Hydronic coil sizing

There are several equations that can be used in conjunction with the Colmac "CoilPRO" selection software program to speed the process of sizing coils. Following is a listing of several of these equations, a description of where they come from, and examples of how they are used.

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Heat Recovery. Power Generation. Process Cooling. Process Heating.Twisting, turning tubes in tanks of steamy, colorful liquids. It is no wonder many still consider designing heat transfer equipment a type of sorcery. Most finishers work diligently at perfecting the chemical, physical and production details required for consistent quality finishes, and they understand that temperature control is critical.

hydronic coil sizing

However, few fully understand how to specify heat transfer equipment and how the design affects production and operating costs. Specifying heating equipment does not need to be confusing. Factors that affect how you boil a pot of water for spaghetti are the same as those influencing heat transfer equipment in the finishing shop. How much water is in the pot?

How long should it take to heat up? How hot will the water get? How hot is the burner? How much of the pot is in contact with the burner? These factors, along with the kind of material heated and how well it is mixed, are used to turn "a little of this and a pinch of that" into precise measurements. Simple calculations determine the proper size heating coil and can help solve a heat-transfer problem. Equation No. The U-factor is usually developed from past experience.

T is a difference in temperature. There are actually two variations of T that will be used in calculations. The first T 1 is the difference in temperature of the solution in the tank before and after heating. The second variation of temperature T 2 is between the heating medium steam or hot water and the final temperature of the solution. For example, suppose the final solution temperature is F and the temperature of the steam at 10 psi is F. As you calculate the required surface area of the heat transfer device, you see where each T value is used.

Q is usually measured in Btus, which is the amount of heat needed to heat one pound of water one degree F. Knowing there are cu ft of water in the tank and that water weighs As some of you may recall, I recent completed a hydronic heating coil replacement at my home. The actual replacement of my heating coil was very straight forward and easily something that the average DIYer could do themselves.

Replacing a coil is simply some standard plumbing — cutting copper piping, soldering, etc. I say very easy as I managed to do it!

hydronic coil sizing

After pouring through a few links I found Heat Exchangers Online which has a fantastic table detailing hydronic heating coil dimensions as well as potential BTU output. Note, this is potential output and varies on a whole lot of factors. One of those factors is the temperature of the water you are going to be sending into the unit. That would potentially produce around 70k BTU. The flow rate and pressure of your water going through the coil also come into play.

My guess was that the existing coil was capable of heating my house so a similar sized coil should also be able to heat my house. I just tracked down the specifications for my Taco Circulator Pump that is used to draw water out of my hot water tank.

The is only capable of a maximum of 10 GPM. I should probably have a Taco Circulator or Taco Circulator to be able to move more water through the coil and thus increase the potential BTU output.

Of course, a higher volume pump would draw more water from the hot water tank which in turn could cause it to heat the water more often thus consuming more gas. One other thing I looked at was the output of my old electric forced air system. It has 4 electric coils, two are 5kW and two are 4. Therefore, my original electric system was capable of around 66k BTU. Good, I was in the right ball park anyways with the heating coil size I was looking at replacing.

The way my system is connected is very simple. Basically, my circulator pump turns on when there is a demand for heat. This draws water out of the hot water tank and pushes it through the coil. After exiting the coil, the water returns to the hot water tank where it mixes with the other water in the tank.What is a hydronic heating coil you ask? Here is a picture of the old one that I replaced today:.

The house actually has an electric forced air system. At some point before we bought the house, the previous owner did a retrofit to add this hydronic heating coil system. We heat water with a Polaris high efficiency natural gas hot water tank. That unit has two sets of outlets, one for the domestic hot water and the other for a heating system loop. For some reason, the coil I had started to spring these little pin-hole leaks. If you notice in the picture above, the unit on the right hand side is my blower and all of the electrical connections are on the bottom side.

Further right are all of the relays and the actual electric heating elements. I contacted a couple of the local heating companies, even had one come in and just recommend we replace the whole system with a new furnace. Instead I hit up Google to see what I could find. Now, the time line of this is a little out of whack. I actually started searching Google just before having one of the local heating companies come in.

That was almost 3 months ago. The second company got back to me just before Christmas. In the meantime, Google had helped me find a whole lot of places where I could buy a replacement coil, once I knew what to search for.

How to Make Sense of Heating Coils?

