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# Heat pump and domestic hot water control

• 30-12-2021 8:33am
Registered Users Posts: 1,571 ✭✭✭

Hi all,

Our 2006 or 2007 Dimplex can heat the hot water. It’s currently not set to do that, as we were isolating the cause of a pump fault. I am wondering if I should bother turning it back on, is it much better than using immersion?

what is the system logic though? Or what are the options?

i understand the pump could bring water to 45 degrees give or take a degree. And then the immersion could top up the heat to a higher temperature.

Thinking about efficiency, when does the pump heat the water? Is it after it’s done heating house UFH or is it throwing excess energy into water when it has it? When would I know to set the immersion to top it up?

ideally I suppose I’d like heat pump to have water base temp up in the night to avail of night rate electricity, then shot of immersion at 6am before people shower and before the night rate ends?

Not sure the pump thinks like this or has such settings though?

😎

• Registered Users Posts: 1,571 ✭✭✭

And how many degrees per hour would a pump heat water tank? Or given it will vary, how do I calculate an approximate?

😎

• Moderators, Home & Garden Moderators Posts: 4,994 Mod ✭✭✭✭

Size of the water tank and the energy output of the heater. Eg an immersion is 3kw.

The calculation is based around the specific heat capacity of water (amount of energy to raise 1kg of water 1degree C/K, in joules)

• Moderators, Education Moderators, Home & Garden Moderators Posts: 7,919 Mod ✭✭✭✭

Calculator here: https://www.omnicalculator.com/physics/water-heating

An immersion is considered to be 100% efficient. A wet system would be less efficient. Note I am talking about heating efficiency, not overall system efficiency, in which case a heat pump obviously more efficient than resistive heating.

• Registered Users Posts: 1,571 ✭✭✭

900e bill has arrived :(

😎

• Registered Users Posts: 438 ✭✭

Ring your provider, they can split that bill over several months. I did that with a €600 bill with Electric Ireland due to faulty water pump for the well a few years ago.