Thread: Hot Water Systems - Lpg V's Offpeak Electric

Originally Posted by q9

Energy prices here aren't really directly comparable (I think, not 100%) but basically hot water in Japan is almost always the instant gas variety. Have never seen an electric hot water tank. Not having nanny-state laws, limiting output to 40 deg C delivering tepid at best water where you need it, they are great. We have a rental unit in Aus that has one of those heat pump systems. How do you quantify the energy savings vs the high cost of repairs when something goes wrong? We were told we needed a new fan last year. After costing it, I told the agent it would have to fail completely and deliver no hotvwater before being replaced. Nice idea, but too expensive to buy and maintain.

Electric powered storage hot water systems probably rare in Japan because of the space they take up...space at a premium in most Japanese residences. Electricity is also generally more expensive in Japan than in other countries...even more so now alot of it's nuclear power plants have been shut down post Fukushima.

Originally Posted by Mr Brush

What's to go wrong? A heat pump is basically a refrigerator in reverse. Ours has outlasted any other conventional water heater we've had at any house. Zero maintenance, zero problems in 12 years. Mind you, Quantum have probably the longest track record with heat pumps - maybe some of the new makers on the block have issues?

I think Siddons have been at it longer than Quantum, we had a Siddons heat pump system installed about 30 years ago. They now have what they call a bolt on system that uses you existing tank and I presume that the element in that could be used as back up if necessary. I might give them a ring and have a chat tomorrow.

Well there is a fan for a start... replacement cost over $400.

Dunno where you get your idea that electricity is expensive here. It is about 11 yen/kWh. When I left qld it was hitting 17c

Oh, and last time I had a gas connection in Australia, I had to pay a daily connection fee, regardless of use. Not the case here. You get reamed in Australia for energy costs. Not looking forward to going back...

The nice thing is that when our solar system is powering the house it will provide the electricity to power the heat pump hot water system. And when I get batteries they will provide the electricity overnight. From looking at brands I'm thinking Siddons or Sanden. Might be expensive to install, but I have a hankering to use our solar to power the entire house (eventually, when we get batteries).

I made the switch from off peak to a Rinnai about 10 years ago after the off peak died (water everywhere). We have noticed a drop in our power bill but that wasn't the only reason we did it. We now have the option of gas heating and cooking and/or electric heating cooking. This is important as we have long blackouts in our neck of the woods when the east coast lows hit.

I can't see the logic of re heating water I've already paid to heat the night before.

TT

RE- - the quantum system, just had one installed(in the last 6 weeks) for around $600 all inclusive(supplied and installed) there is some government rebate thing going on, to replace the regular hot water storage systems, it is not heavily publicized but worth looking into. It will be interesting to see the next power bill.

Have a look at the vacuum tube solar systems. We put one on the roof of a three bedroom house in 2013. Cost about $2400 all up, 200 litre hot water storage, mains pressure, works all year, electric backup hardly ever kicks in, perfect for a small family. These things are miles cheaper than anything else. I am looking at putting one as a preheater to our gas water heater at home. It will be very cheap to install because there will be no electrical connection and the plumbing will only be re-routing the cold to the gas hot water through the solar. The one I am looking at has a 200litre reservoir of hot water at atmospheric pressure and the mains pressure cold supply runs through a big coil in the hot water and gets heated up. If you do go this way don't get the ones that have the hot reservoir separate from the vacuum tubes because they rely on a pump and the pumps keep breaking down and are very costly to replace. Go for the ones that have the reservoir on the roof attached to the vacuum tubes.
Funny someone mentioned the 'nanny state' and 40 degree water...the water coming out of the one we put in was literally boiling and quite lethal so tempering valves are compulsory which mix in cold water and bring the temperature down to about 65-70 degrees C. Still hot enough to get a first degree burn but not the instant second or third degree burn you would get from the boiling water.

Originally Posted by Toymaker Len

Have a look at the vacuum tube solar systems. ..... If you do go this way don't get the ones that have the hot reservoir separate from the vacuum tubes because they rely on a pump and the pumps keep breaking down and are very costly to replace. Go for the ones that have the reservoir on the roof attached to the vacuum tubes.

I have one of this kind, they work extreamly wellfor heating water, but as there is no way to stop them heating the water in summer. When they boil they dump boiling water to replace it with cold water to cool the tank. With a horizontal tank they dump a huge amount of water to cool off and can dump several times a day. With mine I plumbed this water back to a storage tank to avoid loosing a lot of water.

Not all evacuated tube systems do that. Mine certainly doesn't. Just got through winter hear with a total water heating cost of $6 for the off peak booster power used. So that's the total annual running cost. Absolutely awesome! The circulation pump runs on solar power and the panels are angled very steeply to optimise winter heating. Its never dumped water, though does get to 186 deg c in summer so tempering is needed.

Bodan you just cover them a little with some shade cloth or bamboo screen or something. They are ferocious little beasties when they start spitting boiling water eh?

Tempering valve.... I fail to see the point of heating the water then cooling it again apart from protecting children and the aged/infirm. We've got a tempering valve in the guest room HWS which only gets turned on when we've got guests. We asked the plumber not to fit one in the main HWS when we built the house. I got the sparkie to turn the thermostat down to 50C and fit a timer in the circuit. The timer comes on for a couple of hours in the afternoon and can be overridden when necessary.
Geoff.

Geoff,

Holding water at <60 deg C is a breeding tank for bacteria, like legionella. A dangerous beastie. See:

Tempering Valves - Hot Water Mixing Valves Explained | ELGAS - LPG Gas for Home & Business

Heating up, then mixing back to a usable temp is not much hassle, and may save you or your guests a nasty illness.. I make sure my system hits 70 degrees every 24 hrs. Mostly this happens with the suns heat, but the thermostat will kick in at night if needed to ensure the bugs are dead and not brewing. I'm pretty sure this is a legl requirement in most states?

Thanks Elver I hadn't thought of the risk of bacteria in the water and is a concern as we're on rainwater out here. I think I'll turn the thermostat back up. Thanks for the info.
The guest room has a separate 50L HWS because it is down the other end of the house, keeping the plumbing runs as short as possible to avoid running it for 5 minutes waiting for the hot to come through, it has got a tempering valve installed.
Cheers,
Geoff.