About Panel Radiators
Hot water steel panel radiators have been used throughout Europe for many decades as a compact, versatile, energy efficient and aesthetically-pleasing heating solution. They offer:
*Beacon Morris 21 & 22 series radiators compared to typical residential baseboard series, such as Slant-Fin Fine/Line 30, Argo Lo Trim II, Sterling Heatrim and similar. Data taken at 180°F supply temperature.
- 2-4 times higher BTU output per linear ft and nearly x2 times higher BTU output per sqft than baseboards* (great for moderate to cold environments with space limitations)
- Individual radiator temperature control
- Integrated air vent and drainage
- Flexibility in piping configurations (can be used with all 3 piping methods – dedicated/homerun, 1-pipe with diverter valves or 2-pipe parallel)
- Higher levels of comfort (better temperature distribution)
- Very compact, space-saving design (11 and 21 radiator series are only as thick as standard baseboard heaters)
- Good long-term resistance to damage (powder epoxy coated and elevated from the floor, where most damage from vacuuming and moping occurs)
- Easily accessible connections allow for quick repair, replacement or maintenance.
- Easy replacement of existing baseboards or older cast iron radiators with little to none piping/system modifications
- Works with 120-180F hot water temperature range, easily integrated with existing radiant floor heating systems and at low temperatures (i.e. 130°F and below return for NG) is ultra efficient with condensing boilers
- Better looks
- Virtually silent operation (no creaking like baseboards, caused by thermal expansion)
- Variety of sizes and output options to fit any project needs (from as little as 500 to as high as 18,000 BTUs output per unit)
- Compatible with SSM and BSM series manifolds sold at PexUniverse (for supply temperatures below 160F), which can significantly simplify the installation and reduce material costs
Difference between panel radiators and baseboard heaters
Unlike standard baseboards (copper pipe with aluminum fins), which rely almost exclusively on hot air convection, panel radiators are designed to utilize another additional method of heat transfer - radiant heat, which is more energy efficient and creates a noticeably more comfortable environment with better heat distribution.
In baseboard radiators, the heating element located inside and is separated from the room with a cover and an air gap, which reduces radiant heating effect to a minimum. In panel-style radiators, the front panel (1 out of 2, through which hot water circulates) is exposed to the room, radiating heat in the same manner a radiant floor heating system does and naturally heating not only the air, but all the objects and persons in the room. At the same time, front and back panels are separated with a convector channel, through and around which natural convection occurs and air in the room is also heated. As a result, heating efficiency in panel radiators is nearly twice higher than in baseboard heaters under similar conditions.
Heating system compatibility
Panel radiators operate in a wide temperature range, from 120°F to 180°F, ensuring compatibility with both traditional (cast iron
) and condensing
types of boilers. They can be used as a primary heat source or installed as an addition to existing heating system - whether hot water (hydronic) or forced-air.
Hot water panel radiators are an optimal match for systems with gas condensing boilers, since the latter operate at their peak efficiency with low return water temperature (i.e. 130°F return water temperature for natural gas-fired boilers), allowing for maximum energy efficiency and cost savings.
They also work well with existing hydronic radiant floor heating systems, which commonly operate in the 120-135°F supply temperature range, allowing to reduce or eliminate the need for additional equipment.
Panel radiators are commonly piped using the following 3 methods:
1. Dedicated (Home-Run) Piping Method:
Home-run piping method involves running dedicated supply and return lines from the radiator to the multi-loop (multi-zone) distribution manifold, such as SSM or BSM series available at PexUniverse or similar. It offers multiple advantages:
- Very simple - no special consideration for pressure drop, uneven temperature distribution, complex piping or balancing is needed
- Easy zoning - a single manifold can combine several radiators into zones, allowing for individual temperature control in multiple rooms with different heat loss factors
- Cost effective - no additional radiator accessories (thermostatic heads, bypass valves, etc.) are required
In our opinion, this method is the best choice for a simple and efficient installation without complex hydronic calculations and special parts or equipment. The piping of choice should be oxygen barrier PEX tubing
or PEX-AL-PEX tubing
(Everhot, Sioux Chief, Viega, Watts, Uponor or similar) due to it’s flexibility and cost advantage over copper pipe.
