Installing SlabHeat™.
The spacing of the SlabHeat cable will help determine how much heated area can be covered by a single SlabHeat coil. SlabHeat can be installed on either 4” (15 W/sf) or 6” (10 W/sf) centers, depending on the amount of heat required for the area. A heat loss calculation is required to know which spacing is right for the project. If the SlabHeat system is to be used for floor warming only, installing the cable at 6” on center is sufficient.
Another consideration to take into account when designing a SlabHeat system is to know the available amperage. A 120 VAC system will pull twice the amps as a 240 VAC system. If amp capacity is a factor, it may be better designing for 240 VAC. Make sure the voltage supplied matches the voltage requirement of the SlabHeat cable. Failure to do so may result in either an over-heating or under-heating condition.
SlabHeat can be installed in either a new slab pour or over an existing slab with a concrete cap. For new concrete pours, just zip-tie the cable to the rewire/rebar and elevate to the middle of the slab. If installing over an existing slab, it will be necessary to install CableStrap™ to hold the SlabHeat cable in place.
When finished the only visible part to the system is the wall mounted SunStat thermostat.
A nice feature of the SlabHeat system is there is no annual maintenance required. Hydronic systems can require periodic cycling of the circulators to prevent the impellers from locking up during periods of non-use. Hydronic systems may also require fluid testing, treatment, and periodic system purges. SlabHeat systems are simple and easy.
Selecting the right product for the application is a breeze with SlabHeat. Since there are fewer parts needed to run a system, just thecable and control, ordering is easier than with a hydronic system. Just make sure to purchase the correct voltage, either 120 VAC or 240 VAC, and the correct number of thermostats or relays.
Controlling a SlabHeat system is also simple. Choose between two types of SunStat controls: programmable and non-programmable. Either one can be set up to respond to either a set floor or air temperature. SunStats are also dual voltage, meaning a single SunStat control can operate either a 120 VAC or 240 VAC system directly (one or the other, not both at the same time). This eliminates the need for cumbersome contactors, transformers, and complicated wiring as seen with other types of heating systems.
Whether heating a small sunroom or an entire warehouse, SlabHeat is the simple solution.
Christopher Campfield
Watts Radiant System Designer
Wednesday, August 24, 2011
Tuesday, August 23, 2011
Introducing SlabHeat
Introducing SlabHeat™.
Up Next: Installation...
Christopher Campfield
Watts Radiant System Designer
SlabHeat expands upon our successful electric floor warming product lines. Designed as a robust, job site resistant cable, SlabHeat is an electric radiant system installed directly in concrete. A combination of strength, durability, and simplicity lies at the heart of SlabHeat. Engineered to provide room heating as well as floor warming for a wide range of applications, SlabHeat is the perfect solution for even the toughest heating project.
Why choose SlabHeat over a traditional hydronic radiant system?
One of SlabHeat’s benefits is the lack of a complicated mechanical room. With SlabHeat there is no need for a heat source such as a boiler; the cable is the heat source! For new construction, as well as remodel, trying to add a dedicated heat source can create its own set of challenges. Hydronic heat sources require a dedicated space, venting, power, and fuel. Hard piping is also needed to circulate the heated water. SlabHeat has none of these obstacles. With SlabHeat all that is required is to run the cable across the space and connect to the SunStat® thermostat. Then, simply pull dedicated 120 VAC or 240 VAC power to the area to be heated. When using a SunStat thermostat, the rest is as easy as wiring a light switch.
Designing a SlabHeat system is much simpler than designing a typical hydronic radiant system. First, figure the gross square footage (wall to wall), then multiply that number by 90%. This square footage will be your heated area. The area to be heated will help determine if a 120 VAC or a 240 VAC system should be used. For a 120 VAC system this is approximately 115 square feet of heated floor area at 4” on center. For a 240 VAC system this is about 225 square feet of heated floor area at 4” on center. This is determined by the SunStat 15 amp limit. If larger areas are to be heated one of two things need to happen. Either add additional SunStat thermostats (one for each additional 115 or 225 square feet of heated area) or add SunStat Relays to the control strategy (one Relay for each additional 115 or 225 square foot of heated area).
