Hi,
We are building a home with in-slab hydronics in Norh Central Victoria (Castlemaine region) and I just found out that the Sanden C02 heat pumps that were meant to heat the slab according to the supplier in fact are not suitable for hydronics (Sanden confirmed this). What are suitable heat pumps (designed for hydronics) that would have a good COP at low temperatures in a cool climate, or what alternatives might there be to consider?
I'm grateful for any feedback!
Cold climate heat pump for in-slab hydronics
(24 posts) (10 voices)-
Henriette
MemberPosted Tuesday 16 Aug 2016 @ 1:50:13 am from IP # -
Your question is a good one. When Sanden’s CO2 heat pump was released it was indeed marketed as being suitable for use with in-slab hydronics but there must have been problems because I now see that they now preclude that kind of use. Perhaps there was a misunderstanding with the importer? Who knows – anyway, what it means is that you need to find an alternate heat pump or risk a non-warrantied Sanden installation.
I took the cheap route and sourced a 7kW heat pump from ebay. It was old stock of a non-descript brand who I can find barely any trace of on the internet. The price was right and the system seemed about the right capacity so I went ahead with it. We didn’t anticipate much load anyway as we are in Sydney. What I have found is that it is really intended for use in even warmer climates (think tropical SE Asia) and that it struggles somewhat to keep up when the ambient temperature is low. You will not likely find another one like this but in case you are googling, the brand of ours was Taitron. Another issue I found in relation to the intended environment of the unit was that my compressor would stall if it was left to cool down to sub 10 degree temperatures. A stalled compressor drew massive current until the circuit breaker tripped which shut down the whole system. The fix to that problem was to install a crankcase heater which uses a resistive electric heat element to keep the compressor warm. It’s a little ironic that we were forced to install resistive electric heating to keep our heater warm enough!
Anyway – that’s a long story that doesn’t help you much but does perhaps provide a little bit of a heads-up as to the sorts of issues you could experience if you take short-cuts like I did during system installation. As for where you should look – one supplier names Skyline energy appears to have some experience in the area. They have, at least, been around for a few years now which is more than you can say for many importers of heat pumps who pop up and disappear with alarming regularity. They also have a website which shows more than just vapourware so probably have some practical experience. I have no direct experience with them or their products though. The current gold standard appears to be the Daikin Altherma but I understand that its a pretty expensive option.It’s a tricky market to buy into – good luck and may you make a better go of it than we did!
Posted Tuesday 16 Aug 2016 @ 2:41:19 am from IP # -
Henriette
MemberThanks munter for your feedback. Yes, I have come across both skyline and altherna in my searches today, so I will look into those as alternatives but worry that the costs may be prohibitive. As it appears I will have to establish a way of weighing up extra upfront outlay costs vs greater or lesser energy savings, so will probably need to contact the manufacturers for some more specific info on COP at low temperatures. Thanks again for your feedback, hope your unit will last you well & effectively for a long time!
Posted Tuesday 16 Aug 2016 @ 4:08:34 am from IP # -
aoliver
MemberCheck Renew Issue 135 April?June 2016 page 81 for Hydronic Suppliers Summary. I went for the Intaflow Heat Pump only because it was supplied with the kit I purchased. I'm a bit disappointed in the efficiency with a COP of about 2.4 but if I had a choice would have looked at Tivok Energy or Nibe. The price for the Daiken Altherma was about double what I ended up paying.
Posted Tuesday 16 Aug 2016 @ 6:17:26 am from IP # -
axess
MemberHenriette,
What about another fuel? Would a wood or pellett fired boiler be more appropriate for you if you would prefer not to use either LPG or Natural gas?
Is your house pretty tight and well insulated? Perhaps you could make do for the winter heating season with less demand for wood or pelletts by reducing the overall heat loss with a tight, well insulated build.
Or how about the skirting board heaters combined with a Siddons heat pump?
Posted Tuesday 16 Aug 2016 @ 9:03:24 am from IP # -
Henriette
MemberYes, I have considered whether a pellet heater might be suitable but thus far we favor the heat pump scenario since it has the prospect of being supported by a pv solar system in the future. And since the heating coils have already been laid we will not switch to another space heating setup. I don't know much about pellet heater running costs and the upfront/installation costs but from a brief look it appears a heat pump would be more economical, I could be wrong though. Slab conditioned size is 230sqm in a 7.4 star rated build.