If used, this method would require:
2(a) 1-Pipe Method with Bypass Valves:
- A supply & return manifold with 24V zone valves or actuators - our SSM or BSM series manifolds with 2-wire or 4-wire actuators would work (for supply temperatures below 160°F). Alternatively, a pair of copper headers with standard 24V zone valves (Taco, Honeywell, White Rodgers or other brands) would work.
- A 24V thermostat for every room where radiators are installed (any brand or style would work)
- Zone valve control - such as Taco ZVC series, will act as a hub for thermostats, zone valves (actuators) and circulator pump
In a 1-pipe system, there’s no separate return line, as return water from each radiator water drain into the main supply line and this (mixed) water is then utilized by all radiators further down the line in the same manner. We do not recommend this method unless all radiators are installed in a single room (zone), their number is limited and their size is carefully selected (to match decreasing supply temperature downstream). Otherwise, there could potentially be a large head loss resulting in a hard-to-balance temperature output.
1-pipe systems would often utilize thermostatic valve heads as a means of individual radiator temperature output control and would use diverter/bypass valves to achieve proper hydraulic separation (1 per radiator). This piping method does not require room thermostats if thermostatic valve heads are used, but would require a single central thermostat or an outdoor reset (w/ constant recirculation) for the system to function. The maximum allowed combined flow rate for a loop (circuit) with bypass valves is 2.0 GPM due to possible turbulence and noise issues above this threshold.
2(b) 1-Pipe Method with Venturi Tees:
A variation of the above method with Venturi (MonoFlo/Monoflow) tees instead of the bypass valves. Venturi tees lack the adjustable functionality of the radiator diverter valves and thus the system should be carefully sized to ensure proper operation. We do not recommend this method unless calculations and installation are performed by an experienced professional.
3(a) 2-Pipe Method with Direct Return:
A two-pipe system implies separate (1) main supply and (1) main return lines which will feed the hot water to the radiators and collect it, returning to the boiler. Its’ distinct advantage over a 1-pipe system is an unlimited number of radiators which can be installed (given main lines are properly sized), allowing to overcome size restrictions present in the above methods. A 2-pipe method is best used for large zones with multiple (possibly different size) radiators, since it delivers the same temperature hot water to all the radiators and eliminates the need for complex temperature balancing. It is also a preferred method (over dedicated/home-run with PEX lines) where copper is the pipe of choice for cost reasons.
"Direct return" refers to a piping arrangement where the 1st
radiator in line also has the shortest return path to the boiler, whereas the last radiator in line will be the farthest on the return line and farthest from the boiler. In other words, supply and return lines will flow in the opposite directions.
Such system can utilize either a central thermostat (for On/Off control) with thermostatic valve heads (1 for ea. radiator) or a dedicated room thermostat. If thermostatic valves are used in a 2-pipe system, a pressure differential bypass valve, such as Taco 3196
must be used to prevent dead-heading of the circulator pump. The latter is not needed if no thermostatic valve heads are used.
3(b) 2-Pipe Method with Reverse Return:
A variation of the above 2-pipe method where supply and return lines flow in the same direction and the 1st
radiator in line will have the longest return path to the boiler, whereas the last radiator in line will be the closest to it.
thermostatic valve heads cannot be used with a 1-pipe series method (all water flows through all radiators - no venture/monoflow tees or diverter valves), since a single valve head may shut off the flow for all the radiators down the line.
Parts and accessories
The only part which is not included and must be purchased with the radiator, is a pair (set of 2) pipe adapters, which connect Copper, PEX or PEX-AL-PEX supply and return pipes to the radiator
. All other parts are optional
and may or may not be needed depending on piping configuration and desired temperature control specifics.
