Central heating vs heat pumps.

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rayonline

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Topic # 216696 8-Jul-2017 17:49

I saw someone's place, yes in NZ with central heating. We don't like many.

1. Is central heating quieter than heat pump?

2. Is natural gas (Contact Energy etc) cheaper to run than electric heat pumps? I've heard before that heat pumps are "the" most cost efficient but not sure how much that is fact.

3. Is natural gas central heating cost efficient by itself, or are they about the same as individual gas heaters?

Heat pumps do cooling as well. The house does look a lot tidier without them thou :)

Cheers.

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Reply # 1815967 8-Jul-2017 17:59

1. it can be, it all depends on flow rate and diffuser design. a wall mounted unit on high fan speed can be noisy.

2. with a heat pump, for 1kw of energy in you can usually get 3+kw's of energy out of it. + the fact they can cool which gas cant do. have a look at this: https://d3c7odttnp7a2d.cloudfront.net/assets/4322/CNZ_Heating_Guide_2017__member_DESKTOP.pdf

jonathan18

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Reply # 1815976 8-Jul-2017 18:21

I'm confused by your question, TBH. Central heating doesn't refer to a particular method of heating, but that heat from a single source is distributed around the building. Central heating can be gas-powered, diesel-powered, heat-pump-based...

So are you specifically talking about GAS central heating?

timmmay

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Reply # 1815978 8-Jul-2017 18:25

The advantage of radiators is noise - standalone heat pumps can be quite loud. Not sure about ducted. We heat around 8 months of the year and cool around 10 days, so heating is clearly the priority.

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jonathan18

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Reply # 1815979 8-Jul-2017 18:29

timmmay:

The advantage of radiators is noise - standalone heat pumps can be quite loud. Not sure about ducted.

Ducted heat-pumps aren't loud but in the dead of the night this can be still frustrating when sleeping; ours often wakes me up when it turns on, or disrupts my sleep if we leave it on over-night.

@rayonline - have a search through GZ for a bunch of detailed relevant threads on central heating from various sources - you'll find lots of information!

rayonline

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Reply # 1815980 8-Jul-2017 18:30

jonathan18:

So are you specifically talking about GAS central heating?

Yes, probably. They didn't have any heat pump or aircon units there. It was just some rectangle vent grills on the corner carpet or lower wall. I also imagine it's not diesel, just in suburbia Wellington.

andrewNZ

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Reply # 1815984 8-Jul-2017 18:59

A friend had a gas heating system installed a few years back, said it was very expensive to run.

Knew someone who had radiator central heating heated with LPG, cost around $600/month to run in winter for a reasonable sized two story home.

Location: Dunedin

rdjacobs

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Reply # 1816004 8-Jul-2017 19:25

http://www.centralheating.co.nz/wp-content/uploads/Cost-Comparison-Sheet.pdf

Comparison cost

Had a John Guest Underfloor System installed 2 years ago. Has been fantastic for winter, and running cost around $1200, with a 14KW air and water heat pump.

We have polished concrete and tiles in the bathrooms. Floor probes were also added to the concrete slab for floor protection.

Have multi-zone control with JG Aura thermostats and App control.

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Technofreak

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Reply # 1816073 8-Jul-2017 22:34

So far as cost of heating goes you won't beat a heat pump in my opinion.

We've just put one in it's so new in fact we are still to get our first power bill since it was installed. I am expecting the power bill to be reduced. It does a fantastic job. We're heating a larger area than we were with the old electric heater and heating to a higher temperature. I am expecting the power bill to be reduced. There is a bit of background fan noise when it's going but it's not too bad. I programme it to turn on before the alarm goes off in thenmorning and thus have a warm house when we get up.

We have a floor model and don't find it intrusive. It only sticks out from the wall by 200mm.

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elpenguino

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Reply # 1816083 8-Jul-2017 23:30

Jase2985:

1. it can be, it all depends on flow rate and diffuser design. a wall mounted unit on high fan speed can be noisy.

2. with a heat pump, for 1kw of energy in you can usually get 3+kw's of energy out of it. + the fact they can cool which gas cant do. have a look at this: https://d3c7odttnp7a2d.cloudfront.net/assets/4322/CNZ_Heating_Guide_2017__member_DESKTOP.pdf

For one kW worth of gas you (I) pay 1/3rd of the cost for 1 kW of electricity.

Cooling is useful if you live somewhere that gets hot. OTOH if you use it for cooling you're going to use more energy year round in total than you would use with gas heating.

I live in wellington so cooling is not something I need. Well actually, there was that one time...

I used to rent a villa with central heating and the gas bill was about $400/month - 10 years ago. I doubt the place was insulated.

mattwnz

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Reply # 1816093 9-Jul-2017 00:41

elpenguino:

Jase2985:

1. it can be, it all depends on flow rate and diffuser design. a wall mounted unit on high fan speed can be noisy.

