Hot to cold water mixture

Bob1000 · Apr 5, 2007

I think the botom line should read ..
Se that switch pressure LOW enough so that it can stay on with the low municipality pressure and switch the pump off only in case of almost no pressure when there is no water there ( dry condition)
Hope I could explain what i understand about the low pressure switch .

valveman said:
I have a reduced pressure chart on a 1" size regulator at this link. Bottom of the page.

http://cyclestopvalves.com/prod_csv1w_specs.html

You can see that at 5 GPM flow the pressure is 5 PSI lower than at 0 flow. The more water you use and the smaller the regulator, the more pressure drop. Set your regulator to 50 PSI, and when you are using 5 GPM you will only have 45 PSI. Still not much difference, so not a bad way to do it.

They are very common but, not all regulators have the thermal bypass.

Flow switches are more trouble than they are worth. You can use a motor protector device that looks for low amperage. Here is one example you can read about.

http://cyclestopvalves.com/prod_sensor_geninfo.html

I think the best way to protect the pump from a lose of suction is with a low pressure or loss of prime pressure switch. Square D has one, some people call then a reverse acting switch. You need to install this switch on a tee with a 1 gallon pressure tank, and then attach the other side of the tee to the suction line of the pump. The 1 gallon tank will keep the switch from bouncing the pump off when it tries to start. Until the water gets moving there is low pressure in the suction line, the little tank keeps the switch from seeing it. Set this switch high enough that the pump can easily build enough pressure to shut itself off

Valveman · Apr 5, 2007

Say your pump can increase the incoming pressure by 40 PSI. If your on/off pressure switch is set at 40/65, then the incoming pressure must be at least 25 PSI for this pump to be able to shut itself off. I would give myself a little cushion and set the low suction pressure switch to shut the pump off if the incoming pressure falls below 30 PSI.

Sponsor · 2022-01-29T12:20:58-0800

Jadnashua · Apr 5, 2007

One of the big unknowns is the health of the galvanized pipes in the system. These are know to grow internally with rust and while the pipe could be 1" (25mm?), it could be acting as a much smaller pipe.

Would a much larger storage tank help here? Maybe not, since, unless it was atmospheric, you could easily be sucking water out of it faster than it was coming in with your local pump. Any clue what gpm the supply line can actually supply?

Bob1000 · Apr 6, 2007

Poor incoming pressure ( not very often)

Yes it happened few times to me that the pump could not build that high pressure to stop itself because of poor incoming pressure ....... what i can do in that problem??? luckly I was there at home and I switched off the power but what if I was not there?

valveman said:
Couple more things on using a pressure reducing valve on each flat. Make sure you get a valve that has a poppet to reverse flow for thermal expansion. Otherwise you will need to put a small tank on each flat to keep the expansion of the water heater from blowing something up.

Also, if you run your pressure switch up to keep the pump from cycling while running one shower, you are now completely dependant on the incoming pressure to shut off your pump. If the incoming pressure is low one day for some reason, you will come home to a pump that has not been able to build enough pressure to shut itself off. It doesn't take very long running like this for the pump to destroy itself.

Bob NH · Apr 6, 2007

First, put a pressure gauge on the incoming water line. Check it several times per day, and at various times, especially when the supply pressure is low, see how much water (liters or gallons per minute) you can get from the largest available cold water faucet, without the pump pressure.

You should never try to pump more than that amount of water.

You need to do whatever is necessary to keep demand below that quantity. You can do it by restricting usage, or by increasing storage in the building, or a combination of those things.

After you find out how much water is available, it will be possible to design a system to make things work. Until then, we are all guessing.

There is a flow control valve, usually called a "Dole valve", that can be used to restrict flow. You could put one in the line to each flat. The problem is, they will reduce the pressure somewhat and that should not be done unless nothing else works.

Valveman · Apr 8, 2007

Donâ€™t use a Dole Valve. You already have a pressure problem and the Dole will make it worse. Your shower head and faucets are your restrictors, make sure they cannot let out more water than your system can supply.

The low suction pressure switch will automatically shut the pump off, if the incoming supply is too low. Running your pressure switch up high to keep the pump from cycling is the problem. Use a CSV on the pump instead of the regulators on the lines, and you wonâ€™t have to turn up the pressure switch to keep the pump from cycling. The CSV keeps the pump from cycling. It also holds a constant 50 PSI which should keep you from seeing changes in the pressure or temperature while in the shower.

Use a 50 PSI Cycle Stop Valve with a 40/60 pressure switch. This will give you more cushion on the incoming pressure by 5 PSI, over setting the switch to 40/65. It will also keep the pressure leaving the pump at a steady 50 PSI, no matter if one or two showers are running at one time.

Hot to cold water mixture

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