Radiator Sizing

heatmeister

Sorry if this cannot be answered, but here it goes.

I have decided to use euro panel radiators with TRV's as the solution for retrofitting my home from copper fin baseboard. If I use lower operating temps when designing the system i.e. 150 degrees versus 180 degrees can these questions be answered.

Home is 55years old 4 inch walls, all new windows/siding, 2600square feet above grade in Minnesota:

1) How much larger in % terms do I need to upsize each radiator?

2) How much would I save approximately in operating costs at these lower temps in percentage terms?

3) Will I also get a reasonable payback by now using HIGH Efficient i.e. Vitoden 200 vs. a traditional cast iron like the Buderus 142.

4) Lastly, if given a choice, starting a system from scratch with all new "everything" including piping, is the lower operating temp approach preferred?

Thanks.

Unknown

whoa

1)It depends on the radiator. All manufactures have charts or multipliers to adapt to lower water temps. Thisis NOT a linear curve!!!

2) Rule of thumb 3F = 1%, studies done say you will save at leats 14% annually.

3)Comparing apples to oranges. Vitodens will save you when you are not running at peak AND save using weather responsive controls AND save you because of the ultra low mass and no stack loss. 96% eff compared to 86% eff... of course you will save. How long to get Pay back???? Never if you lose one control on a electrical shock.... and that is on BOTH sides (Vito control vs smart valve). Where the true payback is in the effect to the environment while using the Viessmann Vitodens.. low NOx, low fuel usage etc.

(4) See #2. Lower is always better. Less wear, less fuel usage, less fluctuation on indoor temp, less expansion and contraction, longer product life.

ALH_3

Radiators

1) Your radiator manufacturer should have a chart that gives a multiplier for radiator outputs at reduced temps.

2) Difficult to predict. There are all sorts of stories of retrofits saving quite a bit. However the old boiler was generally very old and inefficient to start with so the comparison isn't really fair. Also many times additional controls are installed at the time of the retrofit, which also skews the results.

3) It depends on how much fuel you use. If you insulate the house better, the payback period is longer. There are too many variables to predict exactly. The Vitodens has so many other selling points that the "payback" also contains things like: reduced complexity(usually), reduced number of pumps and valves, fuel conservation, fewer vent penetrations, smaller mechanical room, etc. The list is long.

4) Reduced system temperatures and constant circulation are almost always preferred. The benefits include: less possibility of tubing/pipe expansion noise when zones call, increased fuel efficiency of the boiler, more even heating of rooms, less possibility of overshooting thermostat setpoints. I'm sure there are more. Be careful of your pipe and radiator sizing.

If at all possible, use a stainless indirect DHW tank.

-Andrew

[Deleted User]

If you have

the wall space, why not design for 130* max. Then a condensing boiler would always operate in its' most efficient range. The land from which the V's & B's come has a 130* max mandate on new systems.

steve sola

munchkin good or bad?

does anyone know about the Munchkin
boiler good or bad?

Mike T., Swampeast MO

I have a reasonably confirmed suspicion that if you design using a Manual J heat loss, use TRVs and a condensing/modulating boiler and go by mfgr supplied outputs @ 150° or so that your actual average panel temperature will be 130° or below excepting highly unusual circumstance.

Size at 130° and those panels get really large unless you have exceptional insulation and "super" windows.

If I recall correctly, in the land of Vs and Bs the climate is generally much less variable than here in the US.

vhlaundry

Radiator Sizing

It never ceases to amaze that I pick up some snippit of knowledge each time I come to this sight.

All very good points:
Never thought of lower temps mean lower expansion contraction and could mean less noise,.... that 150degrees means more like 130 degrees at the radiator to touch,...never knew that in Deutschland they do run much lower temps than here.

Anyone have two cents on the quality with the various panel makers, ie, Radson, Myson, Vasco, Buderus and DiaNorm?

I also plan on getting the Viessmann indirect water heater with this configuration.

Thanks for everyone's input.

Unknown

size for highest output

heatmeister,

IF you are doing weather responsive controls, size your radiator for the max output you desire. For instance the Vitodens 200 will only deliver 168F MAX. which is where this boiler is still operating at high efficiency (unlike other 90%+ boilers that will go to 196F, beyond LOW efficiency, even if you don't want them to).

I have worked with Radson, Myson, and Vasco. Out of those I prefer the Vasco and Myson because of their price points and fast delivery (on stock units)!!The Radson's are super looking but are a little pricey... great quality! I have also worked a lot with Runtal.... the finish on these is second to none but the price is a little higher then Vasco and Myson. Each manufacture mentioned has standard units and then seperate themselves with different models. For instance, you can ot buy a heated bench except from Myson!