Has anyone tried building their own in-slab Hydronic heating control system? We are looking into smart wiring (not that audio visual fluffy gimmicky stuff but real “smart” control for passive / sustainable heating and cooling methods. i.e. Automatic windows for purging, roof cavity ventilation, water and slab heating control etc). Most Solar Hydronic suppliers/installers have understandably been reluctant to provide advice on systems that do not use their own control systems. However, we have identified a number of pitfalls in existing “on the market” control systems. (willing to discuss if you are interested) . Has anyone had any experiences with DIY control systems? If you have, or know somebody who has then we would really love you to get in touch. Many Thanks.
Hydronic heating control systems
(5 posts) (3 voices)-
Littlehouse18
MemberPosted Saturday 21 Apr 2012 @ 4:11:08 am from IP # -
We will have quite an agricultural control system for our hydronics. Basically we are just using an aube thermostat to control a circulation pump which will circulate the water that otherwise sits in the storage tank. We are planning on using a tempering valve to mix in enough hot tank water to keep the circuit temperature about right. I don't really know if this will work but it's a start. I'm sure a smart system could do much more but time and talent may not permit me to proceed with one.
Posted Sunday 22 Apr 2012 @ 9:04:30 am from IP # -
Alison Gould
MemberI'm going to be piecing mine together using KNX (http://www.knx.org/) building automation components.
Will be using KNX-controlled windows etc., plus thermostats all around the house etc. to control the settings of the hydronic valves.
The coils are in the slab, and the vendor of those was quite happy to work with me interfacing the valves into his standard manifolds, or else have me supply a manifold with valves in place and he'd just run the heating pipes into that.
At this rate we probably won't connect it up until next winter, however I've done a lot of planning if you are interested in hearing more.Posted Monday 23 Apr 2012 @ 2:53:35 am from IP # -
Littlehouse18
MemberYes, we would love to hear more timreverb! It is very interesting to read you mention KNX because this is also the preferable type of automation we are interested in using in our new build (including window and Hydronics control) To elaborate on our first post, there were a number of pitfalls we initially identified with “off the shelf” systems.
1) It was recommended by one installer we use a 100lt thermal store. When we mentioned that we thought this might be a bit small we were informed that the Gas Booster would ensure the 100lts was always able to provide enough heating. So, if the gas booster runs through the night (for instance) , what role do the evacuated tubes play the following day (obviously rather redundant). We were then told that you could control the times that the gas booster ran by plugging in a $30 electric timer purchased from Bunning’s! (This was the solution for a system we were quoted over $15k to install).
2) The air thermostats seem to be quite an agricultural control mechanism and subjected to external temperature fluctuations and do not relate directly to the energy demands/supply of the slab. We are considering KNX temp. sensors to measure the water circuit return line temperatures. By comparing this with the inlet manifold temperature, we have a logical resultant of what the slab is actually demanding/absorbing (or omitting possibly).
3) Standard Hydronics systems have a safety valve to prevent overly hot water entering the system and jeopardizing the concrete slab. But what if we really want all that heat to enter a slab that demands it? Munter (2 posts above. Thanks munter) mentioned using a tempering valve to mix enough hot water to keep the water below a maximum temp. and to keep it running. We have looked into using a variable 3 way mixing solenoid that the KNX system could control, effectively mixing a percentage of return water with a percentage of available hot water .
4) We will be having about 6 different zones throughout the dwelling. All will have greatly varying demands (i.e. some with lots of winter sun and some with none at all). Standard Hydronics systems use one or two single speed pumps. There is going to be a dramatic difference between these pumps servicing one circuit opposed to running all six. Nobody seems to be using variable speed pumps that improve that could improve the energy efficiency.
Anyhow we would love to hear more about how your system is going to be set up. Just out of interest timreverb, do you mind letting us know which state/city you live in? Who is helping you with the KNX ?Posted Monday 23 Apr 2012 @ 4:55:13 am from IP # -
Alison Gould
MemberYou raise a number of questions about the heating aspect and overall system design that I haven't yet thought through myself - I have a quote from one company based on geothermal, and have seen enough statements that solar isn't worth the hassle due to not enough heat when you need it.
However I now suspect I'd actually go with air-source heat pump, enlarging out PV array to offset the usage. Therefore I haven't given a lot of thought to thermal stores.I have embedded temperature sensors in my slab, and each on-wall KNX thermostat control also has a temperature sensor. We will have 6 zones plus heated towel rails, which is around 12 loops in total (can't remember exactly - building the entire house right now so brain is rather taxed!). Each loop will have a separate KNX-controlled valve, and each zone has a separate thermostat. I believe I'll be able to balance the different heating requirements well, plus the house is a long E-W solar-passive design so almost everything gets good winter sun, and strawbale so the heat should stay in.
Your details around the actual design of the heating components are mostly advanced than mine - we rushed to get the coils in the slab during the build process, and most other thoughts are currently parked due to funding - the limiting factor as always.
I'm doing all the KNX work - I do IT for a living, and managed to get the basics all running. (I'm writing my own KNX controlling software too for phone/tablet interfaces, logging, reacting to PV output, etc. - this will undoubtedly get a heating component when I reach that point).
I'm just out of Sydney, a fair way from WA I'm afraid
Posted Monday 23 Apr 2012 @ 5:18:34 am from IP #
