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Freeze Protection for HVAC Equipment

Much of the country is currently in the single digit temperatures, and “polar vortex” has been officially added to the list of meteorological buzzwords (right on the heels of the “Asperatus Cloud”… how can the weather man keep up?). So it is no surprise that we’ve been fielding calls from adjusters relating to HVAC equipment freeze and water damage from pipe bursts.

The figure below explains why pipes burst when they freeze. It’s all about how the graph curves back down between 4C and 0C.

Density Graph - Freeze Protection

Put simply, water expands by about 9% as it approaches the freeze point. Water is not timid about its need to expand, it does so with lots of force. This simple fact of physics creates billions of dollars in water damage losses for insurance companies. Unfortunately, the alternative is worse; if water didn’t have this destructive little feature, our lakes, oceans and rivers would freeze from the bottom up, causing a major food chain and climate disruption at best, or the end of life on Earth at worst. So, we accept the pipe bursts, whilst nature has provided the fish with a most accommodating under ice environment during the winter months.

There are numerous scenarios that can cause a loss related to pipes freezing. As with most losses, the fault can lie with the owner, installer, manufacturer or a combination these parties. Some common origins of water freeze damage include:

Defective Installation

The National Building Code (encompassing the Electrical and Mechanical Codes) goes a long way to promote pipe freeze protection in equipment and buildings. These codes are normally adopted by state law, and and contractors must adhere to them. The codes increase in complexity every year, and through lack of training or sometimes through willful efforts to cut costs, installation requirements are missed and the building is consequently not compliant with code. Relating to HVAC equipment and plumbing, the codes specify things like minimum insulation R values, acceptable places in the building to install HVAC and electrical equipment, pipe insulation types, freeze protection features and workmanship standards. Some hydronic HVAC systems are required to have chemical freeze protection such as ethylene or propylene glycol. These agents have the undesired effect of reducing the system performance during normal operation, so their use is a tradeoff. But if omitted, or present in too low of a concentration for the regional weather conditions, the results can be disastrous.

Defective Equipment

Since the dawn of the HVAC industry in the late 1800’s, the systems have grown in complexity every year. The complexity often results from our desire to reduce energy costs since HVAC equipment is responsible for a substantial part of most commercial and residential energy use. With complexity comes the possibility for more failure modes. As an example, designers often employ a feature known as “outdoor reset” on heating systems which saves energy by reducing pump speeds and / or boiler water temperature during periods of unseasonably warm outdoor temperatures. A failure in the outdoor reset circuitry, or even mounting the outdoor reset sensor in an incorrect location such as in direct sunlight can cause the “smart” heating system to think it is warmer outside than it is.  The boiler, thinking it is warm outside, reduces or stops heat transfer into the building, and a pipe ruptures. Freeze stats, rupture , heat trace tape and other equipment can also be used to guard against water damage. Each of these devices can fail, and be applied improperly contributing to a loss.

Operator Error

Improper operation of equipment by owners or facilities managers contributes to many freeze accidents. Proper thermostat setting is among the most basic actions that can prevent loss, and insurance policies often carry a requirement to maintain minimum thermostat settings for this reason. Elimination of cold air leaks in the building shell, and proper protection of HVAC elements and piping located in or near outside walls offers a level of protection. Homeowners and enterprise facility managers alike should consider the use of a cold weather checklist to protect property. It is particularly useful to plan for power loss scenarios. Since loss of utility electric power is not an infrequent event, it is advisable not to rely on the presence of utility power as the sole means of freeze protection. Simple procedural steps in a checklist such as “shut of water main if outage duration exceeds 1 hour and outdoor temperatures less than 20F” can save millions of dollars in damages.

Freeze Protection

If you are an owner, counsel or adjuster in need of expert advice on a freeze claim, we can help. Contact Kleinholz Inc. today for more details.

