The importance of correct heat pump sizing

[@Umski]

Thanks, this confirms my thinking that undersizing need not be a big problem if heat loss can be reduced further with more insulation in due course - if I’m not mistaken the usual temperature used to calculate heat loss is -3C which happens for maybe a couple of weeks in the year as has happened recently - if that’s true then for the majority of the year the HP would technically be oversized so erring on the side of smaller isn’t as bad as oversizing…

[@victorsr6708]

Great video!! Does this apply to inverter technology compressors with variable speed condenser fans, ECM indoor motors & communicating thermostats? I’v gone to several manufacturers classes and what they teach is that with the configuration I mentioned the equipments will self adjust to the load due to constant communication between the outdoor temp, indoor temp & desired set point. The system has programmed algorithms to compensate. I’m working on units that vary the loads between 15% to 100% load. Perhaps your talking about single stage compressors?

[@jdv1975]

This also is relevant for invertor compressors

[@julianchamberlain5399]

I've had two quotes for a heat pump. One calculated that I'd need a 12kw and the other a 7kw...

[@jimmaxwell2259]

The main issue with heat pumps is inflexibility. The system needs to be tailored exactly for the individual house, but then, when you for example get new windows with better insulation, the heat pump effectively becomes 'oversized' for the load. If you decide to stick on a small extension/conservatory etc, suddenly your heat pump can be very much undersized for the load. The issue is, you are not just throwing in a new £1500 Gas boiler to compensate, you are looking at a minimum of £5k to get a new tailored pump. Heat pumps are a 20 year investment, but life changes along the way and the HP system is just a little inflexible, imho.

[@JohnnyMotel99]

If the HP becomes oversized for any reason, why not reduce the flow temp and increase the SCOP.

[@jimmaxwell2259]

@@JohnnyMotel99 Because, that change of circumstance has occurred long after the installation and 'joe bloggs' wont know either how to change the flow rate or heat curve. Depending on oversizing, the heat pump might not go 'down' low enough to maximise the potential efficiencies. Few homeowners are even remotely interested in how their system works...they just want it to work. With Gas boilers, you have a much greater tolerance to changes. Inefficient HP can be extremely costly. Doesn't have the same latitude for mistakes. ps i love the idea of properly installed heat pumps.

[@romanpajak9215]

Is there anything I can do if my heat pump is oversized? We have a atherma 3 daikin 9kw with a heat loss of 5kw at -2? its running about an scop just under 3-1

[@zoranstojanovic4255]

For 130 m2 how many need power pump in KW?

[@martiruda]

If you reply to this message in 4 months I will let you know, I will install a 3kwh heatpump at my super insulated home. 3ple glazed windows and ICF.

[@davefroman4700]

I know I am going to get some push back here but hear me out. In places like Canada it can be -40C for weeks. And as amazing as this technology is getting, at those temperatures you may as well be throwing credit cards into the fireplace for the energy loads. What if we could provide a passive seasonal heat source to work with that is MUCH hotter? You can store a lot of energy in 3 yards of sand at 500F for a very long time. And all of it can come from excess renewable. Think of it as a piggy bank for a dump load, instead exporting to the grid for peanuts.

[@JohnnyMotel99]

they do exist, your sand batteries, just with more effective materials.

[@davefroman4700]

@@JohnnyMotel99 Sure, but those materials are pricey, and fail over time. Sand is an inert semi solid that will not fail.

[@normanboyes4983]

Not the best explanation tbh. Rather than use imaginary lines on graphs, real world examples would carry credibility and be easier for the presenter to use convincingly.Sorry.

[@Allegedly2right]

Back up heater why don’t you Just admit Heat Pumps are not economical,far too many loop holes if if if you don’t do your heat loss if you don’t size it proper if you turn one rad off haha pull the other one.I am on my second one over two years costing a fortune.

[@mynameisfake6217]

Sounds to me like you just need a better heat pump or need to work with a better installer. I live where it gets below -20C 20 days out of the year. Back up heat only needs to come on less then 50% of the time when it gets that cold.

[@Pierceb2]

You might want to hire a consultant if you don’t trust your contractor to optimize your configuration and the thermostat controls etc, Then set it and forget it There are quite a few videos on KZbin that show you the math and studies of real world users who run them right or run them wrong and the impacts of those choices in terms of costs, efficiency and comfort.