Circ Pump Size

J Matthers_2

I have 7 zones of radiant. 1 for the basement, 2 for the main section first floor, one for an ell section of the house, 1 for the attached garage and two on the second floor. I was not getting enough heat in the ell and the garage. (Heat loss done all is sized correctlly)Both zones had a large Delta T so we tried 0011's on those zones. 007's on the rest. Once we made the change I got less heat in the zones preceding the 0011's on the manifold. I lost circulation in the second floor (remote manifolds)and in one zone on the first floor. At least in seemed like I lost circulation. I lost heat and the return was cold. I moved the 0011's to the second floor loops, (3/4 inch feed to remotes)putting the 007's back on the other two zones and re-purged the whole system. I have full circulation on all loops. The second story is now cooking however I still have lass heat then I did on the zones in front of the 0011's on the manifond and I lost heat in the zones (ell and garage) I put the 007's back on.

Will the larger pumps starve the other zones when up agenst smaller pumps? I was under the impression that if it is a closed system it should'nt make any differance.

Your thoughts.

radiantdave

circ pump size

is this primary secondary? where did you put pump in regards to primary pump ? do you maintain 6 " center on distribution tees ?all zones ? show me a drawing of pipe arrangment. i design boiler pipeing for a living radiant heat is my favorite . (cool stuff to pipe)mixing valves taco?

J Matthers_2

more info

my system uses geothermal or "ground sorce heat pump". The system water is heated by the geo unit and stored in a 40 gal buffer tank. No mixing valves are neccesary. The set point on the buffer is 128 with a 10 Degree prop. Back up heat is provided via a Flatplate heat exchanger piped on the return side of the system using a Takagi water heater. This is set up to kick on when the tank temp drop is more than 14 degrees. A 1" primary manifold ditributes water to seven heating zone cerculators and two cooling zone cerculators cerculating chilled water to two unico air handlers during the summer. The geo goes both ways. It is realy a very simple system with each zone cerc controlled by the zone thermostat. No zone valves.

I have 23 1/2" loops in all running through Warmboard. My problem may be that the supply and return manifolds are to small the handle the flow when all zones are calling. The two 0011's pumps seam to "starve" the other zones when running. Additionally, although the Flatplate is rated for 11 GPM it seems to be restricting the return. I opened the bypass and got better circulation right away.

The math for the flow is a little beyond me. You should know I have put this system together with the help of a plumber freind, the warmboard people, my supplier and The Wall. I read Dan's book on radiant systems as well.

The heat loss calcs are all acurate with 20 degrees the low. We are a bit past that at the moment, about 0, but the back up works well keeping the tank temp at or about set point. It is just the flow that seems the problem.

Thanks for your time.

kevin coppinger_4

definately.....

sounds like you have too small a primary loop...what is the heat loss for the whole radiant? Was there one done, if so the there should have been a flow rate given for each loop/zone.A 0011 seems like an awfully big circ.why that size? A 1" primary loop can only carry 80,000 btu based on a 20* temp drop. kpc

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J Matthers_2

Flow

The total heat loss is 68,000 BTUH. I will have to pull out the paperwork and cheak the total flow.
The 0011's were the suggestion of a radiant pro move the water faster through the ell and garage zones to lower the Delta T and allow the geo to recover faster.
By the way, the house is constructed with SIPS, very tight construction, walls r38.
Last night I partily closed the valve on the two upstairs zones that now have the 0011's, and cracked the bypass valve on the Flatplate. The second floor was toasty but my feet froze when I came down stairs to temps of 58 and 60. I opened the bypass some more and saw imidiate results. floors started warming. I am thinking that I should loss the 0011's and put back the 007's. I'll check the total flow first and maybe wait until it warms up on Sunday. In the mean time I need to build a fire.

J Matthers_2

Flow rate

total radiant surface = 6,268 Sq ft
Heat Loss 65,379 BTUH
Total Flow rate = 6.53 GPM
Ave Supply temp = 105 Deg
Loops = 23
Primary Manifold size = 1"

steve gates

are there check valves or anything to keep the other zones from flowing backwards? Some other oddity?

J Matthers_2

check valves

Check on the check valves.

J Matthers_2

original Q

Will the larger pumps on the manifold "starve" the other zones when running?

Mark Wolff

Manifold Problem

Your manifold/primary piping is not large enough to allow equal flow to all zones.

Two options are available, the first and best being to install balancing valves on each zone supply. They will limit the volume and velocity of the water flowing through each zone. When the zones are properly balanced you may well find that the 007's you originally installed for each zone are in fact too large for the demand. There is absolutely no need for an 0011 to be used as a zone pump. As I stated in another thread the 0011 is designed for high head pumping situations (like 30 feet of head). It is not a correct application to install it as a zone pump.

Check the manifold piping size. If your manifold/primary piping is less than 1 1/2" you will encounter the exact problems you are describing. 1 1/4" is borderline but too many times is abused. Also check your supply and relief piping in your p/s piping arrangement. If the entire house is feeding off the loop make sure it is large enough. I have on occasion had to increase piping to 1" to supply the injection manifold due to btu requirements.

As for check valves, they will eliminate reverse flow in a system but are not really going to address this problem. Balance the zones with balancing valves not different pumps.

Mark Wolff

Yes

hr

1\" copper

will easily carry 75,000 BTU of 140° water, even at a 15° delta T.
It works out to 10.2 gpm at 3.7 fps velocity. 4.9 ft of head per 100 feet. Still below the 4 fps threshold, generally accepted.

65,000 at 8.8 gpm 3.2 fps.

I don't think pipe size is your problem.

hot rod

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Larry Larkin

Pump Sizing & Flow

Attached is a handy "Pump Syzer" rules of thumb sizing guide. This guide is avialable as a free download from our company website www.thermoflo.com. Hopefully it will be helpful.

J Matthers_2

With the geo and the heat exchanger off the waterheater I am producing 130 deg water max. I am going to ditch the 0011's and replace the spring checks with gravity flow checks. I can see that, at times, I am getting backflow. At some point I think I will put in a Munchkin 80 and put the Garage zone and this ell zone on that and use it as a backup for the whole house. the return from the garage is consistantly 50 to 70 degs depending on outside temp and it lowers the overall return temp significantly. With a boiler that may not be a problem but with thee Geo producing just 120 degs it just can't recover. Good year in the northeast to test this stuff out!

How important is it to have the your manifold takeoffs close and equally spaced?

Mark Wolff

Vital.