Small older home that has in-wall cast iron radiators throughout the house in a single zone. Hot water not steam. When the kitchen was remodeled years ago the cast iron radiator was removed because it would have been behind the new fridge location. The idea was that it would be moved to a different location but years later it's still on the todo list.

I have been exploring other options but it seems like the easiest most cost effective thing to do would be to add a kickspace hydronic heater under one of the kitchen cabinets.

Is it okay to mix the kickspace heater on the same single zone as the cast iron radiators?

Some additional info if it factors in... The smallest kickspace heater I can find is almost twice the BTU needed for that room. The 1st floor where the kitchen is is all open and generally colder than upstairs.

The main heating pipe is 1" copper tubing I believe or there abouts. For each cast iron radiator there's a venturi T fitting on the supply and return 1/2" copper piping. I was going to plumb the kickspace heater into the existing supply and return pipes that go to the old radiator which is removed and capped off.


You can mix a kick-space heater with cast iron radiators in the same zone but it is not recommended. My choice would be a "Beacon Morris". It comes in 3 models (sizes), and It has a built in thermostat that allows the fan to run when the water temperature is above 110 degrees F. The best installation would be with a monoflo tee on both the supply and return lines, however one on the supply will still work. I am guessing that the systems pump runs all the time and is controlled by a reverse acting control that turns the pump on when the water temp. is above about 110 degrees F. You may desire to add a thermostat to control the fan's heater to stop heat over-runs. For best results I have also installed Danfoss radiator valves on each radiator to control the heat in each room.

  • Thanks. Can you expand on why it's not a recommended setup and what I would experience if I did it that way? Adding a different zone would be very difficult/costly. Cast iron baseboard rads probably prefferred but costly and difficult to plumb. I saw Danfoss has a non-electric valve with remote sensor that I might add in the future if necessary. Looks like they pop on to existing valve stem? Leaving the venturri t's on the supply and return would be similar to monoflows right? – OrganicLawnDIY Mar 13 '17 at 15:16
  • The venturi tees are the same as Monoflo tees. The Danfoss valves use their own valves not the existing valves. Google Danfoss, and you will see the valves and thermostats. They run about $ 80.00 a set "valve and thermostat" depending on where you buy them. They work great. For operation, cast iron rads heat by both radiation (think the sun) and by convection. The kick space heater heats by convection only, so you may need more heat than you think you will need. If you add a thermostat then you could install a larger unit than figured and not have to worry about not enough or too little heat – d.george Mar 13 '17 at 17:12
  • I took a quick look at the RA 200 Thermsotatic Operators and thought they could install on any valve stem but guess only the Danfoss valve bodies. The kickspace heater is about twice the btu capacity I need. I might install the kickspace heater without the thermostatic valve but put a couple of ball valves on the supply and return lines to make it easier to add one in the future if necessary. – OrganicLawnDIY Mar 13 '17 at 17:37
  • By the way, I did not mean to install a thermostatic valve, I was referring to a wall thermostat to cycle the fan on and off to control the room temperature. That was why I said that the size of the heater would not matter if a thermostat was installed. You may not get the heat out of the kick-space heater you require since cast iron rads may run at a lower temperature than you used to size the heater. Cast iron rads are a great way to heat as long as you don't mind the look of the rad. – d.george Mar 13 '17 at 22:40
  • Thought the thermostatic valve made more sense since restricting the water flow would keep the fan from cycling too. Double checked and the venturi tee is only on one side. Might be return side unless I'm looking at it wrong. Can you elaborate on what I would expect with it on the same zone? Would it cause problems? With no radiator currently in the kitchen would the kitchen be more comfortable than now? Would it cause problems in other rooms? I might go ahead and put in a couple of zone valves and thermostat just for the kitchen depending on my budget when I do it. – OrganicLawnDIY Mar 16 '17 at 18:59

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