Thermostatic radiator valve head
- replaces manual adjustment cap which comes by default with the radiator, and allows to control the radiator temperature output automatically. They are installed over the thermostatic valve body (insert). Each valve head has several pre-set numbered dials, which represent fixed ambient air temperatures (80F, 75F, 68F, etc.). When a desired temperature (dial) is selected, the valve will automatically adjust the hot water flow to maintain this pre-set temperature, regardless of the flow rate or temperature fluctuation of the hot water supply. These valve heads are non-electric and do not require any wiring or additional controls to operate.
Required or recommended where:
Not required or not recommended where:
- There’s no thermostat in the room (no means of temperature control)
- There’s only (1) radiator in the room (i.e. bathroom, walk-in closet, etc.)
- There are multiple radiators in the room and individual temperature control for each is desired (ex. higher for the unit near the window, lower near the bed, etc.)
- 1-pipe method is used
- Radiators have dedicated supply and return lines (Home Run system)
- Temperature control in the room is done via a standard thermostat, which controls the operation of boiler, circulator pump or zone valve assigned to this particular zone (room)
- Individual temperature output control for each radiator in the room is not required or desired.
In summary, thermostatic valve heads are non-essential and are not needed if panel radiators are installed in a room temperature is regulated via an electronic thermostat. They lack the precision of the latter and are only used where electronic temperature regulation is not available or is impractical to install.
Isolation & bypass (diverter) valve
- is required only for 1-pipe systems
, where the outlet (return) piping from the first radiator directly connects to the inlet (supply) of the next radiator in line. The valve has an adjustable bypass (factory set to 35% flow / 65% bypass), which allows to distribute the hot water supply more evenly among multiple radiators in the room.
Required or recommended where:
Not required or not recommended where:
- 1-pipe method is used (without Venturi tees)
- Balancing the radiators is necessary (i.e. room has many, possibly different size radiators, and it is necessary to adjust the hot water flow so as to equalize the heat output)
- Individual radiator shut-off capability is desired (this feature is useful where it is necessary to repair or replace the radiator without interruptions to the rest of the system).
- 1-pipe system with Venturi (Monoflo) tees is used
- Each radiator has a dedicated supply/return line, running to the manifold and/or controlled by a separate zone valve or circulator pump
In summary, bypass valves are very specific to the supply/return piping arrangement, and in most circumstances, are non-essential.
Panel radiator sizing and selection
When selecting panel radiators, the following factors must be considered:
1. Heat loss - radiators must be sized to at least match the heat loss. Over-sizing is not an issue, since radiator heat output is easily adjustable in multiple ways.
2. Available space, location and floor to window height limitations - these determine the physical size (dimensions) of radiators. Examples include installing a 36" wide radiator under a 3ft window, positioning radiators between existing or planned furniture locations or simply installing multiple units for more even heat distribution.
3. Piping method - may require additional parts which are not included with the radiator by default.
4. Comfort level - panel radiators are very versatile and allow for basic, intermediate and advanced methods for room temperature control. Basic method uses manual cap (included) for simple flow volume adjustment. Intermediate requires thermostatic valve head (not included) and allows for automatic temperature regulation in ~5°F pre-sets. Advanced would require using a room thermostat, which offers best comfort level adjustment (+/- 1°F), but also requires the thermostat itself and additional wiring/controls.
1. Radiator comes with (4) plastic plugs (2 on each side), which must be removed prior to the installation. The top left and right side openings are for the installation of the air vent and the thermostatic valve body (insert). The bottom left and right side outlets are most commonly used for drainage and are generally plugged with (2) drain plugs (which are included).
2. The (2) outlets at the very bottom of (underneath) the radiator are for hot water supply and return lines and are closed with metal caps which can easily be removed with standard crescent wrench or pliers. Supply connection is the one closer to the center of the radiator, while return is closer to the edge - these should not be confused. Adapters which connect the piping of choice to the radiator are not included and must be purchased separately.
