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Pex for hot water heating system

On the NY Brownstone project TOH showed adapting steam raditors to hot water and they were using PEX lines. I had been considering the same thing but the upper temperature limit seemed to be too close to the limit of the PEX. I don't remember exactly what that upper limit was but I'm thinking it was only around 200. Is there a special type of PEX that should be used with this type of system?

Re: Pex for hot water heating system

There are a lot of issues connected with converting a steam system to hot water---the PEX tubing is usually not a problem, as it is usually rated above 200 degrees & there is a high limit shutoff on HW systems that turns off the burner at 180 degrees.

The major problem with the conversion is that most cast iron steam rads (single pipe systems) are built differently along the top & are thus unable to transmit the hot water & it is nearly impossible to vent the air that is accumulated along the tops of the rads.

I saw just the tail end of the episode mentioned, but IIRC Trethewey was working with the cast iron rads from a two-pipe steam system (relatively rare) and was able to convert them to hot water.

The heating help.com site below explains the problems & solutions that are attempted if the rads & steam piping is not too old & is not clogged with rust & residue.

Also Google "converting steam boiler to hot water" and "converting steam radiators to hot water" to get numerous sites & info on this topic.

Consult your local heating supply houses for the proper type of pex piping & price compare with internet sources such as the one below for ThermaPEX (LKPEX) at pexsupply.com, which sells for $234 for 300 feet @ 3/4" rated at 200 degrees, or .78 cents/ft---enter "pex piping" in their search box.

If PEX is used, it has to be supported at much smaller intervals with strapping from the boiler room ceiling, than would metal pipes---make sure you buy the strapping at the same time as the pipe & ask the counterman for the recommended distance between PEX runs to avoid sagging pipes.


Re: Pex for hot water heating system

Thanks for the help.

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