1/2" Copper Question

boulderz

I have a baseboard hot water system with 4 baseboard zones. 1 zone is for the main living area and 3 zones are each floor of a 3 story tower (1 room on each floor). The 1st floor is above an unconditioned insulated crawl space and the 2nd/3rd floor have vaulted ceilings and many windows. I ran a heat loss calc on the 3rd floor alone and came up with 18' of baseboard (that floor currently has only about 8', partially along one wall). Third floor is where my office is and needless to say, when it's cold I'm freezin. The first 2 floors have 1 wall (or about 12') runs of baseboard. Construction is post and beam with SIPs.

I need to add more heat and am considering more baseboard or panel radiators. Construction is post and beam so very hard to get more baseboard to other walls. So that is 1 problem.

I have a question though about piping to the baseboard zones. From the boiler, 3/4" copper is reduced to 1/2" copper which then travels (twists and turns) about 26' through the basement and over to the tower crawlspace. From there it runs to each floor to 3/4" hydronic baseboard runs, then returns are 1/2". 3 supplies, 3 returns all 1/2". Is the 1/2" copper supplies/returns OK for this? I was told the 1/2" is causing a lot of heat loss and could be replaced with 3/4" pex which would perform better.

I am looking for opinions as I plan to redo this and want it done right. I may convert 1st floor to radiant.. Thanks!

Zman

The 1/2" copper can carry 32,000 btu/hr. It seems unlikely it is the problem. By the sounds of it, you do not have enough radiation. Panel radiators like Runtal may be a good solution. You would need to post more info to get a solid plan.

Gordy

32500 btus would be 3.25 gpm@ 20 delta. Over 15' of head for every 100' of developed length. What's the circulator size?

boulderz

The boiler is a Laars Endurance EBP110 which has an internal pump capable of providing flow for two heating zones (up to 67 feet of 3/4" baseboard). Each zone also has a Taco 007-F5-IFC at the end of the run. The boiler is plumbed primary/secondary. Each zone has a Taco flow check valve at the beginning of the run. Any other info needed?

Was thinking this morning, maybe just replace the baseboard with panel radiators of cumulative higher output since getting another run of baseboard on an opposite wall would be very hard due to the construction.

Brewbeer

Can you post the results of your heat loss for each floor, and can you estimate the total length of the piping for each zone?

boulderz

Zone 1 1st Floor (7,798 BTU/hr): 35' to 12' Baseboard to 50' return = 97'

Zone 2 2nd Floor (7,445 BTU/hr): 45' to 12' baseboard to 57' return = 114'

Zone 3 3rd Floor = (10,564 BTU/hr): 57' to 8' baseboard to 66' return = 131'

Heat loss calculation from Slant/Fin. One thing I noticed and I wonder how it affects operation, on the 1st floor baseboard run the 1/2' copper return runs back on top of the baseboard (what I mean by that is the copper return pipe rests on top of the aluminum fins). On the 2nd floor, both the 3rd floor 1/2" copper supply and 2nd floor 1/2" copper return run on top of the baseboard. I'm guessing that cannot help matters..

Brewbeer

I main issue with your top floor baseboard zone is it is not long enough.

Different models of baseboard have different heat outputs, but a fairly typical run of the mill baseboard will put out 600 BTU/hr at an average water temp (AWT) of 170 degrees at 1 gpm. You need about 18 feet of baseboard to get to 10,500 BTUs/hr with an AWT of 170F, (or 21 feet of baseboard at an AWT of 160F).

The head loss of 130 feet of 1/2 inch piping is 20.8 feet of head at 1 gallon per minute. (www.taco-hvac.com/uploads/FileLibrary/SelectingCirculators.pdf) The Taco 007 pump curve indicates that it moves 1 gpm at 10 feet of head. So in essence, the pump is probably supplying under 1/2 gpm to the zone.

You need more baseboard. If you know the brand and model of baseboard, and have room to add more, it's relatively simple to add on additional baseboard to the existing loop. Otherwise, an appropriately sized panel radiator is in your future. If you stay with the pump and piping you have now, you should probably size the panel for 1/2 gpm using an AWT of less than 160, since P/S piping and heat loss along the way probably means you aren't going to see supply temps of 180F.

CMadatMe

20' of head at 1gpm? Don't think so.

Friction Loss for 1/2M .007psi per ft of pipe
Friction Loss for 1/2L .008psi per ft of pipe

.008 x 131 = 1.048 PSI

2.31 PSI per ft of head

Even using the Fudge IBR Method of:
Longest run x 1.5 x .04 gives you 6' head per 100'

There's also 560 btu/hr in a ft of baseboard at a 1GPM flow rate with avg water temp of 180 degrees. Taco 007 is a flat curve pump and the right one unless you'd like to stick the new Taco VR1816 into the mix. At his distances worse case 131 x 1.5 x 04 = 7.86' of Head - 007 Correct Pump and at worse case he would be over pumping.

