Design Tips

Curving Runtal Radiators

One of the most useful design features of Runtal is the ability to curve the radiators to match the curved walls of today’s modern building designs. Runtal radiators can be field-curved, or factory-curved, depending on the model chosen and the jobsite conditions.

Field Curving

Field curving is the preferred option, since it is the least expensive, and the most flexible choice. Model types “R” and “RF” in lengths over 15’-0” can be field-curved, as long as the curving radius is over 15’-0” as well.

The longer the radiator, and the larger the curving radius, the easier it is to field-curve.

Long sweeping expanses of glass walls can be effectively and economically heated with field-curved R or RF radiators, creating a custom look heating design at a price only slightly higher than straight wall design.

Factory Curving

Factory curving is the option of choice if the radiator, or the radius, are either less than 15’-0”; or Runtal models R2F or RS2 are required. Factory curving is a more expensive and more inflexible option, with the radiators being hand-built to a specific radius.

Radiator length and curving radius limitations apply, so consultation with a Runtal Representative is highly recommended prior to specifying factory-curved radiators.

Larger Water Temperature Drops

The design water temperature drop through traditional hydronic heating equipment is typically figured at a 20°F drop (20°F DT). This is because traditional heating equipment utilizes round water tubes in its design. At water temperature drops greater than 20°F DT, the water flow rate is so low that it produces laminar flow through the round tube. With laminar flow, there is little or no heat transfer between the water and the round tube, and the heating equipment does not produce heat.

Runtal, on the other hand, utilizes flattened water tubes for our designs. The water flow through flattened water tubes is turbulent, even at extremely low flow rates; assuring excellent heat transfer between the water and the flattened tubes. Water temperature drops of 40°F DT, or even 60°F DT, are possible with Runtal.

Designing with larger design water temperature drops can lead to great savings in the overall cost of a heating system. For example, designing with a 40°F DT in lieu of a 20°F DT means that the required flow rate is cut in half, to provide the same heat output:

Flow Rate = (Heating Capacity) DT (DT X 500)

Half the flow rate means smaller piping, less insulation, smaller pumps, smaller expansion tanks, etc – all leading to a lower cost for the heating system.

In Europe (where energy costs are much higher) almost all hydronic heating systems are designed around water temperature drops of 40°F DT or more to save pumping energy costs.

Perimeter Style vs. Wall Panel Style

When designing with Runtal, there are two main layout options em ployed: perimeter style or wall panel style.

Perimeter Style

Running long lengths of Runtal radiation wall-to-wall or column-to-column is the most popular layout option for commercial and institutional applications. Since the entire length of a Runtal panel is the active heating element, perimeter style Runtal spreads the heat out along the entire perimeter, giving wall-to-wall comfort. Runtal builds radiators in even 2” increments up to 29’-6” in length, so most applications can be served by a custom-sized single long panel, tailored to fit the perimeter space. Typically a pipe trim is provided on each end to hide the connecting piping and valves.

Wall Panel Style

Placing individual wall panels in a room, usually centered under windows, is a more “Euro-style”look for utilizing Runtal. This style is most popular in renovations of old buildings, where individual windows are placed at intervals along the exterior walls, or where niches were originally provided for old cast iron radiators. For the wall panel style radiator, the piping connections to the radiator are typically done with decorative shut-off valves, and no pipe trim covers are used. Depending on the Runtal model chosen, the radiators can either help to modernize the look of the room, or compliment the original classic style of the space.

Same End Piping

Same end piping, where the supply and return heating water piping are both at one end of the radiator, can lead to tremendous savings in on-site piping and cost. Single radiators, or a series of up to three radiators may be piped in a same end series.

An example of this savings potential would be a situation where it would be difficult (or impossible) to get a water return pipe to the far end of the radiator (or series of radiators). Same end piping allows both the supply and return water piping to be at the accessible end of the radiator.

Same end piping also evens out the heat output along the entire length of the radiator series. This is because the warmest supply water on the piped end is coupled with the coolest return water; while at the non-piped end, the coolest supply water is coupled with the warmest return water.

Another important application of same end piping is in multi-story buildings with vertical stacked risers and open perimeter bays. With a single set of centrally located vertical supply and return piping risers, it is possible to run Runtal same-end series radiators up to three bays (at 30’-0” maximum per bay) in each direction from the central riser set. Up to 180’-0” of perimeter could be handled with just one set of risers, with no additional return piping required. Additionally, the heat output is relatively constant along the entire series, assuring a comfortable environment for the entire space.

It is important to note that due to the baffling method used to separate the water flows in same end series radiators, only three radiators (regardless of the radiator’s length) should be piped in series.

Runtal North America, Inc. |  187 Neck Road, PO Box 8278 |  Ward Hill, MA 01835 |  1-800-526-2621 |  Canada: 1-888-829-4901 |  Fax 1-978-372-7140 |  | 2008 Runtal North America, Inc.