Flat, Wall Hung Radiator Noise In One-Pipe System Question

PGB1

Hello All,
In a bathroom, it's been decided that I will remove a cast iron column radiator and install a steel wall-hung, flat panel unit with a BTU rating as close to what I calculate the cast iron radiator to be.

My question concerns noise. I have read some mentions, including a Buderus brochure, that briefly state that flat radiators are not to be used in On-Off systems due to noise.

Our hydronic system is sort of a one-pipe. For Zone 1, there is a loop around the basement. Each radiation unit (mix of fin tube, cast iron column radiators and one toe space heater) is fed via a monoflow tee with balancing ball valves on the inlet to & outlet from the radiation and between the inlet and outlet tapping. The circulation pump runs only during a call for heat. We have boiler output temperature at 180-F during winter and progressively warmer during spring & fall.

In your experience, will this flat panel cause noise problems?

Unrelated: Since these are steel, I know the residual heat will be less than that of the cast iron radiator. Is this a noticeable difference? Also, since the mass is less, should the BTU rating of the flat panel be higher than that of the cast iron radiator?

Thank You for helping & sharing your experience with these flat panel, wall hung units.
Paul

kcopp

What are the pipe sizes on the cast radiator? The pressure drop on the new panel rad may be too steep to work in your system....
You may want to run that by the person who made the decision to swap...

hot_rod

The lower the temperature swing and the less often it swings, the lower the chance of noise. You have quite a blend of heat emitters, all with different operating characteristics 
Panel rads work nicely with TRV control and temperatures around 140 or so. The TRV is a modulating control valve, so less on/off cycling

PGB1

Thanks Kcopp & HotRod for taking time to reply with good thoughts. I appreciate the help.
The cast iron radiator is supplied by 1/2" copper. The zone loop is 3/4"

We sure do have a blend of radiation, Hot_Rod. My inheritance when I bought the house, plus some changes I've made.

About the TRV; I was taught 40 or so years ago (by a dead man) not to use them or a thermostat in bathrooms as the heat from the washing/showering steam will trick the unit to closing, thus cooling the room and allowing condensation on mirrors, tile & such. But, I'm sure the technology has changed, so I don't know if that would work out.

Kcopp mentioned speaking about the decision maker about the pressure drop. That's SWMBO. Don't Mess With SWMBO! (Just kidding. Sort of. If it isn't going to be satisfactory, she'll understand.) Fortunately it was easy to explain why in-floor would not work out for the room.

hot_rod

Out door reset control help minimize temperature swings on the SWT also. But with a mix of emitters like that the settings will be trial and error.

As for shower condensation and temperature, within minutes of opening the door that should dissipate and the TRV goes back to its job. TRVs are common on hydronic towel bars used in bath areas.

PGB1

Thank You Hot_Rod. I appreciate the help you & Kcopp gave.
Paul