Posts Tagged ‘radiant heating system’

Radiant Slab Heating – Insulating Under the Slab

Thursday, February 23rd, 2012

Radiant Heating

In-Slab Systems

Radiant Heating has come to be known as perhaps the most comfortable type of heating available today (next to laying in the sun at least).  In-slab heating is a common option to consider for basements, slab floors, and garages.  While building codes do not necessarily call for it, there is no question that  insulation under the slab will positively impact the performance of any in-slab radiant heating system.  Here is what every contractor should know about insulation and in-slab heating.

Insulating Under the Slab

As was noted in our piece Radiant Heating:  In Slab Systems – What You Need to Know About In-Slab Systems, the first thing to keep in mind is “when heating a slab floor, the goal is to efficiently heat the slab and direct as much of that heat as possible into the living/working space above it – practically speaking  6-8 foot air space above the slab floor.”

The use of an insulation barrier under the  slab is a critical component that will result in much greater efficiencies for the heating system.

Without an insulating barrier, the slab will likely be resting on a bed of sand and/or gravel.  Even though sand is not considered to be a good thermal conductor, it is also not a good insulator.  It will allow heat to escape in a direction that is not in our target area – the 6-8 foot air space above the slab floor.

Insulation options: There are a few different options to provide an insulation barrier for a slab installation.  Three of them are discussed here.

Rigid foam sheets:  If the ground is leveled off well, a 1’ thick layer of blue foam is sometimes used as an insulation layer.  The cost of material is relatively inexpensive.  Because it is typically made of closed cell foam, this can also effectively serve as a vapor barrier, but would need to be taped or sealed somehow where pieces butt together in order not to compromise this functionality.  If working outdoors, care must be taken to hold the pieces in place prior to pouring the slab.  Pieces can be crushed or broken while being walked upon during the installation phase as well, sacrificing performance.  Lastly, while a 1” thick layer of foam will typically provide an R-5 insulation value, the foam itself will still allow some heat from radiant tubing in the slab to pass through it into the ground (i.e. – someplace other than our target area).

Spray foam:  This method has many risks with it.  The foam itself should be closed-cell foam.  If it is not closed cell, it will likely lose its insulation value over time.  Spray foam has no inherent vapor barrier capability.  This would need to be added perhaps through a plastic layer both below and above the foam.  Perhaps the most difficult aspect of using spray foam is the ability to maintain a consistent thickness and density prior to pouring.  For all of the above reasons, using spray foam as an insulation barrier under a slab is strongly discouraged.

Insulating Tarp or blanket:  An insulating tarp provides a built in vapor barrier above and below an insulating InsulTarp6layer of air (much like the bubble-pack used for shipping in packages).  The upper layer of the tarp also serves as a reflective layer to help to maximize the amount of heat being directed to the target area above the floor.  Insulating tarp is easy to work with.  It can simply be unrolled over the desired area.  It can be easily cut and taped down to adjacent pieces in only a few minutes.  It can be walked on by installers without worry to integrity or performance of the product.  It does not take up as much thickness as a rigid foam sheet and best of all, it provides superior insulation performance (typically in the R-6 to R-7 range).

Summary

While the per square foot cost of the insulating tarp may be more than that of rigid foam, it’s benefits during installation (quicker and easier) and its superior insulating performance and contribution to toward the increased efficiency of the radiant heating system provides a quick payback for both the installer and the homeowner.  Going back to the goal of our in-slab system – to efficiently heat the slab (and not the earth below it) and maximize the amount of heat being directed into the air space 6-8 feet directly above the slab – it is easy to see that the use of an insulating tarp makes sense in any in-slab radiant heating system.

What You Need to Know about In-Slab Radiant Heating Systems

Thursday, February 23rd, 2012

Radiant Heating

In-Slab Systems

Radiant Heating has come to be known as perhaps the most comfortable available today (next to laying in the sun at least).  In-slab heating is a common option to consider for basements, slab floors, and garages.  It is also commonly found in commercial buildings and other non-residential structures. Keeping in mind that once the slab is poured, any changes to the system are very difficult and very expensive to accomplish, so careful planning and knowing what is required for both a successful installation as well as a comfortable and efficient heating system is a must.  Here is what you and your customer need to know about in-slab radiant heating systems.

