Feed Your Boiler Enough Air

Jun 23, 2015   //   by Rodney Owen   //   Blog  //  No Comments

combustion-mua-fasBoilers need air to operate efficiently.  Additionally, they operate even more efficiently if that air is warm, which can present a problem in the Winter.  In many cases the operating air for boilers is provided via louvers in the boiler room wall.  This is, or has been, an obvious solution to providing air.  The International Boiler Code prescribes 1 cubic foot per minute of combustion air for every 2,400 BTU/hour of boiler output heat.  When utilizing natural ventilation that converts to 0.1 square foot per boiler HP.  However, utilizing wall louvers per this code can lead to very large wall space demand and inevitably introduces cold air into the boiler room which makes for an uncomfortable environment, possible freezing, and an inefficient boiler.  According to the US Department of Energy, a boiler gains one percentage point of efficiency for every 40 degree temp rise in combustion air temperature.

Fortunately RJ Owen Associates and LJ Wing Company offer an affordable and efficient solution to this with the Model FAS-U Fresh Air Supply Unit for Boiler Combustion Air Preheat.  The FAS-U mounts through the wall utilizing a much smaller space as forced air delivers the required combustion air with much less wall space demand.  The air is then heated through steam or hot water coils integral to the unit, which are modulated for temperature control via LJ Wing’s Integral Face and Bypass design which helps prevent coil freezing.

Contact RJ Owen Associates to speak to a representative about designing a Combustion Air Preheat System for your boiler, at 336-869-7579.

Easy Freeze Protection for Water Lines

Jan 8, 2014   //   by Rodney Owen   //   Blog  //  No Comments

frozen-pipeAs we greet 2014, we are faced with some of the coldest temperatures on record.  A consequence of this is lots of frozen and busted water pipes.  So how do we prevent that?  By leaving some water running?  NO.  Not theoretically.  Water freezes at 32 deg F, whether it’s moving or not.  So moving water freezes just as stagnant water freezes.  However, keeping it running will allow warmer water, from the building or city water main, to displace the colder water in the piping.

So, for example, if you have a water line running outside your building, it will be subject to freezing when the ambient temperature drops below freezing (32 deg F for water).  If, however, the ambient temperature in the building is above freezing, the pipes in the building will be safe from freezing.  So, you may leave the water running from the pipe outside and allow the warmer water from within to displace the freezing water in the pipe and prevent freezing.

This  will work, but it can be problematic.  For one thing, you will have a substantial increase in water flow and increase in your water bill.  Additionally, once the water leaves the pipe it is  again subject to freezing, which could mean a substantial ice sheet outside your building, which could be a safety hazard.  Perhaps a better way would be to control the water flow as needed.

RJ Owen Associates can offer a simple inexpensive way to do just that: control the temperature in exposed piping without running water consistently and without complicated controls systems.  The Therm-Omega-Tech HAT/FP Valve is the prime choice for this job.  It is a mechanical valve with an open setpoint of 35 deg F and a closed setpoint of 40 deg F.  This valve will open to drain any water from a line that is below 40 degrees.  When water in the line reaches 35 degrees, the valve opens to drain.  Once warmer water enters the pipe, the valve will modulate to close off at 40 degrees.  Valves are available in 1/2″ and 3/4″ female pipe thread with either brass or stainless steel internals.  Feel free to contact us for sizing and selection assistance, or visit our online store:  http://mechroom.com/

Mechroom.com is up and running

Aug 8, 2013   //   by Rodney Owen   //   Blog  //  No Comments

RJ Owen Associates, Inc now has a new platform for online product sales, mechroom.com.  Here you can purchase gas detectors, Therm-Omega-Tech products, process controls, and HVAC temperature and humidity controls.  And this is just the beginning.  We will be expanding content over time, adding new products and a broader offering of existing products.

Mechroom.com is an easy to use website that processes payment safely via paypal.  Stop in and visit, and drop us a line to let us know what items you would  like for us to offer.

Can We Cool Our Make-up Air?

