Radiator déjà vu

It’s time to install the radiators – for a second time.

The first time around was a dry run (pun intended). We pressure tested the radiators, the tubing and all connections to make sure they are tight and hold 40 psi.

The idea was to have the system tested once the drywall is up, but before the taping and mudding. If there was a leak behind the drywall, it would have been relatively easy to fix it.

Once the system was airtight, we took the radiators back down and out of the way to proceeded with the taping, mudding, priming and painting. Now that this is all done, the radiators can go back up, this time for good.

Thermal expansion

There is one complicating factor that is not to be ignored: the thermal expansion of the radiators.

This only matters where I have several radiators connected in series, such as in the dining room (see also video above) or living room (see also video below).

I found guidance on how to deal with the expansion in the installation instructions for the radiators:

“Radiators expand a maximum of 0.016 inch per linear foot of length if heated to 215°F. Piping attached to the radiator must provide the necessary expansion compensation.”

Looking at the dining room, this would translate into 1/16” expansion for each of the 44” radiators left and right, and about 1/8” expansion for the 76” unit in the middle. That is, if they are heated to 215°F.

The temperature of our heating system is set to 120°F, to have it compatible with a solar hot water system. 120°F will result in less thermal expansion than 215°F. How much less? I don’t know.

Bottom line, with a maximum expansion of no more than 1/8” between each radiator unit in the dining room, we shouldn’t encounter problems with the hard piping.

The radiators in the library may be more of a problem.

Here, I have one 148” long unit. To absorb any expansion from the long radiator, I used stainless steel flex tubing at both ends.

radiators-016  radiators-017

About Marcus de la fleur

Marcus is a Registered Landscape Architect with a horticultural degree from the School of Horticulture at the Royal Botanic Gardens, Kew, and a Masters in Landscape Architecture from the University of Sheffield, UK. He developed a landscape based sustainable pilot project at 168 Elm Ave. in 2002, and has expanded his skill set to building science. Starting in 2009, Marcus applied the newly acquired expertise to the deep energy retrofit of his 100+ year old home in Chicago.

2 thoughts on “Radiator déjà vu

  1. It’s good to know that you keep your engineering eyes open …

    Thermal expansion can be calculated if the thermal expenasion coefficient is known. But for a radiator constucted of different materials you will not find that coefficient.
    However, the thermal expansion is directly proporital (linear) to the temperatur difference: dubble the raising temperature and you get the dubble expansion. So, if 215 °F gives 0,016 inch per feet you can estimate what 120 °F will result in under the assumtion that the start temperature is the same.

  2. Oliver, I was wondering if the thermal expansion is linear of not. Now that I know it is, I should assume a thermal expansion rate of 0.009 inch per linear foot.

    For dining room, it would translate into 1/32” expansion for each of the 44” radiators left and right, and about 1/16” expansion for the 76” unit in the middle. That is at 120°F.

    The 148″ unit in the library would expand by 1/8″ at 120 °F. Well, in that case the flex connection may have been overkill. But better safe than sorry!

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