Frequently Asked Questions about
Rear Door Heat Exchangers
Describe the coil inside the RDHx?
The fin and tube coil has 12 aluminum fins per inch, 2 rows deep on copper tubing. The highly engineered fins are designed to allow maximum airflow through the coil.
How many RDHx have been installed? How long have they been in service?
Thousands of units are deployed globally. The RDHx has been on the market since 2005, the product is based on mainframe cooling technology that has been field proven since 1964.
What is the effect of the RDHx on rack mounted equipment fan power consumption?
There is negligible impact. Testing has shown that a 15.5kW rack (filled with 39 1U servers) resulted in 0.45% increased power draw (70W total). Lower density racks would see an even lower impact, estimates for an 8kW server rack results in a 0.29% (23W) total increased power draw.
What is the MTBF for the RDHx?
With MTBF being a theoretical calculation, we prefer to rely on actual field failure data. With an install base of thousands of RDHx units since 2005, there are zero reported failures. The product has a 30 year design life.
What is the MTTR for the RDHx?
The RDHx can be replaced and operation restored in approximately 15 minutes, without downtime to IT/Communication Equipment, loss of water, etc.
As rack loading increases beyond the rated cooling capacity how does the RDHx respond?
As heat load increases the heat removed by RDHx increases as well, effectively removing a heat load cooling limit providing you a great deal of flexibility. In very high density racks the RDHx may not cool 100% but only cool 90% as an example. In that circumstance a 30kW rack would have approximately 3kW of excess heat leave the rack to be cooled by adjacent racks with RDHx and excess capacity. Site specific conditions dictate the RDHx performance, consult with your Coolcentric representative regarding your deployment.
Define RDHx Nominal and Maximum cooling capacity.
Using ASHRAE's published recommendations, Nominal Cooling assumes 2500CFM of 80F (27C) air to rack, 12GPM (45LPM) of 55F (12.8C) water to RDHx. Maximum Cooling assumes 2500CFM of 90F (32C) air to rack, 12GPM (45LPM) of 55F (12.8C) water to RDHx; the published values are 100% neutralization at those respective conditions. Actual performance may vary based on site specific conditions. M.
Does the RDHx interfere with the cable management of the enclosure?
No. The RDHx simply replaces the standard rear door of an enclosure and does not intrude into the interior space.
How does a User disconnect a RDHx from the system if the rack that it is attached to needs servicing?
First disconnect the quick release couplings for the supply and return hoses, then lift the RDHx off the hinges. Reverse the steps to reinstall the RDHx.
How is condensation avoided with use of the RDHx?
By using coolant that is maintained above the dew point of the facility whitespace there is no condensate generated on the RDHx coil.
How is the RDHx isolated?
Both the RDHx and Hose Kits use stainless steel ISO 7241-1 Series B fittings which have double shut-off valves. Each mating piece of these fittings automatically seal when they are disconnected. Additional isolation can be provided by the secondary loop distribution system based on site specific requirements.
How much heat is removed from my IT Enclosure using the Rear Door Heat Exchanger (RDHx)?
The cooling capacity will vary depending on the specific model of RDHx deployed and on the site specific operating conditions. Contact Coolcentric to discuss your requirements.
How open are the perforated sheets covering the RDHx coil?
The perforated sheets use a 64% open hexagon pattern.
In our Data Centers we access the cabinets daily. How will this affect the installation of your RDHx?
No impact. The RDHx can be installed onto a rack without downtime.
There are no filters on the door. Will dirt build up on the coil, does it need cleaning and how often?
Data centers are normally clean so dust and dirt build up will be minimal, clean annually if desired. Coil cleaning is included in the Coolcentric Preventative Maintenance Service.
What are the recommended flow rates of water through the RDHx?
Flow rate through the RDHx is typically 4-12 GPM (15 – 45 LPM). Flow rates below 4 GPM (15 LPM) are acceptable, there is no impact other than lower capacity.
What is the pressure drop across the RDHx?
Water side – 7psi at 10 GPM (38 L/min) including coil and quick connects and Air side – 0.035”w.g. at 2000 CFM (3400m3/hr), slightly more that standard perforated doors; both values based on the RDWTW model. Testing with 1U servers indicates increased pressure drop has minimal airflow restriction and has negligible impact on internal server component temperatures.
What is the recommended lifespan of the RDHx?
The RDHx has a 30 year design life.
What kind of monitoring devices ship with the RDHx?
The RDHx is a completely passive cooling door with no on-board monitoring. Coolcentric offers wireless environmental monitoring solutions as an option.
What other components are necessary for using the RDHx?
Coolcentric recommends using a secondary cooling loop in conjunction with the RDHx. This consists of a CDU, internal/external manifolds, flexible hoses and treated water.
What preventive maintenance is required for the RDHx?
Since the RDHx has no moving parts, no maintenance is required.
What racks and equipment is the RDHx compatible with?
Coolcentric RDHx are currently compatible with approximately 70% of the branded IT racks available in the market today, download our Compatibility Chart for the most current list. For racks not shown, new Transition Frames can be engineered quickly. Additionally, the RDHx is designed to cool any IT or Telco gear that has front to back airflow. Side-to-side airflow gear can be cooled with a small rack modification.
What types of racks can the RDHx be fitted to?
We adapt to a wide variety of rack types, including enclosures that are between 600mm and 800mm wide with 42U-48U enclosures heights. Additional rack sizes can be fitted as needed with the development of new Transition Frames.
What types of quick connections are used on the RDHx?
Connections are ¾” quick release couplings meeting requirements of the ISO 7241-1 Series B and constructed of 303 stainless steel.
Which coupling on the RDHx is the supply (inlet)?
The female connection (coupling) is the supply connection to the RDHx. The male connection (coupling) is the return connection.
Why do Top Feed RDHx and Wide RDHx have more cooling capacity?
Top-fed RDHx and Wide RDHx have larger coils than the Bottom Feed, 600mm RDHx that results in greater face surface area and more circuits – thus increased cooling capacity.
How many RDHx can be shipped in a 20 foot and 40 foot ocean container?
A 20 foot container holds 42 RDHx. A 40 foot container holds 90 RDHx.
Does the air pressure drop across the RDHx cause fans to speed up, consume more power, and negate any benefit of using the RDHx?
To provide a quantitative answer to this question Roger Schmidt and Coolcentric generated testing results on a rack populated with 39 1U servers as a worst case
configuration. The attached slides show that a rack with an RDHx sees only a 1.1% fan RPM increase over fans in a rack using a standard perforated rear door. This increased
fan speed results in only an 80 watt increase in fan power used in the rack.
Bottom line: adding an RDHx has negligible impact on total rack power. One more demonstration that the CoolBlue RDHx technology is the most energy efficient cooling solution on the market.
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