Hi,

New to the forum am looking for advice/expertise on sizing a couple Myson radiators for a new 18x22 addition with a walkout basement.  The walls on 1st floor will be double wall construction with 2x6 exterior, 2x3 interior, and 3" gap between, the basement level will be 2x4, 2x3, also 3" gap between.  This setup will yield 11"(R-46) and 9"(R-38) of roxul insulation respectively, the 1st floor will have ~128sqft of windows and basement level with ~65sqft. 

I was thinking of one TK2-5-06 and TK2-5-92 per floor, the ratings for them are 4217 and  6466 btuh at 180 degree temp.  The radiators will connect to the 4th zone of a Utica SSC-100 mod-con with 2 existing heat zones and an indirect DHW, hooked up with a OD reset.  Based on the specs would these 2 radiators be adequate for southern NH climate design temps?  And what's optimal loop run?  Myson recommends "home run piping", is that really the best? Have other had experience with similar setups off a mod-con?

Thanks,

Bruce

I recommend designing for 140 to 150 maximum for a mod/con boiler, 120 max if you want to be well suited for heat pumps/alternative sources. If the mod/con is running to 180 now, I would consider paths forward to bring that down. Including simply turning it down and seeing how it goes, if you can wait till next winter to find out.

home run is best but series can be fine especially if the radiators are in the same room.

Let's start, as always, with an ACCA Manual 'J', room-by-room heat load analysis so we know what we are talking about.

A modcon will start condensing as you return water temperatures below 140°F. So, if your design supply water temperature is 180°F and the Delta T across the system is 40° you have hit the high end of your target. This is the high temperature that will be required for a hand full of days in cold climates. The rest of the season, lower temperatures will prevail the rest of the season.

You must use a factor to lower the AWT and expect the same output. Each manufacturer has a different one, be it Buderus, Myson, Runtal or the more exotic like Jaga radiators.

Here are some preliminary numbers, anyone know how to do air filtration and basement slab analysis? Am going to put 4"(R-5 per 1") of XPS foam under a 4" slab.


design temp 68- (3)=71f

1st floor walls/windows total = 3760 btu/hr

u-factor of walls: 1/R32=.03125
walls: (58' X10')-125 x71 x .03125 =1009 btu/hr
windows: 125' x 71f x.31=2751 btu/hr

attic:

u-factor: 1/R32 = .0312
attic ceiling: 396 x 71 x .03125=878 bth/hr

basement walls/windows total = 2702 btu/hr

u-factor of walls: 1/R30=.033
walls: (76 x 8)-65 x 71f x .033 =1272 btu/hr
windows: 65' x 71f x .31 = 1430 btu/hr


Myson's heat output adjustment factor:

Conditions: Hot water temperature: 150°F
Room air temperature: 68°F
Temperature difference: 82°F

TK2-5-06: 4217 x .71 =2994 btu/hr
TK2-5-92: 6466 x .71 =4590 btu/hr

First, a room-by-room, ACCA Manual 'J' heat load analysis. All else is conjecture.

It's only one room per floor, the 1st floor is 18x22 with 10'ft ceiling and lower level with 8' ceiling.

Using free software on http://www.borstengineeringconstruction.com/Heat_Loss_Analysis_Calculator.html, I came up with the following btu/h.  Because I live in one of those states where unlicensed hvac designers/installers run rampant, finding a pro with manual J experience was a daunting task when I put in my mod-con last year.  Like most DIY's experiences on this board the installer's first advice was "you don't want to under size your boiler", local dudes simply used baseboard ft x 600btu/h to size boilers and these dudes were charging a pretty penny. 

Given the situation and being an engineer who models/designs optimization for a living, I trust my data more than these local dudes.  As engineers we all know any user software is only as good its operator.  Going back to my original ask, would appreciated if anyone can share their experience(s) with radiator panels vs. baseboards in terms of comfort/efficiency  Am sure there have been threads on this topic, but the search function didn't seem to return favorable results.

1st floor
6493 btu/h with R-3.22 windows/R34 walls
5622 btu/h with R-5 windows/R34 walls

7216 btu/h with R-3.22 windows/R14 walls
6345 btu/h with R-5 windows/R14 walls

basement
4020 btu/h with R-3.22 windows/R30 walls
3560 btu/h with R-5 windows/R30 walls

4817 btu/h with R-3.22 windows/R14 walls
4357 btu/h with R-5 windows/R14 walls

I suppose my next task would be to do a fuel cost analysis between a R14 vs. R34 wall to find the optimal trade off.

As an engineer you know that "local" has nothing to do with the software, or operator thereof, and I have yet to find an engineer or competent designer that will design a hydronic system, over the internet, for free.

As to designing wall-hung European-style radiant heating systems using Baxi, Buderus, DiaNorm, Jaga, Myson, Runtal or Thermotec it all comes down to the heat load for a particular room under design conditions. Once you have the load you can size the radiant panel according the temperature your heat source prefers. If you have a hot boiler there is little reason to over-size a radiator for <140°F EWT. If you are driving radiant wall panels with a condensing boiler or water to water geo, you want to use the factor provided by the manufacturer of the particular panel you want to use. We use weather sensitive controls for nearly all of our new hydronic designs and renovation work.

If you can't get the answers to design questions from the people you buy equipment from, then the money you "save" by going around the locals would be well spent on an experienced designer.

European panel radiators are second only to radiant floors, walls and ceilings for comfort and efficiency. We design and sell so many panel radiators here in the Twin Cities that we keep them in stock.

MA,

Appreciate the feedback, have followed you on another forum in the past and you guys provide a hell of a service, if there were such contractors in my area I won't mind to pay for it.  Is there a good network to find local guys who apply manual J heat load analysis?  I only managed to find one during my oil to propane boiler conversion last yr, he was so busy he declined my business.

European panels are rare installs in the north east for whatever reason. Myson's north America HQ is in VT figure there would be half decent chance of finding a few local guys.

We design hydronic heating systems for lots of engineers and regular folks using European-style panel radiators. We start with the Manual 'J' heat loads and then look the heat source, ultimately providing the specification and drawing needed to let the project out to bid. Good mechanics are easier to find than designers and once you have the design...

The only serious concern with DIY is proper setup and service of the heat source. Most should be commissioned and service by qualified, professional service technicians.

Good mechanics are easier to find than designers and once you have the design...

But if you can't find a good designer, just have the mechanic/installer design it. Oh wait, we've seen over and over that that is a very bad idea.

Send the plan we will design it. Problem solved.