Issue more then likely as others have pointed out is not enough baseboard. Instead of adding more could just use the same footprint and add Hi Cap board at 810 Btu/hr per sqft where needed and add just in 13' in that 3rd floor zone.

Mark Eatherton

Remember, back in the day, many of these systems were sized for 200 degree + F water. Energy was cheap back then, and so were the contractors who were designing and installing them. The IBR manual actually suggested this practice as a means of holding installed costs down... (obviously not applicable to this particular project)

Also, if you look at the performance charts for 1/2" versus 3/4" fintube convector, for a given flow and temperature, the 1/2" produces more btu/linear foot. Must be those elusive Reyolds numbers...

It had to have worked right at one point in time or another...

ME

Brewbeer

Chris, my bad, I have a decimal error in my calc, you are correct in the head loss calc, the existing circulator is fine.

But with P/S piping and long pipe run it seems unlikely that the OP is achieving an AWT of 180 degrees in the existing 8 feet of baseboard. The OP's problem is that the zone doesn't have enough radiation capacity, and the solution is to lengthen the baseboard, or installed an appropriately sized panel radiator.

boulderz

Chris said:

20' of head at 1gpm? Issue more then likely as others have pointed out is not enough baseboard. Instead of adding more could just use the same footprint and add Hi Cap board at 810 Btu/hr per sqft where needed and add just in 13' in that 3rd floor zone.

I could certainly add high capacity in floor 1 and 2 (if necessary). But not enough room to add 13' for zone 3, so looks like a panel radiator setup.

But what about the 2nd floor which has two 1/2" pipes resting on top of the fins? Wouldn't this inhibit heat output greatly?

Mark Eatherton

boulderz said:

Chris said:

20' of head at 1gpm? Issue more then likely as others have pointed out is not enough baseboard. Instead of adding more could just use the same footprint and add Hi Cap board at 810 Btu/hr per sqft where needed and add just in 13' in that 3rd floor zone.

I could certainly add high capacity in floor 1 and 2 (if necessary). But not enough room to add 13' for zone 3, so looks like a panel radiator setup.

But what about the 2nd floor which has two 1/2" pipes resting on top of the fins? Wouldn't this inhibit heat output greatly?

Not enough to worry about. It MIGHT interrupt the vertical air flow through the convector, but not enough to make a big difference. Is there ANY heat coming form the baseboards on the second floor, or just flat plain dead cold?

ME

boulderz

No, it's getting heat but the room seems to have trouble heating. I was thinking maybe it had something to do with the pipes blocking but it could just be the heat is getting sapped by the 3rd floor (there is a vaulted area from the 2nd to 3rd so entirely possible). There is also a big bank of windows spanning the vaulted area from 2nd to 3rd floor with NO heat underneath. I may add some heat there.

Mark Eatherton

This sounds like fairly recent construction (P&B with insulated panels). How did the distribution system become so undersized?

What city is this located in (design conditions)?

ME

boulderz

House was built in 92 in VT. I blame it all on the plumber who worked on the house over the years including original install. The Laars Endurance was added in 2005ish - not as P/S. When I moved in his solution was to replace all the flow check valves to no avail of course. I'm done with him, installed the primary loop myself. His final insult to injury was when I discovered even the Tstats were wired to the wrong circs

Mark Eatherton

Got it. You are going to have to start from scratch. You've got a good start in the heat loss calculations, but you have a long way to go to get to complete comfort.

It's not as easy as adding baseboard in every case, and may work in others. It sounds as though you will have to redo the near boiler piping. If you are not comfortable with such work, I'd suggest you get a competent designer to generate a piping schematic of the required near boiler piping, and the associated distribution piping.

The numbers that are commonly used (20 degree F differential in temperature) do have some flexibility (stretch to a 40 degree differential), but you have to be aware of things like average water temperature, resistance to flow, and parasitic power consumed in moving that fluid through small diameter pipes.

You also spoke about possibly doing some radiant floors. That is a whole different colored beast. It will require some means of lowering the supply water temperature to the radiant floor zone, depending upon the method you choose to employ.

Rich McGrath, can you help this gent along with his endeavors? Rich qualifies as a competent designer AND installer and does remote consulting (for a fee of course).

ME

Rich_49

Chris ,

Sure this was a mistake , " 2.31 PSI per ft of head " .

1 PSI = 2.31' head

Boulderz , If you would like to contact me feel free using my information or by pm here on the site . Yes Mark , I can assist .

boulderz

Thanks Rich. I just may do that when I get to righting the system. In the meantime I'm having another issue and am starting a new thread.

Rich_49

I always like seeing when guys run the return over top of the element . Picks up heat from the pipe & fins below meant for the room and returns it to boiler .