Determining the Length of Baseboard for rooms

chris smith

can you dirvect vent any of them?

chris smith

paradise porter maine

a12_2

Is there a rule of thumb, or a simple formula that the contractors use to determine the length of baseboard heat for each room of a house? I'm trying to figure out if each room in my house has the correct amount of baseboard footage. I have a Weil-Mclain gas boiler, forced hot water. Any comments would be appreciated. Thanks

Bill NTSG

Heat Loss

No free lunch , no rule of thumb, But a free heat loss calcualtion at the left hand side of your page. The only accurate way to determine the amount of radiation required is with a heat loss calculation. Other factors like water temperature and where you live [coldest outside temps.] also play a part. Why do you ask, are your rooms not warm enough?

a12_2

a12_2

A few of the rooms seem to be cooler than others and the length of baseboard in these cooler rooms appears to me to be shorter in length than in other houses that I have owned with similar room sizes. So I am curious to find out if what I have is enough for each room. Thanks

Boilerpro

A few things to check for...

Are the vents fully open? If there is carpet, are the baseboards installed on a board to keep the carpet from restricting air flow into the bottom of the units (a standard installation requirement usually ignored in my parts)? Are the fins clean and free of dust? Are the finned elements installed so air passes freely through them (openings up and down)? Dont'know how many houses I've sen where the elements were installed at 90 degrees to the proper position.

Boilerpro

Chris Maderia

Rule of Thumb

Take square footage of room x 32. This will put you right in the ball park. I generally find that I'm a a little bit high with this figure when I do the actual heat loss. Generally around 500 btu's.

Unknown

Chris,

Does location matter?

Seems a little vague, considering that design temperatures change from Miami to Montreal, and since construction types and glass areas aren't always the same, building to building.

A heat loss survey is required to get accurate balance from room to room, and so that you don't buy too much baseboard for the job; or too little.

It is also important in sizing the boiler, so that it doesn't short cycle and live a shortened life.

Noel

Steve Levine

You have been lucky

It helps at least that you are in one geographic area so that the outdoor design tmeperature does not change from job to job. But, if you look at a heat loss calculation, your method can not work. With variances in outside was area, wall heights, glass area, infiltration variables, insulation etc., the heat loss can vary dramatically.

Steve

Frank Cheng

a non-expert's opinion

I own a few houses that have this kind of problem. The plumbers did not do much calculation and designed the schemes poorly. It will take me quite some time to fix them one by one. I have used the following strategy that has been working for me all the time and will be using it in the future. I take the length of the baseboards equal to the length of the exterior walls. Use double fin-coil baseboards if saving space is necessary. Use an outdoor reset control together with constant circulation setup (this save energy and increases comfort level a lot). In one 3-story 7 bedroom house, I even mixed the use of baseboards together with cast iron radiators with a TRV on. The system is circulated by only one built-in pump that comes with the boiler. Every floor has its temperature control, one by thermostat (in the coldest area), the other two by TRVs. The house is warm evenly and moderately. Everybody, particularly my tenants feel comfortable and happy about the heating there.

My rule of thumb for forced water system: outdoor reset control and constant (or long cycle) circulation are almost a "must" in my design. Radiators or baseboard calculation will be much easier if you have this "must" in, simply because this kind of systems will tolerate over-built much better than under-built. So I am slightly inclined toward overbuilding baseboards overall, but of course based on the heat loss factor (exterior wall length, windows, doors, etc.).

Frank

Chris Maderia

Let me clarify

The gentlemen was aking for a rule of thumb. In my area we use a outside design temp of 0 degrees and a room set point at 70 degrees. For the last 15 years I have used 32btu's per sqft and I have ALWAYS, ALWAYS been over my actual heat loss. When we say rule of thumb we mean an ESTIMATE not a figure that we use to size either a boiler or the baseboard itself. What this does is gives us an idea for a quick quote for the customer. This has nothing to do with being lucky. What is has to do with is experience in sizing in my area. By the way how accurate do you actually think a computer generated heat loss is anyway. Don't you think that there is some type of fudge factor in their. No heat loss is every 100 percent accurate.

Steve Levine

I'm sorry, I don't agree

> The gentlemen was aking for a rule of thumb. In

> my area we use a outside design temp of 0 degrees

> and a room set point at 70 degrees. For the last

> 15 years I have used 32btu's per sqft and I have

> ALWAYS, ALWAYS been over my actual heat loss.

