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Can somebody explain to me how or when a coil will freeze. More specifically, if I have a pre-heat coil, and even if the mixed air temperature entering the coil is below freezing, it seems to me that as long as the pump(s) are actively circulating hot water (160-180 Deg F) through the coil how...

What sequence of operation is best to use on the VAV box when you have a reheat coil. One company I worked for had it customary to have the VAV box in maximum airflow setting when needing heating from the reheat coil. They would size the reheat coil based on the VAV box maximum airflow rate...

So what about heating it in the winter ?

I think I posted this thread in the wrong place the first time. I am designing a four story hotel with a commercial laundry room on the first floor. We were given a prototype design to follow, but the problem is the prototype was designed for Atlanta and the hotel is located in Michigan. The...

The elevator manufacturer should be able to tell you what is the heat gain to space is of the elevator equipment and what the maximum space design temperature should be. That is the quickest and most accurate way to get the information. I always contact the elevator company for this...

Thanks for responding. The Rep happens to be a mechanical engineer that specializes in hydronics, pumps and hydronic accessories, and holds training seminars on such subject matters. So he is a qualified professional. Having said that, our design showed the pressure relief valve on the...

The Kitchen is generally supposed to be negative compared to the surrounding areas so I am assuming you are already drawing some air from the main area. Is this a commercial kitchen with exhaust hoods ? How else are you making up the Kitchen exhaust. Are you dumping untempered air directly...

I have a quick question. I have a hydronics Rep telling me to put the pressure relief valve of a hot water system containing a heater exchanger on the suction side of the pump (right after the expansion tank). Is this philosophy correct. Shouldn't it be on the discharge side of the pump where...

For IEQ credit 5 in LEED 2009 "Indoor Chemical Source Control" They require you to state what the average differential pressure is across a particular room. ASHRAE lists a formula (Q=2610*A*√∆P) Which tells you the differential across a door, but does anyone know what LEED means when they...

In theory all those things you mention should be factored into calculating pump head, and every company I've worked with does it differently. Bell and Gossett (or any manufacturer) typically has charts you can use to approx. pressure drop across air seperators, Suction diffusers, etc. There...

I am trying to do some calculations on a spreadsheet on how much energy savings can be incurred by a building if they add Hot Water Reset controls to the boiler. During my internet searches for knowledge on the subject and hints on the calculations I came across an article that said there is an...

Unless the Ventilation tables specifically say that all air be exhausted to the outdoors, you can recirculate the remaining 2/3 of the supply air. I'm quite sure you don't need to exhaust the retail space. When the code says exhaust it typically means that you must remove air from the space...

I live in Chicago and have designed many buildings here. I'm not sure if this answers your question or not, but what the code says is that 1/3 of the CODE REQUIRED air be from outdoors. So for an office space which by code requires 0.6 cfm per sq. ft., 0.2 cfm/sq ft. must be OA. Some people...

If I go with hot water make-up air units. Will I need to provide a face and bypass damper. Is freezing the coil going to be an issue ?

OK guys, I need some advice. I am designing a 3 story apartment building. Per the owners request we will have condensing boilers to heat the aparments via hot water fin tube. Cooling will be done with a "thru-the-window" AC unit. Each apartment has a local toilet exhaust fan interlocked...

I don't know for sure, but if I had to guess the 10' requirements are for snow and other debris to keep out and for exhaust, to keep people from breathomg in noxious air. the 10' is out of the breathing zone should somebody walk by.

I dont' typically see expansion tanks on the secondary loops if there is one present in the primary loop. Is it even needed ?

I think you still need exhaust. According to the international mechanical code it specifically mentions a "mechanical exhaust capacity"

You might also want to try CDC (Center for Disease Control) Guidelines. They might have something to help too.

0.2" WC with a max velocity of 2000 fpm