Mar 7, 2013   //   by Rodney Owen   //   Blog  //  No Comments

custom_heaterA common challenge for industrial spaces that utilize make-up air, especially in hot humid environments, is keeping the air cool in the Summer months.  Spaces that exhaust large amounts of air need to replace that air with make-up air, typically from outside.  Conditioning that air in the Winter months is relatively simple.  We just heat the air as it comes in, typically with gas-fired burners directly in the air stream or indirectly via a heat exchanger.  Conditioning that same air in the Summer months can be more of a challenge, as in most cases 100% of the air in the space is exhausted with no recirculation.  Therefore, 100% of that air must be made-up with the make-up air unit.  That can represent a fairly high load.  However it can be done.

What is required for cooling 100% outside air make-up units is a condensing unit that is designed for such a load.  It is tough to find these through most commercial HVAC companies, as their units are typically designed for the usual commercial application, which would obviously include large amounts of recirculated air.  RJ Owen Associates can design heated and cooled air make-up units utilizing the newest technology from Weather-Rite, LLC.  Weather-Rite is a world leader in industrial make-up air and is now offering complete heat and cooling units for 100% outside air.  This can be accomplished with DX cooling using a Weather-Rite RC Series Condenser, or through chilled water cooling, depending on the specific conditions of the application.

Upgrading HVAC Coils

Jan 23, 2013   //   by Rodney Owen   //   Blog  //  No Comments

sd-coil-blueThere are several things to consider when replacing HVAC coils.  The first of which is, why did the coil fail?  As with any replacement component, the technician should consider why this component failed.  If it was because of age, the component reaching its full service life, there may not be anything else to consider.  But then again, by upgrading the coil, the owner may be able to increase the serviceability of the unit.  The same consideration may apply to early failure.  If there was early failure because of a related component in the system, for example freeze protection failure, then that process should be addressed.  However, if the original design is just not sturdy enough for the application, an upgrade may be in order.

There are several things to consider in the design of HVAC coils.  In terms of upgrading coils, the primary concern is typically materials of construction.  For example, corrosive environments can wreak havoc on coils.  Depending on the conditions, there are several possibilities for coil construction.  The most common arrangement is copper tubes with aluminum fins.  However, it is possible to have aluminum with aluminum; copper with copper; steel with aluminum; steel with steel; stainless steel; and baked phenolic coatings.  Another thing to consider is the thickness of the tubes, the thickness of the fins, and the spacing between the fins.  The designer must keep in mind that varying the material and the thickness of the material will change the heat transfer rate.

RJ Owen Associates offers a full range of HVAC and Industrial Process coils.  We can design for the specific job, offer upgraded replacement coils in various configurations, and help with the design of new coils.  Contact us today for all your coil needs.

Controlling for Temperature with Steam

Nov 13, 2012   //   by Rodney Owen   //   Blog  //  No Comments

The theory behind temperature control and steam flow through a heat exchanger ( a term which includes air heating coils) is represented as Q= UxAxdT.  In this expression, Q= flow; U = a fixed number, based on the conductivity of the tubes; A= the area of heat exchange; and dT is the temperature difference, or temperature rise through the heat exchanger.  Thus, if we want to vary dT, we will need to modulate one of the other variables.  In the most common application of steam coils and steam-to-water heat exchangers, steam flow, Q, is modulated to provide variation in temperature rise.  This is often done with a steam control valve, much as is commonly seen in hydronic heat exchangers utilizing water as the medium of transfer.  However, with steam we often run into a condition of coil stall, where at a certain position of the control valve we have reduced the flow and corresponding pressure to a point where we no longer have sufficient upstream pressure to move condensate back to the boiler.  At this point, the condensate will back up into the heat exchanger and can result in numerous problems, from carbonic acid to freezing.

However, there are other approaches to temperature control that can deliver optimal performance without the resulting condensate problems.  One of the best approaches is to reconsider the heat flow formula noted above.  Rather than manipulating Q to control dT, one may consider manipulating A.  Typically U is not an option since it is a fixed value.  However, in steam systems it is entirely plausible to maintain steam flow, Q, at full flow/full pressure and vary the area that is exposed to exchange.  This is exactly the formula used in the LJ Wing Integral Face and Bypass Coil.  The same theory can be applied to steam-to-water heat exchangers and other processes utilizing steam as a heating medium.

It is worth considering temperature control options when designing the steam system, as the problems associated with poor or marginal design often outweigh the costs of a more creative approach.  In many cases there are products available on the market.  However, even when said products are not easily available, we can generally provide a design solution and/or custom product to do the job.

