Oversizing radson radiator

Big Ed

Check out some of the off the shelf pump stations.You need a pressure system bypass not to dead end the pump when all the trv shut down .The non mixing stations make a neat job and sport the bypass.....

Sparky Bill

oversizing Radson Radiators

I am working on a project that incorporates a Viessmann boiler and how water radiators individaully controlled with danfoss valves. The Radson sales rep is suggesting oversizing each radiator for better control and confort.

Does this sound like a good idea or a sales scheme?

Any other advice on a system like this would be appreciated.

John Ketterman

> Does this sound like a good idea or a sales scheme?


Both. I'm sure they will make more money off of it, but oversizing radiators is always a smart thing to do. If these are wall panels, they don't take much space anyway.

Uni R

Bad spin

The sales rep shouldn't say that you are over-sizing them as that indicates waste and inefficiency. What the rep is really suggesting is sizing them for a lower water temperature, which will help efficiency.

Ted_5

You both are right!

I will size panel rads at 2 X the BTU's needed. That way I know I am good for low water temps about 130 AWT. That is the best for condencing boilers.

Ted
Viessmann sales rep.

Ragu

Same Scenario Here

I had the same situation a month ago; Viessmann boiler/Radson panel rads w/TRV's and Outdoor Reset.

Basically it involved designing the system around utilizing low water temps and utilizing the Radson Table Of Correction Factors to determine the sizes of the individual panel rads.

Lower water temps dictate larger radiation to maintain indoor comfort levels on design days. Ted said 2X as a rule of thumb and that is not far off. The tables show 1.8 to 1.9. It's not a sales hype. Extrapolate the projected fuel savings over time and it will become apparent that it makes sense.

S Ebels

That's SOP for us

Standard Operating Procedure

"Oversizing" isn't the correct term for what your contractor is recommending. What he's doing for you is allowing your system to produce the required BTU's at a lower water temperature. This is a good thing. Lower water temps mean higher system efficiency and better, more even comfort. I always, yes always, design our panel rad systems for a max water temp of 140-150*. If your using a condensing boiler this will ensure that the boiler will run in the condensing mode 99% of the time which will save you energy $$ from day one.

mac

How about 79*F rad supply at ..

a 27*F outside temperature? We went with the "low temp" design for sizing the rads w/Vitodens and eureka!: low, low system temps. Coldest boiler temp all winter was 112*F at an outside temperature of 15*F at night. (Had to keep psetting curve down till 0.6 reset ratio!) Condensing like crazy and the boilers pulling all those btu's out of the condensate before it leaves the boiler.

Comfort???..constant circ???..oh yeah!