Central heating vs heat pumps.

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iistudio

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#1852141 24-Aug-2017 21:23

My house got 4 bedroom upstairs and looking to either ducted central heating or multi-split heat pump systems

My reception is multi-split system you can control each individual unit (high wall 2kw to 3.5kw) so thats more efficient

as oppose to ducted system you only got 1 control so if 2 rooms are empty, you would still have to use the full capacity

( I know you can shut the outlet off but I think it just transfer more heat to other outlets)

I also think for multi-split heat pumps even you just run 2 units indoor, the outdoor

unit probably will use more power than 2 separate heat pumps....

Can anyone please verify that my theory is correct? thanks

Jase2985

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#1852344 25-Aug-2017 09:57

if you are still heating the same area ie with rooms closed off it still takes the same energy to heat it. so with a ducted system with rooms closed off it will just heat the rest of the space faster for the same fan speed setting, or you could just turn the fan down.

i dont imagine there would be any significant difference in power usage between the 2 setups.

iistudio

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#1852387 25-Aug-2017 10:39

Jase2985:

if you are still heating the same area ie with rooms closed off it still takes the same energy to heat it. so with a ducted system with rooms closed off it will just heat the rest of the space faster for the same fan speed setting, or you could just turn the fan down.

i dont imagine there would be any significant difference in power usage between the 2 setups.

Thanks Jase2985,

What I am curious about is that if both systems are running for 4 hours (for example)

and you only need to heat 2 rooms

ducted you always running at full capacity I would imagine?

multi-split if you only turn on 2/4 units in two rooms. so would be at least 1/3 if not 1/2 power saved?

cheers

jonathan18

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#1852573 25-Aug-2017 14:00

iistudio:

Jase2985:

if you are still heating the same area ie with rooms closed off it still takes the same energy to heat it. so with a ducted system with rooms closed off it will just heat the rest of the space faster for the same fan speed setting, or you could just turn the fan down.

i dont imagine there would be any significant difference in power usage between the 2 setups.

Thanks Jase2985,

What I am curious about is that if both systems are running for 4 hours (for example)

and you only need to heat 2 rooms

ducted you always running at full capacity I would imagine?

multi-split if you only turn on 2/4 units in two rooms. so would be at least 1/3 if not 1/2 power saved?

cheers

Don't forget you can elect to put dampers in a ducted system so have control over what zones get heated; these can be automated, and some brands can also be controlled by the same panel as the heat pump - eg, with our Daikin system, we can elect to have a timer set to heat a specific zone.

Also, we're talking heat pumps - even a large ducted system is relatively cheap to run. If I could be bothered I guess I could shut off the vent in our spare bedroom, but personally I just like the fact that all rooms in the house are heated.

mdf

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#1852607 25-Aug-2017 14:49

Another factor to bear in mind is that heat pumps and ducted central heating both work by convection. Central heating will suck air at a central return vent as well as blow warm air from the outlets. Heat pumps only blow.

We had a heat pump and now have gas central heating. That room warms up much quicker with the return since you get a much better convection current going. It's also quieter since all the fan work is being done elsewhere (though any room above or below the central heating unit will pay that price).

I'm sure there's some theoretical maths to work this out precisely. But if you can get your room up to temperature quicker, I'm assuming it uses less power to do it.

House overall feels drier too since the air is being mechanically circulated. We do have the fresh air ventilation add on too, which we run when we're not home (in winter) and that might be more responsible for that.

mdf

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#1852608 25-Aug-2017 14:49

Sorry double post for some reason.

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Jase2985

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#1852724 25-Aug-2017 16:35

iistudio:

Jase2985:

if you are still heating the same area ie with rooms closed off it still takes the same energy to heat it. so with a ducted system with rooms closed off it will just heat the rest of the space faster for the same fan speed setting, or you could just turn the fan down.

i dont imagine there would be any significant difference in power usage between the 2 setups.

Thanks Jase2985,

What I am curious about is that if both systems are running for 4 hours (for example)

and you only need to heat 2 rooms

ducted you always running at full capacity I would imagine?

multi-split if you only turn on 2/4 units in two rooms. so would be at least 1/3 if not 1/2 power saved?

cheers

why would the ducted system be different?

it works just the same in principal as a high mount wall one

any form of heat pump works off a thermostat, and will start outputting max heat and as the temperature comes closer to the set temperature it will output less and less heat till its at the set temperature when only the fan will be running, then the temp will drop a little and it will start heating again but because it is close to the set temperature it only needs to use a little heat to warm the room up.

here is an image of my heat pump in action, this is power usage in Kwh, vs time.

the heatpump started heating about 725 (another heater else where in the house turned off at 730 which is the dip there) then over the next hour its heating away and and you can see the power it uses gets less and less as the room warms up.

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