Controlling Carbon Monoxide Through Ventilation and Gas Detectors

Oct 18, 2012   //   by Rodney Owen   //   Blog  //  No Comments

In spaces where there is the possibility of carbon monoxide fumes, garages, repair bays, indoor race tracks, etc…, carbon monoxide can be a potential problem.  However, it doesn’t have to be.  The simplest and most efficient way to control carbon monoxide fumes is through ventilation, monitored and controlled with an effective Carbon Monoxide Gas Detector.  A Carbon Monoxide Gas Detector can be set up to control ventilation in a couple of different ways.  It can close a set of contacts at a certain prescribed level of carbon monoxide detected, which can in turn be utilized to energize exhaust fans.  Further sets of contacts can be further used to keep fresh air supply in high enough supply to overcome the parts per million reading of carbon monoxide in the space.  Alternatively, or in conjunction with contacts, the gas detector can send an analog signal to open a damper or control the speed of fan motors.  Additional options on Carbon Monoxide Gas Detectors are audible alarms, alarm contacts, and LED readouts.

Keep in mind that space balancing requirements may necessitate some form of make-up air if exhaust fans are used to remove carbon monoxide.  Remember, for every cubic foot of air exhausted from a space, a cubic foot of make-up air needs to be replaced.  In most smaller applications, exhaust fans and a supply louver will likely suffice.  However, larger requirements many necessitate forced make-up air, and room balancing.  Of course, design considerations vary.  It’s always best to consult a mechanical engineer or ventilation specialist to be sure.

Carbon monoxide is known as the silent killer, and with good reason.  It is not easily detected and can cause immediate and long-term health damage, including instant death.  Investing in Carbon Monoxide Gas Detection Equipment is just plain smart, not to mention required by law.  Carbon Monoxide Gas Detectors are simple and effective solutions to the ventilation challenges of spaces with carbon monoxide present.  RJ Owen Associates has Carbon Monoxide Gas Detectors available in our online store.  Feel free to call our office for any information on this technology: 336-869-7579

Balancing Room Pressure

Oct 2, 2012   //   by Rodney Owen   //   Blog  //  No Comments

A specific problem, especially with industrial ventilation, is negative pressure in the space.  As noted in an earlier post, the remedy for this is Make-up Air, simply replacing each cubic foot of air that is exhausted.  This can be a challenge if the load varies, for instance if there are several exhaust fans that may stage on and off at various times, or if loading doors are opened and closed, thus changing the space pressure.  If exhaust fans drop out, the obvious result will be positive space pressure, which can be as problematic in a different way as negative pressure.  In most cases the goal is to keep the space as close to neutral as possible.

One way to accomplish this balance is through varying the make-up air supply.  This can be done with either a variable frequency drive (VFD) on the supply fan motor, or by varying the position of an integral discharge damper, as in Weather-Rite’s Volumatic System.  To accomplish this a space pressure sensor is utilized.  This sensor will either be configured as a floating point or will send an analog signal to address the VFD or discharge damper.  The sensor will always seek zero and will act to either increase or decrease airflow in to the space.  There are specific design issues to be considered, such as the supply fan curve and the degree of anticipated pressure drop in the space.  If the drop is larger than the unit fan curve will allow, multiple units may have to utilized and staged according to demand.  Utilizing a variable air configuration on make-up air  units is practical and affordable, and should be considered in any application with varying discharge demands.

RJ Owen Associates is an authorized Weather-Rite full service representative.  We can help with design, installation, commissioning, operation, and maintenance of industrial ventilation systems.

Recovering Condensate Part 3: Flash Steam

Jul 18, 2012   //   by Rodney Owen   //   Blog  //  No Comments

Our goal in condensate management is to recover as much of the treated water and heat energy as we can, and return this to the boiler.  To that end, a significant challenge we are faced with is the potential losses via flash steam.  10% to 15% of condensate is subject to flash back to a steam state due to a drop in pressure and the corresponding pressure/temperature/volume relationship given in the steam tables.  In short, a portion of the higher pressure, higher temperature condensate formed in the heat exchanger will flash to steam as it is introduced to the lower pressure, lower temperature environment existing in the condensate return system.  This is a natural occurance that, while troublesome can be utilized to advantage with efficient design.

