Radiator Covers???

Bruce_4

Is there any concerns or considerations with regard to making and useing covers. Is there any degradetion of heating???? They do look a hell of lot better than bare radiators.Thanks in advance

DanHolohan

Look in Hot Tech Topics

Scroll to Radiator Enclosures.

It pays to wander off the Wall.

Mike T., Swampeast MO

Lots of concerns/considerations

Most radiator enclosures result in decreased output. All enclosures have a significant effect on HOW the radiator liberates its heat.

All diminish the radiant portion of the output. The method of construction determines how much the convective portion is enhanced to overcome this. You essentially want to turn a radiator into a convector.

Below from enclosure studies where the quantity of condensate produced by a steam radiator painted black was used to determine differences in output. Water radiators AT HIGH TEMPERATURE (around 180°) are said to have nearly identical characteristics when covered.

Manufactured metal covers reduce the output by about 15%.

The most efficient typical enclosure leaves an open "slot" about 5" high at the bottom of the radiator. The top contains a grille the same depth and length as the radiator itself. TOP AND FRONT PLACED 2½" from the corresponding faces of the radiator. Placement of side panels (solid) has little or no effect. About 2/3 of the grille should be open. This type of enclosure results in about an 8% reduction.

Output can be INCREASED if you do not use a top and instead cover the front and sides. Again, leave an OPEN slot at the bottom AT LEAST 1/5 the height of a tall radiator or 1/3 the height of a shorter radiator. Taller is better regarding the size of this slot.

A TOP ONLY "cover" should not be installed directly on top of the radiator. It should be at least 3" above the radiator. If the shelf only projects to the mid-line of the radiator it has no affect when 3" or higher. If shelf projects to the front edge of the radiator try to keep it 4" or move above the radiator.

Low "window-type" radiators were ALREADY designed to enhance convection. The output reduction effect is MAGNIFIED when covering low radiators. Generally output will be reduced by AT LEAST 25%.

In general, use the 2½" distance away from front and top and try to keep the area of the outlet larger than the inlet.

EFFECTS ON COMFORT:

Increased output does not necessarily translate to increased comfort and vice-versa. As all enclosures eliminate much of the radiant output there is a corresponding increase in convective output with those that are well-designed. Higher convection usually translates to higher temperature stratification in the space. So, while the "open top" example may be producing more heat, much of this is just zooming to the ceiling with cold air being pulled across the floor with increased velocity.

It is possible to design an enclosure to counter this effect--it essentially tries to "project" the convection into the room instead of letting it rise to the ceiling. "With a well-designed enclosure having a large free area of grille work at front and ends with a solid top and a back carried down to the floor, a tubular cast iron radiator may operate to produce higher useful temperatures in the living zone below the breathing line and lower temperatures in the upper part of the room for a given breathing line temperature and at the same time condense less steam than the same bare radiator."

Again, these studies are either with steam or very hot water. With modern control, insulation and weatherization, old water radiators generally operate at MUCH lower temperature than their design. As the temperature of the radiator decreases so does output, BUT convection decreases more rapidly than radiation. Temperature stratification decreases as well. This contributes GREATLY to the comfort of these old systems and covering the radiators negates this benefit. When old oversized water radiators are controlled proportionally, many will claim that they approach radiant floor comfort.

Because iron radiators are now typically quite oversized, a radiator cover (even one poorly designed) most likely won't result in not enough heat. BUT in a simple unzoned system you may well upset the temperature balance compared to other uncovered radiators in different rooms. The rooms with uncovered radiators may now overheat.

If at all possible I would try NOT to enclose the radiators. A good cleaning (a pressure washer with zero-degree nozzle works great) and repainting can do wonders. Modern "bronzing" can be extremely attractive.

Modern "bronzing" is NOT the same as old bronzing which actually contained metal particles. Modern bronzing is actually mica in most colors. As best as I can determine, "paint" made of mica powder and linseed oil has an emissivity only slightly lower than standard paint, so the effect on radiant output is very small.

Dennis - Reliable Services

your rads are probably over sized for the areas that they heat,

> Most radiator enclosures result in decreased

> output. All enclosures have a significant effect

> on HOW the radiator liberates its heat.

>

> All

> diminish the radiant portion of the output. The

> method of construction determines how much the

> convective portion is enhanced to overcome this.