What you need to know about in-slab heating

When heating a slab floor, the goal is to efficiently heat the slab and direct as much of that heat as possible into the living/working space above it – practically speaking the 6-8 foot air space above the slab floor.

Slab System in Finished Basement

Slab System in Finished Basement

Items that need to be taken into consideration to maximize the performance of an in-slab radiant heating system:

Insulation:  Insulating beneath the slab is strongly recommended.  Ideally, the use of an insulation tarp that provides both a vapor barrier and a reflective layer over the insulation will ensure that the majority of heat suppied to the slab will make its way to the intended area, i.e, the 6-8 ft area above the slab.

See our separate white paper Radiant Heating:  In-slab Systems – Insulating Under the Slab for a more detailed discussion on this aspect of in-slab radiant heating.

Desired heated space vs. slab size: Does the slab extend beyond the area where heat is required?

A slab represents a thermal mass.  It will absorb heat as well as transmit it.  If only a portion of a slab is heated, it can be expected that some of the supplied heat will be lost to areas of the slab that are not being heated and therefore will not reach it’s intended area, i.e., the 6-8 ft area above the slab.  Sometimes this may be acceptable, but it is best to make sure that expectations of the system performance are clear.  If this is not acceptable, then the placement of thermal breaks into the slab floor should be considered by the appropriate party (homeowner, builder, designer, etc.).

For this reason, it is usually recommended that each segment of slab be treated as a single zone.  If there are thermal breaks in the slab, then multiple heating zones can be considered accordingly.

Thickness of the slab: In an in-slab radiant heating application, you are effectively transferring heat from the hydronic system into the thermal mass.  The greater the amount of thermal mass, the longer it will take to transfer enough heat to allow the mass to pass heat to the desired area (the 6-8 ft area above the floor).  We say longer because it is important to know that concrete has a certain rate of heat absorption.  If there is more of it to heat up, it is going to take a longer time to accomplish this.  The good news is that once the slab is heated, a thicker slab should give off this heat into our desired area for a longer period of time before requiring another injection of heat from our hydronic radiant system.

Size of the tubing:  From time to time, we hear about people wanting to use tubing with a larger diameter than ½” PEX in their in-slab heating application.  This is not recommended.  As mentioned above, concrete has a specific absorption rate.  We design our systems to optimize the performance of the overall system taking into account all the equipment involved with the creation and transfer of the heat.  Changing the size of the tubing will have an effect of the overall system efficiency (not necessarily a positive one) and would need to be accounted for in the overall system design. In addition, larger diameter radiant tubing may likely require a more powerful circulator in order to achieve the turbulent flow required for efficient heat transfer.   Bigger is NOT better when specifying tubing for a radiant heating system.  A larger circulator will increase the size and cost of your radiant system, and may not produce quantifiable benefits.

Manifold placement: In general, manifolds are located in or on a wall in a spot that is (a) hidden or otherwise out of the way yet (b) still accessible for occasional maintenance and (c) where it can be easily reached by the rough-in Pex-Al-Pex tubing from the mechanical room/area.   Care should be taken during the construction phase to make sure that any electrical wires are located safely away from the same area as the manifolds.

Spacing and Position of the tubing within the slab:  Spacing 12” on center using ½” Pex tubing.  Depth of tubing should be in the bottom third of the slab with the top of the tubing at least 2” to 2-1/2” below the top surface of the slab (deep enough to be below any fasteners that might be driven into the slab during or anytime after construction is completed).  It is important that the tubing not be at the very bottom of the slab where it might not be fully encased by the concrete when it is poured.  This would greatly reduce the efficiency of the heat transfer into the slab.

Heat SourceHow much heat and expected performance

Geo vs boiler system:  While boilers are capable of generating much hotter water than geo heat pumps, both types of heat sources should work very well in a radiant slab application.  If all aspects of the slab construction and radiant system installation guidelines are followed, there will be an appropriate amount of heat provided to allow the slab heating to work effectively and efficiently.