> When we say rule of thumb we mean an ESTIMATE not

> a figure that we use to size either a boiler or

> the baseboard itself. What this does is gives us

> an idea for a quick quote for the customer. This

> has nothing to do with being lucky. What is has

> to do with is experience in sizing in my area.

> By the way how accurate do you actually think a

> computer generated heat loss is anyway. Don't

> you think that there is some type of fudge factor

> in their. No heat loss is every 100 percent

> accurate.

Steve Levine

I'm sorry, I don't agree

He is not looking for a rule of thumb 'to estimate' the amount of baseboard, he asked for a simple way to determnine the amount of baseboard needed. I think we assunmed he was looking for a rule of thumb. As far as I am concerned any heat loss program is simple and accurate.

I do have concern with Bill Wright's "average". An average is just that, an average. If Bill's data base has so many jobs, I would find it hard to understand if there was not a big spread of BTU./SQ.FT/HR from each end of the extremes, and maybe more importantly, the spread from job to job for rooms with similar sq. footage would also to large.

Using averages ALWAYS results in oversizing!

Steve

Chris Maderia

Oversizing

Take a look at my post above maybe this will anwser any of your questions. By the way, since you are so worried with oversizing and you work for a boiler manufacturer, when does your company plan on coming out with a 2 section hot water oil boiler. Since 3/4 of the houses in our area don't require a 3 section boiler since our heat losses are generally around 40,000-50,000.

Steve Levine

We do have

two section oil boilers. The Liberty LD-20 79,000 MBH net IBR, (availabe for more than 10 years)and the XL-2000 XL-20, 68,000 MBH net IBR (available for more than 4 years). Unfortunately firing oil units at much lower GPH presents some problems.

Dick Olsen

Good idea

Your approach works well in my experience. Use of control valves regulate the rooms. Boiler size then becomes the issue, but is also easily handled. Just notice what climate you are in (Latitude). We have to do the calculation to back all this up so that we enginers can get paid!

hr

With series baseboard loops

the boards at the end of the loop will see a lower supply temperature. Every board along the string will drop the water temperature. The rooms at the end of the loops may need more baseboard footage to give you the same BTU/ foot output as the first on the series. Watch your total loop lengths also. Pretty common to see them pushed beyond the comfort zone.

If your into number crunching try this link.

http://www.pmengineer.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2732,78558,00.html

hot rod

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hvacfreak

Rule of thumb

Run baseboard fin tube where ever you have wall , don't forget the flex connecter for the door...hope this helps..lol...kidding you know.

Roger Litman

Baseboard length

If the room where the thermostat is located has too much baseboard relative to the cool rooms, then the system is shutting down before the cool rooms get heated. The important thing is that the rooms baseboard and the room's loss are balanced with the other rooms in the house( maybe overradiating the bathroom). This is not perfect as the loss on a sunny day and a dark night are not equal.As a quick trial, you can block the some of the fins in the well heated room with the thermostat with aluminum foil and this may help the cool rooms.

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Frank Cheng

blocking baseboard

One of my subcontractor put in too many baseboards in one living room (where the T-stat is) with a little sections of exterior walls. Before I took out some baseboard sections, I suggest to my tenants to block some of them. One tenant used toilet issues to block those baseboards and then close the caps. It is more convenient and easier than my standard way. It works. ^_^

Steve Levine

Not Yet

NM

Steve Levine

The most effective,

the easiest, and the cleanest way is to use strips of aluminum foil over the fins. It really cuts the heat output.

Frank Cheng

Good idea

Frank G

Adding baseboard Fins

I would like to add more fins to my existing baseboard. The room needs more heat and I have about 12 feet of dummy piping in the baseboard. Does anyone know of a product or a way of adding fins to the dummy piping without opening the loop and sweating a new section of fin tube in?

Mark Hunt

If you


ever saw how the fins are placed on the tubing, you would understand why that is best left to the machines!

It would be easier and far less costly to just install element.

Mark H

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ScottMP

Is 'nt the easyest

Just to close the dampers ?????

scott

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Bob Bona_4

I know

you are holding back, Mark..thank you for being polite:)

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Frank Cheng

it is hard to completely close the damper often times

particularly for long bbs. Even if they completely close, there will still be a lot of heat coming out sometimes.