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Sanden Heat pump HWS - Any comments?

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Started 7 years ago by alfresco24
Latest reply from scott drew

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alfresco24
Member

Am considering what to replace my dead gas storage HWS system with.
I don't want to use solar HWS which need circulating pumps and avoid the summer over-heat-venting and winter anti-frost-heating issues.
Electric heat pump set to run with solar PV hours seems the best logical solution.

The Sanden system seems a logical choice with very good performance spec's but it's quite expensive and I'm concerned about the short warranty (3 years) on the compressor - which costs $2500+GST (today's money) if needs replacing.

Has anyone had one of these more than 3 years?
Any empirical based advice?

Posted Thursday 9 Jul 2015 @ 10:50:18 am from IP #
darrynm
Member

As far as I know they're a reliable option. Where do you live as this greatly will affect what your best option would be.

Posted Thursday 9 Jul 2015 @ 11:43:42 am from IP #
dmaunder
Member

I have had one for about 12 months and it is excellent. Runs during the day, takes 2-4 hour, constant draw of 1000w. We are in Melbourne

Posted Thursday 9 Jul 2015 @ 11:50:55 am from IP #
tezz
Member

Virtually the same comments as dmaunder. Only one at home, so daytime heating session usually takes an hour in summer, 1 hr 15 min in winter. Temperature here is often 5 degrees colder than Melbourne. Very economical, as well as quiet.

Posted Thursday 9 Jul 2015 @ 1:03:58 pm from IP #
alfresco24
Member

Thanks for the comments.
I'm in Adelaide, on the Adelaide plain, so the minimum (effective) temperature in winter rarely gets down to near zero.
According to reports Sanden is the only heat pump that can still heat water, without the need for a booster element, below 5'C and can still heat the tank water to 60'C+ in ambient of -10'C.
With a maximum COP of 4.5 this is one impressive piece of technology. Expensive but impressive.

Posted Friday 10 Jul 2015 @ 12:57:04 am from IP #
Bushwalker
Member

I agree the Sanden is a good unit.

We have the Siddons split unit (one of the early versions, 2008) and we are in the Adelaide hills. I can confirm the system has had no problems producing hot water since then, and we regularly see sub 5C and occasionally sub zero overnight in winter. The system runs on offpeak so it often hits the cold time of night during winter.

Summer quarterly use is around 200kWh, ~2.2kWh per day, Winter ~300kWh, 3.3kWh per day. Family of 3-4, one is flying the coop.

On that basis, the Sanden should be a little better, but depends on use of hot water more than brand of unit at these numbers if you consider the above posters in Vic have Sandens running between 1 and 4 hours.

Posted Friday 10 Jul 2015 @ 1:28:08 am from IP #
alfresco24
Member

Thanks for the insights Bushwalker.
I won't be adding a J-Tariff circuit so running on the peak tariff will obviously cost me a lot more until such time as I install PV and set the timer accordingly.
Sanden claim the max Power consumption is 1kW (perhaps 1.2kW including the control system, standby and internal anti-frost heater). If my averaged daily hot water consumption is half the tank capacity then I should expect the Energy use to average 0.6 to 0.7 kWh daily.
I'll be very interested to see what the Power Factor is and therefore what the 'headroom' off the PV will need to be.
A key aspect to getting efficient with my home hot water consumption will be to stop my wife using it in the washing machine
My long term goal is add enough storage to take my home off the electricity grid within the next 2 years.

Posted Friday 10 Jul 2015 @ 2:57:38 am from IP #
Benny
Member

Try putting a secret plug in the HW pipe going in to washing machine ? But that could mean the washing machine heats up the water with its own element - so uses even more electricity than the HP. Then you need to disconnect WM heater....

Posted Friday 10 Jul 2015 @ 7:59:46 am from IP #
Bushwalker
Member

alfresco24 said:
internal anti-frost heater

A point of difference there with the Siddons then. The Siddons does not have an anti-frost heater, it uses a reverse cycle valve to defrost, consuming less energy in the process. I'm kinda surprised the Sanden has a resistance element.