Posted Tuesday 16 Aug 2016 @ 10:51:10 am from IP # -
Alwyn
MemberWe have gone with systems supplied by http://www.skylineenergy.com.au/, Sean and Pete are extremely helpful and will come up with a systems I am sure will do the job nicely.
We are using separate Heat Pumps for in slab Hydronic heating and for Hot water.Solar PV panels and will compensate for power consumption. NO GAS.
All the best with your project.Posted Tuesday 16 Aug 2016 @ 10:32:03 pm from IP # -
Alwyn
MemberOh and by the way, we also installed 2 electrical power phases to the house as the initial loads when the heat pumps start can be quite high. Thus the heat pumps and air-cons will be on their own circuits and the remainder of power and lighting will be on an other. This scenario is not always possible, you would need to check with your power supplier. Anyhow you can never do to much research.
Cheers, AlwynPosted Tuesday 16 Aug 2016 @ 10:37:02 pm from IP # -
Henriette
MemberAlwyn, we are in the same situation, no gas. We too will run hot water and slab on separate systems. It does look like skyline have the right type of heat pumps for our climate, so I'll get in touch with them soon. Have to check what the power situation is though, so hopefully having to run the slab heat pump on its own circuit will be possible. Otherwise we'll have a problem (we also will be going induction cooking, same reason: no gas). May I ask you how your skyline heat pumps perform in winter, e.g. COP at very low ambient trmperature..?
CheersPosted Thursday 18 Aug 2016 @ 3:43:35 am from IP # -
Alwyn
MemberHello Henriette,
Would love to be able to give you some performance assessment but our home is still under construction.
The reason we went with Skyline was they were the only ones with the expertise to provide what we were after. Unfortunately there are plenty of providers stuck in the old world and some struggle to grasp the newer technologies quickly.
If you are not running Reverse Cycle A/C as we are you might be able to get away with having only the one phase into your property.
PM me at any time if you have any other questions or queries.
All the very best, AlwynPosted Friday 19 Aug 2016 @ 12:57:56 am from IP # -
Alwyn
MemberHello Henriette, From my understanding the benefit of using heat pumps over Solar thermal technology is the efficiency is all year round.
The disadvantage for solar thermal (like the current breed of solar hot water) is that in our cool climate we only get that advantage of sun during the warmer months.
Hence the reason we have gone with heat pumps and to supplement energy consumption with solar photo voltaic panels on the roof. PV panels only need light, not heat from the sun to operate efficiently.Posted Sunday 21 Aug 2016 @ 3:08:49 am from IP # -
nicholas
MemberHi Henriette- I have one going in now, it's calculated to have a 96% solar thermal contribution. I love the idea of stabilising massive thermal mass this way and beng able to open the doors and feel the outside- nature...
It works in Germany so in Australia in even cloudy conditions it's very effective.
Posted Sunday 21 Aug 2016 @ 1:37:21 pm from IP # -
Henriette
MemberThanks again for your input Alvin and nicholas. Initially I was quite dismissive of solar thermal as an option as I was of the understanding that this may not be efficientenough in Victorian cold climates. However, looking into it more is making me think... There is a system that combines heat pump and solar thermal (evacuated u-tube collectors) that appears to share some ground with how your Solvis units work, nicholas. It's by Tivok and looks like it might suit our needs. The original idea (2 years ago) was to run the slab & hot water on Sanden C02 heat pumps (COP 4.5), on separate circuits of course (at the time these heat pumps were promoted as suitable for heating) and to install pv panels later down the track to run the heat pumps of solar power whenever possible. The pumps were going to draw a total of 4kw power (1 kW for hot water,the other 3 for slab), so a PV system would need to be 4kw upwards if it was to run anything else as well in winter. Now, the Tivok system could run the slab (230sqm conditioned area) on 2x 7.2kw heat pumps (drawing 1.8kw each) to deliver a comparable heating output, with the benefit that potable hot water would be generated via an inbuilt in-tank heat exchanger. To offset the running cost of the heat pumps originally, as said, the idea was to install a pv system later down the track. I'm wondering now though if it would make more sense to integrate some u-tube collectors into the system (since the Tivok system is designed to be run as a hybrid)) and utilize solar thermal to an extent. We would still have it combined with heat pump, but maybe that could reduce the size of the heat pump system or at least reduce how often they need to be run? When I'm comparing costs for solar thermal and pv I wonder if pv is worth the outlay if in winter pretty much all of its capacity will be swallowed up by heat pumps, and if weather is unfavorable we still need to rely on heat pump running on grid and the associated costs... Seems more economical to integrate some solar thermal into the system now, or am I making a thinking mistake?