2. with a heat pump, for 1kw of energy in you can usually get 3+kw's of energy out of it. + the fact they can cool which gas cant do. have a look at this: https://d3c7odttnp7a2d.cloudfront.net/assets/4322/CNZ_Heating_Guide_2017__member_DESKTOP.pdf

For one kW worth of gas you (I) pay 1/3rd of the cost for 1 kW of electricity.

Cooling is useful if you live somewhere that gets hot. OTOH if you use it for cooling you're going to use more energy year round in total than you would use with gas heating.

I live in wellington so cooling is not something I need. Well actually, there was that one time...

I used to rent a villa with central heating and the gas bill was about $400/month - 10 years ago. I doubt the place was insulated.

So wouldn't that make the cost of gas about the same as a heat pump per kW of heat? But the benefit of a heat pump is that it also cools. I guess the other thing to look at is how long the actual hardware lasts for, and how much maintenance it needs. I know that underfloor heating tubes require some maintenance, and flushing out with special cleaning fluid every year or so.

jonathan18

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Reply # 1816110 9-Jul-2017 07:35

An advantage of gas is (I assume) that it'll operate equally efficiently no matter the conditions, whereas heatpumps become less efficient in lower temps.

As a couple of us have posted on another thread, our ducted heatpump systems struggle to heat the house in a cold morning; I've resorted to running a standard heater on really cold mornings (for our Electric Kiwi free hour, using a timer), which helps somewhat, but it is frustrating.

An alternative may be to run the heater all night so it doesn't have to bring the temperature up to the same degree, but note my earlier point re the noise/air flow annoying me at night (though it doesn't seem to be an issue for the rest of my family).

Or, if we had gone with a larger model, perhaps we'd not have had this problem; interestingly, though, all four quotes we had recommended the same capacity.

timmmay

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Reply # 1816111 9-Jul-2017 07:36

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Technofreak:

We've just put one in it's so new in fact we are still to get our first power bill since it was installed. I am expecting the power bill to be reduced. It does a fantastic job. We're heating a larger area than we were with the old electric heater and heating to a higher temperature. I am expecting the power bill to be reduced. There is a bit of background fan noise when it's going but it's not too bad. I programme it to turn on before the alarm goes off in thenmorning and thus have a warm house when we get up.

I wouldn't bet on heating a larger area to a higher temperature reducing your bill. Yes they're more efficient than a standard heater, but they're not magic. It's not uncommon for people with a new heat pump to get a huge bill. Go have a look at your meter, get a reading, and compare it to your last reading.

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mentalinc

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Reply # 1816132 9-Jul-2017 09:14

Some friends have underfloor heating using water set to 35 degrees in 400+sqm house and use around $400 of deisel a month, so would not be recommending that route. they Might ned to do some fine tuning on their setup but far from economical.

I'd vote ducted heatpump so long as the temp sensors that drive it are installed appropriately.

We just had it done and control unit is set to 17 degrees but the rooms run around 22 degrees! much work required by installer to sort it out still.

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Technofreak

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Reply # 1817148 9-Jul-2017 11:17

timmmay:

I wouldn't bet on heating a larger area to a higher temperature reducing your bill. Yes they're more efficient than a standard heater, but they're not magic. It's not uncommon for people with a new heat pump to get a huge bill. Go have a look at your meter, get a reading, and compare it to your last reading.

Yes, this is a possibility.

I have based my expectations on the fact the heat pump we have installed uses 30% less power than the old heater and produces up to 2.5 times the amount of heat.

I suspect where people have experienced a much larger bill than expected is where the heat pump is spending a significant amount of time defrosting. Our unit has rarely needed to defrost. I think the other issue is the one mentalinc talks about in his/her post. That is the disparity between the temperature set on the controller and the actual room temperature.

In our case a temperature setting of 18 degrees gives about 23 degrees room temperature. That is because the temperature sensor is in the unit which is mounted on the floor. The temperature measurement is taken from the air being drawn into the heat pump and when the room temperature is 23 degrees the air temperature at floor level is 18 degrees.

In this case if you were purely setting the desired room temperature by reference to the setting on the controller you would be attempting to achieve a room temperature of around 28 degrees and as such wasting a lot of energy.

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Technofreak

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Reply # 1817150 9-Jul-2017 11:24

mentalinc: I'd vote ducted heatpump so long as the temp sensors that drive it are installed appropriately.

We just had it done and control unit is set to 17 degrees but the rooms run around 22 degrees! much work required by installer to sort it out still.

Not an easy problem to solve I suspect now that it's been installed. You'd expect with a ducted system the sensors would be at a height or position in the room that gave a room temperature that matched the temperature set on the unit.

I suspect many heat pump users never bother the check the actual temperature and just accept that the temperature showing on the controller is indeed the room temperature.

In our case which I mentioned in the post above, I realise the limitations of how our unit measures the room temperature and adjust the settings accordingly.

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