Summary

An in-slab radiant heating system can be both efficient and comfortable.  Investment in the proper components and attention to detail on all aspects of the design and installation should result in a radiant heating system that will perform optimally on a daily basis.

Heat Transfer Plates for Radiant Heating Applications

Monday, January 9th, 2012

What You Need to Know About Heat Transfer Plates

The first thing to understand about heat transfer plates is their purpose as a critical part of a radiant heating system.  It is easy to say, “It’s obvious.  They transfer heat from the hot water in the PEX tubes to the floor!”  This basic premise is true, but the purpose of our heat transfer plates goes beyond that.  Radiantmax heat transfer plates are designed to transfer the maximum amount of heat to the greatest amount of floor area with the greatest possible efficiency.

Radiantmax Heat Transfer Plates

Radiantmax Heat Transfer Plates

How do we do that?  Here’s some information worth knowing.

Our heat transfer plates are made with .020” thick type 3003 aluminum.  Using thinner aluminum would certainly cost less, but this also reduces the efficiency of the heat transfer process.

The channels formed in our plates are designed to be in contact with the PEX tube over 75% of it’s surface area.  Other products on the market with more of a “V” groove or straight lazy “U” groove may be in contact with only 25% of the PEX tube, making their ability to transfer heat to the floor much less efficient.

The channels formed in our plates are also designed to hold the PEX tubing up to the surface directly above it actually forcing it to be in direct contact with it – exactly the place we want the heat to go (up through the floor).

Our plates are pressed into shape in such a way that they will hold their shape over time.  Applying or drawing away heat too quickly from aluminum during the forming process can effect it’s ability to hold it’s shape over time.   Remember that the plate is trying to transfer heat from the PEX tube and send it up through the floor.  Over time, as a plate formed this way experiences expansion and contraction, it may lose it’s shape and make less contact with the PEX tubing, again making it less efficient.

Thermal conductivity is a complicated concept to explain.  Among the key factors are surface area, mass of the material, and the amount of heat we are looking to dissipate.  All of this, of course, effects not only the amount of heat that can be transferred but also the rate at which it can be transferred.  A thin piece of aluminum has less capacity to transfer heat than a thicker piece.  At the same time, it is not practical or efficient to have too much thickness in the plate as well.  Our plates are designed to provide the optimal balance between heat transfer efficiency, practical application, and ease of use.

So is it enough to say that our heat transfer plates are better because they are thicker and made better?  No, there is still more to it.  Let’s talk a little more about efficiency as it relates to heating – including radiant heating.

People don’t just want to feel comfortable and warm from their heating system.  They want to be comfortable and warm for the least amount of operational effort and cost. People buy high efficiency gas boilers and hot water heaters because they turn more gas into heat and that means they save money by wasting less energy.  The same concept is true when you talk about efficiency of heat transfer plates.  A difference of, say, 10% in ability of a heat transfer plate to transmit heat into the floor above it means that there needs to be 10% more heat from the source available to make up the difference.  Sure you can get your floors warm, but how high did you have to turn the heat source up to achieve that level of comfort?

This speaks directly to the concept of spacing of the heat transfer plates.  Eagle Mountain recommends end-to-end spacing of ½” apart. Other systems allow spacing as much as 6” apart.  This could reduce the effective amount of surface area in contact with a heat transfer plate by as much as 25% all by itself.  This is really asking the heat source to work harder to heat the floor.   Stop and think.  If you are using a plate that is anywhere from 10-20% less efficient because of the way it is made and now are spacing it in a way that reduces the efficiency of the entire radiant system by 25%, then how can you expect to make up for that inefficiency?  There isn’t much choice but to provide more heat at a higher temperature for a longer time.  That will cost you money.

Let’s talk about the effect of high heat temperatures on a wood floor.  Did you know that most hardwood floor manufacturers recommend the floor surface to be no higher than 85 degrees (F)?  An inefficient radiant system could require a boiler temperature of between 160 and 180 degrees to generate enough heat transfer through the floor to the living area (where the heat is needed).  This could result in areas of the floor being exposed to too much heat.  This could affect appearance, adhesion ability of glue in the sub floor and joists, and resulting noise in the floor.  If the floor material is something other than wood (tile, thin carpet), the problems could be even more apparent.