An Engineer’s Thoughts on the Superbowl Power Outage

Superdome-NightWell, it’s been a few days and all the headlines still seem to be appended with “…cause not yet pinpointed”. This never stops the media from hastily putting together some scripts with all the right buzz words in them however. I have to admit, I was enjoying the announcer’s commentary on the outage as much as the game and commercials (skechers was my personal fav) themselves. Said one, “As you can see a power surge has hit the stadium and now the lights are slowly getting brighter as they restore power”. Umm…. not really I thought. They restored power 20 min ago, and the HID metal halide lighting is just going through its normal restrike and run-up cycle. Also, a surge, normally defined as a multi-cycle moderate voltage increase, is a fairly rare power anomaly and was almost certainly not the cause. In a way the reporting reminded me of the Fukushima nuclear accident in Japan – listening to the news as a former nuclear engineer, the fabrications of respected news agencies were embarrassing. I could picture some producer behind the scenes telling the reporters, “look, no one understands this stuff anyway, just be creative and fill in the gaps”.  It’s not only the reporters troweling out these inaccuracies.  Greg Boyce, CEO of Peabody said the outage was a “convincing visual demonstration to counter those who’ve envisioned a world without coal”.  Really Greg?  Regardless of your views on global warming, I’m pretty sure coal was not a root cause here.

Anyway, it is also unlikely that an overloaded feeder problem existed, as has been reported. In large part, the superdome is either on or off. The lighting, ventilation, the guy cooking hot dogs, none of them use any more power for the superbowl than any other event. There is not much of a per-occupant electrical burden, and the place only has a fixed number of seats anyway. Further, design engineers are notoriously conservative in sizing wires and breakers, because they don’t have to pay for the oversizing and the consequences of undersizing are severe. In general, owners under-appreciate the cost savings of right-sizing, but the engineer will get slapped with back charges or even sued if things are undersized – we recently investigated just such a case and estimated corrective action to be over 175% of initial project cost due to demolition expense.

Ok then, so what was the cause and how might it have been prevented?

My guess, and without having personally investigated that’s all it is, is the incident was related to improper protective action coordination. In my experience, improper trip coordination is the biggest cause of unintended partial facility outages. I’ve never done a coordination study and not found instances of mis-coordination. In simple terms, the purpose of coordinated protective action in electrical distribution systems is to ensure that faults are isolated with minimal impact to the rest of the distribution. With thousands of pieces of equipment running in the superdome, the probability of a fault developing in one of them is fairly large – we should expect it. What is important is that the branch circuit breaker feeding the faulted equipment has a trip curve that is below and to the left on a time-current plot of the feeder breaker(s) upstream. In plain english, this means that when something goes wrong electrically, the branch breaker trips first and isolates the fault without any power interruption to other loads. With metal halide (MH) stadium lighting, it is particularly important to rigorously apply coordination to protect against any voltage dips on the panels feeding the lighting. Why? MH lighting (and other HID lighting) is vulnerable to even brief power interruptions, and once it’s off, as we all saw, it takes a long time to restart. Even a 15% voltage drop for a fraction of a second (and a fault in 1 decent size motor can easily cause this) is enough to knock out MH lighting. These lights work by vaporizing mercury in an arc tube, and the tube temperature & pressure have to be allowed to decrease by natural cooling for 10 or more minutes before “re-striking” the arc. Manufacturers do have “instant restrike” lights available, but they are expensive. Once the arc is re-ignited, it then can take another 15 min or so to reach full intensity as the cooled metal halides are again fully re-vaporized. This causes the “sunrise” effect that we saw in the stadium.

Assuming my mis-coordination theory is correct, the design engineer’s coordination study should have involved plotting the lighting manufacturers time-voltage tolerance curve right on same plot as the adjacent breaker trip curves. This method makes it immediately apparent whether it is possible for any other branch breakers to “let through” a fault that could allow the MH lighting arcs to extinguish. If so, we make adjustments to the trip settings, select different breakers, or even add fusing and plot the curves again until we achieve adequate coordination. Notwithstanding code requirements, the rigor with which this process is applied must increase when the economic impact of the unavailability of the involved loads increases. In other words, if the HID lights in a Walmart parking lot go out for 30 min, it’s not a huge deal, but when 1/3 of the country is watching an event that suddenly goes dark…..

