how to triger operation of circulating pump?

[reganracelis]

were about to test run the our water system:

6 units of electric water heater
2 units of circulating pump
2 units of booster pump..
6 units of expansion tank for every water heater
1 unit of bladder tank

pressure switch was installed to run booster pump cut in / off - 20 psi - 40 osi..
we must maintain the hot supply of water at the hospital.. so circulating pump must run to maintain hot water...
is it thermostatic swicth or pressure switch will be installed to run ciculating pump?

hope u can help me to this guys.. im running out of time... project turn over are so closed... tnx..

[chillin out]

Circulating pump should run all the time in a closed loop system.

Chillin

[reganracelis]

ok tnx... but my problem is what devices that will trigger to on/off of pumps? it must run alternate... im thinking of thermostatic switch that siutable for the opeation of pumps... setting of cut in / off of temp is my problem & what capacity ? brand? hope u can help me to this... thank's..

[Magoo]

The primary consideratio is maintaining constant water flow and pressure at each tap/outlet, sothe circulation pump should run continuosly as in a closed loop system [ hopefully ] to maintain constant temperature.
The bladder tank with be fead by town supply water to maintain top up water to system with a pressure reducing feed valve. The bladder tank will be pressure compensated with air to absorb pumping pulsation and water make-up.
The header tanks on HX will provide constant head on HX's and act as air in system elliminators but should be high enough above system pressure as to not overflow,[ 2.3 feet of head equals 1 psig. ]. They will probably have ballcck make up vlves as well
The booster pump should be pressure started to maintain constant closed loop pressures during high draw down of water at taps.
Apart from all above, generally a total nightmare to commission. Been there done that.

[reganracelis]

thanks for well explain info... now i have idea to go on...
wee done test run of booster pump... bladder tank pressure and pressure switch have set to 20 psi ( cut in) 40 psi ( cut off)...
in auto mode operation, booster pump 1 run and cut off in exactly 40 psi... we then now open valve of bladder tank, we expect that in 20 psi booster pump # 2 will run... it reaches 16 psi to make it happen...
i try to adjust the pressure swicth ( coarse adjustment) but nothing happens..
can u help me guys how to set pressure swicth?
also for the control of circulating pump which is temperature switch?

tnx to all... hope u can give more info to this..