Archive for the ‘Overfloor Systems’ Category

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.