proper baseboard sizing

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Old 12-13-11, 01:53 PM
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proper baseboard sizing

My 1950 (levitt) slab house. ranch. With origonal radiant heat (starting to leak in spots) is on its way out. And i am planning a full baseboard conversion. 3/4 pex for the whole job and slant fin 30 baseboards.

I ran the numbers through the slant fin program to calclate baseboard size. and i am wondering if this sounds right

The house is a 2x4 construction with fiberglass batt insulation, slab with carpet, and tile in bath and kitchen. The room dimensions are as follows and the size baseboard slant fin came up with. Are the program numbers accurate? the house has new vinyl with 1/2 plywood and 1/2 foam over tyvek. new roof and new double pane replacement windows.

Office 12x18 with 20' exterior walls. 2 24x44 windows = 9' fin line 30
bedroom 12x12 with 12' exterior walls 2 35x50 windows =12' fin line 30
bath 5x8 with 5' exterior one 44x24 window = 3' fin line 30
kitchen 11x13 13' exterior Bay window 48hx80= 6' fin line 30
living room 22x17 sliding door 34' exterior 18' fin line 30
master bed 14x17 21' exterior 2 26x40 windows 17' fin line 30 (this room is under unheated space (attic)
hall 8x4 witha 32" door 3' fin line 30

some people have told me to follow these numbers and some people have told me to just loop the whole exterior walls of the house with fin line 15

this will be pushed off of a peerless wbv 03 110 w with a riello head

the first floor will be 2 zones, one for the master bed room one for teh rest of the hosue.

the second floor already has baseboard
 
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Old 12-13-11, 05:09 PM
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Hello SS
I vote for the continuous loop, except split it into two parallel circuits.
Long time ago a wize plumber taught me, that "you can never have enough radiation."
I believe this to be true, budget allowing.
The bedroom zone might give short short cycle problems, is there anything else that might go with it?


Peter
 
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Old 12-13-11, 05:13 PM
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You should size your radiation to your heat loss. There is also a limit of how much baseboard you can have on one loop. I think putting baseboard on all the exterior walls is a horrible idea. I had the misfortune of growing up in a house like that. The room heating was terribly uneven. Stifling hot in one room and freezing cold in another.
 
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Old 12-13-11, 05:17 PM
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Short of taking your input data and running it in some heat-loss program, I don't think we can verify your results - and that's a bit beyond what we normally do here. How long did it take you to do that? That's probably how long it would take us to do it. People get paid to do that.

But tell us this: what was your design outdoor temp and the calculated heat loss, Btu/hr? What was the rating of your existing system, and how did it perform?
 
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Old 12-13-11, 05:20 PM
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Some people prefer to have the baseboard cabinet to be continuous around the room perimeter for aesthetic reasons but install the finned element based on the calculated heat loss. Having more finned element than necessary can be beneficial as it allows for lower circulating water temperatures and increased comfort. It is pretty easy to reduce the output of finned element if necessary by simply wrapping the excess element with heavy duty aluminum foil.
 
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Old 12-13-11, 06:12 PM
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"you can never have enough radiation."
And this is possibly true... because as Furd mentions it allows lower water temps to heat the home... which costs less...

But Droo has a good point also.

If you install MORE baseboard than the program tells you to, make the amount in each room PROPORTIONAL to the heat load of each room so you have some 'balance'.

Interior hallways don't need heating elements installed... I notice you had listed a hallway.
 
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Old 12-13-11, 06:15 PM
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I don't think I would use the '15' either... if I had any new baseboard to install, I would take a look at the Smith stuff:

Smith Environmental Hydronic Baseboards. THeating Edge Hydronic Heating Systems - Radiant Heating System, Solar Heating, Geothermal Heating
 
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Old 12-13-11, 06:18 PM
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The biggest problem in the house I grew up in was that the baseboard at the beginning of the loop got the hottest water and then it was ice cold by the time it got to the end. So loss in water temp at the end of the zone should also be taken into consideration.
 
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Old 12-13-11, 07:47 PM
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Hey guys let's not forget he has a second floor with baseboard. I believe considering what was done there is important. To add a lot of extra baseboard and it may not be done on the second floor will not allow for lower water temps unless he mixes it down. But that means still heating up to higher temps.
Determine what is required and installed on the second floor and maybe match the same installation ideas. If they are wall to wall than do it. If the second floor is 10% over per room then make the bottom floor 10% over per room. Do not worry about overheating just do ODR and dial it down or constant circulation to balance out the rooms.
 
