Heating System Control - any suggestions

tails_naf

The electrician is on to me about the heating system control. There are lots of ways to wire it up, and of course I want to figure out the best way to do it.

I was thinking of the following but would appreciate input - does it make sense, am making a mess of it...etc.

System:
60 tube solar.
oil boiler
2 300L tripple coil tanks (one for hot water, other is a buffer for underfloor heating/rads/towel rails)


Proposed Control:

1) Solar controller - this will ensure that the hot water tank is heated first. When this hits 70C at the top of the tank, it will auto switch to heat the other (underfloor buffer) tank - (this is all handled by the solar controller)
2) If the hot water tank is not warm by 2pm on a given day (via stat+timer) - oil boiler will kick in, and heat it up to 70, then shut off.
3) under-floor heating tank: IF the tank drops below 45C, AND the underfloor heating is looking for heat - start the oil boiler until tank is at 65C. (may also put a time of day when it can do this)

a few other things - if the hot water tank goes above 75, auto turn on heated towel rail pump, else turn them on a timer. don't really care about this tho.

the idea is to let the solar do as much work as it can. only call in the oil boiler if its really needed. Does this make sense?

Can anyone recommend a stat/controller that would be suitable, or have used with good results?

knx

What solar controller are you using ?

Wally Runs

No idea about controllers but would suggest that you have all of the them together in the main living area so you can see what is going on. I have the main boiler controls in the kitchen but the solar in the basement (beside the tank). I can see that the HW boiler has kicked in but I have to go the basement to see the tank temp and figure out why. Makes tweaking the system complicated.

Wolfhound14

I am thinking of a similar setup with the Solar and oil, but I am curious why you decided to go with 2 tanks? I am thinking of going with a larger stratified tank, maybe 1000L, with Oil and solar connected. In the future I may integrate a HP or replace the oil with a HP if it becomes more economical.

tails_naf

I went with two tanks as I may keep them at different temperatures.

I know you can get large tanks with different compartments integrated, but I didn't really see the advantage in this.

In fairness it's fairly hard to get good solid advice on these matters from the web. And every retailer I contacted only really wanted to give advice that made their product seem like the only sensible solution - so hardly impartial, sound advice. Most plumbers I talked to were fairly unaware of the technicalities and advantages of different systems.


I did hear recently that solar can consistently get a tank up to 25-30C all winter. So if this is true, I might actually get the solar to run the UFH by default, rather than the hot water. Sounds like i'd get 'free' heating all winter long, and only have to use the boiler for hot water.
The solar won't ever turn on in the winter for the hot water tank, as the tank would always be hotter than the panel.

Hard to know which one to go with by default!

ghoeky

I am a plumber, and have installed systems like what your proposing, in my experiance the best and most straight forward is a twin coil cylinder with solar and boiler connected if you have a buffer tank, and I have, dont expect the solar system to heat the house even if you have low temp UFH, the benifits will be minimal, as the heating will use up the heat in the tank very quick and then the boiler will kick in.On another note I have UFH in my house upstairs and downstairs and if i had a choice I woul have used rads or at least combine the two I always tell my clients now that its just not suited to our climate, and because of the reaction times its not ideal,you could have a lovely warm house on a cold day and later that day its warm outside and your roasting inside you may have to open windows to let the heat out, I found that you need very good control to have the house warm all the time.if you had rads you can control everything a lot better with almost instant heat anyway thats my opinion, and on control systems I have installed a system called Heatmiser its state of the art and not very expensive it gives you digital stats in each room and you control the whole house from a touch screen in say the kitchen it all runs over cat 5 cable and you can even control it remotely from a phone or internet.You can get manifolds and actuators to control rads just like UFH ,hope this helps.