Pump on timer won't turn off when heater is on!

bostonpool

Well-known member
May 29, 2017
80
Worcester, MA
Hi folks:

Our pump is on a timer "wheel" that I've set to run the pump and SWG for 12 hours a day (7 AM to 7 PM).

It's starting to get cool here in the northeast. So I turned on our pool heater, which is an older yet functional Heat Pump located downstream from the pump and upstream from the SWG.

I was expecting the heater to run until 7 PM when the timer kicks the pump off. Then the heater should stop due to lack of flow.

Except...7 PM came and went, and the pump didn't kick off. I went out at about 8 PM and manually threw the switch on the timer, and still the pump ran. It only turned off when I shut the pool heater off. Then the pump stopped as it typically does.

Is this supposed to work this way? Is it some sort of freeze / frost protection to prevent the pump from turning off if the heater is calling for heat?

Or is this somehow wired wrong?
 

JamesW

TFP Expert
Mar 2, 2011
16,791
There are some systems where the heater will override a timer so that the pool reaches the set temperature. Can you describe your system better?
 

bostonpool

Well-known member
May 29, 2017
80
Worcester, MA
I figured it out. (Read the manual...ha.)

My pool heater is an old Raypak RHP Heat Pump, long since discontinued.

It has the ability to be wired into a time clock in 3 different ways:
1)Thermostat Control Including Restart - This is the default setting and is the way my current unit is wired. It basically means the heater will run as long as the thermostat indicates it is calling for heat. This happens regardless of the timer setting. If the unit is calling for heat and the timer shuts the pump off, the heater keeps the pump running until it reaches the proper temperature. It then shuts off. If the unit calls for heat again, it turns the pump on again, even if the timer is still telling the pump to turn off.

2)Thermostat Control Without Restart - This is almost the same as option 1, except it will keep the pump running if the unit is calling for heat when the timer shuts off. But once the target setpoint is met, the unit will shut off, and shut the pump off. And the pump will not restart until the timer turns it back on at the regular start time. There will be no further heating for the night.

3) Time Clock Control Only - This is the setting I want. Whereby the pump shuts off at the desired time, which therefore shuts the heater off. The heater can't override the time clock.


I guess I can understand why someone would want option 1. Being in New England, we sometimes get frost in October. I guess if the unit calls for heat on a cold night, the pump turns on and prevents things from freezing, etc.

My criticism is, when the pump is off the water around the thermostat isn't moving and will cool down really quickly just sitting in the pipes. So the heater will call for "heat" when it really doesn't need it. Once it is on, it doesn't seem to shut off quickly. It stays on at night for hours.