally enclosed). Load banks designed to be used in wet weather usually have higher second digits in the IP number (IP 23, 24, 25, 53, 54, 55). Cables entering or leaving the load bank are shrouded and exit in a way that any rain on them runs away from the load bank. The cables must be in good condition and sized so that the insulation alone provides sufficient lowering of potential so that partial corona discharges can not occur between wet or submerged cables. The genset side of the connection MUST BE DRY. The cables should have drip loops to make sure any rain water running along the cables can not reach the generator connections. The load bank manual will have additional information on safety procedures when operating the load bank. Load bank setup and operation should be done by a certified electrician who is familiar with current safety practices. There will be a help line number in the load bank manual, and if you rent the equipment, there will also be a technical contact number for the rental company so WHEN IN DOUBT, ASK.


The Electrical Generating Systems Association (EGSA), an industry trade association, is in the process of developing a load bank safety training class. When it is available, it will be announced on their website www.egsa.org .

by stm3
on ‎08-25-2016 01:39 AM

Dear All

we are installing our Cat 3512B Diesel enigne mounted radiator to a remote location due to some plant designe issue.

the Fan has a poewr of 50 Bkw and 0.627 Pully ratio.can any one tell us about the correct motor size to run the fan remotly. i heve red above that if a fan power has 100 bkw it will required 110bkw electric load but i want th motor size with calculation so that i can better understand the sizing calcualtion. 

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