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Old 12-13-11, 09:20 PM
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Good point rbeck... that's the proportional thing I mentioned... and you do need to take into account the existing install on the 2nd floor to do those proportions.

and Droo said this:

There is also a limit of how much baseboard you can have on one loop.
Since you are probably going to run 3/4" tubing, you should know that in general you will shoot for a 4 GPM flow in that tubing.

You can move 10K BTU for every GPM of flow, so your 3/4" tubing at 4 GPM will move 40K BTU total. This should give you close to a 20F differential from the beginning of the loop to the end... 180 in, 160 out.

For standard Fine Line 30 this works out to about 66 feet MAXIMUM ELEMENTS (not total length, just the elements) on a given 3/4" loop. Any longer than that, and as Droo said, you start running out of heat at the end of the loop and those rooms end up being cold.

Many designers compensate for this by bumping extra footage on the end rooms of the loop.
 
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Old 12-14-11, 04:59 AM
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Wow thanks for all of the replies. What a helpfull forum. I sized my system using 70deg inside and 0 outside.

The second floor was already done when i bought the house. We got the house cause the major things were done already. (roof siding, windows, and bath) but we knew we were going to have to replace the heating system. I got the boiler from a friend for free and its only 3 years old(score!)

I was planning on having 2 loops, the office and bedroom on one, and the rest of the house on the other.

also being that it is a slab house i am trying to break up the concrete as little as possible, and will be running the main feed and return to the far end of the house (boiler in attached garage) through the ceiling's

Somoene mentioned to clean the boiler before i install it. just flush out the feed and returns with a garden hose?
 
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Old 12-14-11, 06:24 AM
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The used 3 year old boiler is only a score if it is close to the proper size and everything works!
 
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Old 12-14-11, 09:03 AM
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same boiler that the oil company wanted to install for me, in 100% working order. was just removed last week (he converted to gas) i dont have gas in my area
 
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Old 12-14-11, 10:18 AM
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Even if it is the same BTU output as the oil company wanted to sell you it could still be grossly oversized.

Be VERY cautious about "micro-zoning", having small areas being their own zone, as it can actually turn out to be LESS efficient in the real world than maintaining the same temperature throughout the house.

Flushing out the waterside is a good idea but absolutely you want to clean the firesides thoroughly BEFORE installation.
 
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Old 12-14-11, 07:20 PM
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Well... that adds up to 68 ft of element for the first floor. 65 if you take out the (presumably) interior hallway. That's 35.7-37.4k BTU/hr total output using an average 550 BTU/hr/ft.

So following the 40k/zone limit, you're ok there.

Address the proportionality issue room to room and floor to floor. Probably best to compare installed and proposed radiation rather than the heat loss calcs. Although you could do the heat loss for the 2nd floor and compare what slantfinware tells you to what you actually have.

Keep in mind heat loss calcs are often overstated by around 20-30%, which means that the suggested baseboard lengths are also overstated. But as others said, you can exploit that by running at lower water temperatures, e.g., with an outdoor reset control.

The wbv03 is rather oversized, but according to peerless it is possible downsize the nozzle to 0.60 and get DOE output 75k BTU/hr, so probably not quite twice as large as needed when you factor 2nd floor.
 
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Old 12-15-11, 05:23 AM
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xiphias, thanks for the info.

I am wondering now if i will have enough for a indirect water heater.

Right now we have a tankless coil, i have not run my research on these though. i see some people use the coil for it and some people run a new zone for it.

But thats a whole other can of worms
 
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Old 12-15-11, 05:32 AM
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For efficiency always treat it like another zone, never off a domestic h/w coil. You do not have to increase boiler size unless you have a very large hot water demand.
 
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Old 12-15-11, 03:34 PM
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You also want to put the indirect a priority. So when it makes a call for heat, it will shut down the heating zones. You should have no worry about the house getting cold with this setup unless you have a hot water demand for 2 hours straight.
 
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Old 12-15-11, 03:44 PM
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i see some people use the coil for it
I wouldn't think so for a TRUE indirect water heater.

It's possible that what you saw is what is known as an 'aqua booster'... basically just an 'add on storage tank' for the coil. They DO improve matters somewhat in that you do have a store of hot water available, but the boiler still remains as a warm start and wastes fuel for that same reason.
 
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Old 12-15-11, 06:32 PM
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Indirect on priority, no problem with that boiler. Don't use the coil.
 
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