If my averaged daily hot water consumption is half the tank capacity then I should expect the Energy use to average 0.6 to 0.7 kWh daily.

How will that work? The other Sanden users above quote between 1 and 4 kWhr per day, how will you use less than tezz who is a sole occupant and uses at least 1kWhr per day, which is pretty lean hot water use?

Running washing on hot water from a heat pump system is more efficient than an internal heater in the washer. Even more efficient is to do most washing in cold water...

Posted Friday 10 Jul 2015 @ 8:30:10 am from IP #
dmaunder
Member

The Sanden doesn't have a resistance element, and my monitoring shows it uses very close to a constant 1000w apart from the first 5 mins or so when it spikes up to 1500w or thereabouts. Mine runs during the day when temps are higher and is largely fed by PV. I haven't worked out a way to track the monthly import usage for it yet, still trying to see a reasonable way to calculate it.

Posted Friday 10 Jul 2015 @ 3:40:09 pm from IP #
Bushwalker
Member

Cool. So how does it defrost? Like the Siddons or something else?

Posted Saturday 11 Jul 2015 @ 12:56:42 am from IP #
alfresco24
Member

Sorry for the confusion Bushwalker, my phrasing may have misled you.
The Sanden does NOT have a heating element in the storage tank - it has a small heating element in the compressor/control unit that kicks in to keep the electronics and controls from freezing when frosts occur.
It's storage tank circulates the bottom cooler water to the top hot water, and therefore there is no stratification. The whole tank contains hot water. This also means I can size a slightly smaller tank than would otherwise be 'wise' with conventional gas or electric storage tanks.

dmaunder - I will have a dedicated monitor circuit on the Sanden and will be able to plot the power and energy use in 5 seconds and 5 minute intervals. I'll let you know the results after I've accumulated 4 seasons of data.

Posted Sunday 12 Jul 2015 @ 2:41:46 am from IP #
arttt
Member

if your hot water usage is low (and it looks like for the OP it is) then the cost of a heatpump system might not be justified. You may be able to get that same result cheaper with an electric storage system and enough extra pv to cover the usage.*
Its been a couple of years since i checked the maths and it depends on FiTs and if you can get the heating cycle to run when the solar panels are producing etc etc.

- I would work out my hot water usage in KWh (include tank losses)
- work out how many KWh that would be if a sanden unit was used.

then look at these 3 options:
option 1 - get a price on a sanden system supply and install and on the solar pv your thinking of putting in (sized to cover your sanden and anything else you want)
or
option 2 - get a price on a resistive storage HWS supply and install of the same size AND solar PV upsized to cover the additional KWh needed by the HWS (probably work with winter PV generation estimate for this).
or
option 3 - get a price on a resistive storage HWS supply and install of the same size AND solar PV upsized to make the same total price as option 1.

for each option
- make some adjustment for the extra grid power each HWS will use on overcast days
- make some adjustment for the excess solar PV available for use in your house or sold to the grid. Extra allowance if the house is left empty for long periods and all pv power can be sold.
- consider the lifetime/maintenance/warranty of components
- dont forget install costs - trades are expensive

At relatively low hot water usage options 2 and 3 come out ahead. At high usage option 1 comes out ahead. Where the switch over point is depends.

hope that helps

*you obviously need to have the roof space to install the extra pv

Posted Sunday 12 Jul 2015 @ 3:19:12 am from IP #
Bushwalker
Member

alfresco24 said:
Sorry for the confusion Bushwalker, my phrasing may have misled you.
The Sanden does NOT have a heating element in the storage tank - it has a small heating element in the compressor/control unit that kicks in to keep the electronics and controls from freezing when frosts occur.
It's storage tank circulates the bottom cooler water to the top hot water, and therefore there is no stratification. The whole tank contains hot water. This also means I can size a slightly smaller tank than would otherwise be 'wise' with conventional gas or electric storage tanks.

Ok, no worries. Still doesn't explain the outside coil defrost cycle though. A heating element for the electronics would be pretty low wattage, so not a big deal, but a heating element for the coil would be significant watts.

Elimination of stratification is a good feature.

