Recently installed a Stuart Turner Monsoon Universal Twin 3.0 Bar pump as a whole house pump. Bath fillers take gravity feed for cold and hot from the HW cylinder. All other taps throughout the house are mains-fed for the cold and are a combination of mixers and separate hot/cold taps. The problem is the mixer shower in the en-suite is mains-fed for the cold (no clue why it was installed like that), so whenever this is in use, the pump will be pumping single-ended for several minutes at a time. Stuart Turner advised it's fine to run the pump single-ended (eg. hot side only) for short periods, such as filling a basin, for example, but definitely not for longer periods such as taking a shower. They advised re-plumbing the shower for gravity-fed cold, or installing a single-ended pump specifically for the shower. My preferred option would be to re-plumb to gravity-fed cold, but although the plumbing job is simple, it would require a lot of making good in terms of retiling, decorating, etc. In the interim, I'm going to just run a pumped cold tap while taking a shower so both ends of the pump are operating.
I'm interested to understand what the issue is with running a twin pump single-ended. I get that the cold side would be operating against a closed valve (no taps open), so the physical resistance would be high against the impeller. I can also see the load on the motor would consequently be higher. So, would pump life be reduced simply because the pump motor would be working harder, or is there a more serious issue that could result in the pump failing more quickly (days/weeks as opposed to it lasting 5 years instead of 10, for example). Just would like to understand the mechanics of what's going-on in the pump.
I'm interested to understand what the issue is with running a twin pump single-ended. I get that the cold side would be operating against a closed valve (no taps open), so the physical resistance would be high against the impeller. I can also see the load on the motor would consequently be higher. So, would pump life be reduced simply because the pump motor would be working harder, or is there a more serious issue that could result in the pump failing more quickly (days/weeks as opposed to it lasting 5 years instead of 10, for example). Just would like to understand the mechanics of what's going-on in the pump.