Let’s revisit our initial design premise: Radiantmax heat transfer plates are designed to transfer the maximum amount of heat to the greatest amount of floor area with the greatest possible efficiency.

When evaluating a radiant heating system, we suggest that in addition to evaluating the components, you evaluate the complete system. Will the system provide the maximum amount of comfort to the entire living area with the greatest possible efficiency?  Saving money on lower cost components during installation may cost you more in the long run. Keep focused on what you are trying to achieve with your project and buy the system that gives you the best performance for a reasonable investment.

Radiantmax radiant heating systems are designed to deliver the right amount of heat to the right place with the maximum amount of efficiency.  You’re not buying just the plate.  You’re buying a proven system.

Hydronic Control Panels – What You Should Expect to Find.

Monday, January 9th, 2012

Hydronic Control Panels
What should you expect to find in a control panel?

WHAT IS THE VALUE OF A HYDRONIC CONTROL PANEL?

The control panel is the heart of the hydronic system. It should include all components that are not only compatible with the rest of the equipment connected to the HVAC system but allow the system to provide optimal performance. It should be easy to install. It should include all mechanical and electrical connection points. It must provide equipment that protects both the system and the home in case of equipment malfunctions. It should provide for ease of serviceability during routine and emergency maintenance. As it is perhaps the most visible system component in a customer installation, it should also provide a clean and professional appearance.

When considering a hydronic control panel design, the following should be taken into consideration:

  • Functionality
  • Installation
  • Durability and Appearance
  • Serviceability

FUNCTIONALITY

By definition the control panel is the main system component where the hydronic system should be controlled or operated from. This means that it should include as many of the system control elements as possible as well as be the electrical center for all equipment attached to the hydronic system.
Standard elements that should be included in a control panel design include: feed water regulator and backflow preventer, expansion tank, air eliminator, zone valves, circulating pumps, pressure gauge, temperature measurement for supply and return with delta, system controls, master power switch, electrical wiring connection points, and fill and flush connections.

Visio-showroom panel labeled.vsd

Basic Elements of a Hydronic Control Panel

Other items that can be included:

  • Fittings for a variety of piping types
  • Strainer or Dirt Separator
  • 3-way or variable speed mixing
  • DHW Piping and controls
  • Heat Exchangers
  • Glycol Feeders

Integrated Control Options

  • Variable Speed Mixing
  • Setpoint Controls
  • Ice and Snow Melting
  • Ecô Energy Management System

Wiring Connection Terminations for:

  • All thermostats and sensors
  • Circulation pumps
  • Actuators
  • All heat pumps, boilers, air handlers, and any other active equipment being controlled in the HVAC system.

INSTALLATION

As all control panels are essentially customized to a specific installation, the contractor essentially has two choices:

Option 1 – Build it on-site:

  • Pre-design or design-on-the-fly
  • Specify and obtain components
  • Work in potentially unconditioned and uncontrolled environment
  • Incur travel & labor costs
  • Test system on site
  • Make any revisions to panel at on-site labor costs plus travel

There are a lot of variables in this equation. Even with experienced personnel, costs can be unpredictable and difficult to control.

Option 2 – Have it designed and fabricated off-site for easy and quick installation:

Using Eagle Mountain/Hydronic Systems this provides the following advantages:

  • Full Control panel is designed and reviewed ahead of time for physical layout, components, connectivity, wiring layout, and panel size – before any fabrication begins.
  • Panel is fabricated in a controlled environment at factory labor rates.
  • All electrical control connection points are brought to a single electrical box mounted on the panel.
  • Panel is tested before leaving the factory.
  • The only labor required on the job site is for mounting the panel and making the physical connections to the rest of the system.
  • Cost of the panel is known up-front. Installation costs are not only predictable and more easily controlled, they are also greatly reduced.

