circulation pump

johnjohn89

Heating experts! We know most hot water boiler 12 psi cold ,less 30 psi hot in residential! One thing I don’t understand is boiler already got 12 psi from water regulator,n 12 psi can lift 27.72 feet’s but why still need circulation pump? Can anyone explain? Thanks

EdTheHeaterMan

There are 2 pressures that we need to understand. Static pressure is what you explained above. Pump head pressure is the force needed to move the water thru the heating system.

No pump needed if you come off of a 150,000 BTUh boiler with 2" pipe then branch off with 3/4" to the first cast iron radiator and maybe the second and third. then you can reduce to 1-1/2" pipe and take of 2 or 3 more radiators. After that you can drop to 1-1/4" pipe, then 1"pipe and so on down the the last 2 or 3 radiators. The returns from those radiators need to increase the same way in reverse so the closest radiators connect to the boiler thru a 2" main pipe. Because these large pipes offer very little friction to the movement of water, those old gravity systems worked very well without circ pumps/

But to design this type system today, with the cost of copper and iron or steel pipe would be very expensive. To over come the friction loss that the smaller pipes offer, selecting the proper pump is essential to efficient quiet operation. In selecting that pump. there are 2 numbers that we need to consider. The flow rate in Gallons per minute, and the Pump Head measured in feet. *(Yep we are going to use the same 2.3 feet per pound of pressure of pump head. That is because when pumps were invented, they were rated by their ability to lift the water from the well or body of water. If a pump could lift water 25 feet higher than the source, that pump was rated at 25 ft of head (not 10.8 PSI)

So we are stuck with these old school measuring methods.

If you were to calculate the pump needed for a large commercial job, you would need to look at every foot of pipe, every valve, every elbow, every tee, every accessory and calculate the equivalent length of each component. But for small residential jobs, the pump choices are fewer and more forgiving. But you still need to know if that Taco 007 is large enough for that mini McMansion in suburbia USA. Or if the Grundfos UP 26-116 is overkill for that 2 bedroom rancher.

Have you ever looked at this text I mention in earlier posts https://www.xylem.com/siteassets/brand/bell-amp-gossett/resources/technical-brochure/fh-z100b-bg-zoning-made-easy-2.pdf

This is a great place to start. Easy to understand and lots of basic knowledge you have to understand in order to know why stuff works the way it does. Your original Query is answered in this booklet. If you want one, I have several copies of the original Red and White cover booklet that covers some discontinued items that B&G has deleted from this current edition. Just PM me with your mailing address. I will even send you the quiz that comes with that book

neilc

the 12 psi is how tall the cup (building) is filled, 27 feet,
but the cup just sits there,
someone needs to stir the cup,
that's the circulator,
when I add milk to my coffee the cold milk will stratify to the bottom of the cup,
I drink from a glass 20oz iced tea fountain glass,
I use an iced tea, extended spoon to circulate the milk and coffee evenly throughout the cup,

johnjohn89

EdTheHeaterMan said:

There are 2 pressures that we need to understand. Static pressure is what you explained above. Pump head pressure is the force needed to move the water thru the heating system. No pump needed if you come off of a 150,000 BTUh boiler with 2" pipe then branch off with 3/4" to the first cast iron radiator and maybe the second and third. then you can reduce to 1-1/2" pipe and take of 2 or 3 more radiators. After that you can drop to 1-1/4" pipe, then 1"pipe and so on down the the last 2 or 3 radiators. The returns from those radiators need to increase the same way in reverse so the closest radiators connect to the boiler thru a 2" main pipe. Because these large pipes offer very little friction to the movement of water, those old gravity systems worked very well without circ pumps/ But to design this type system today, with the cost of copper and iron or steel pipe would be very expensive. To over come the friction loss that the smaller pipes offer, selecting the proper pump is essential to efficient quiet operation. In selecting that pump. there are 2 numbers that we need to consider. The flow rate in Gallons per minute, and the Pump Head measured in feet. *(Yep we are going to use the same 2.3 feet per pound of pressure of pump head. That is because when pumps were invented, they were rated by their ability to lift the water from the well or body of water. If a pump could lift water 25 feet higher than the source, that pump was rated at 25 ft of head (not 10.8 PSI) So we are stuck with these old school measuring methods. If you were to calculate the pump needed for a large commercial job, you would need to look at every foot of pipe, every valve, every elbow, every tee, every accessory and calculate the equivalent length of each component. But for small residential jobs, the pump choices are fewer and more forgiving. But you still need to know if that Taco 007 is large enough for that mini McMansion in suburbia USA. Or if the Grundfos UP 26-116 is overkill for that 2 bedroom rancher. Have you ever looked at this text I mention in earlier posts https://www.xylem.com/siteassets/brand/bell-amp-gossett/resources/technical-brochure/fh-z100b-bg-zoning-made-easy-2.pdf This is a great place to start. Easy to understand and lots of basic knowledge you have to understand in order to know why stuff works the way it does. Your original Query is answered in this booklet. If you want one, I have several copies of the original Red and White cover booklet that covers some discontinued items that B&G has deleted from this current edition. Just PM me with your mailing address. I will even send you the quiz that comes with that book

Will take look during weekend thanks

hot_rod

A few more good reads
https://www.caleffi.com/sites/default/files/file/idronics_12_na_2019.pdf
Also # 19

johnjohn89

@all thanks a lot all of you