Holdfast Training Services Trial Blog

Another day another project. I have started to become increasingly involved in ‘Building 2001’ in Harrisburg, which is the home of the enormous Eastern Distribution Centre (EDC). I say increasingly involved, though yesterday I narrowly avoided arrest, more about that later. The building is pretty large, mainly dominated by a warehouse but with an admin section about twice the size of Denison strapped to the side. The current contract is to replace the roof, change some lighting, improve the ventilation and replace, more or less like for like the HVAC system. And so far the most important lesson I have learned is: Avoid dealing with refits wherever possible! I will expand.

To follow on from Guz’s theme of invention and Rich’s point on people actually leaving their desks to look at stuff. Two things this week have lead me to believe that the designers didn’t actually bother coming to do a detailed survey of this huge building before cracking on with their designs and just assumed the as built drawings were complete and correct.

The building has three plant rooms. The main plant room has the steam distribution and the main elements of the chilled water distribution. The other two smaller plant rooms each service their respective admin floors with an Air Handling Unit (AHU) and some minor switchgear. As it begins to get warm here we are starting to cobble together a temporary system whilst we wait to get the main cooling system on line. So as we were talking through the system in a meeting, so at least better than a chance conversation, the contractor stated that the plant room housing the ground floor AHU was getting really hot; suboptimal in cooling season. We asked why and he said it was obviously because of the two condensers that were stationed in there from some retrofit air conditioning systems.

Just heating the room that is trying to cool the rest of the floor. Outside is a mere 20′ away.

Some pipe hunting later and we found that these fed two computing classrooms that had obviously required extra cooling at some point in the last 10 years. Checking the contract these aren’t to be replaced. Now I haven’t checked the as built drawings, but I don’t need to because the photo above clearly shows exactly where these condensers are. So my question is, which idiot put them there and which idiot decided to leave them there in a comprehensive refit of the building’s mechanical equipment. My conclusions are that it comes down either to incompetence or money. But, based on the next example, it is difficult to say it was just a cost saving measure as incorporating a couple of extra outlets into a room to increase the cooling capacity would have been pretty cheap in the grand scheme of things: I think the designer didn’t know they were there.

So to observation two. The biggest reason the air conditioning system is not running is that the cooling towers (condensers) on the roof aren’t connected. This is because someone forgot to design the structural steel to hang the pipes from. So due to the rising mercury we have hired a trailer mounted condenser, complete with pumps. So the question is merely what size?

After a chat between the contractor, mechanical engineer and myself we decided on 500 tons, ordered it and it arrived. When it turned up we proudly went out to observe our $40,000 a month lease and the installation electrical engineer asked when the other one was coming? And that was when email tennis started.

The 500 ton temporary system in the foreground. The new chillers (1300 tons) up high.

The original system was designed at 1800 tons (2 x 900 ton cooling towers) and in the design guide produced by the design consultant there was a magical figure of 1220 tons as the load. The new system is designed at 1300 tons and so the installation decided 1000 tons was the minimum possible. The installation engineers therefore stated that our temporary chiller would simply not be large enough and kicked up a stink with explanations of the old system working flat out and hardly being able to keep pace.

So the proof will clearly be on Tuesday when the system is turned on and the temperature is set to be in the high 80’s for the week. However, I will justify our decision now. The contractor has worked on this building for the last 2 summers and swears that there has only been one cooling tower operating at a time; indeed last year one of them was out of service. He also said that when he removed the old cooling towers he’d called the manufacturer with the serial number and asked the size: 600 tons (for some reason it wasn’t on the nameplate). Additional factors are a number of smaller AHUs have been removed and the temporary power supply wouldn’t run a 750 ton unit. When designing the controls, before my time, we had been told the permanent 1300 ton system was to give redundancy, as out here everything has redundancy.

Conclusions

Having read the design handbook for this project nowhere was there actually a calculation of the load, just an assumption with no justification. Remembering back to the design projects writing why an assumption was made seemed frustrating as it got in the way of moving onto the next calculation. However, the reasoning behind these assumptions are vital in the real world for someone to understand your calculations so they can make decisions later down the line; especially if the situation changes. This applies to references too as a reader can understand your thinking better if they can trace it back to source. It the light of contradictory evidence empirical evidence should take precedence.

As built drawings are not 100% reliable. They may be but it depends on whether someone has the time or funding to keep them up to date. In the EDC there are a number of different organisations with little pots of money doing self help projects all the time so some might not even know where to get hold of the master set of drawings; if there even is one. Thinking forward to doing DfID style projects the odds of getting BIM are pretty long! Therefore time spent on recce…

Oh and my near arrest. Well despite having been working in this building for three weeks it appears I don’t have clearance. Yesterday I tried going in through the main entrance and was told my name wasn’t on the list by the DLA Police. The building is about as secure from entrance as a sieve is from water and holds nothing remotely of interest to a thief or spy but rules is rules. It turns out I just need to present a letter that I am not allowed to see the contents of to the head of security and it should be fine! I can only imagine the pain Brad has been through and I’m pretty glad that the engineer I work with is the base commander’s wife as that probably prevented bracelets.