Designing a zone with radiant heat AND a panel radiator

maine_way

Hello All,

I'm installing a condensing NG boiler in an old Victorian, and mixing radiation types. For the kitchen, I am installing new radiant floor, since the current flooring is removed and replaced by tile. There is a large breakfast bump-out that would be more comfortable with a panel radiator added to the wall under the windows. I want to be able to feel the radiant heat here when eating breakfast and dinner.

Should I add another zone for this, balance it on the same zone with a valve in the basement, or balance it with a separate thermostatic valve in the kitchen? Maybe it should be the first element on the heating loop so it has the hottest water? I was looking to divide the kitchen radiant floor into two parallel runs joined by a manifold for more even heating. Perhaps best to add a loop for the radiator from this manifold?

Along the same lines, upstairs I will be using radiant for bathrooms. Is it a good idea to combine the master bath radiant floor with the master bedroom cast iron baseboard in one zone, and mix them in basement, since these rooms will be occupied together?

Jamie Hall

A radiant floor typically uses water temperatures of 120 F or less and are on all the time. Panel radiators generally need somewhat higher temperatures to be satisfactory, though not as high as cast iron, and normally are controlled by a room thermostat. Cast iron baseboard uses even higher temperatures, and is almost always controlled by a room thermostat.

So... though you can obviously use just the one boiler, you will need to have separate controls and manifolds for your radiant floors, your panel radiators, and your cast itron baseboard.

maine_way

Hello Jamie,

Thank you for the feedback. What you say makes a lot of sense.

One of the goals of this system is to have low EWT so the condensing boiler can run efficiently. For that reason I wondered if there may be a way to combine the floors and radiator in the kitchen on the same zone. If warmer water enters the panel radiator, then branches to the floor, already lower temp, then runs through the floor before entering the boiler, we can achieve low EWT. Alternately some type of mixing valves to control temperatures? Having the panel radiator on a separate zone could work as long as the return water is mixed down with colder water. Perhaps I am overcomplicating.

I will be installing the cast iron baseboard, and plan to provide double the run required for the room in order to allow for lower temperatures. So, again, in the interest of reducing zones as well as proving low EWT, I imagined the water entering the cast baseboard first, and then the floor, to return at 90 or 100 degrees.

TAG

What heats the house now?

I rebuilt an old stone colonial heated with CI radiators -- most of the time those big radiators have enough surface that you can get away with some level of ODR . But, you really have to do your math -- get a room by room load done.

Same with any type of new .... I have used CI baseboard, Runtal and Buderus panels ... all have a place. The Buderus panels are nice as you can feed them with PEX using the bypass valve and each unit has a thermo head.

If you do a good job with the radiant -- the water temp is going to be too low for the other radiation. I have added small radiant zones to two projects (kitchen /baths) w/ Runtal towel racks. The radiant temp is enough to get the rack warm for the towels .. not to heat a full space.

I'm doing the same thing with my new build ... towel rack in the master bath ... the house is all radiant so I only have low temp water.

With a staple up and no plates -- that needs high temp water . That would work for the radiation ... but makes for poor radiant.

What boiler are you using ..... you may be under estimating the units ability to condense

maine_way

It sounds like you have has a lot of experience with different systems, and particularly with low boiler water temperature recently.

I've got a rough room-by-room which anticipates added blown-in cellulose in the walls and a few additional replacement windows to complete the ones that never got replaced before. The wall between kitchen and dining has been removed, and the foyer door is removed (open to the stairway above). So, 30 percent of the house is not really closed off. Exceptions are bedrooms and two living rooms.

I'm planning on using a Navien NFC-175as a new install. Is this a good choice?

The house was a foreclosure. The system in place was a cast iron oil fired boiler that was converted to NG when it became available form the street. That system used all the original radiators in the house. Since it froze up, the boiler jacket and every radiator in the house has sections that popped. The steel existing heating piping has unknown number of leaks. Copper water supply piping will all be replaced with pet as well, given initial tests for leaks.

I've removed all old piping and radiators.

I've purchased about 200 feet of used cast baseboard and plan to use this in 6 rooms. I'll stack the runs agains exterior walls (double runs, one over the other). Entry foyer, dining, and kitchen will all get pex tubing set in grooves in a second subfloor with aluminum plates and topped by cement board and tiled over. All cement board will be marked for pipe position below before screwed and glued.

I've attached a plan showing radiant floor area (tiled area) and two living rooms, which will have runs of CI baseboard. The kitchen panel radiator is planned for the center window.

TAG

The boiler and type are all dependent on the overall load .. most of my systems have been higher heat retrofits with CI german boilers.

CI baseboard is very nice and I have it in NYC ... I'm not sure I would like the the look of stacking them .. I have added small sections to an already existing system in one house

I'm an old house guy .... always have a project going someplace. Although -- I'm not doing them as fast as I once did. It's a shame the original system was so damaged -- getting that working would have been ideal.

You need to do a calculation on the tile floors and heat load ... the floor may well be enough. It's all math there. I used the Buderus panels in one full retrofit -- old house with forced air. The main level was mostly gutted so easy ... but the upper floors not. So I used PEX to connect up the panels to the upper floors --mostly under each window. The boiler used ODR ..

I get that you want to use the lowest water .... but ..it's all about that heat loss and outputs

spgdsl

Baseboard generally relies on air current to emit heat (convention), and relies on higher water temperatures to create that airflow. So if you aim to keep the supply temperatures as low as possible consistent with the floor supply temperature, you should consider panel radiators. Others have already mentioned Budurus. Runtal sells them too. The Budurus may be effective under the kitchen bump-out because they have flutes inside, which create some convection (offsetting cold downward currents from the windows), in addition to thermal radiation. Another consideration is fan-enhanced panel radiators, which are specifically designed to be effective with low water temperatures. I don't know all the brands on the market, but to get an idea, check out chiltrix (https://www.chiltrix.com/documents/FCU-fan-coils.pdf), and Spacepack (https://www.chiltrix.com/documents/FCU-fan-coils.pdf). This might be just the option you need.