DURABILITY AND APPEARANCE

Panel Material
It is common to find control panels mounted on materials ranging from plywood to steel sheets. While these materials are readily available and may be relatively inexpensive, they are not ideal for hydronic systems. By their nature, hydronic systems involve water. Components can collect moisture on external surfaces that eventually can migrate to other components in the system. This moisture will eventually weaken and warp wood materials potentially compromising the structural integrity of the control panel. Similarly, steel sheets may be subject to corrosion that may also bring similar risks to the structural integrity of the overall control panel.

An ideal material for control panels is a high-density polyethylene (HDPE) board. This material provides adequate strength and stiffness to accommodate all the control panel components, is completely impervious to the effects of moisture, and also provides a professional appearance in the home or facility where the control panel is mounted.

Panel Mounting
Any prefabricated panel should come with a mounting system that allows for simple and quick wall-mounting by one or two people (depending on the size of the panel). Connection to the rest of the system should be simple and easily accomplished once the board is mounted. Remember, one of the primary purposes of the prefabricated hydronic control panel is to reduce on-site labor.

Copper and Brass Handling
During fabrication, the copper and brass components should not be touched by hand due to the salts on the skin, or exposed to environments that can produce oxidation. Fabrication should be done using gloves designed for handling copper and brass that eliminate the salts transfer.

Cleaning
The piping and fittings need to be cleaned of the flux material used during the assembly to prohibit accelerated corrosion of the copper. The copper may also have surface oxidation from the assembly process as well as salts from shipping and/or handling of the copper by hand. These salts will accelerate the oxidation producing discoloration and eventually corrosion of the copper and brass components in the system. The panel should be thoroughly cleaned and polished to prevent any corrosion of the components.

Following installation, the control panel is perhaps the most visible component to any hydronic-based HVAC system. In addition to the serviceability issues discussed above, the value of a clean and well organized control panel that will stand the test of time should serve any contractor well as a showpiece for the type of installation and work that potential customers can expect from them.

SERVICEABILITY

Next to the ease of installation, the most significant criteria in control panel design have to do with serviceability. As the system is mechanical in nature, over time there is a significant likelihood that maintenance of some sort will be required. Chances are, if a service call is required, the first place a technician will need to go is the control panel. A well-designed control panel allows for easy access to all of the system controls in a consistent manner and provides appropriate access to all components. This design should include removable actuators and sufficient valves and drains to isolate any component for service or easy replacement.

Another benefit inherent with pre-fabricated control panels is that the contractor will have access to a drawing of the control panel available to them to review in the event of a service call. Having this information available will help technicians with remote trouble-shooting and save money in service calls benefitting both the business and their customers.

SUMMARY

Together, all of the elements discussed above add up to the value that the hydronic control panel can bring to your business. Each of these elements is important to both the contractor and the end-user. The decisions made around the design and installation of the hydronic control panel can have both immediate and long-term impact to the system functionality as well as to the relationship between the contractor and the system owner. Care should be taken to consider future maintenance as well as potential changes to the system. Weight should be given to the desired optimal performance of the system when determining system components and layout. All electrical wiring and controls need to be taken into account when designing and evaluating control panel solutions. Eagle Mountain’s hydronic control panels provide a high-value solution to any hydronic-based HVAC system.

Process to change Geothermal from Heating to Cooling

Monday, June 7th, 2010
Jason Murphy

Jason Murphy

Geothermal systems provide both heating and cooling.

If you have a forced-air geothermal system using a water-to-air geothermal heat pump, simply change your thermostats from heating to cooling mode, and you are done. Forced-air geothermal systems are the easiest to change from heating to cooling mode.

Cooling with Hydronic Geothermal Heat Pumps

If you have a radiant heating system, your hydronic geothermal heat pump provides cooling via high-velocity or low-velocity air handlers.

Step 1: Locate your Hydronic Control Panel


If you have a hydronic system, the first step is to locate your hyrdonic control panel in the mechanical room.  You control panel will look like this:

Hydronic Control Panel

Hydronic Control Panel

Step 2: Determine if you have 1 or 2 Tekmar Controls


The device that tells your heat pump to make either hot or cold water is a Tekmar 152 two stage setpoint control.  Your control panel will either have one or two Tekmar controls.

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