Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit

Flow rate of a Taco 007 vs 008?

Steve_75Steve_75 Posts: 20Member
Could someone tell me the standard flow rate for a Taco 007 and a 008? I have installed the 007 on my radiant heat loops which are between 300 and 1200 feet (6 zones) and used a 008 for the heat exchanger. I am much more at home with baseboard and/or radiators where flow is less critical. Seems though a few of the zones are returning water fairly hot - water out at 120-130 and returning at 100 compared to my poured floor zones out at 140 return at 90-100.Should I slow the flow down in some zones via the ball valves? Zones are heating fine I was just wondering if I was wasting energy by not getting more out of the water temp.


  • WeezboWeezbo Posts: 6,232Member
    Taco has a flow rate chart on the new IFC's..

    the 008ifc and the 007 are very close flow the 008 though head is around 15 ft of head near as i can see it is a higher head circ...the plain jane 008 on the chart seems to read less flow higher head...i have no idea how you have these zones piped ...or what your control stradgey might be, however at the momment i would vote that you have just started it up and thats what the large temp differential maybe attributed to thought would be to turn the temps back to closer to room temp and let it roll for a longer time period vs hurrying it up by boosting the temps...
  • Mark Eatherton1Mark Eatherton1 Posts: 2,542Member
    Sounds like

    the difference between staple up versus tube in cement. Lack of transfer = low btu transfer. When you say between 300 and 1200 feet, I hope you meant in parallel.I have a software program that can analyze your flow rates with the different pumps, but need to know how many loops of what length in what applications.

    Tell me that and I'll tell you what the pump'll do.

  • SteamheadSteamhead Posts: 12,423Member
    That depends on the head

    but in general a lower flow rate will increase your delta-T. The next smaller circs I know of are the Taco 005, the Grundfos 15-42F and the B&G NRF-9. The 005 and NRF-9 have flatter curves and are made for low-head zones- the 005 tops out at about 10 feet and the NRF-9 at about 9. The Grundfos tops out at about 15 and the Taco 008 at about 17 feet. You can find charts at, and .

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • Joe MattielloJoe Mattiello Posts: 557Member
    centrifugal pumps are variable flow

    Centrifugal pumps net flow is dictated by the system resistance. Pump size is based on the load, and the flow rate required satisfying the load. For your reference I have attached the submittal data information on the Taco 007, and 008 circulators. The 007 has a flatter curve is more forgiving when zoning with valves and one pump, because the system dynamics change frequently. The 008 will do a better job if the resistance through a zone is high because of a long loop. Always consider velocity issues when using a low flow high head circulator.
    Taco, Inc.
    Joe Mattiello
    Technical Service Technician
    [email protected]
    401-942-8000 X 484
    Joe Mattiello
    N. E. Regional Manger, Commercial Products
    Taco Comfort Solutions
  • Steve_75Steve_75 Posts: 20Member

    Thanks all for the replies. I have been out of the loop for a few days hense the delayed response. I do not use this forum that often and I am not sure if this reply goes to all or just the last message? I will answer/ask thinking all people will see this.

    First, on the zones between 300 and 1200 feetI should have said 300' to 900' - no single loop is greater then 300' of 1/2" with each zone going back to a 3/4" copper feed and return line or a short 3/4" manifold with each zone on a pump - 3 differnt water temps, concrete, tile and wood flooring.
    2 Zones have 3 loops of 300'
    3 zones have 1 loop of 300
    1 zone is 1 loop of 100'

    Second - Joe I continue to have an issue with my Taco EXP switching relays not playing well together - I will ask in another message - this one is getting long.
  • hrhr Posts: 6,106Member
    Back up a few steps, Steve

    do you have a heat loss calc and radiant design? This should spell out the required gpm and pressure drop of the various zones.

    It should also tell you required water temperature for the various installs and the delta t the system was designed around. Some designs will even tell you the brand and size of pump required, for those zones.

    Best ones will show balance valves and settings needed to dial all this flow rate in.

    Is the system having problems keeping up in some areas? Or just curious on the temperature differences?

    All these answers can be had after the fact (home constructed and lived in) if you run a heatloss calc and do the design. Most small errors can be corrected as hydronics is somewhat forgiving. But first we need better data.

    hot rod

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Steve_75Steve_75 Posts: 20Member

    I did the heat loss (IBR certified) and brought that to my supply house where the resident heat guy layed out the pumps needed. He is very good but radiant is not widely used in Maine.

    The system is actually working great (except for Taco switching relay issues) the info was more for my understanding. Initialy I adjusted a few loops within a zone down to decrease the flow and I was wondering what effect that would have on the pumps. The 008 question was because it is on the longest loop and I was wondering if it really made a difference - wondering mind syndrone.

