Replacing old cast iron radiator


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Old 09-20-08, 11:58 AM
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Replacing old cast iron radiator

I am looking to replace a cast iron radiator with a smaller more modern type.

I see the incoming feed pipe has a shut off.
the return line obviously does not have a shut off.
will I drain back that whole zone when I disconect the return?

Thanks Brian
 
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Old 09-20-08, 04:04 PM
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Brian, do you know if it's a steam or a hot water system ?

If it's hot water, you will have to drain something ...

You wanna replace with a smaller unit ? Make sure the new radiator has the same BTU output as the old one, or you may be unhappy that you don't get enough heat ...
 
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Old 09-20-08, 08:59 PM
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It is a hot water system....
So I supose I will need to drain the entire zone....?

I have the BTU calculations taken care of but would like input on the easiest way to drain....

Do I simply need to close the valves on the other zones and drain the complete zone in question before breaking the lines...???

thanks
 
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Old 09-20-08, 09:46 PM
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It all depends on how exactly it's piped as to how much you need to drain. You want to drain as little as possible to do the work. The less fresh water you add to the system when refilling, the easier a job you will have to bleed the air out when finished.

You do need to at the very least drop the pressure in the system to zero ... then, any of the other zones that can be valved off don't need to be drained.

Can you describe how the system is piped ? Do the supply and return for this rad 'home run' back to the boiler ? Or, do you know if it's tied into a main pipe with 'diverter tee' fittings ?

The more info you can provide, the better an answer you will get ... every system is different ...
 
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Old 09-21-08, 10:29 AM
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this particular radiator is piped into a main line so I am guessing I will need to drain quite a bit out....

can I just close the other zones and open up the main boiler drain right at the boiler to do this?

after install of new rad is complete, and I've added water back to the system, do I need to bleed the air out with the boiler temp up or do I just bleed air, fill more water, bleed air ..repeat.
 
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Old 09-21-08, 02:19 PM
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Are BOTH the supply and return to the radiator tapped into the SAME main line ? If so, then you probably have what's known as a 'diverter tee' or 'monoflo' system.

Once you relieve the pressure on the system by opening a drain to let the pressure down (AFTER closing the water feed line valve to the boiler), you will have to drain some water.

How much depends on some things.

Where is this radiator in relation to all the others ? Is it maybe the highest point in the system ? Are there pipes full of water above this radiator ? Is the boiler in the basement, below this radiator ? Answers to these questions will determine the answer to yours.

After you fill the system back up, it's probably best to open the air bleeds and get out as much air as you can before you fire it up. Since you will be adding fresh water, once that water is heated it will release the trapped air that is entrained in that fresh water. You may have to bleed it several times over a span of time in order to get all the air out.
 
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Old 09-22-08, 05:33 PM
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No, the supply and return are 2 separate mains.
One comes out on one side of the boiler, the other comes in on the opposite side.

Please advise
Thanks again.
 
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Old 09-22-08, 05:36 PM
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One more thing...
In your last post, you stated that I relieve the pressure in the system "AFTER Closing the water feed valve" Is the water feed valve supposed to be on at all times??
It is in the off position except if I needed to add water to the system.
 
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Old 09-22-08, 06:07 PM
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Is the water feed valve supposed to be on at all times??
It depends... first off, there should be a pressure regulating valve in line with the water feed to the boiler that is designed to not go above 12-15 PSI. If you have one of those, and it's working properly, then you _could_ leave it open all the time. It would only feed water when the boiler pressure dropped below the setting of the regulating valve.

There's reasons to leave it open, and reasons to close it.

Leaving it open all the time would pretty much insure that you never run the boiler dry, for example, if you sprung a leak. But then, you would have water damage. A small leak may go undetected for a long time.

Leaving it closed, if you did spring a leak, water damage would be minimal, but if the boiler happened to run dry, there's a very real chance of destroying the boiler, and an equally real chance of starting a fire.

Probably the best of both worlds would be to have a LWCO (Low Water Cut Off) installed on the boiler if there isn't already one there. If the boiler went dry, it wouldn't fire up ... no boiler damage, no chance of fire, and minimized chance of major water damage from a leak in the system.

It's a choice only you can make based on the info at hand.

About draining... I asked some questions previously that would help us answer yours.

Remember that when you open that return line, ALL the water that is in the system at a higher level than the radiator you are working with is going to come out that pipe. It's all up to gravity.
 
 

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