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flow rate in copper pipe

hot_rod Member Posts: 15,065
System Syzer. It will calculate the flows and pipe size for you. You can play with different delta T's to see the relationship. I think the B&G site has an online version, and plenty of other good tech topics and reading.

Read up on Dan's and Siggy's past articles regarding flow, pressure drop, velocity, and how they all play together. You need to know how the answer was arrived at, and why :)

hot rod
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream


  • sootmonkey
    sootmonkey Member Posts: 158

    hello, im a good wrench swinger,poor typer/speller. went to a customers home on friday. he has a new yorker boiler that is fired @ .85. he has 2 zones of heat and 1 zone piped to a 40 gal. phase 3, indirect water heater. (water heater was installed +/- 2 months ago to existing heating system) these zones are "controled" with taco zone valves. customer complant is "i run out of hot water when running 2 showers @ the same time." yes i can see that this system has many strikes against it. i.e. time delay in zone valves, low firing rate, and no prioty control. my question is this. this model indirect heater comes with 1 inch tappings for the boiler supply/return water. the tappings were bushed down to 3/4 inch when it was installed. the specks on this unit give a 1 foot head loss through the unit. i would guess that there would be an additional 1 foot head loss in the supply lines to the unit. what is the flow rate through this system with taco 007 circulator? remember this is 3/4 inch pipe. am i right in saying that it would be greater than 4 gals. per min.? would it be less than 8 gpm? thank you. long time lurker, big fan of dans books
  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083

    Phase 3 is it, the 36 gallon or the 45? Or is it the new Smart series?

    Don't concern yourself with the head loss, it's BTU/flow rate that counts here. 2 showers at the same time, eh? What is the combined GPM of the heads? From here I think they are hoping and wishing they will get that kind of draw out of a 40 gallon indirect with all the deficiencies you just isn't gonna happen!

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  • sootmonkey
    sootmonkey Member Posts: 158
    flow rate

    thank you for the responce bob. i would guess that each shower head would flow about 2.5 gals. per min. that would be a combined load of 5 +/- gpm of 110 +/- degree water. i would guess a well water temp of 45 degrees +/-. i did a rough calculation i my head, and came up with 195,000 btu net output to sustain this load. i have always heard that you can figure a 4 gallon per min. flow rate through 3/4 inch copper when pipeing a seris loop heating system. (useing fin tube radition) i would have to look up the flow rate for 1 inch pipe in the same system. (dans book). my question is, (so far nobody has been able to tell me, and i have asked several knowing people) how much water can you flow through a 3/4 inch pipe with a 2 foot head loss and useing a taco 007. do you just go by the pump curve that taco puts out? the pamplete that came with the indirect said the the head loss through the unit is 1 foot. i am guessing that there would be a 1 foot head loss in the supply pipeing also. am i wrong? if you can only flow 4 gpm in a seris loop system, how can you flow more in an indirect applcation? you are right that this system will never be able to keep up with this load, or anything close to it. but my question goes back much, much further than this system. again, thank you.
  • Steamhead
    Steamhead Member Posts: 14,863
    Zone flow rates with zone valves

    will vary depending on how many valves are open. Obviously with this setup you will get more flow to the indirect if the two heating zones are not calling for heat as well.

    The Taco 007 will pump 20 GPM at a 2-foot head. Each 3/4" copper pipe can carry a maximum of 4 GPM according to Dan's "Pumping Away". Therefore each 3/4" pipe zone can support 40,000 BTUH. So theoretically, if there is not too much head, the 007 can supply four 3/4" zones.

    A 1" pipe will carry 8 GPM- 80,000 BTUH. This is why the indirect has 1" tappings.

    Long baseboard runs will have much more head, especially if there are many elbows. Add to this the resistance you find in many zone valves, unless they are the full-port-ball-valve type. Now you start to see how flow can drop below the needed rate.

    You would need 19.5 GPH to support your calculated load of 195,000 BTUH. Tha't's just about what a 007 will pump at 2 feet of head. Based on this it is clear a single 007 will not support the load.

    I've had good luck on this type of job with a circulator and a flow-check on each zone. On your job I'd dump the zone valves and install a 007 and flow-check for each zone. Run 1" lines to the indirect and use 1" circ flanges and flow-check on that zone. This way you get full flow in each zone and the indirect regardless of what the other zones are doing. This would be a good time to convert to Pumping Away also.

    If you use the 007s with built-in relays, wiring is a lot simpler. If the boiler's capacity is limited, either increase the firing rate (assuming the boiler is approved for a higher rate) or use a priority relay on the indirect zone.

