Radiator sizing questoins

HenryT

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Hello, I have a questions regarding radiator sizing.



Is it better to have more sections than columns or vice versa if they give you the same EDR output? For example a 4 tube 6 section with EDR of 30 versus a 6 tube 3 sections with the same EDR?

The same goes with height. If an 19" and and 25" radiator gives you the same EDR output, are there advantages with one over another?

Thanks</span>

Jamie Hall

From the heat transfer

point of view, any differences are negligible -- in fact, the EDR rating rather tells you that!



The real question is -- what fits?

HenryT

Thanks

Thanks Jamie, I figured that but I wanted confirmation.

come to think of it, the question kinda looks silly in hindsight

HenryT

Another Question

For lack of available radiators out there in the market and strap for funds to get a new one built, is sizing a radiator slightly bigger than needed a bad thing? Will it result in negative affects?  I have an oversized IN5 that can accomodate the larger radiator. I calculated that I need a radiator of 36 EDR but the one im purchasing is 43.2 EDR.

Just wanted to make sure before i pull the trigger.

Thanks!

Big-Al_2

If the room winds up too hot . . .

It's easier to get less heat out of a large radiator than to get more heat out of a small one . . . On a single pipe system, you could de-tune it with a slow vent or even a TRV.  On a two-pipe system, you could just turn down the supply valve.

HenryT

Thanks AL.

The BIGGER the better right.. haha. pulling the trigger.

HenryT

EDR HELP!

Can someone please share some insight for the EDR of this radiator.

I'm  unable to size it based on colonial supply's charts. As i believe these are tubes, but the chart has no data for 4 tubes 22" height rads.



Thasnk

Dave in QCA

Column type radiator

You have a column type radiator.  You have 4 columns per section.  

Checking several charts for various manufacturers, they are all consistent at 4 sq ft / section on a cast iron, 4 column, 22" tall radiator. 

HenryT

Thanks.

Thanks Dave.

I thought this was a tube all along!!

Dave in QCA

tube style radiators

I am putting in a link to a Capitol Radiator catalog.  http://www.heatinghelp.com/files/articles/1281/66.pdf

It shows you what large tube radiators look like.

They have the same 2 1/2" spacing per section as column type. 



There are also small tube or thin tube radiators.  The spacing per section is 1 3/4" per section.  Here is a link to Burnham Cast Iron, they still make radiators of various types. http://www.usboiler.burnham.com/products/baseboard-radiators/slenderized

HenryT

Thanks

Thanks Dave, you're awesome. This is very helpful to me now.

HenryT

last question

Sorry, i hope i am not beating a dead horse.

You mentioned that the radiator above has 4sq ft of EDR per section so I can expect that radiator is 48 total sq ft EDR (4*12 sections).

But per page for of the first link, this radiator can output 2 2/12 per column so 30 total square feet for 12 sections.

Do you see where the confusion is?

Thanks DAVE

HenryT

EDR help.

All, i have attached some pictures in my quest to find the correct size radiator.



Can someone please chime in on the EDR of this radiator. It appears to be a victorian radiator.  So my question is, are victorian radiators considered tube types? This radiator has 3 tubes and 10 sections.  Per the charts its  2.33 EDR per tube so this radiator is 23.30 total EDR? The height is 26"

I just want to confirm my calcs are good.

Thanks everyone.

Dave in QCA

You have column type radiators

The EDR for a 3 column radiator, 26 " tall, is 3.75 sq ft per section. (from the Ideal Fitter, 1909)  If you have 10 sections, that would be a total of 37.5 sq ft.

By the way, the pics are fuzzy, can't see the number of columns, nor the pattern in great detail, but it sure looks like American Radiator Roccocco Pattern.

Dave in QCA

column vs large tube radiators

I am attaching a file so that you will see what a large tube radiator looks like.  You keep thinking your column type radiators are tube type.  Take a look so that you will know the difference.

HenryT

Thanks DAVE

Dave, I cant thank you enough for your guidance.

I think I found the radiator. I can accomodate 37.5 EDR in my room.



Thanks!!!

HenryT

Last Radiator question

Happy New Year!

Dave, would I be incorrect if i say that for a radiator this type, the EDR should be based off a tube type?  This looks like a slenderized radiator hence a tube type, but Im confused because it is 30"W and 8"Depth and 25"H

It has 12 sections across and 5 tubes deep.

if slenderized the EDR is 28.8

if not slenderized, then the EDR is 42 (assuming its tube 3.50 x 12 sections for a 5 tube 26"H radiator.

or if this is a column type, then the EDR 84 (assuming its column, then 7 x 12 sections for a 5 tube 26"H radiator).

