Converting Hot Water Radiator to in-floor radiant

justin_6

I am currently renovating my new home. In the kitchen, there 2 radiators; both have been disconnected. In addition, the pipes have broken as the result of freezing and thawing (the house has been vacant for 12 years). Since the kitchen is rather small, I would like to remove the radiators all together and go with an in-floor radiant system. I know that the water temperature serving the other radiators in the house is too high for a radiant system, but is it possible to connect into this somehow with a temperature control? Or do I need a separate boiler? The entire kitchen floor needs to be removed and rebuilt so I figure this is the best chance I have to change the system, but I haven't been able to find anyone in my area who can give me a good answer.

P.S. Using an electric radiant system will likely require a serious upgrade in my electric service, which is currently only 100 amp.

Thanks

Brad White_107

First you make a roux

Sorry, wrong cookbook, "Cajun Men Cook".... Ahem...

First thing is make a detailed heat loss of the space, transmission, infiltration, the works. Only then will you know what you are dealing with.

Knowing the existing radiator sizes (outputs) relative to other radiators will also give you a point of reference as to how well it worked when "alive".

The other part you have to know is how much "usable" floor you have, that which is not obscured by cabinets, islands, steps, the dog-cat feeding station, etc.

(You may have a 150 SF kitchen of which only 75 SF is net walkable radiant area so your density will be twice what it otherwise would be for a typical open room.)

As a "check figure" only, the heat loss divided by available SF should not be over 35 (BTU's per hour per SF). If over that the floor temperature might be too warm (over 85 degrees F) which is warmer than the surface temperature of the averaged clothed body). You would feel at the least overheated. At worst you would be doing the hot foot dance which can lead to rain or drought at the whim of the gods.

You absolutely do not need a separate boiler. A separate circulator (pump) is required, however, along with a mixing device and manifolds to which you connect your Pex or Pex-Al-Pex, and some controls. The water that formerly fed the radiators is blended into the RFH circuit to give you what you need.

IF your radiant floor area is not sufficient (floor would be too hot or the room would be too cold, -neither a choice) you may have to keep a radiator on primary hot water to make up the difference. Until you calculate you will not know.

If you are doing major renovation as you say, you have options for above-floor methods in addition to below-floor staple-up methods. Options are good in the planning stage. Just remember that insulation below and to the edges is critical.

Even in all of this, you may consider outdoor reset and TRV's on the other radiators in the house. You are fortunate in that you have a higher temperature available to mix-down, but you can still save fuel by reducing that temperature, which will always have to be at or above your RFH water temperature of course.

Good Luck!

Brad

Rob_34

Ultrafin website

Check out www.ultra-fin.com for info on infloor heat.