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Lessons from leaks

 
Thermostats, TRVs, Pumps, Valves, Radiators & Controls
Last Post by robl 2 years ago
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 Mike Patrick
(@mike-patrick)
Reputable Member Member
1603 kWhs
Joined: 3 years ago
Posts: 152
Topic starter 08/06/2022 4:27 pm  

A few days ago the joint above this pump on our heating system started to leak. I was alerted to it by the RCD tripping in the fusebox due to the water ingress into the pump's electrical supply. A plumber (turned out to be the same guy who had replaced a faulty main PCB on our Grant heat pump 2 years ago) soon fixed the leak by replacing a seal inside the joint.

It was then that he said this is the auxiliary pump which just speeds up delivery of hot water. It's optional, you don't have to have one. You can turn it off and save electricity if you don't mind waiting longer for the taps or shower to deliver.

If he's right then I think it was installed incorrectly. It is wired into the Honeywell timer which is set to switch space heating off when the water is being heated and vice-versa. The pump can only come on when the timer is set for the heat pump to heat the water. When space heating is on (ie most of the time) then the pump is off. So, it can't be speeding up the supply of hot water when a tap is turned on.

It appears to me me that, as wired, this pump (a £200 componenet) serves no useful purpose. Could I be right?

Mike

Leak

Grant Aerona HPID10 10kWh ASHP


   
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 robl
(@robl)
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2289 kWhs
Joined: 2 years ago
Posts: 179
09/06/2022 7:49 am  

I'm guessing the pump is there to boost the flow of the water, in a low pressure DHW system?  Try turning it off somehow, or turning it down, see if you can tell the difference!

Alternatively, in larger houses and hotels, it's common to have a hot water return line, so the hot water is circulated back to a tank either on demand (eg when the bathroom light is turned on) or constantly.  This means that when you turn on a hot tap, it's much quicker to give hot water.  They obviously waste a lot of elec and heat.  A better solution in a home is likely to use smaller bore pipes direct to the tap - the flow speed will be a lot higher, so there will be less wasted water before it gets hot, and less wasted heat afterwards.


   
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