Frozen Steam Coils: How Do You Prevent This?

Regardless if you have steam coils or steam distributing (non-freeze) coil, you can freeze ANY coil.  When freezes happen, everyone immediately looks to the steam coil as the cause.  When in fact, there are numerous reasons that must be looked at well before the coil.

Freezes generally happen in older systems, however if your new system is not maintained properly or correctly installed, your steam coil can and will freeze.  For instance, you’d be surprised at how many times dampers are left open, controls fail, freezestats don’t work, etc.Steam Coils

In a Standard Steam or Steam Distributing Coil, a freeze-up can occur when condensate freezes within the tubes of the steam coil.  The two most common reasons for freezing steam coils are the steam trap and the vacuum breaker.  The function of steam trap is to remove the condensate as soon as it forms.  Condensate usually collects in the lowest part of the coil.  If your steam trap isn’t installed properly, that condensate will lay in the coil and it will inevitably freeze as soon as it sees outside air.  The vacuum breaker also helps clear the condensate, minimizes water hammers, and helps with uneven temperatures. This must be installed on the control valve and always above the steam trap.

Unfortunately, there are no ways to determine exactly where your steam coil will freeze.  And a common misnomer is that the condensate turns to ice and the expansion is what causes the tubes of the coil to pop.  In reality, it’s the pressure that builds up between freeze points.

Here’s couple tips in your coil design that can help prevent your standard steam and steam distributing coils from freezing:

  • Standard steam coils should NEVER see any outside air below 40 degrees.  If it does, steam distributing is the only way to go!
  • 5/8” OD Steam distributing coils over 72” long are recommended to have a dual supply
  • 1” OD Steam distributing coils over 120” long are recommended to have a dual supply
  • Make sure your steam coil is pitched if possible.  This slopes the condensate to the return connection making it easier to remove the condensate

Give Capital Coil & Air a try on your next project. Our engineering, pricing and service is the best in the industry!

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Coil Costs: What Will Make Your HVAC Coils More Expensive?

We get questions all the time about how we build our HVAC coils, and what will add costs and what will not. This post will address the many inaccuracies other “mass production” manufacturers Hot Water Coilshave put out there. It’s very simple. There are only three areas on a coil that will add costs: the casing, the tubing, and the fins. Now we’ll deal with the many inaccuracies that most manufacturers try and “upsell” to you.

  • Connection sizes: There should be no additional cost switching from a 2” MPT connection to a 3” MPT connection. Only on rare cases with a 4” or 5” connection, should you ever see an adder in price.
  • Pitching the casing in a steam coil: All steam coils should be pitched. There is not some mysterious adder you need to pay to have you coil built the right way.
  • Casing depth and dimensions: Whether you want your coil 4” deep or 8“ deep, or want a 2” flange instead of a 1” flange, there should be no cost associated with simply more sheet metal.
  • Distributors on a DX Coil. This is our favorite. We actually had a call from a contractor who asked how much extra it was to get a distributor on his DX Coil. Distributors come standard with DX coils!
  • Flanges for “stackable” coils. This is just standard practice to meet the needs of your customer.

Coil Casing Adders: Most HVAC coils we manufacture are built with 16 ga. galvanized steel casing. We offer 3 other options that are slightly more expensive, but it all depends on your application if any of them are actually needed. Stainless steel casings are used in a corrosive atmosphere and are the most expensive option (even then, it’s only 10-15% more). 14 ga. galvanized steel casings are used primarily in coil banks where you might have between 2-4 coils stacked on one another. This adder for 14 ga. casing is only roughly 2-3% per coil.

Tubing Adders: There are many materials options in tubing and we offer all of them. Whether you need stainless steel, carbon steel, cupro-nickel, or standard copper tubes, we can build exactly what you need. Like any product, the more unusual the material, the more expensive the cost is. For most jobs with just copper tubes, adding a thicker tube wall will add only 10-15% in cost to the job and could double the life of your coil. For just a couple hundred dollars, that coil that would last 10 years could last 20. Some applications, like high pressure steam coils, require a thicker tube wall or more durable material or the life span of that coil will be extremely short. You’d be surprised at how many other manufacturers’ coils we’re asked to rebuild with the correct materials.

Fin Adders: Most coils are offered with aluminum fins with a thickness of .006”. The adders to go up in fin thickness are not much, but always remember, the thicker the fin, the more air pressure drop it’s going to add to your coil. The most costly adder you can do to a coil is adding copper fins. It will double the cost of your coil, and in some cases, be 2.5 to 3 times more expensive. This wasn’t the case 20 years ago, but the price of copper has risen over the last few years. We usually recommend coating your coils instead. It’s far more economical and only adds a week to the lead time.

Capital Coil & Air understands that people do business with you like and who you trust. Coil manufacturers should be an open book with this information. Unfortunately, most try and prey on what you don’t know. Hopefully, this helps with any confusion. Capital Coil & Air looks forward to working with you!

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