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  • Ben_3
    Ben_3 Member Posts: 71

    Dear sootmonkey,
    The gpm listings you see in the books are rules of thumb for heating. For example, 3/4" pipe will carry 4 gpm trouble free, this is related to the speed of the water, if it to slow the water will not carry the entrained air, if it's to fast it will cause noise and turbulence. I beleive what is confusing you is the btuh load. You see we are all trained that on a 20 degree drop in the piping we can carry 10,000 btus per gpm. This is the standard for almost all heating systems. But you can actually carry as many as you want, it's directly related to the temp drop for the system. For example, as Steamhead said 195,000 btuh translates to 19.5 [email protected] a 20 deg. drop. If you sized for a 30 deg. drop you would only need about 13.5 gpm. In the first case you would use say 1 1/2" pipe and in the second case you could use 1 1/4" pipe. This is how we can get more btus out of the same flow rate. 3/4" @ 4 gpm/20 deg. drop is 40,000, 3/4" @ 4gpm/30 deg. drop is almost 60,000 btuh. However this useful for p/s pumping and shuttle loops to other zones, etc. In your case I,m sure the mfger data is based on a 20 deg. drop for the boiler side of your dhw to be able get it's rated recovery and supply since 20 deg. is the standard. I would suggest putting the dhw on priority and increase your pump size as well as the supply lines to the dhw and then you should be able to maintain your load. However, I also agree with Steamhead that zoning with pumps and flow checks is definitely a better way to go. But I guess it will probably all depend on the cost, not whats best. Hope this helps, good luck.
  • sootmonkey
    sootmonkey Member Posts: 158

    will a taco 007 circulate 20 gpm through a 3/4 inch pipe @ 2 feet of head? i don't know. will a taco 007 circulate 20 gpm through a 1/2 inch pipe? i don't know. will a taco 007 circulate 20 gpm through a 1 inch pipe? i don't know. how do you figure head loss in different pipe sizes? is there a chart? the system i described above is not one that i designed or would recommed. the customers beef is that the system was bushed down to 3/4 inch and thats why he can't take 2 showers at the same time. my thought is that he has many strikes against him and that he might be getting all the btus that he is producing through that 3/4 inch line.(.85 fireing rate at 80% +/- effiencey.) that would be assuming that the other heat zones wern't calling. your thoughts? ben i understand every thing you are saying and agree with you. except for one point. i belive that no matter how this is piped or what circ. you use, that there just aint enough btus here to do the job. this thing aint got a hemi. but my question involves more than just this job. thank you for your responces
  • tim from Reed Wright
    tim from Reed Wright Member Posts: 113
    head loss of pipe

    Yes, there are many different charts for different types and sizes of pipe. Grundfos in there circulator sizing chart book has a pretty good one. Also Ashrae has a very good one. They will specify rough or smoot, copper type L or K or M. Schedule 40, 80. Good books to have around
  • Mad Russian
    Mad Russian Member Posts: 29

    Don't worry about water flow from boiler to indirect.According to the curve for 007 circulator at 2feet head you will have 20 GPM flow. There is an error in your calculation. It's only 156,000 BTUH for two shower heads:
    5x8x60x(110-45)=156,000 BTUH.
    Believe you or not, the problem partly in the indirect itself: you better off with tankless coil instead of indirect.3secion boiler with 1 GPH nozzle and tankless coil provides 3.25 GPM hot water with 100*F temperature rise (intermittent draw). It gives us: 3.25x8x60x100=156,000 BTUH
    40 gallon indirect provides 2.5 GPM hot water with temperature rise 90*F. IT gives us 2.5x8x60x90=108,000 BTUH,
    or only 70% compare to tankless coil. In any ivent indirect
    can not provide more hot water then the boiler.
  • check your math

    A 1.00 GPH input on a boiler won't give you 156,000 BTUH output.

    The number is based on intermittant draw, remember.

  • Steamhead
    Steamhead Member Posts: 14,863
    In order to properly answer you

    we need to know the length of each loop, how many fittings there are on each loop and what type of fittings they are, and how much fin-tube is there. That's why I've replied in such general terms. I don't have a System Syzer yet, if you get one you can calculate head as well as I.

    I can tell you that pumping 20 GPM thru a 1/2" or 3/4" pipe will be quite noisy, and a 007 probably couldn't do it. According to Dan, a 3/4" copper pipe should be pumped at no more than 4 GPM and a 1/2" no more than 1.5 GPM to avoid this. A 1" pipe should be limited to 8 GPM, but on a short run between the boiler and indirect you could probably get away with more and it wouldn't bother anyone.

    There is probably enough head in those baseboard loops to limit the flow to the point where it wouldn't make noise. The System Syzer will tell you for sure.

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