Posted Monday 22 Aug 2016 @ 12:04:38 am from IP # -
The integration of solar thermal should yield benefits but can be tricky to implement. Our system has 55 x 1.8m evacuated tubes bolted to the north side of our house where they can collect plenty of winter sun. Collector area is approximately 5.9m^2 and our heated floor area is about 100m^2. At the moment they are sitting disconnected as I haven’t had the time to do it properly. Keep in mind that you need a solar controller, pump and an appropriate storage tank to make it all work. When I had the system running originally it didn’t seem to capture quite as much heat as I had hoped and could barely heat a tank of water in a day. With limited free time I haven’t had the chance to de-bug the system sufficiently to warrant connecting the pipes back up yet.
Posted Monday 22 Aug 2016 @ 2:21:16 am from IP # -
arttt
Membermake sure you check the performance of the heat pump at the likely operating temps. You should be able to get a graph of cop v outside temp. Note for some units the cop drops significantly. You need to factor that into your system sizing and running cost calculation.
For example (not picking this as a good or bad example) the tivok unit you mentioned has a cop of about 4 at 20c and more like 2 at slightly negative temps. The full graph is in one of the manuals on their website.Posted Monday 22 Aug 2016 @ 1:13:23 pm from IP # -
Henriette
MemberYes, the COP declination of heat pumps in cold ambient temperatures is an issue. I've looked at the graphs of several pumps to compare their performance but haven't yet found one that can rival or come close to a CO2 heat pump. Unfortunately Sanden's are no longer sold as suitable for hydronics. If I have overlooked any high performing heat pumps I'm grateful for suggestions! On the upside, since we only need to heat the water to a lower temp, say 40-45, for slab, any pump will have a higher COP at that range when compared to having to heat up to 55-65 degrees.
Posted Monday 22 Aug 2016 @ 2:17:14 pm from IP # -
After balking at the price of any Australian based retailer I purchased a heat pump (~10KW, single phase, draws 2.5-3KW) direct from China. It has been in place for a year now and it's great - runs for 3-4 hours a day on our off peak 2 meter so running costs are quite low.
All up the cost to get it to our place was around $3K (the unit was $2K, duties etc were $1K). The supplier had a number of other options but any larger would require three phase power.
Obviously doing it this way you're taking on the risk & responsibility of warranty issues and servicing. Plus you'll need to find a good plumber who can work with this kind of gear.
Posted Wednesday 24 Aug 2016 @ 12:00:03 am from IP # -
FenceFurniture
MemberAny chance of an update on this thread, 12 months later? Interested to hear how munter and Henriette (and anyone else) have faired with their systems.
Posted Tuesday 12 Sep 2017 @ 5:40:01 am from IP # -
Hi FF. I revised my system again this season. I removed the heat pump completely and now just run a single circuit from collectors straight to the floor. The floor has such large thermal mass that the return water is a relatively constant temperature so the collector panels are always warming water up from a relatively cool starting point. Typically the collectors add around ten degrees of warmth to the water and that is all absorbed by the floor during its trip around the circuits. I now have no boost or back-up heat supply in the circuit at all so I need to use other heating if there is a cold cloudy spell but because I am in Sydney, the temperatures aren't too low anyway.
I removed the heat pump because it just seemed to draw so much electricity that it wasn't worth it. It also didn't seem to produce all that much heat. I think it was a poor model selection (by me) that meant the unit was not really right for the application. I am now much happier just running on the solar floor. I've started blogging about it all again after a long break. The site is here:
https://renovations08.blogspot.com.au/Posted Wednesday 13 Sep 2017 @ 12:26:21 pm from IP # -
Samuel J
MemberHello all, I am wondering if any of you folks have heard of the new Q-ton air to water CO2 heat pump from Mitsubishi Heavy Industries. It is supposed to be capable of water temps of 60 to 90 degrees. The video on YouTube shows it working at a building in Japan - covered in snow.
I have a hybrid mud brick and reverse brick veneer house that I renovated with wall panels for heating. Location Melbourne. The original plan was to use condensing boilers but the cost of bringing gas to the house was prohibitive as was the cost of running from LPG.
Posted Friday 1 Dec 2017 @ 1:04:01 am from IP #
All the best with your build!
