How to best heat the SLAB ?

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Re: How to best heat the SLAB ?

Postby tonyruff » Fri Jun 01, 2018 2:41 pm

I think hydronic heating would be one of the most viable ways to heat the SLAB. Also great if anyone in your family has allergies as this type of system doesn't blow particles around, and you get a consistent comfortable flow of warm air throughout your rooms. I used a company called http://www.hydronicsupplies.com.au/ Mark there was super helpful and I'm sure he could provide advice on evacuated tubes and heat pumps and other options to customise something that is best suited for your specific situation.
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Re: How to best heat the SLAB ?

Postby Gordon-Loomberah » Fri Jun 01, 2018 3:40 pm

hmm, talk about raising a thread from the dead! Last post Wed Nov 18, 2009
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Re: How to best heat the SLAB ?

Postby munter » Fri Jun 01, 2018 3:48 pm

10 years on and its about time to revisit the topic. Since my last post in this thread I have commissioned our solar slab heating. It worked poorly for a couple of years with various different configurations until I hit upon the special combination last season. Now it works reasonably well. 55 heat-pipe evacuated tubes, a single circulating pump and about 100m2 of tiled slab. The feeling of a warm slab underfoot on a cold night is fantastic.
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Re: How to best heat the SLAB ?

Postby Gordon-Loomberah » Fri Jun 01, 2018 3:57 pm

Do you have any (hot) water storage in the system, or does the slab provide all the heat storage?
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Re: How to best heat the SLAB ?

Postby munter » Fri Jun 01, 2018 4:04 pm

No separate hot water storage in the current configuration (just a small balance tank of <20L to ensure the pump always has feed water). Earlier configurations did have water storage (300L, 400L) but I had problems with these earlier attempts. I suspect that the deletion of storage has helped minimise standing heat losses and maximises collection efficiency as it keeps the maximum temperatures low. It has also simplified the system controls as there is now just a single circulating pump which is controlled by the collector/return water temperature difference. The reaction times of the slab are so slow that it doesn’t really matter than I can’t separately control the circulation through the slab and the circulation through the collector manifolds.
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Re: How to best heat the SLAB ?

Postby tonyruff » Fri Jun 01, 2018 4:22 pm

10 years is the perfect amount of time to bring a thread back from the dead lol! Good to hear Munter that you finally worked out a combination that works well! Agreed, there's nothing better on a winters night than feeling the warm slab under your feet...especially when enduring a 3am walk to the bathroom! :D
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Re: How to best heat the SLAB ?

Postby australsolarier » Sun Jun 03, 2018 8:40 am

55 heat pipes are a bit on the lower margin trying to heat a house.
just wondering what happens to the system in the summer when you do not want to heat your house.
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Re: How to best heat the SLAB ?

Postby Gordon-Loomberah » Sun Jun 03, 2018 8:47 am

australsolarier wrote:55 heat pipes...


Indeed, I was using 78 evacuated tubes with hydronics heaters in the house, and it was enough in sunny weather, but no good when raining/heavy overcast for more than a day. We've since installed a wood heater and use the hydronics heat via a heat exchanger for adding heat to the house hot water (30 evac tubes) in extended cloudy weather, and I plan to also use some heat from it in the bathroom.
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Re: How to best heat the SLAB ?

Postby Warpspeed » Sun Jun 03, 2018 11:15 am

One of the basic problems with slab heating is that its very slow, and really must be kept running continuously twenty four hours per day if its going to maintain a reasonable comfort level.
For that reason its going to be pretty power hungry no matter what the energy source.

My strategy would be to run the slab only to provide absolute minimal tolerable background heating, and employ some quite separate method of bringing individual rooms up to full comfort level very quickly, and only as required.
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Re: How to best heat the SLAB ?

Postby australsolarier » Sun Jun 03, 2018 12:31 pm

warpspeed,
ever heard of the heatsink effect?
obviously munter's system is not that much different from the heat sink behind the northern window.

as for solar hot water heating as compared to pv solar heating:
i have both. 100 heat pipes and 3000l storage. 20kwp solar pv. with hindsight i probably wouldn't build the hydronic system anymore. pv works much better in difuse and cloudy light. it is much easier to install the aircon. easier and probably cheaper to install the pv system. also there are no leaks , etc.
having both, i mostly heat with the aircon. but the stored hot water comes in handy when there really is a dark cloudy day. and it is easier on the battery bank early in the morning.
with the hydronic space heating, i had to light the fire between 16 and 45 days a year. the pv brought this down to zero, though light the fire just to burn off some wood.
(for fairness' sake i am at the coast, quite temperate and the house is insulated above average and makeshift double glazed.)
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