I guess I am still confused b/w a column and a slenderized radiator. My guess is choice B, can you tell me if its right?

Thanks!

Dave in QCA

Back to Radiator Sizing Basics

Henry,  I am not sure where to begin.  With the information that is available, it is very easy to examine a radiator and determine the EDR.  However, you don't seem to be getting it.  You have not given me enough information on the current radiator to determine the EDR.  I cannot tell from the pictures whether it is a large tube, or a small tube.  You didn't give me the width dimension of one section.

So, lets start over from the beginning.  I will provide pictures, a pdf of sizing data, and some basic explanation of how you tell what kind of radiator you have.



First, Let omit the VERY old style tubular pipe radiators.  There is very little chance that you will be working with one of those.  Example attachment 1. 



Next, you need to know what a ColumnType Radiator looks like.  These are considered to be the "old style" radiators.  Sometimes they are highly ornamented, sometimes they are smooth.  As Victorian decoration went out of style, they made them smooth because that looked more modern.   See the examples in the next six photos.  These examples of the old standard 38" tall x 3 columns, a 45" tall x 5 column, 17" tall x 5 column, and 38" tall x 1 column.   The width of a column is always 2 1/2" inches.  These dimension are illustrated in the tables in the PDF attached below.



Next, Large Tube Radiators.  The have the castings in the shape of tubes that are smaller than the columns in a column type radiator.  However, in a large tube radiator, each section is 2 1/2", the same dimension as the column type.  Pictures 8, 9, and 10 are large column radiators.



Next, we have Small Tube Radiators.  The overall dimensions of these radiators is smaller.  The are considered "slenderized", and the width of each section is only 1 3/4" inches.  So, you will see the the sections are narrower than the large tube radiators, and the sections set closer together.  See Picture 11.

The PDF document at the end is Chapter 55 from the 1965 ASHRAE (American Society of Heating, Refrigeration, & Air Conditioning Engineers) Guide and Data book.  It is a very useful resource.



I hope this helps you sort things out.  If you are still confused after studying what I have posted here, I will be glad to help, and to confirm things for you.  But Henry, these are VERY basic steam radiator issues.  If you are going to be working on your system yourself, you need to grasp the basics.

HenryT

Thanks Dave

Dave, i think i got it now.

The radiator im looking at is 26"H, 30"W and 8.5" Deep.

It has 12 Sections and 5 Tubes.

From the capitol radiator chart you gave me, i believe this radiator is a large tube type radiator with an EDR of 42.

Thank so much for the clarification yet again.

Dave in QCA

BINGO

Henry,

42 sq ft is what I come with too.  The one additional piece that confirms the large tube type, is each section measure 2 1/2".  That can be measured from seam to seam, where the sections are joined.

salt_point

A few further questions about radiator sizing

I know this is a strictly steam forum, but for purposes of calculation,

my question, which concerns hot water heat will fit here I think.  We're

retrofitting an old house with antique radiators, and a new triangle

tube 175,000 BTU boiler as well as a biomass boiler.  We did all our

room heat load calculations, and then bought radiators sized to suit the

rooms.

We realized our hangup last night between column type and

tube type radiators.  Maybe this has already been well covered in this

forum, but the colonial supply pages, which are top google hits are very

misleading about radiator types:

http://www.colonialsupply.com/resources/radiator2.htm.  At different

times in the same article, the same radiators are referred to as both column and

tube type radiators.  We went out and bought 8 radiators, thinking they

were column type and did our calculations accordingly.  We've now

pressure tested them, started to repaint, and last night we brought our

first one into the house, only to realize that they are in fact large

tube type radiators (2.5" on center), and therefore produce a different

btu/h.  My questions, then are:

1.  Why do the "old style" column radiators, like the first attachment, below, borrowed from Dave's earlier post seem to produce more heat per pound of iron than the newer ones like the second attachment below?  It had seemed to us that with more surface area of iron to radiate, these large-tube type radiators would actually generate more, rather than less heat.  In fact, we passed on getting the column type, because they cost more and (we thought) produced less heat.  It's easier to rationalize buying a more expensive radiator if it makes more heat.

2.  Is my btu/h calculation correct in the following: a large tube type radiator with 5 tubes @ 37" high per section, total of 9 sections (overall dimensions 37" x 22.5" x 8.5").  Using the capitol catalog (I think this particular radiator may, in fact, be a capitol) I get a sq ft EDR of 45.  With hot water heat, @ 70 degrees room temp, then, I calculate a btu/h of 45*170=7,650.  Does this seem right?

Thanks in advance.

Sam

salt_point

A few further questions about radiator sizing

Dave in QCA

You're Close

You have the EDR of your radiator correct.  It is 45 sq ft.  However, the rest of your calculation is wrong.