Up Next: Installation...
Christopher Campfield
Watts Radiant System Designer
Monday, August 15, 2011
Basic Design of Hydronic Freezer Panel Systems
Description:
A typical freezer application consists of an industrial sized, permanent freezer above a soil or compacted base. One issue resulting from this application involves the ground directly below the freezer heaving due to the moisture in the soil freezing. This heaving can sacrifice the integrity of the structure and should be avoided or mitigated if possible.
Solution:
To remedy the freezing and subsequent heaving of the soil, circulate hot water through piping in the soil to maintain a temperature above freezing. The ideal solution is to heat the soil enough to prevent freezing, while not causing excessive heat to transfer to the freezer itself, reducing efficiency and increasing load on the mechanical systems.
Design:
The design for the necessary supply fluid temperature is extrapolated from ASHRAE heating load calculations. The output of the surface of the soil is dependent on the freezer design. Freezers with internal temperature ranges between 20 °F and 30 °F are designed with loads of 3 BTU/h-ft², the ambient temperature is set at 50 °F directly above the soil, with a maximum ground surface temperature of 55 °F. These assumptions yield a solution that results in the soil staying above freezing (32 °F), while limiting the surface
temperature of the soil as to minimize the negative effects on the freezer mechanical system. As we are not concerned with striping or stratification on the surface, as we would be in a standard heating application, designs are computed around 36” or 48” tube spacing. NOTE: The diameter and length of the tubing are irrelevant when determining a supply fluid temperature and should be selected to optimize cost, availability, and mechanical room and pumping solutions.
Results:
Empirical data shows that the resulting supply fluid temperatures within temperate climates range from 60 °F to 65 °F. With supply fluid temperatures that range close to the ground temperature, the back and edge losses from the soil are negligible. Dozens of these systems have been designed by Watts Radiant and are performing as expected for many years. The best results have been realized when combining intelligent controls that monitor ground temperatures with a heat source that harvests the waste heat produced from the freezer system. By doing this, a hydronic freeze protection system can be an attractive, simple solution that can be run with minimal cost to the owner.
-MDR
A typical freezer application consists of an industrial sized, permanent freezer above a soil or compacted base. One issue resulting from this application involves the ground directly below the freezer heaving due to the moisture in the soil freezing. This heaving can sacrifice the integrity of the structure and should be avoided or mitigated if possible.
Solution:
To remedy the freezing and subsequent heaving of the soil, circulate hot water through piping in the soil to maintain a temperature above freezing. The ideal solution is to heat the soil enough to prevent freezing, while not causing excessive heat to transfer to the freezer itself, reducing efficiency and increasing load on the mechanical systems.
Design:
The design for the necessary supply fluid temperature is extrapolated from ASHRAE heating load calculations. The output of the surface of the soil is dependent on the freezer design. Freezers with internal temperature ranges between 20 °F and 30 °F are designed with loads of 3 BTU/h-ft², the ambient temperature is set at 50 °F directly above the soil, with a maximum ground surface temperature of 55 °F. These assumptions yield a solution that results in the soil staying above freezing (32 °F), while limiting the surface
temperature of the soil as to minimize the negative effects on the freezer mechanical system. As we are not concerned with striping or stratification on the surface, as we would be in a standard heating application, designs are computed around 36” or 48” tube spacing. NOTE: The diameter and length of the tubing are irrelevant when determining a supply fluid temperature and should be selected to optimize cost, availability, and mechanical room and pumping solutions.Results:
Empirical data shows that the resulting supply fluid temperatures within temperate climates range from 60 °F to 65 °F. With supply fluid temperatures that range close to the ground temperature, the back and edge losses from the soil are negligible. Dozens of these systems have been designed by Watts Radiant and are performing as expected for many years. The best results have been realized when combining intelligent controls that monitor ground temperatures with a heat source that harvests the waste heat produced from the freezer system. By doing this, a hydronic freeze protection system can be an attractive, simple solution that can be run with minimal cost to the owner.
-MDR
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