3. Radiator valve body (insert) is installed inside the top side outlet, directly above the supply and return connections, and is used to regulate the flow of hot water through the radiator, offering basic temperature control (allowing for more or less hot water flow) with the help of the manual valve cap, which is included. A thermostatic valve head (such as part# 551013066, 551011365 or similar) can optionally be installed instead of the cap, converting the operation to automatic and allowing for a more precise temperature regulation. Note: thermostatic valve head is not required when using a dedicated piping method as described above in "Piping Methods".
4. A non-automatic, bleeder-style air vent which is included with the radiator is installed into the top opening, directly opposite the valve insert. It is recommended to install the vent with bleeder opening pointing down.
The remainder of the set-up process is installation-specific.
Frequently Asked Questions
Q: Is it possible to balance multiple radiators in a single zone without thermostatic valve heads or bypass valves?
A: Yes, the valve insert includes a cap which allows for manual regulation of flow rate through each radiator individually. However, it does not offer any feedback in terms of output temperature, so if a more precise balancing is needed, an infrared thermometer can be used to check the temperature of other radiators in the room and adjust the flow accordingly. Also, using a home-run piping method eliminates these need for the above-mentioned accessories.
Q: What is the maximum flow rate through a radiator?
A: These panel radiators have a 2.5 GPM (Gallons Per Minute) flow limit. However, selected size piping (and adapters) also has a limiting factor, for example:
Max allowed flow through 1/2" copper or PEX pipe is 1.5 GPM
Max allowed flow through 5/8" PEX pipe is 2.0 GPM
Q: Is the air vent automatic or manual?
A: The air vent is a manual, bleeder style, and is used to purge the excess air from the radiator during the initial start-up or following maintenance.
Q: How to open the air vent?
A: With a flat head screwdriver.
Q: How to select proper pipe size for the radiator?
A: Pipe size should be selected based on maximum radiator BTU output, since each pipe size has different heat carrying capacity. For example:
1/2" copper pipe can deliver 15,000 BTU’s @ 1.5 GPM flow and 20°F delta T (difference between supply and return water temperature in the radiator). This BTU number is increased by 7,500 BTU’s for every additional 10°F temperature drop - i.e. 22,500 BTU’s at 30°F delta T or 30,000 BTU’s at 40°F delta T.
For 5/8" PEX, the numbers are 20,000 BTU’s @ 2.0 GPM & 20°F delta T; 30,000 BTU at 30°F delta T or 40,000 BTU’s at 40°F delta T.
Thus, when multiple radiators are supplied by a single pipe, larger size should be considered (e.x. 5/8" PEX). In dedicated (home-run) configuration, 1/2" PEX pipe (and even 3/8" PEX for smaller models) should have more than sufficient heat carrying capacity.
Q: What are the clearance requirements?
A: 2-4" top, 2-4" on the air vent side, 5" on the thermostatic valve head side (if not used, then 2-4"). Bottom clearance is 2" if no diverter (bypass) valves are used. With diverter valve installed, min. bottom clearance is 4" for angle and 5" for straight version.
Q: How much do the brackets offset the panel radiator from the wall?
A: About 1-1/4" - 1-1/2"
Q: Can panel radiators be recessed?
A: No, they are not designed for recessed installations.
Q: Should radiator piping be insulated?
A: Pipe insulation
is required whenever supply/return lines run near or along the outside wall. For other scenarios, insulation is recommended (to increase efficiency), but not required.
Q: How do you cover the pipes which come up from the floor and connect to the radiator?
A: The hole in the floor around the pipe can be covered with escutcheon, such as part# 551016674. The supply and return pipes themselves can optionally be covered with a larger diameter PVC pipe or any other rigid plastic pipe by sleeving the latter over the former. To cover 1/2" copper or PEX pipe, use 3/4" PVC pipe, for 5/8" PEX - 1".
Q: Which manifold type/brand is best for a Home-Run piping approach?
A: We recommend either radiant heat style manifold with actuators (up to 160F supply temp.) or copper headers with zone valves (up to 180F supply temp.) as explained above in "Piping Methods". Note that despite the name, Viega Manabloc manifolds cannot be used for Home-Run hydronic heating applications, and are intended for plumbing applications only.