Hopefully the outage didn’t ruin your superbowl experience. If the 49ers had pulled it off, I think the NFL might have someday been using words like “legendary” and “famous” to describe this power outage and its alleged effect on the game. Personally, I didn’t mind it. I just feel bad for the facilities guys down in the pits of the stadium. Think about it – they were probably getting yelled at on their radios before the 7 second network delay allowed them to see it on their little TV in the electrical shack. Then they ran down the hall, and reset the tripped breaker, lets say, within 3 minutes. Then for the next 31 minutes, they were getting blasted with irate inquiries and demands, trying to explain things like “restrike time” to a bunch of execs. But in fact they had already done all they could and it was just a waiting game. Now for weeks they will be interrogated by experts and investigators sniffing around for clues, writing their reports. Poor guys. Anyway, I sent my CV over to Doug Thornton, superdome manager, so maybe with a little luck I’ll get to meet them.

Electromagnetic Interference

With the proliferation of electronic equipment that is a part of our homes & businesses today, has come a cacophony of electronic noise.  This noise, can exist in nearly any part of the electromagnetic spectrum from DC through microwave and beyond.  We’ve all heard the hum of electromagnetic noise Perhaps the most problematic is noise in the 2.5GHz range which has the annoying side effect of interfering with our wifi networks.  While this is certainly a real problem, and I have identified it as the source of legitimate interference in the past when diagnosing wifi network problems, I happen to also believe it is a convenient scapegoat used by IT-folk when at their wits end about why your wifi connection keeps getting dropped.

But either way, to illustrate a simpler case, I’ll explain a scenario I encountered with a client in the healthcare industry.  A hospital contacted me saying they were experiencing intermittent noise on an ECG (electrocardiogram) machine so severe that for some patients the ECG output was completely unreadable by the doctor.  As a result the patient had to be moved to a different part of the hospital or asked to return at a different time when hopefully the machine would work.  They had already beat up the vendor of the machine, and replaced an expensive set of skin electrodes and associated wiring.  They provided me with scrolls of logs indicating what times of day and for whom the machine would not work properly.  I examined these, looking for periodicity that could point us to a cycling load, a certain operator, etc.  Nothing.  It was random.  I had an assistant lie down and get a “free” ECG from the nurse so we could see whether the offending electrical noise was currently present.  Of course not.  But we returned another day armed with a wide range spectrum analyzer and a couple different antennas, some directional.  The spectrum was relatively quiet throughout, except the 60Hz background electromagnet radiation that you expect to find in any building with 60Hz electrical service.  The intensity of the 60Hz energy varied a lot as we moved around, and there was definitely some present at the point of use.  The ECG’s I had been provided had a time scale that didn’t permit inspection of the waveform of the trace on the printout.  But it turned out that we could zoom in on the trace while it was on the screen.  The noise was periodic, and counting the divisions on the screen revealed it was in large part the same 60Hz spectral content that I was seeing on the spectrum analyzer.  From there it was a simple matter of systematically shutting off equipment one load at a time to see where the noise was originating from.  In this case it turned out to be a simple floor standing lamp near the examining table.   As supplementary lighting, it was on sometimes, not others, the staff reporting that they used it as needed.  It was also moved around the room to some extent.  With my assistant again reluctantly on the ECG machine, we flipped the lamp on & off and observed the noise on the trace appear and disappear accordingly.  There is nothing better than finding a very simple solution to a tricky problem.

I would have like to do a leakage current test on the lamp, but the hospital opted to discard it.  There are specific guidelines for maximum leakage currents in patient care areas, which vary by proximity, equipment, and procedure.  Electromagnetic noise is among the less important symptoms of leakage current, patient electrocution being the foremost.  Healthcare providers should have periodic leakage current measurements as part of their electrical safety program.  There are specific ANSI, UL, NFPA and IEC standards governing allowable leakage values depending on many factors.  If your business is experiencing EMI problems, or your healthcare facility needs an updated electrical safety program before the next JCAHO inspection, we can help.

Technical Training Solutions

Kleinholz Inc. offers a wide array of technical training solutions and we specialize in making complex topics easily understandable by everyone. Our tech-friendly in-person or online training services include:

  • Electrical and HVAC topics
  • Hands on demonstrations
  • Power System Theory
  • OSHA required Arc Flash training
  • NFPA 70E
  • Standard for Electrical Safety in the Workplace
  • HVAC systems & theory
  • ASHRAE standards