New zone question - baseboard heat


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Old 09-02-06, 10:15 PM
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New zone question - baseboard heat

Hi all,

I am about to run baseboards in the new extension that was added to the house. The total lenght of elements is about 110 feet.

1- Can I place all baseboards on one zone? (most rooms are bedrooms)
2- What is the max no of feet on one zone if the water is at 170-180 deg?
3- Would it be better to make it a split zone, where a 1 inch pipe comes from the boiler and splits into 2 3/4 pipes (running away from eachother) to the baseboards, and then the returns from the baseboards join eachother to another 1 inch pipe back to boiler?
I think this would prevent the last elements on the loop from being colder.
4- I used the (L X W X H X 5 / 600) = baseboard lenght formula.
I know it is not very accurate, will I regret using it? All the software I have seen for calculation is too complicated.

Thanks for your help.
Mike
 
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Old 09-03-06, 03:58 AM
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110 ft of baseboard heating element, or 110ft of total straight pipe? My 2100 sf house has 106 ft of baseboard heating element, in two zones.

I would not put 110ft of heating element on one zone. The last elements in that zone would be dealing with pretty cold water.

A series loop(s) system with multiple zones would be the simplest to figure up and pipe. You need to think about how you'd divide the zones to satisfy your comfort needs and plumbing layout logistics.

Your alternative piping scheme is kind of like a mono-flow tee system, which is easy to get right, painful to get wrong.

The formula you are using now typically results in about twice the radiation output you need. Been there, done that. It would save time and lots of money to figure out the software to do a proper heat loss.

www.slantfin.com/he2/

would easily do what you need. We can help you through this. Takes an hour or two to learn. I can do a whole house now in about 30 minutes, once measured.
 
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Old 09-03-06, 06:21 AM
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More thoughts and more direct answers to questions.

1 - It depends. You want to make sure the heat is distributed properly. If they are all bedrooms, one neat option would be to use baseboard elements or panel radiators with thermostatic regulator valves. These would take the place of a room thermostat and allow each bedroom to be run at a different temperature. You'd need to pipe a bypass for this. No biggie if this is new construction, some baseboard comes preassembled with a bypass, I think. If you go standard series loop(s), pay attention to where you locate the thermostat(s).

2 - It depends. Supply and return temps for a loop usually strive for a 20F difference between supply and return. Also known as delta-T. Bare pipe loses a certain number of BTUs per foot (~10), and baseboard loses it's rated output per foot (say 550-600 BTU/hr/ft). So if you're pumping ~ 4gpm, look at the ratings for your baseboard, add a bit for bare pipe loss, and see what you get. My system at ~57 ft of element at 4 gpm sees a delta-T of about 15F using 180F supply water. In practice, it's a bit touugh to get a system that really sees a 20F delta-T, but that's what to shoot for.

3 - It depends. I partially take back what I said above about monoflow. You could do this as split loops off a main supply and return. However, you need to make sure you do the flow calculations and size the pipes correctly or you will get too much or too little flow. Get this right or you will be ripping it out and starting over. You might consider seeing if your local supply house will do designs for you. Some charge a nominal fee, some waive the fee if you buy the materials from them. My local house let me set up an account, gives me the contractor price, and they give good advice. Cheaper and better than a big box could ever do! Personally, for DIY, without seeing the floor plan, I would go with two or more series loop zones.

4 - As above, this is a no-no. You will almost certainly be way overradiated. That formula goes back to the days when houses literally had no insulation. Overradiating costs money, is harder to control the heat, etc. etc. etc. Do a heat loss or get one done. Most supply houses also do this.

Don't be in a rush. Do it once. Do it right. (Hey that ought to be a corporate slogan! Oops, it is: Taco).

Good luck.
 
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Old 09-03-06, 12:35 PM
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Thanks for your reply.
I installed the program from the slantfin site, and tried it for one of the rooms. It gave me a baseboard measurement of 3 feet for a room that measures 12 X 15 and has a 9 foot ceiling. The attic insulation is R30 and it has one outside wall with R19!! I may not have done it right as I think it is way too small.

The screenshot is here:
http://img3.freeimagehosting.net/image.php?3e15781fcb.jpg
Please let me know what you think.
Thanks,
Mike
 
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Old 09-03-06, 01:07 PM
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Heat loss

My knee jerk reaction is that 3 feet of bsbd would not be enough but the 13.5 feet woud be way too much. I was going to do a calculation based on Burnham's short form but not having any window or floor information I couldn't. If you will supply that info, we can get a third opinion.
 