A radiator filled with steam at 2 psi will normally have an output of 240 BTU/sq ft if placed in a room where the ambient temperature is 70F.   Hot water systems do not run as warm, so the output BTU/sq ft is less.  Hot water systems generally have the high limit set for 180F.  This means that the hotest the water will ever be, leaving the boiler will be 180F.  It is general convention to assume that in this case, the mean temperature of the radiator will be 175F, as the water coming in will be cooling in the radiator and the whole thing will not be at 180.  The coldest parts may very well be 170F.  The adjustment factor for the output of a radiator is .65 where for a temperature of 175F   (See page 860 in the pdf link located in previous parts of this post, it's entitled Radiator Sizing Information.)

The calculation is this:   45 sq ft x 240 BTU/sq ft x  .65 BTU/1BTU =  7020 BTU.    An easier way is to simply take the BTU/EDR of 240 for steam, multiply by .65 which equals 156 BTU/sq ft, and use that number for your hot water system.     45 EDR x 156=7020.   Many folks will round off to 155.  The number is still close enough for your purposes. 

salt_point

column/tube

thank you dave, much appreciated.

any thoughts on why the large tube radiators throw less heat than the column ones?

sam

Dave in QCA

I don't see it that way....

The amount of heat that is given off is determined by the EDR, i.e., the surface area of the radiator.  It is not determined by the weight.  In a column type of radiator, a 30 sq ft radiator will give off the same amount of heat as a 30 sq ft large tube radiator.  The two types have very similar measurements as well.  On a column type radiator consisting of 6  3 column sections, each 38" tall, the EDR will be 30 sq ft.   On a very similar large tube radiator, consisting of 6 sections, each with 5 tubes, and 38" tall, the total EDR will be 30 sq ft.  They are the same.  But, you can't equate the number of tubes to the number of columns, they are not the same.  In my experience, while I have never actually put comparale radiators on a scale and weighed them, I have moved quite a few of these beasts and I would say that the tube style radiator in the above example would weigh less than the column type radiator.  Even, amongs column type raditors, different models and differenct manufactures had different weights per EDR.

It is my guess that the industry went to the tube style because the technical ability to cast iron became more advanced.  They could cast the sections with less iron, smaller passages, and still maintain the needed EDR capacity and a good reliable casting that had uniform thickness so that it was reliable and durable, and not prone to leaks or failures.  The appearance was also simpler and more in line with changing tastes.

Mike Kusiak_2

Actual output under real world conditions

A possible difference in output might be explained by the difference in their thermal mass. Although their output may be identical under steady state conditions,  two radiators with the same EDR may not have identical thermal characteristics. The larger, heavier radiator may continue to supply heat after steaming ends for a longer period of time, thereby actually heating the room more effectively.



The extreme case would be to compare a fin convector and cast iron radiator with the same EDR. The convector will cool almost immediately, while the radiator will remain hot for a considerable time, continuing to heat the room long after the convector is stone cold.



The convector will heat quicker initially, but provided there is an adequate supply of steam, the cast iron radiator can absorb more BTU of latent heat to charge its thermal mass. This additional heat (which could be considered part of the pick up factor) does not figure in the EDR calculation, and is released after the steam supply ends.



So there may be more to the output of two different cast iron radiators than just their EDR.

Dave in QCA

precisely correct

Mike, you are correct.  I decided not to go down that path with my answer.  It appears that the writer is confused about radiator ratings, and I was afraid of adding to the confusion. 



To be correct, I should have stated in my calculations and discussion the ratings in BTU/Hr/Sq Ft.   Once heated (and that is the key phrase) any heat disseminater will have the same output per sq ft of surface area.  Devices with a low mass will heat faster and begin putting out heat faster, but they will cool faster once the flow of water or steam has ceased, and they will cool faster and stop cooling.  Fin Tube convectors and steam coils will heat up and cool down quite fast and tend to behave in "On Off" heating characteristics.  Devices with high mass will take longer to heat and longer to cool down, but the ability to disseminate heat is still determined by the EDR.   Likewise, a radiator used on a hot water system, that has a high internal volume, will also cool down slower because of the mass of the water contained inside the radiator.



The thermal mass characteristics are one of the wonderful attributes of cast iron systems.  They behave as huge heat sinks, and slowly put the heat into the space over a longer period of time, and by doing so eliminate the unevenness associated with ON/OFF systems such as forced air.

salt_point

Thank you

Dave, and Mike,

Thanks for the explanation.  Apparently I'm the confused one that Dave referred to, but what you both have you have said makes sense to me.  We're very excited to have these large cast iron radiators which will continue to radiate heat even after the boiler cycles "off."  Thanks again for your insights.

Sam