    The temps (and controls)were more of a concern. As one of the people posted I tended to "blast" hotter water than needed as it was a start up and I was impatiant. Now that it is up with all zones heating I have been able to back off the temps. As I mentioned I have three mixing valves, one for each floor type and I wanted to have an idea what to expect for temp drop through each.
    The pump question was to see if I was moving water to fast through the system not giving a chance for good heat trasfer. I can close down on the return valves but didn't want to do harm to the pumps.
  • Mark Eatherton1Mark Eatherton1 Posts: 2,542Member
    Temp drop is related to load...

    When you first start up a system, it will probably never see a load greater than that initial start up load. Once the flywheel is moving, it won't take as much energy to keep it rolling along. That means, when you first started it up, the slab will see a big delta. Once running, unless you're at design conditions, the delta will be less than designed for.

    Also, the design delta may have been shallow (10 degrees F is not uncommon from some manufacturers programs).

    Bottom line, if you're comfortable, and the end users comfortable, DON'T WORRY, be happy:-)

  • Ronco_2Ronco_2 Posts: 4Member
    007&008 vs grunfoss

    We recently switched to gundfoss because 007's were getting noisey and the brute was equivelent to a 008 and is cheaper.
    Since then we switched to the 3speed grundfoss. We find it will handle hw zones, indirects,radiant zones,and primary pumping well. Now we just carry the one pump on the trucks. It costs a little more but reduce the number of circs on the trucks.
  • hrhr Posts: 6,106Member
    Steve, slowing the flow

    through a radiant circuit or HW baseboard, air coil, etc will slow the heat transfer not increase it.

    There is a limit to how fast of course, velocity and noise are a couple factors.

    It's not about how long the fluid "lingers" in the pipes or the emitters, but the average temperature of the fluid.

    Slowing the flow in radiant floor loops will be noticeable at the tail ends of those loops. Less temperature= less output. You will feel this, on the floor surface, in the rooms or areas where the fluid stream has run out of sufficient BTUs to drive the HX.

    If fluid goes in at 180 and returns at 160 you have an average of 170 degree water to give off heat.

    If it goes in at 180 and return at 170 you have an average of 175 degree water to give off heat.

    Which temperature will supply more heat?

    You will notice some radiant design software allow you to choose 10 or 20 degree delta T. 10° will provide a more even and consistent floor temperature.

    It is a commonly misunderstood concept in the hydronic design world :)

    Keep the flow rates where they were designed to be if the system is operating to your satisfaction.

    hot rod

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Jed_2Jed_2 Posts: 781Member
    couple o' things, Steve

    "Radiant is not widely used in Maine"? I beg to differ.
    (IBR certified) heat loss calculation. Did this calculation give you a RADIANT DESIGN ANALYSIS for gpm, temperature differential, Zone Temperature Supply Water Temperature Requirements, and pressure drop information?

    Also, you mentioned you have "three mixing valves". What is your HEAT SOURCE? Are you protecting your heat source if it is a conventional cast iron boiler? Three way thermostatic mixing valves are a serious "dumb down" method of low temperature heating systems, in Maine, or anywhere else. I run in to this all too often! You need some intelligence in your heating system these days, period.

  • hrhr Posts: 6,106Member
    3 way thermostatics can gobble

    a lot of pump capacity. And be real careful of the Cv and available BTU carring capacity.

    Over the years Watts Radiant has use a half a dozen different brands of 3 way thermostatics on their HydroContro panels. Hoffman, Watts, Sparco, Honeywell, even some special designed ones (larger ports)from Watts Regulator division.

    The challange was to buld a big enough one for high flow, larger BTU requirements, and have the same valve behave and track accuratly at low flows. It just never paned out well. Better to add additional ones than a big one, me thinks.

    Some good tips on 3 way magic at this link! I like to pointer about four times the boiler output as a "rule of thumb" before return protection should be considered.,2379,96144,00.html

    hot rod

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Steve_75Steve_75 Posts: 20Member

    Jed I am confused by your post. It appears you are taking exception to several of my comments? Radiant is not widely used in Maine. Yes there is more then ever going in but of several thousand oil accounts at my old company around 25-50 were radiant. We still have more steam then radiant at least in the greater Portland area. I do agree this is changing and maybe you are familer with a different community.
    As for an IBR heat loss - it is as the name implies - a heat loss not a system design. I brought this heat loss to someone who could do the radiant analysis as my background is in water and steam.
    The boiler is a steel low mass that heats mostly trough base board, it is a cold start running up to high limit thus the need for mixing valves. Before you say it yes I agree it would be nice to have a different heat source but this is what I have.
    As far as "intelligence in your heating system" One thing I have learned over the years is that you sure can spend a lot of money for very little benifit. I heat a 3500 square foot house and hot water for a family with two teenagers for around $1,000 per year - seems pretty intelegant to me.
This discussion has been closed.


It looks like you're new here. If you want to get involved, click one of these buttons!