Gas Central Heating - NZ gas supplies

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shk292

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#2049162 4-Jul-2018 17:29

With the shift towards renewable energy - requiring domestic use to be electrical - and the huge installed base of water-based central heating in places like the UK, I'd be surprised if someone didn't start marketing a heat-pump replacement for a gas boiler in the next few years. This would allow use of existing radiators for heat distribution from the renewable source.

Scott3

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#2049169 4-Jul-2018 17:49

shk292:

With the shift towards renewable energy - requiring domestic use to be electrical - and the huge installed base of water-based central heating in places like the UK, I'd be surprised if someone didn't start marketing a heat-pump replacement for a gas boiler in the next few years. This would allow use of existing radiators for heat distribution from the renewable source.

You can already get air to water heat pumps. (or water to water if you are going ground sourced, or have access to a pond or river).

The issue is that the refrigeration cycles performance drops as the input to output temperature increases.

To use 10 degree outside air to heat your house to 24 degrees is not too hard (per unit heat output). To use 10 degree outside air to heat hot water to 70 degree's is much harder (per unit heat output).

If you want heat pump based hydronic central heating, you need either massive radiators, fancoils, or underfloor heating (as for effichency you need to keep your input water temp fairly low).

Traditional UK radiators are sized based on having very hot water coming in from a gas boiler/water heater, so are to small for heat pump duty.

shk292

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#2049208 4-Jul-2018 19:36

Scott3:

You can already get air to water heat pumps. (or water to water if you are going ground sourced, or have access to a pond or river).

The issue is that the refrigeration cycles performance drops as the input to output temperature increases.

To use 10 degree outside air to heat your house to 24 degrees is not too hard (per unit heat output). To use 10 degree outside air to heat hot water to 70 degree's is much harder (per unit heat output).

If you want heat pump based hydronic central heating, you need either massive radiators, fancoils, or underfloor heating (as for effichency you need to keep your input water temp fairly low).

Traditional UK radiators are sized based on having very hot water coming in from a gas boiler/water heater, so are to small for heat pump duty.

I hadn't realised that but it makes a lot of sense, thanks. Not sure what the replacement for gas boilers will be in that case, although I'm far from convinced we're anywhere near running out

Scott3

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#2049212 4-Jul-2018 19:43

shk292:
I hadn't realised that but it makes a lot of sense, thanks. Not sure what the replacement for gas boilers will be in that case, although I'm far from convinced we're anywhere near running out

Well, it can be done, but your co-coefficients of performance are lower, sending running costs, and capital costs higher.

Bobdn

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#2049295 4-Jul-2018 22:08

old3eyes:

Several people I know here in Morrinsville have pulled out their gas connection for central heating due to paying $46 / month line charge for using nothing over the summer. They installed aircon units.

Genesis charges me 98.5 cents per day or around $30 a month. Who were they with?

Aredwood

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#2049345 4-Jul-2018 22:41

Wazza69: Great discussion here. To update from my first post on our situation. Our house is in Kapiti, outside of Wellington. We have mains gas outside our house. Our house is single story and really long. For some reason the previous owner installed a log burner down one end and no heating at the other (where the bedrooms are). It has gas bottles and a external boiler for the water and a separate bbq style bottle for the cooker. All very weird. Our preference is for gas radiators and convert the cooker and water to mains gas. Especially as my wife is English and is used to radiators. My main concern is the gas supply.

I dug into the issue with the heat pump capacity as i wasn’t at home when it was quoted. Apparently the issue is the electricity connection is too small for the large single unit that would be required. A bit strange since our house is only 6 years old.

Thanks

No surprises that the electricity connection doesn't have any spare capacity. As property developers work on the lowest price for everything. So the original electrician would have only designed for the minimum capacity needed to comply with the electrical regulations.

Get your electrician to install a circuit breaker on your mains cable that is rated to whatever the mains cable complies to. Then you can get your big heatpump installed. You will just have to be careful that you don't have the clothes dryer or oven going when you first switch on the heatpump, so you don't trip that breaker. When the house has reached the set temp, the run current should then be low enough so you can then use the dryer and oven.

Guessing that you use plug in heaters in the bedrooms at the moment. So the extra load from the heatpump would be offset by not needing the plug in heaters anymore.

Jaxson

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#2049386 5-Jul-2018 02:39

Good thread to read. Some points jumped out:

Yep, standards are treated as targets here, rather than minimum specs. That can change where the owner is involved with the build, but won’t where it’s a large developer constructing the houses before selling.

Log fires are sold on a ‘suitable for an x number bedrooms house’ approach, without any thought given as to how this heat is going magically make it to the other end of the house, through closed doors at night etc. very common to find the lounge super hot, and the bedrooms damp and cold.

How long will the gas last? Nobody is sure. They’re about the same cost to run in winter as heat pumps, due to lower energy cost per unit than electricity, and their output is a constant regardless of outdoor temperature. They can’t cool in summer though, and the line charge issue is real, and a bit silly if you have nothing else on there as well (eg cooking/water heating).

Heat pumps function in your room like a fan heater. They’re more efficient than a fan heater, and can cool, but they’re still a fan device mounted on the wall. You still have the issue of how the heat/cooling gets from the unit to the many rooms you want it to reach, and that’s the same with gas too. Some people expect miracles from them, and some marketing suggests this too.

Gas devices do they to be cheaper, though the modern ones can be just as complex with all the electronic internals. My lounge gas heater won’t run in a power cut for example.

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Scott3

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#2049430 5-Jul-2018 09:35

Jaxson:

...
Heat pumps function in your room like a fan heater. They’re more efficient than a fan heater, and can cool, but they’re still a fan device mounted on the wall. You still have the issue of how the heat/cooling gets from the unit to the many rooms you want it to reach, and that’s the same with gas too. Some people expect miracles from them, and some marketing suggests this too.
...

The thread is discussing central heating. The heat-pump option would likely be ducted to every room, where with gas, both ducted, and hydronic system (radiators) can be considered. You can do hydronic heat pump powered central heating, but this works best with underfloor heating, which would be a very expensive retrofit.

old3eyes

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#2049660 5-Jul-2018 11:55

Bobdn:

old3eyes:

Several people I know here in Morrinsville have pulled out their gas connection for central heating due to paying $46 / month line charge for using nothing over the summer. They installed aircon units.

Genesis charges me 98.5 cents per day or around $30 a month. Who were they with?

Mercury.

Regards,

Old3eyes

langers1972

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#2049830 5-Jul-2018 14:28

shk292:

With the shift towards renewable energy - requiring domestic use to be electrical - and the huge installed base of water-based central heating in places like the UK, I'd be surprised if someone didn't start marketing a heat-pump replacement for a gas boiler in the next few years. This would allow use of existing radiators for heat distribution from the renewable source.

That's the common mistake most people make about radiators, they aren't exclusively heated by gas boilers. The water in them can be heated by any source you like.

The argument that you're paying for nothing during the summer is also pretty ridiculous as you can get your hot water and cooking using gas if you go to the trouble of getting it connected.

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