Posted Sunday 12 Jul 2015 @ 3:32:10 am from IP #
alfresco24
Member

Thanks arttt
I did go through that exercise and you're right, but it's line ball.
In the end what influenced my final decision is that with a COP of 4.5 the Sanden uses far less energy to produce a full (smaller capacity needed) tank of hot water.

At this time I don't have any solar PV (due to existing poor staggered roof line & orientation) but am building a new garage that will allow me to place enough panels East & West to have the HWS draw energy during a very wide window.

The downside to the Sanden is the cost. It's by far the most expensive as a stand alone HWS, and the compressor unit is not very serviceable. If/when the compressor unit fails you have to replace the whole unit at a cost of $2k.

By the way I asked the energy retailers for their offers on a solution that involved passive solar HWS with electric or gas boost. In all cases their offers were 10-20% more expensive than buying the Sanden solution and installing with a good experienced plumber.

Posted Sunday 12 Jul 2015 @ 3:38:30 am from IP #
Bushwalker
Member

arttt said:
then look at these 3 options:
option 1 - get a price on a sanden system supply and install and on the solar pv your thinking of putting in (sized to cover your sanden and anything else you want)
or
option 2 - get a price on a resistive storage HWS supply and install of the same size AND solar PV upsized to cover the additional KWh needed by the HWS (probably work with winter PV generation estimate for this).
or
option 3 - get a price on a resistive storage HWS supply and install of the same size AND solar PV upsized to make the same total price as option 1.

Careful...

https://www.sa.gov.au/topics/water-energy-and-environment/electrical-gas-and-plumbing-safety-and-technical-regulation/plumbing-trades/residential-water-heater-requirements/water-heater-installation-requirements

It's a bit tricky, but the requirements state that if you have reticulated gas connection, you must install a low emission type water heater. If no gas connection, then you are able to install an electric resistance storage heater up to 250L or an electric instantaneous water heater up to 15kW (electrical input) and maximum storage capacity of 1 litre.

As the OP has an existing gas HWS, there is no option to install an electric storage HWS as a replacement.

Posted Sunday 12 Jul 2015 @ 3:43:06 am from IP #
alfresco24
Member

Good point Bushwalker.
State regulations may limit your choices. Check with your local Gestapo.

Posted Sunday 12 Jul 2015 @ 4:41:33 am from IP #
arttt
Member

alfresco24 said:
Thanks arttt
I did go through that exercise and you're right, but it's line ball.

Good to hear you looked at it and to know the result. It worked for me but on a very different FiT then is available now.

Bushwalker, I think the idea is in the spirit of the rules even if not to the letter of them. I agree an issue. I used an 'existing' HWS to avoid the issue.

The solar hot water systems are a bit over priced arnt they...relative to the heat pump.

One way to offset the heatpump price is to make it do double duty for some space heating. The sanden is obviously capable of it http://www.enter-shop.com.au/catalogue/c90/p705/cp4

Posted Sunday 12 Jul 2015 @ 12:36:18 pm from IP #
Bushwalker
Member

arttt said:
One way to offset the heatpump price is to make it do double duty for some space heating. The sanden is obviously capable of it http://www.enter-shop.com.au/catalogue/c90/p705/cp4

Thanks for the link, hydronic heating via PV stored hot water is on my list of possibilities.

Posted Monday 13 Jul 2015 @ 12:16:00 am from IP #
Johnnojack
Member

The above link once again reinforced my view that a lot of the 'Grand Design' architect designed homes showcased with all their glass walls and claims to be ecologically designed with low energy use actually are energy hogs. How can a house which houses just one family claim 'eco' status with a row of heat pumps sitting outside?
Incidentally placing heatpumps next to one another like that reduces their efficiency as the hot or cold air from one can be recirculated through the one next to it. Here's a pic of the worst example I have seen, the outlet from one HWS heat pump directed straight into the inlet of the next. Once I explained what was happening to the caravan park owner he elected to leave the centre one switched off. https://farm4.staticflickr.com/3707/19473547149_828bf984a8_z.jpg

Posted Monday 13 Jul 2015 @ 11:29:16 am from IP #
arttt
Member

Agreed, i was amazed to see multiple of these things. Definitely not efficient houses no matter what form of heating they have.