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Old 09-03-06, 01:17 PM
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Hi Grady,
the room has unheated garage below with R19 in between. There is 1 Andersen window 48"X48".
thanks for your help.
Mike

EDIT:
I just tried the Burnham calculator and got:
(cut&paste)
Based on:

Area (ft2) H.M. (BTU/Hr.) Heat Loss
1. Windows & Doors 16 X 30 = 480
2. Net Walls 470 X 4 = 1880
3. Ceiling 180 X 2 = 360
4. Floor 180 X 3 = 540
5. Infiltration 1620 X 1.07 = 1733.4

--------------------------------------------------------------------------------

Total Heat Loss for 60O F Temp. Diff. = 4,993.40
Total Heat Loss for 70O F Temp. Diff. = 5,892.21
Total Heat Loss for 80O F Temp. Diff. = 6,691.16

(end- cut&paste)


Which number would I use?
If this means 6000 btu heat loss then does that mean 10 feet of baseboard?
 

Last edited by Michael7278; 09-03-06 at 01:27 PM.
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Old 09-03-06, 07:10 PM
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for the slantfin stuff, I think your outdoor design temp is probably off. the other entries look ok at first glance. go to the jobs menu and click on the pencil to "edit job" and you will see where you can enter the outdoor temp and the supply water temp, among other things. there is a list of outdoor design temps at

http://www.crownboiler.com/educate/heatloss.asp

way down the page.

here are the values for cities in NY.

NEW YORK
Albany 0°
Auburn 2°
Binghamton 1°
Buffalo 6°
Glens Falls -5°
Kingston 2°
Massena -8°
New York City 15°
Oneonta -4°
Oswego 7°
Plattsburg -8°
Rochester 5°
Rome -5°
Schenectady 1°
Suffolk County 10°
Syracuse 2°
Utica -6°
Watertown -6°

Is the r19 wall done with 2x6 studs?

quick test, for an ODT of 0F, IDT of 70, and guesses on most factors based on r30 attic and one r19 wall and r19 floor, I get about 4000 btu/hr or about 7-8 ft of FineLine 15 or FineLine 30.
 
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Old 09-03-06, 09:50 PM
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xiphias,
Thanks for the info.
I adjusted the ODT to 15 deg since I am on long island (NYC).
IDT is set to 70 and water temp is set at 170.
The one exposed wall is 2X6 framing with R19. R19 in floor and R30 in attic. one window 48" X 48" double insulated.
I wasnt sure what to use for inflitration, so I picked "weather stripped" and now I get 5.5 feet.
Still a little different than your calculation.

Stupid question, but what happens if all the rooms have more baseboard than design calls for? other than the cost of the baseboards, Wouldnt that mean that the rooms will rise in temprature faster? So why would that be uncomfortable if the thermostat shuts it off when it has reached 70?

Thanks,
Mike
 
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Old 09-04-06, 07:26 AM
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Oversizing

Mike,
If the baseboard is grossly oversized you will experience "overrun".

The thermostat controls the circulator. When the thermostat is satisfied it shuts off the circulator. If you have a lot of extra baseboard, it still contains hot water & will continue to radiate heat until it cools thus causing overheating of the room. This is not as severe with baseboard as with cast iron radiators but it still happens.

The ODT for your area is the same as mine (15). Nobody around here uses 15 simply because it is not low enough. We & probably you too, sometimes experience days where the temperature does not reach 15. I use & suggest an ODT of 0.
 
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Old 09-04-06, 01:53 PM
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I would use 5 or 10F ODT unless you are right in the city.

Slightly overradiating is not bad. Better than underradiating. The thing to avoid is way way overradiating. If the rest of the house is standard 180F baseboard, then design for that.
 
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Old 09-05-06, 08:20 PM
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What about hallways?
There is a hallway that has no outside walls and is 4 feet wide with a 2x3 skylight.
any need for baseboard there, or is the heat in the rooms sufficient to heat the hallway?

Thanks,
Mike
 
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Old 09-06-06, 05:24 AM
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Probably fine without heat unless it's super long or has very high ceilings. Defer to Grady on that, though.
 
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Old 09-06-06, 02:10 PM
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Hallway

The skylight scares me. Do the load for the hallway just to see what you get. You probably won't get a lot of loss there but it's easy enough to do the calc. just to be sure. You could share it among the rooms if the doors are usually open.
 
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Old 09-07-06, 06:36 AM
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Thank you both for your help.
I will let you know how it turns out.

Mike
 
 

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