the amount of btuh per ft. of baseboard

Kal Row

1gpm will give you 1.3ftps in 1/2" and .6 in 3/4 - more water more heat, up to the point where the flow gets so turbulant, that the heat transfer suffers - and there is also noise and pipe erosion (yes pipes ware out at high flow rates), i never use more than 4gpm in 3/4" - we usualy branch it so that 1gpm carries 10,000 btu

jim_29

hot water baseboard

could you tell me the average amount of btuh per ft. of baseboard?

Bob Sweet

There are a few variables

standard grade BB @180*@1gpm 580btu. Standard grade BB @180*@4gpm 610btu. Depends on the rated output of the BB your using.

hr

You should be able to find this data online

Did you try the www,slantfin site?

I use the HDS software to design my baseboard systems.

It takes into account the temperature drop through each baseboard section, as the last bb sees much lower temperature than the first.

As you can see this small 4 board zone has a 166 temperature entering the last section. Need to know that to correctly size the system.

This job has 5/8 PAP chosen as the piping. Very nice tube to use on baseboard as there are no elbows to figure in the piping loss, save the board ends.

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Bob Sweet

hr that is a really program

I drool everytime I see it. I'm sure you've said before but where might I check it out at?

A.J.

Bob check it out at

www.hydronicpros.com it is a very nice program.

Kal Row

slant-fin tbg series....

while the TBG series is meant for commercial use - there is no law that says you cant use it at home – though the lady might balk at the 17” total height – but you can paint it to blend in – it’s a convector not a radiator so paint “ain-no-thang”

it has many advantages - lots of btu's per foot, very sturdy, and to me the most important - is the double sloped design - almost guarantees airflow – and unless you cover a whole wall of it with wall bookcases, the air will somehow convect in from the bottom - cant tell you how many reg baseboards i have seen nullified with a carpet install that effectively stopped convective flow through the baseboard

I would use the 24” two tier ones under windows - at 1613btu per foot at 180f, having a couple of feet of it under each window - may be all a room needs - gives you back furniture placement freedom for the rest of the room

see attached pdf... while the TBG series is meant for commercial use - there is no law that says you cant use it at home – though the lady might balk at the 17” height and 5.5" thick – but you can paint it to blend in – it’s a convector not a radiator so paint “ain-no-thang”


it has many advantages - lots of btu's per foot, very sturdy, and to me the most important - is the double sloped design - almost guarantees airflow – and unless you cover a whole wall of it with wall bookcases, the air will somehow convect in from the bottom - cant tell you how many reg baseboards i have seen nullified with a carpet install that effectively stopped convective flow through the baseboard - i am sick to death of hearing cold complaints and finding convention nullified baseboard

I would use the 24” two tier ones under windows - at 1613btu per foot at 180f 3/4"copper, having a few of feet of it under each window - may be all a room needs - gives you back furniture placement freedom for the rest of the room

see attached pdf...

also download the free heat loss software from them and do a heat loss per room to start
http://www.slantfin.com/hydronic/index.html

tip: i put raw fin tube of a baseboard at the bottom of the inside wall of a bathtub 2" off the floor to keep it warm - (no direct contact of course - as we don’t want to burn the kiddy-poos)
also - you can pipe those really hard runs with pex-al-pex -as they now have those cool Chinese cuff O-ring connectors to go from pex to copper very reliably (made by cash-acme)

David Woycio

Speedheat

Have you ever used "Speedheat" from spirotherm for low temp. baseboard applications? We have a job that we may spec. this product out. I guess a big consideration is that there is no face plate. You need to fab. something up yourself.

It's a little pricey but if your looking to throw 120 ish deg feed temps to your loads this might just be the answer.

Bob Sweet

Kal,

thats some serious btu/ ft. What,s the cost difference % wise.

Kal Row

i dont keep price lists, - however noel murdough...

of slant fin might be able to give you the list price difference - and you can figure it from there

nmurdough@slantfin.com

Kal Row

speedheat elements are especially useful...

in custom enclosures and work really well at lower setback temps, but are to much "todo" for the avg installer - they are for now a "diamond in the rough" so to speak,
but if you can find them and want to build you own under the window convection box - you can with 2 tiers, get apx 4000btu from one 24wx20h box (14xxBtu at 120f supply 1 gpm, a really quiet way to maintain temp)

http://www.spirotherm.com/docs/brochures/Speedheat4.pdf

Bob Sweet

I've got a question about

speedheat, why does the 1/2" produce greater output than the 3/4". Or am I misreading this?

Bob Sweet

Kal , If you would'nt mind

just so I understand. @ 1.2 gpm ,3/4" pipe would deliver 10,000 btu, doubling the output of speedheat at .6/ft/sec. Appreciate the help.

Forget what I just said!

OK I think I've got it, @ 1.3ft/sec 3/4" will produce 20,000btu as opposed to 1/2" producing 10,000 btu @ 1.3 ft/ sec. Forgive me for thinking out loud, just trying to put it together. Thanks.

hr

Bob

Two more modules in the HDS that would help you see this. First the Hydronic Circuit Simulator. In this example I put 60 feet of 3/4" baseboard and 40 feet of 3/4" M copper. Then you can scroll through the 3 speeds of a Grundfos Super Brute and see the btu output move.

Then the Pipe sizer allows you to input that data and watch the velocity in feet per second change.

As Kal mentions, the faster you move water through a convector, the higher the output. If the temperature entered a string of baseboard at 180 and exited at 160, you have an average temperature of 170. Look at the baseboared output at 170. If the temperature entered at 180 and left at 140, the average would be 160. Which would give you less btu/ foot of board.

That is an often misunderstood concept. Often times one would think the slower the flow, the longer the water lingered in the pipes, the more heat emitted. The opposite, is in fact true.

Baseboard output charts also show that. Usually they show both 1 and 4 gpm output numbers.

But you want to watch velocity to keep the noise and erosion at bay, It's a balancing act. The pipe size AND rate of flow determines the velocity in the pipe.

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Bob Sweet

hr , one more question and I'll qiut asking

questions for atleast a day. With reference to delta T, let's say a pump is moving 4 gpm with a 10* delta T it's cap. is 20 MBH, the same 4 GPM with a 20*delta T has capacity of 40 MBH. I'm thinking more gpm more capacity, where's my mistake(other than thinking above my means)? Thanks

This may be hard to believe but, with the help of "Primary/ Seondary made easy" I figured it out. (maybe I can sleep now).Thanks anyway hr your always a big help.

David Woycio

Lowest temp

Cal what are some of the lower temps you have used in a speedheat application?

Thanks

Kal Row

havent....it's just that as a private pilot...

i know good aerodynamics when i see it, and the speedheat has such low air resistance, that minimum air heating at low water temps would still generate buoyant convective flow, as opposed to the air resistance of fins which would precluded getting much buoyant convective flow at temp differentials approaching 20f above ambient - of course the enclosure design has a lot to do with it too, it’s a factor in slant fin’s large commercial enclosures – less air resistance = more btu’s convected

hr

Delta T Bob

correct you are. Wide delta t will move and store more energy. There have been some excellent posts about that subject here. Robert Bean does and excellent job with that subject, and has written about it in several trade mags. it is a much under-utilized concept in this country.

But for getting heat energy off that baseboard, or fan coil, the higher the " average" temperature, across the entire length, the higher the output.

Put a fan behind a piece of baseboard (kick space heater) and look at the output, as you are now forcing convection. same with a convection oven

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