HVAC Electrical Room Cooling Dilema

You could have prevented the issue altogether by planning for it before hand.

So, first, fire the person responsible for the installing the system without giving any thought to the additional heat load.

Then, with that person gone, hire someone who can see the entire installation first hand to solve the problem. There's no magic window here.

Without numbers and more site information, all you can do is maybe run a cooling hose out the door, or maybe through the roof.

Good luck.

Can you install an in-line duct fan that will pull more of the cooled air into this room? This does not require any increase to the existing HVAC system, nor any additional ducting. If other parts of the building suffer as a result of sending more air to the electrical room, an additional HVAC system could be added elsewhere where it would be more conveniently installed.

http://www.espenergy.com/in_line_duct_fan.htm

GA from me. My first thought, before reading any comments, was that this would be an ideal situation for a mini split. -- JHF

How about louvers in the door to the room.

One in the top and another in the bottom will encourage a sort of thermosiphon. I have used this technique with success a number of times.

You mentioned a fire rated wall. Is the door in a rated wall? If yes, there are fusible link louvers available for fire rated doors.

Johnroy is right. Do as suggested.

You will have a hell of a time balancing two independent cooling system in one airspace. Increase the present one's under one controller, or as a poor second watch carefully and regularly them. The problem is, that, if the smaller happens to be set a bit lower, it does not cycle off, and accumulates ice, freezing up.

Blank off the air duct of the existing and use the Split A.C. We do that in Control panel rooms and face no problem.

Hi Kiran,

If your door panel is swing out. what about to put an ducted exhaust fan directly from the new electrical equipment cabinet connected to the top portion of door panel with the rectangular end hole, the end point of the duct must be self sealed when you close the door, then you can remove the heat load directly coming from the new cabinet, this is i think most economical way. we did this in one of my project in the past and work efficiently with out additional cost in investing Split AC and low in operational and maintenance cost compare to split Ac.

Kind regards

Roman

Tell us about the walls of this room. Are any of them the exterior wall of the building? What is their make up.

How about the roof? Metal? Rolled roofing?

Could raising the solar reflectivity of the exterior surfaces enough to drop the heat gain of the building by around 50% help your problem? We have done that many times in commercial buildings with our coating.

Hal

If you have a clean compressed air supply, you could use a vortex chiller on the new cabinet, it cools the internal area of the cabinet in the same way a carburetor chills the fuel/air mixture entering an engine. Drawback, can be noisy if not silenced on exit. Used this on Navy test stands where fuel vapors were prevalent and sparks of an electric motor could be an issue.

No matter what the heat is still in the room. It has just been moved from the cabinet.

As John stated the best solution is the Mini split. Depending on the building and its design, the condenser can be located in a return air plenum just outside the room keeping the cost down on installation. Or if located on an outside wall, core it and fire caulk it so you don't have to use a pump in the room for condensate. The inline pumps the MFT sells are crap and die leaking water into the room. If you need a pump look to a sump style (little Giant) pump to be wall mounted in the room.

The new electrical equipment and the instrument cabinet can be fitted with an independent panel cooler and the exhaust of this panel cooler could be connected directly to the control room exhaust. If you could furnish some of the details of the additional heat load like the physical sizes and the control room general layout, it might be possible to suggest a better alternative.

I would suggest a heat pipe based heat exchanger to throw the warm air from inside the panel to outside ambient air. However, as others asked, geometry of walls as well as placement of panel w.r.t. wall distance is to be known.

There is a possibility to handle this heat independently.

Had the same problem in Malaysia, ambient outside 30C

Thyristor drive was added in the switchroom with another 10kW-20kW of waste heat, and no one anticipated that these would be added in the design some 20 years earlier.

The equipment cabinet had its own fans, we used these to duct the air outside with a sheet metal ducting made locally to fit, with a mesh at the outlet to stop flies/vermin. Not much more than a hood as this was an outside wall. This pulls in more via the HVAC makeup air which was around 10%, i.e. fresh air from outside. You need to consult with the HVAC designers to adjust the existing vents for make up air which is already happening, the system doesn't recirculate the same air, it adds a percentage of fresh air based on occupancy & other factors. This way all the heat from the thyristors went directly out and did not have any effect on the switchroom HVAC.

I did consider an independent inlet and outlet with extra fans, with flexible ducting to the outside air. The thyristor drive cabinet was designed to operate at ambient temperatures above 30C so with sufficient air movement and monitoring to check cabinet temperatures I considered it a workable solution. But the last paragraph design has been working for over 10 years now with no problems.

Its a good thing that you guys planned ahead.....

Who would have thought that additional electrical equipment would be adding heat to an existing room ..?????!!

We have used Liebert Units in our IT Data Center rooms and they provide very good temp and humidity control. Your firewall will have to be penetrated for set lines (seal with fire caulk) and you will need space for a condenser pad outside, etc.

With a different type of solution you add a new supply ducting and more return air ducting. You will then need to add fire dampers in the ducting.

We have several computer server rooms that utilize a small (wall mounted) split system similar to what Johnroy noted in his posting. Condensate is removed via a small pump and dumped to drain in another room. While the heat load is not as large for these applications as an mcc room, larger split systems are available. As a precaution, we installed a temperature alarm system to call the IT department if the room temperature exceeds a certain value; if you have concern that equipment may shut down unexpectantly if the electrical room temperature gets too hot then you might want to consder this notification feature.

Hi Kiran:

A split system with an air cooled condensing unit outdoors and an air handling unit (AHU) in the electrical room sounds like the easiest approach. There would be two refrigerant lines conecting the cooling coil in the AHU with the condensing unit requiring two round holes in the fire rated wall. Properly sealed they will not comprimise the fire rating. It is imperative the condensing unit has the necessarycontrols for proper starting and operation during the coldest winter conditions expected.

It's not rocket science but you will need a contactor who is qualified in the HVAC field. It will be important this contractor includes a control system designed to stage the existing and the new system for their proper sequencing. Well designed, the entire system will be simple and stright ahead. No bells and whistles required if done right. After installation the system will need to be professionally maintained to provide you with reliable and economiocal operation and longevity just as you hope the airline of your choice is providing for the plane you happen to be flying on.

Good luck,

Lou Bindner

Denver, CO

One hole penetration for the insulated copper, drain line and EMT should suffice. Just be sure to seal it well.

As far as taking control of the system....stage it. Use the existing house system to control the room temp to the desired set point (though I understand it will not get there on its own now) and stage the remote style stat that comes with the mini split 5 degrees higher. So when the room warms both units run and when the room begins to drop in temp to set point the mini split will turn off having the house system carry the load until it warms up again. Hopefully once you get the concrete in the room cold it will help maintain the thermal load evening out run times.

Thanks every one for the valuable comments. I see great people are always here to help.

Since I am not an HVAC person, we will consider each of comments with the HVAC specialist to move forward to the resolution.

Kiran

My suggestion of a 'split system" was too general. Providing that the additional capacity required falls within the capacity range of mini-split systems that would be my choice also. The added cost of a two stage control system which will automatically bring on the added second stage when needed will be funds well invested.

I wouldn't advise attempting an "exhaust system" unless the temperature of the makeup air is the same as the desired temperature you are trying to maintain in the space in question. Go with a design/build team who will...keep it simple, keep it simple, keep it simple. This is not brain surgery as long as your design/build team knows their stuff. Attention to low ambient control of the added system is paramount.

Good luck

Lou Bindner