Panel radiator sizing/design temp?

Pulse

I want to design my system around a 120 degree SWT(condensing boiler).

What is the proper design temperature to use? It seems my area has an average temp of ~20 degrees, while 1% of the time it is ~7 degrees or less. (If someone knows a good site to view weather history/stats per year, please let me know.)

I can greatly decrease my radiator sizes using the 20 degrees outside temp instead of 7 degrees. Wouldn't it make sense to size rads that way and just increase the SWT to 130-140 on those 1% days to meet the BTU demand?

EdTheHeaterMan

How much wall space are you willing to give up in order to use this lower temperature radiator system? For example, a 20" x 24" panel radiator with 180° average water temperature might offer 2,700 BTUh of heat into a room. to do that with 140° water temperature you would need a 20" x 48" radiator of the same model. I can only imagine the having a maximum temperature of 120° in the radiator, you might need to have more that one row of radiators. I wonder how that might look with some pictures hanging on them.
180° max home

120° max temp home

That could be a look you might want to go for, OR not.

Since the low outdoor temperature only happens 1% of the year, You might consider a max temperature a little higher, like 140°. Then your boiler will have most of the heating season at or below 125°, and your walls can have more space to show off some tchotchkes.

Just a thought

hot_rod

BIN data graph is what you want. ASHRAE has it, but I think you need to be a member. If you are good at navigating sites, you can find 20 and 30 year history at www.ncei.noaa.gov

Its a gamble on that lowest expected temperature. Your reasoning is sound to just boost temperature for design or below periods. The boiler with ODR will do it for you

Pulse

@EdTheHeaterMan

I have been using Beacon Morris as a baseline, but basically all these panel rad companies have the same radiators putting out the same BTUs.

I plan to use ~16" height and ~4" depth radiator. My entire house load on a design day of 7 degrees is only 33k BTU, so it isnt that bad..lol

Below are the specs for Beacon Morris:

hot_rod

Pulse said:

@EdTheHeaterMan

I have been using Beacon Morris as a baseline, but basically all these panel rad companies have the same radiators putting out the same BTUs.

I plan to use ~16" height and ~4" depth radiator. Below are the specs for Beacon Morris:

I think Myson or Runtal now have a boost add on like Jaga has had for years. Basically some small computer muffin fans that force some convection. Sometimes a better option to increasing panel size.

https://jaga.com/en/products/horizontal/dbh-upgrade.html

EdTheHeaterMan

As far as weather data, try https://www.weather.gov/ there is a section for weather history and another for heating/cooling
Bob has a good point about keeping the radiator size down too
But selecting the design water temperature to match the design outdoor temperature, since it rarely happens, Design for a slightly higher water temperature, Otherwise you need 3x the radiator.

What ever you decide, Know that you can increase the design water temperature curve to make your home a tropical paradise in January with a simple water temperature adjustment.

I think the ribbed wall design is growing on me a little

Pulse

@EdTheHeaterMan
Thank you for the website, confirmed my average of 20 degrees is correct.

As an example: one of my bedrooms has a heatloss of 1960 BTU @ 20 degrees or 2450 BTU @ 7 degrees

Designing at 20 allows me to use a 16x48x4" vs a 16x56x4", then just bump up to ~130 SWT if needed, while still condensing

I can decreases by ~12" per rad in every single room

@hot_rod
Jaga is a company I did not know about, but their panels look expensive.

I do not like the idea of fans though, haha

EdTheHeaterMan

Pulse said:

@EdTheHeaterMan
Thank you for the website...

...I do not like the idea of fans though, haha

OK. I will take you off my list of those I admire. I was just getting the @Pulse Fan Club charter documents together too.

It is official, let the record show "I am no longer a Fan of @Pulse" because he does not like fans."