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# Dead Men Tales: Learning from the 1930s

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edited November 2022

Learning from the 1930s

In this episode, Dan Holohan takes us back to the 1930s when half of the buildings in the U.S. that had central heating had hydronics.

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Thanks to SupplyHouse.com for sponsoring this podcast.

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They must have used some sort of flux. Without flux the solder just beads up and rolls off. We learned to cut glass tubing in high school chemistry class like that. If you've ever seen a good glazier work they can make all sorts of cuts in glass with just a glass cutter by scoring it in the right place and snapping it in the right place.
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@DanHolohan said "Consider the definition of EDR (Equivalent Direct Radiation). One square foot of EDR will give up 240 Btu when there is 70-degree air on the outside of the radiator and 215-degree steam (or hot water) on the inside of the radiator. Latent heat means nothing when it comes to sizing radiators; only the temperature of the gas or liquid matters."
Dan, could you elaborate on this? I thought the heat given off during condensation inside the radiator allows sizing a smaller radiator. Wouldn't this be the same as the condenser on an AC system on a car? If the steam radiator is able to condense, don't we transfer more heat? Thank you.
I DIY.
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With one pipe we can assume condensation. With two pipe some of the steam coming in to the radiator might leave without condensing. Is 240 Btu per square foot of EDR assuming 100 percent condensation?
I DIY.
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Sure. The radiator doesn't care about latent heat. It's all about the difference in temperature between what's inside the radiator and the air outside temperature. If you circulate 215-degree liquid water it will put out the same amount of heat as a radiator containing about 1-psi steam. Both radiators would be the same size. The change in size comes when you use cooler water (say, 170 F) is flowing through the radiator. That radiator has to be larger if you want it to do what the steam radiator does.
Retired and loving it.
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edited November 2022
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Dan said "It's all about the difference in temperature between what's inside the radiator and the air outside temperature." I agree.
Dan said "If you circulate 215-degree liquid water it will put out the same amount of heat as a radiator containing about 1-psi steam." I agree that if we fill two identically sized radiators, one with 1 psi steam, the other with 215 F liquid water, they will initially transfer the same amount of heat to the cast iron.
In my head I'm picturing shutting off the circulator on the HW system, and valving off the steam on the one pipe steam system immediately after this initial fill. What happens going forward as the 215 F liquid water and 1 psi steam transfer their heat to the cast iron? I'm thinking over the next 10 minutes, the radiator filled with 1 psi steam will transfer more heat into the cast iron.
I DIY.
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Have you had a chance to listen to this? It may help:
Retired and loving it.
• Member Posts: 8,153
edited November 2022
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WMno57 said:

In my head which can be a scary place I'm picturing shutting off the circulator on the HW system, and valving off the steam on the one pipe steam system immediately after this initial fill. What happens going forward as the 215 F liquid water and 1 psi steam transfer their heat to the cast iron? I'm thinking over the next 10 minutes, the radiator filled with 1 psi steam will transfer more heat into the cast iron.

under normal operating conditions, who is going to be there to shut off the radiator valve? Real world V. Academic. How the heat is made back in the boiler, steam or hot water, is where you will find the difference in efficiency. Consider that 970 BTU of latent heat that is put into the steam in the boiler room. that will travel to the radiator (except for that which condenses in the piping) then release itself in the radiator, and turn back into condensation giving up the latent heat.

Now consider the sensible heat in the boiler at 12+ psi pressure. It also looses some heat in the pipes on the way to the radiator, however, when it gets there it is 225° on the inlet and then exist at 205° to average out at 215°. (you can set the operating controls to make that happen). How much coal, oil, or natural gas was used to make that happen? If the same boiler was used to make steam, then the same boiler was refitted to make hot water, the combustion efficiency would virtually be the same. In my mind, (which ia an even more scary place) a BTU is a BTU and the amount of fuel used to maintain 70° in that room would most likely be the same.

There may be some efficiency difference because to get the 215° average water temperature the boiler needs to have 225 or more degrees water temperature. That boiler is operating at about 10 degrees hotter than the steam boiler. That might raise the stack temperature. Assuming the flame temperature is the same, the combustion efficiency would be a bit lower on the steam boiler

Go a step further and operate at a lower water temperature and replace the radiator with a larger one that will give off the same BTUh at a lower temperature, you might see a savings on the water boiler operating at 180° limit temperature.

(one scary mind to another)

Edward Young Retired

After you make that expensive repair and you still have the same problem, What will you check next?

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I can't remember what they used for flux but I will have to look in some of my old books and repost because they did use something. I never saw copper fittings with groves cut in them but I have seen plenty of old fittings wit holes in them to apply the solder
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edited November 2022
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Furnace is popular in temperate regions, not because it's cheap but the popularity of AC and air ducts.
If you already have air handler and air ducts installed, you don't need another set of pipes to distribute heat.
Hydronics are still popular in cold regions like New England, Canada and Siberia. Pipes and radiators are cheaper than insulated air ducts.
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Just bought "Classic Hydronics" - thanks for making it available on Kindle!