Ironically, I ended up getting the coil through my neighbour two houses away. We were chatting one day and he started asking some detailed questions about the sizing of the coil. Only then did I find out he actually works with outdoor wood furnaces and they use hydronic coils for all of their heat transfer. Within a matter of a few days I had my replacement coil and I started collecting all the stuff I needed to change around the copper connections.

Oh, yeah, time for some plumbing! Well, no leaks yet. The old coil had both connections at the top. In the picture, the little blue cylindrical device is my Taco circulator pump.

Basically, I can heat water using any number of sources.Quality replacement hot water coils to fit your exact needs for new equipment or replacement. Hot water coils are heat exchangers used to heat air streams, and are at the heart of your heating system. The coils consist of rows of tubes that pass through sheets of formed fins. As cold air passes through the coils, heat transfers from the hot water flowing through the tubes to the air in the coil.

Replacement hot water coils are our top-selling product, because they are widely used in commercial applications and need to be replaced quickly should they fail.

Hot water coils are used for a variety of applications, including preheating, reheating, comfort heating, booster heating, waste heat reclamation, and fluid process heat. We custom build replacement hot water coils for your exact situation. We commonly replace duct mounted coils sometimes called booster coils in commercial buildings with large occupancy space and onsite boilers. We can build an exact replacement of an original equipment manufacture OEM coil for a fraction of the price.

Give us a call at Coil-Now. Hot water coils are used to heat air streams. Air moves through the fin contact area, and hot water usually around degrees Fahrenheit moves through the tubes. Hot Water Coils come in a variety of shapes and sizes, but there are some properties that are common in most hot water coils:.

Back to Basics: Useful Equations When Sizing Coils With CoilPro

With hot water coils operating at high temperatures typically degrees Fahrenheitwe commonly see 1 or 2 row hot water coils. This tube size is perfect for minimizing fluid pressure drop while maintaining heat transfer. Smaller coils may use copper sweat connections.

Grooved connection types are becoming increasingly popular, and are available upon special request. Headers range from 0. Coil performance varies greatly from application to application. Flow rates and temperatures for both fin and tube sides will greatly influence the performance characteristics for any given coil. We have state of the art software that we can use to quote performance.A control valve is the single most important element in any fluid handling system.

Selecting the proper valve will have great effect on the efficiency of a system. There are volumes of information on the science of valve sizing and fluid mechanics. To properly size a control valve, a design engineer would take into consideration the entire system; pumps, piping geometry factors, Reynolds numbers, correction factors, specific heat factors, velocity of approach, pressure recovery, etc.

Valve sizing in the real world is not an exact science, but an art. The basic plan in sizing a valve is to determine the CV required and to match it with a valve having that CV. CV is the flow coefficient of a valve. Valve manufacturers test their valves and list their CV factors in their valve specifications.

The CV of a valve is a standard, and knowing the correct CV allows us to compare valves of different manufacturers. By looking at the formula, it is obvious we need to know the maximum flow rate required and the pressure drop the valve takes.

Anything we do to pick a valve without knowing flow rate and pressure drop will result in guessing at what is required and the valve selected may or may not work as required. There will be other things we need to know to select a valve, but CV is the focal point of valve sizing. It is the first, most important step in valve selection.

Flow rates are expressed in standard units. For fluids, this is gallons per minute GPM.

How A Heat Pump Works - HVAC

The flow rate must be specified to determine the proper valve size. There is no way we can intelligently make a guess at a flow rate. The other part of the CV formula, the DP across the valve is as important as flow rate.

Hydronic Heating Coil Replacement

All valves impose a pressure drop on the flow. The DP has nothing to do with the static pressure. If a gauge is installed on the inlet side of a valve and a gauge on the outlet side, and flow established, the inlet gauge will always read higher than the outlet gauge. The difference is the DP across the valve. In Figure 1, with the valve wide open, the inlet gauge reads psig, the outlet gauge 90 psig.

With a flow rate and a DP known, we can then find the all-important CV factor. If the flow media is water, we can solve the formula. Better yet, many manufacturers print charts from which one can find the CV factor required.Log In. Thank you for helping keep Eng-Tips Forums free from inappropriate posts. The Eng-Tips staff will check this out and take appropriate action.

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hydronic coil sizing

I don't usually see this, but the reason would be load. In cooling, you're limited to a delta-T air side of 15 to 20 degrees F.