Above average pressure as heat pump is at high level.

Pool pumps, pool filters and the plumbing of
swimming pools. Sand filters, cartridge filters,
fabric filters and alternative filter media.
stg

Above average pressure as heat pump is at high level.

Postby stg » Tue 02 Feb, 2010 08:38

I had to install the heat pump at high level (above garage, 3m above pool surface) due to noise considerations. Pump is 1.6 hp, filter 760 dia. Design total flow rate 220 l/m.(heat pump required flow rate 133 l/m.) A bypass valve is fixed after filter to divert partial water to heat pump. But when the bypass valve is partially closed to achieve the flow the pressure shoots up to 1.7 bar (25 psi) which was initially at 1.2 bar (18 psi). I would like to know if this pressure is normal. Will this damage the filter? The pump room is underground.


NYC003

Above average pressure as heat pump is at high level.

Postby NYC003 » Tue 02 Feb, 2010 16:53

What are the diameters and lengths of all pipes?

How far below ground is the pump and filter?

Is the pump's total horsepower 1.6? Is it a 1.0 H.P pump with a 1.6 S.F?

How are you determining the correct amount to close the bypass to get the correct flow rate to the heat pump?

What is your total flow rate? Do you have a flow-meter?
stg

Above average pressure as heat pump is at high level.

Postby stg » Wed 03 Feb, 2010 00:25

Pipe dia is 63mm. The plant room is 2 meters underground in between the pool and garage which are very close by (hardly 4 meters).Pump total kw is (1675 watts motor input power, 1200 watts motor output power).I have a flow meter installed near the heat pump above garage. Bypass valve is inside the plant room. Design total flow rate is 3.5 l/s and required flow for heat pump is 2 l/s.
NYC003

Above average pressure as heat pump is at high level.

Postby NYC003 » Wed 03 Feb, 2010 01:25

A 7 psi increase is somewhat high for the situation you describe. The fact that the heat pump is 5 meters above the pump and filter does work out to 7 psi, but the pressure increase should be offset by the water going back down to the pool.

Some heat pumps are not made by pool equipment manufacturers and I have found that heat pumps made by companies that do not make swimming pool equipment often do not get the hydraulics right. They will often make the water lines too small. Who is the manufacturer of the heat pump?

Your system pressure is somewhat higher than I would expect given the information you have provided, but not enough to be a serious problem. I suspect that there is some restriction in the system causing the higher than expected pressure.

You might want to consider a smaller pump or a variable speed pump such as the Jandy ePump or the Pentair IntelliFlo. The ability to control the flow rate will allow you to save money on electricity and reduce excessive system pressure.
shijotg
Pool Newbie
Pool Newbie
Posts: 1
Joined: Tue 02 Feb, 2010 07:56
My Pool: 13mx5.5m pool. 760 dia filter. 70kw heating and 45 kw cooling heat pump. Domestic use out door pool.
Location: UAE

Above average pressure as heat pump is at high level.

Postby shijotg » Wed 03 Feb, 2010 09:07

Above average pressure as heat pump is at high level.
NYC003

Above average pressure as heat pump is at high level.

Postby NYC003 » Wed 03 Feb, 2010 10:43

5.3 meters of pressure drop corresponds to 7.5 psi. That is too much for a pool heater and I think indicates a poor design. The Calorex heat pumps that I have seen have internal piping that is too small for pool flow rates. That is why they have such a large pressure drop.

The small internal piping can also become clogged with debris and cause the heater to malfunction. The best thing you can do to reduce pressure drop is to reduce the flow rate to the heater to the minimum flow rate that the heater specifies as the minimum. It is important to monitor the flow rate going through the heater to make sure it is not clogged. If it runs while clogged, it can overheat and burn up.

You should install a flow switch inline with the heater that can turn off the heater if the flow drops below a minimum level. The heater does have a pressure switch that is supposed to work as a flow switch but it is not reliable and will not turn off the heater if the heater becomes clogged.

25 psi should not damage your filter, but it is less than ideal. I don't think that you should put a smaller pump after your filter. If possible, you should consider replacing your current pump with a smaller one or with a variable speed pump. Using a variable speed pump, you can adjust the flow rate to exactly what is required for the conditions.

What is minimum flow rate for the heat pump?
How many liters is your pool?
How many hours a day do you run the pump?
stg

Above average pressure as heat pump is at high level.

Postby stg » Thu 04 Feb, 2010 04:18

Thanks again for the advice. The minimum flow rate of the heat pump is 120 l/m(2 l/s). The flow is now set at this minimum flow. I have already installed a flow switch near the heat pump for additional safety even if the heat pump has its own internal safety. The total pool volume is 90,000 liters. I have total 2 nos pumps, one working and another standby. The pumps switch loads every 2 hrs controlled by a timer. Is it advisable to stop the filtration process for some time a day? Is there a problem if the filter works for 24 hrs? What are the normal standards in this regard?
NYC003

Above average pressure as heat pump is at high level.

Postby NYC003 » Thu 04 Feb, 2010 17:48

Why do you have two pumps? The pumps should be rated for continuous duty. There is no problem to running the pumps continuously.

If your filter is 760 mm, then it should be rated for about 367 liters per minute and would require about 220 liters per minute to backwash.

Some people only run their pumps for about 8 hours a day to reduce the amount of electricity that they use. I don't like for the water to sit still for any length of time. I like to keep the water circulating.

Some people use a two speed or variable speed pump to reduce electricity costs. Running the pumps for longer times at slower speeds can save a lot of electricity.

If you could reduce your system flow rates down to 120 liters per minute, you could save a lot of electricity.

You would have to increase the flow rate to 220 gpm to backwash the sand filter.

Return to “Pool Pumps, Filters, Plumbing & Piping”

Who is online at the Pool Help Forum

Users browsing this forum: No registered users and 1 guest