Flash steam is typically recovered with two different types of systems: open systems and closed systems.  In an open system, several steam traps at various pressures discharge to a common condensate receiver that is vented to the atmosphere.  The key to conserving heat in this application is in the size of the vent line.  As long as the vent line is sized large enough, atmospheric pressure will be maintained in the tank and a bare minimum of steam will escape through the vent.  Vent sizing is crucial and is based on the system’s condensate load.  A typical problem with many systems occurs when further load is added to a previously properly sized receiver and vent.  The additional load will exceed that required for the installed vent and result in steam escaping through the vent.  This is often misdiagnosed as a failed steam trap(s), when a correct solution may be an increased vent line.

A closed loop system is utilized for a single piece of equipment.  The vent line is tied back into the heat exchanger, allowing for an equalization in pressure.  This allows the condensate to drain via gravity to the pump.  There should be an appropriately-sized steam trap at the outlet of the pump.  As long as the modulating steam supply off the heat exchanger is high enough to remove the condensate, the steam trap is the only operative piece of condensate removal equipment at this point in the system.  If the steam supply pressure drops below the condensate back pressure, the pressure powered pump will work to remove the condensate.  There is not a flash steam problem in this type system, since there is not a mixing of various steam pressures and the receiver is vented back to the exchanger.  However, it is not uncommon for a condensate recovery system of this type to be fed into a separate vented receiver before condensate is returned to the boiler.

There are cases where there is an excess of flash steam that cannot be effectively dealt with through condensate tank/vent line design.  In these cases, the flash steam will still escape to the atmosphere.  The most common way of recovering this energy is to direct the vented steam to a point of usage, typically a low pressure heat exchanger to pre-heat domestic water, or boiler feed water, or some other process.  The specifics of utilization and recovery system design will depend on the application, waste steam load, and the facility.

To summarize, flash steam is typically a given in many systems, especially with various operating pressures.  However, flash steam does not necessarily equal waste steam.  With efficient and often creative design, most of the energy in a typical steam system can be utilized effectively.

Recovering Condensate Part 2: Condensate Return Lines

Jun 20, 2012   //   by Rodney Owen   //   Blog  //  No Comments

One of the biggest mistakes made when sizing condensate return lines is to size them based on water flow in GPM.  There are formulas and charts for determining liquid pipe sizing based on gallons per minute.  However, this is not the correct way to size condensate return lines as they carry two-phase flow.  Because hot condensate is discharged from higher pressure steam traps to lower pressure condensate systems, a portion of the condensate–typically 10%-15%–will re-evaporate, or flash into steam.  And steam, being a gas, takes up much more space than water.  The specific volume of water at 0 psig is 0.16 cubic feet.  The specific volume of steam at 0 psig is 26.8 cubic feet.  So, as we can see, if a portion of the condensate flashes to steam the volume it requires is quite substantial.  If condensate return lines are sized for water flow alone they will not be able to accommodate the increase in volume and the flow will be reduced substantially.

The specifics on condensate return line sizing varies with the system, the primary factors being the pressure of the steam system and the pressure of the condensate system.  The resulting pressure differential along with flow, in pounds per hour, determines the amount of flash steam as a percentage.  The condensate flow is then multiplied by the percent of flash to determine the flow rate of flash steam.  The condensate return line size is based on the amount of flash steam flow at a given pressure in the effective pipe size that will keep the flow between 4,000 and 6,000 feet per minute.

There is no easy, one-size-fits-all approach to condensate line sizing.  The complete system should be considered, including motive pressure, back pressure, lift, pressure differential, and pipe lengths.  Considering all aspects of the system, an optimal return system can be designed.

A key aspect of condensate line sizing is understanding flash steam.  Flash steam will occur when there is a pressure drop.  And there will typically always be a pressure drop.  Pressure differential is the motive for steam flow, as pressure always flows from higher to lower seeking equalization.  So flash steam is a given in a condensate return system.  In terms of condensate lines flash steam can be a big problem if not allowed for.  However, if given proper consideration in the design process it can be another component of a smooth operation.  But even though we allow for it in line sizing, we often still have to deal with it before everything is properly returned to the boiler.  The next installment in this series will consider flash steam recovery and utilization.

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