How to interpret radiator specs

[DavidP]

On the blueprints for my house, the hot water radiators are marked in two different ways. Inside the rectangle showing where the radiator is to go there is a number followed by what looks like a little square then a single vertical tick. Next to the rectangle is a number of inches. See the attached snippet of blueprint. The radiator shown here is actually 38" wide by 38" high, but what does the other indication mean? Could this be an older way of marking square feet? But the room is actually about 135 sq ft, not 60.

[Mick_VT]

Square with a tick is a way I was taught to indicate square feet.

I wonder if that is somehow the size / rating of the radiator i.e. heats about 60 square foot, or has 60 square feet of surface area? If they are cast radiators then they could conceivably have that amount of surface area with the ribs.

[Mick_VT]

looks like it is surface area from a scan of this

http://www.antiqueplumbingandradiators.com/askpage.html

[DavidP]

Thanks, Mick. For some reason I don't recall being taught that method of notating square feet. So that's solved.

I looked at the link you gave and it seems that we are looking at square feet of surface area of the radiator. Based on what that site says (assuming I've understood it right), the radiator in my dining room has 56 sq ft of surface area, which isn't far from the 60' specified on the blueprints.

[jharkin]

The one and only place you ever need to go on the web for heating questions:

https://heatinghelp.com/


the guy who runs it - Dan Holohan - is the god of steam and other antique heating technology.


Radiators are rated in "square feet EDR" EDR means Equivalent Direct Radiation. In other words, your 60EDR radiator has the same surface area as a flat plate of metal 60 square feet. This measure was invented by early heating techs to calculate how much heat radiators of various shaps put out compared to a simple flat panel radiator (factoid - the earliest radiators where simple flat iron panels, such as Golds Mattress Radiator)

One square foot EDR in a steam radiator puts out 240BTU/hr. This is exactly what one square foot of iron heated to the temperature of low pressure steam, 215F, will radiate. If its a hot water radiator it puts out a bit less depending on the water temp you are running, but a value of 170BTU/hr is typical.

You mentioned that your system is hot water, so assuming its running the typical 180F temp, 60x170 = 10,200BTU/hr for that radiator.

[DavidP]

Jeremy, thank you for the link and the explanation!