> You essentially want to turn a radiator into a

> convector.

>

> Below from enclosure studies where

> the quantity of condensate produced by a steam

> radiator painted black was used to determine

> differences in output. Water radiators AT HIGH

> TEMPERATURE (around 180°) are said to have nearly

> identical characteristics when

> covered.

>

> Manufactured metal covers reduce the

> output by about 15%.

>

> The most efficient

> typical enclosure leaves an open "slot" about 5"

> high at the bottom of the radiator. The top

> contains a grille the same depth and length as

> the radiator itself. TOP AND FRONT PLACED 2½"

> from the corresponding faces of the radiator.

> Placement of side panels (solid) has little or no

> effect. About 2/3 of the grille should be open.

> This type of enclosure results in about an 8%

> reduction.

>

> Output can be INCREASED if you do

> not use a top and instead cover the front and

> sides. Again, leave an OPEN slot at the bottom

> AT LEAST 1/5 the height of a tall radiator or 1/3

> the height of a shorter radiator. Taller is

> better regarding the size of this slot.

>

> A TOP

> ONLY "cover" should not be installed directly on

> top of the radiator. It should be at least 3"

> above the radiator. If the shelf only projects

> to the mid-line of the radiator it has no affect

> when 3" or higher. If shelf projects to the

> front edge of the radiator try to keep it 4" or

> move above the radiator.

>

> Low "window-type"

> radiators were ALREADY designed to enhance

> convection. The output reduction effect is

> MAGNIFIED when covering low radiators. Generally

> output will be reduced by AT LEAST 25%.

>

> In

> general, use the 2½" distance away from front and

> top and try to keep the area of the outlet larger

> than the inlet.

>

> EFFECTS ON

> COMFORT:

>

> Increased output does not necessarily

> translate to increased comfort and vice-versa.

> As all enclosures eliminate much of the radiant

> output there is a corresponding increase in

> convective output with those that are

> well-designed. Higher convection usually

> translates to higher temperature stratification

> in the space. So, while the "open top" example

> may be producing more heat, much of this is just

> zooming to the ceiling with cold air being pulled

> across the floor with increased velocity.

>

> It

> is possible to design an enclosure to counter

> this effect--it essentially tries to "project"

> the convection into the room instead of letting

> it rise to the ceiling. "With a well-designed

> enclosure having a large free area of grille work

> at front and ends with a solid top and a back

> carried down to the floor, a tubular cast iron

> radiator may operate to produce higher useful

> temperatures in the living zone below the

> breathing line and lower temperatures in the

> upper part of the room for a given breathing line

> temperature and at the same time condense less

> steam than the same bare radiator."

>

> Again,

> these studies are either with steam or very hot

> water. With modern control, insulation and

> weatherization, old water radiators generally

> operate at MUCH lower temperature than their

> design. As the temperature of the radiator

> decreases so does output, BUT convection

> decreases more rapidly than radiation.

> Temperature stratification decreases as well.

> This contributes GREATLY to the comfort of these

> old systems and covering the radiators negates

> this benefit. When old oversized water radiators

> are controlled proportionally, many will claim

> that they approach radiant floor

> comfort.

>

> Because iron radiators are now

> typically quite oversized, a radiator cover (even

> one poorly designed) most likely won't result in

> not enough heat. BUT in a simple unzoned system

> you may well upset the temperature balance

> compared to other uncovered radiators in

> different rooms. The rooms with uncovered

> radiators may now overheat.

>

> If at all possible

> I would try NOT to enclose the radiators. A good

> cleaning (a pressure washer with zero-degree

> nozzle works great) and repainting can do

> wonders. Modern "bronzing" can be extremely

> attractive.

>

> Modern "bronzing" is NOT the same

> as old bronzing which actually contained metal

> particles. Modern bronzing is actually mica in

> most colors. As best as I can determine, "paint"

> made of mica powder and linseed oil has an

> emissivity only slightly lower than standard

> paint, so the effect on radiant output is very

> small.

Dennis - Reliable Services

Your rads are probably oversized for the areas that they heat,

but if you totally box them in like they are in a coffin they will not work very well, if you make the covers out of wood they will crack at the joints, but if you buy the typical metal cover you will be fine, and you'll have a great place to put plants, magazines, and pictures, but your heating man will not like you when he has to bleed your rads.