Theoretically one of these can produce about 100kwh of heat per day. Judging by peoples gas bills in canberra there are plenty of houses that would need 3 or 4 of these heatpumps to meet their heating load.

Once you have built an inefficient house and have done all the retrofitting that you can then having that last little bit of heating from a heat pump makes sense. Even better if you can make extra use of the DHW heatpump.

Posted Tuesday 14 Jul 2015 @ 12:11:14 am from IP #
dlvb19
Member

I was under the impression they multiple compressor systems were for in slab hydronic heating. Subjective as to whether that is 'wasteful' or not.

Posted Tuesday 14 Jul 2015 @ 1:49:00 am from IP #
Catopsilia
Member

alfresco24 said:
The downside to the Sanden is the cost. It's by far the most expensive as a stand alone HWS, and the compressor unit is not very serviceable. If/when the compressor unit fails you have to replace the whole unit at a cost of $2k.

I have a theory, which may be wrong, that the reason heat pump hot water services became affordable in the first place was because suitable compressors had been mass produced for home freezers. Compressors built specially for the tiny market for heat pump hot water services are bound to be pricey.

Posted Tuesday 14 Jul 2015 @ 3:33:15 am from IP #
alfresco24
Member

Dunno Catopsilia - The Sanden uses CO2 as the refrigerant/heating gas, it has a COP of 4.5 is extremely quiet ~38dB and is meant to be durable. Their tank is stainless steel, highly insulated, and has a 15 year guarantee - but the compressor has only a 3 year warranty.

Posted Tuesday 14 Jul 2015 @ 4:25:24 am from IP #
Solgen
Member

The compressors in heat pumps are standard, what is special is the heat exchangers that transfer the heat from the hot gas to the water.
COP of 4.5, who verified that figure? You would probably get that when the water is quite cool (bigger temp differential between the hot gas and the water) but as the water heats up the COP rapidly drops, at water temp of 50 deg, you would be lucky to have a COP of 2.0.

Posted Tuesday 14 Jul 2015 @ 11:32:56 am from IP #
Bushwalker
Member

Solgen said:
The compressors in heat pumps are standard, what is special is the heat exchangers that transfer the heat from the hot gas to the water.
COP of 4.5, who verified that figure? You would probably get that when the water is quite cool (bigger temp differential between the hot gas and the water) but as the water heats up the COP rapidly drops, at water temp of 50 deg, you would be lucky to have a COP of 2.0.

From the above link:

Looks pretty good 0C looks about COP 3.5, but I agree that heating to higher temps lowers efficiency.

The Siddons Bolt-On units show COP reduction at higher output temps:

I would think the Sanden would match or better the Siddons.

Posted Tuesday 14 Jul 2015 @ 12:37:28 pm from IP #
Greg
Member

Maybe this is a more efficient way to store heat -> http://reneweconomy.com.au/2012/solar-thermal-storage-a-concrete-cost-breakthrough-32659

Like to see the maths since concrete has about 1/5 the specific heat of water.

Posted Wednesday 15 Jul 2015 @ 7:21:53 am from IP #
Eco
Member

Greg said:
Maybe this is a more efficient way to store heat -> http://reneweconomy.com.au/2012/solar-thermal-storage-a-concrete-cost-breakthrough-32659

Like to see the maths since concrete has about 1/5 the specific heat of water.

Concrete is about 2.5 times the density of water - so volumetrically it has half the heat capacity. However the article say that the concrete is heated to 600 degrees - water can only go to 100 before changing phase - so can only store over a range of say 70 degrees(?) compared to 500 degrees for the concrete.

Posted Wednesday 15 Jul 2015 @ 11:07:32 am from IP #
Bushwalker
Member

Ok, I'm impressed, how do I get temperatures of 600 degrees from a solar collector on my roof, and how do I stop it from burning the house down?

Posted Wednesday 15 Jul 2015 @ 11:39:45 am from IP #
Eco
Member

Good question!

Posted Wednesday 15 Jul 2015 @ 11:59:07 am from IP #

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