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Home heating automation
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Here's the various pictures you requested deezell.....thanks for your time looking at this.
There doesn't appear to be any thermo on the HW cylinder as I can't see any electrical wires coming off the thank. Only copper pipes.
So, you have a fully pumped 3 zone system, 2 CH and 1 HW. You can currently operate these zones partially independently, by turning down either CH zone thermostat to cut off its pump, or by switching both off at the controller by selecting HW only. You can't select either/ both CH without HW being on also. The reason for this is simple. The boiler is fired by the same terminal on the controller that operates the HW pump. The CH switch and stats only operate the CH pumps. The boiler and HW pump must be on to provide heated water to the CH zones. This type of controller was used in gravity systems, and is characterised by this arrangement whereby HW will be on for all timing instances.
Your system has a third pump, and you say this is the HW circuit only pump. I would agree with this although there may be variations in how this is plumbed. What is important is that the CH zones can be made independent.
To have three independent zones in a heating system requires three different timed/stat controlled switched live (SL) outputs to each zones pump. It also require a SL to fire the boiler for any combination of the three zone SLs. Currently you have one timer zone, HW, which fires the boiler, and both your CH zone pumps require this to be on to supply heated water to the CH pumps. If you install a new 3 independently timed zone controller, you can't just combine the 3 SL outputs to fire the boiler as obviously each zone will then operate the others pumps. This is a shortcoming of all zone controllers, in that they don't provide a separate boiler SL which triggers for any zone SL. At most they have a mode switch to turn the HW zone into the common SL for boiler which is how your controller operates. This is not an issue when zones are selected by motorised valves, as each valve (opened by the controller zone SL), has a relay built in to send an isolated SL to the boiler. Any number of these SLs can be combined at the boiler to fire it, without affecting closed valves.
Pumps do not come with relays, so to combine the various pump SLs to a single one for the boiler, we need to use a relay box like this.
This lex box from NRG Awareness can combine 4 zone calls and provides a central wiring station to and from pumps, stats and boiler. About €115 , here,
https://www.nrgawareness.com/product/nrg-lex-system-control-module/
In my last reply I explained how normally a smart stat is simply wired in place of the mechanical stats like you have, and the old controller would be switched to always on. The problem in your case is that the boiler would be permanently on, cycling constantly until its internal stat cut out, while the HW pump would be going all the time.
You'll need an upgrade to your wiring, with the SL provided by 2 smart stats, and a HW stat or smart timed HW relay (or both), being combined to fire the boiler in all cases, while the individual SLs power each zones pump. Such an arrangement will give you 3 independent zones, and will allow CH independent of HW.
You should examine the pipework to determine if the 3rd pump is exclusively feeding the HW cylinder coil, as its possible this pump is a general circulation pump from the boiler, whose flow is then divided and fed direct to the cylinder and via the two CH pumps to the CH zones. If this is the case it complicates things a bit, in that HW is always a function of the boiler firing.
You have a number of options as to which brand of smart stat you chose. Some options depend on how independent your HW control really is, so I'll wait till you can figure you pump arrangements. Once again, a few pics would help.0 -
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Wow, a serious reply there deezell. Thanks for going into so much detail about what's required to achieve the correct firing if I want 3 independent zones using a new relay box. Not sure I'd have the confidence to wire that in myself, but my brother in law is a sparks so might call in a favour if I decide to go down that route.
Attached is a picture of my pump arrangement. Maybe that helps to answer if HW is possible as an independent zone form CH or always has to be on as a function of the boiler. Using the existing stats I figured out that both pumps to the right are CH. One was obviously replaced at some stage prior to me buying the house as its much newer.
If I was to back things up a little on this project. Do you know of any product that's available whereby I could just upgrade the existing control unit, keeping the current CH/HW arrangement, but the new product allows me do connect to it using an app so I can remotely turn on CH/HW as required?
Or am I limited to using a Smart Stat with the need to upgrade to an NGR relay etc?
Ok, it looks like you have 3 independent pumped zones. I can see the arrowed Non Return Valves (NRVs) on the CH zones. I dont see one on the HW pipes, this is probably deliberate to provide some kind of gravity or bypass circulation to boiler, otherwise there would be no flow circuit from boiler hot out back to cold if no pumps were operating to push open the NRVs. Pumps themselves when off are open to flow. In a motorised valved system there would normally be a small bypass pipe on the boiler, you may already have this. If there is no NRV on the HW loop, operating the two CH pumps while HW is off will have the effect of pulling the heating water backwards through the cylinder coil, effectively cooling it. This could be a nuisance unless the cylinder also has a cheap mechanical stat added to turn on it's pump (provided its timer is on). These are some of the plumbing issues in a pumped zoned system.
Your current setup always runs the HW pump when firing the boiler. I can see two wires exiting your controller on HW terminal 1, I'm betting one goes to the HW pump and one to fire the boiler.
As I stated earlier, the next generation controllers up from yours such as this, output a SL per zone,
one per pump or valve, but with a pumped system you need to combine these via relays to fire the boiler. These type of controllers are also available with internet apps and wireless stats, under the Ember brand, but they are not smart controllers, just app controlled versions of basic timers.
I referred to versions of the above which have a mode switch for gravity mode. In this mode each separate zone timer will turn on its SL, but the one designated HW will turn on for any timed event, so thus would replicate your current arrangement, HW on for any HW or CH timed event. I'd have to dig to find a current 3 zone controller with a gravity mode switch.
There is a discontinued system called Systemlink Homezone (I have one), which consisted of a 3 zone controller with a low voltage cable to a lex relay box. About €300, I see it now for €80.
https://www.mdoshea.ie/systemlink-homezone-3-zone-heating-programmer-and-controller
This is not a smart programmer, but you can incorporate smart stats in place of the manual ones. It also has a built in stat for the living zone, which can be used or disabled if you later fit a smart one. At €80 its less than the cost of the relay box alone, it could be a good starting point for you.
Final option is any combination of 2 smart stats with a HW option. Hive, Nest, Tado etc. You get 3 SLs from this and you connect to a relay box to get one SL for the boiler.
Now it may be possible using 2 Tado stats and the Tado ext kit to dispense with the relay box, as the Tado ext. kit can be programmed by tado support to operate in Gravity mode. In this arrangement the HW relay on the ext. kit operates for HW calls and also for calls from either of the 2 stats, so its connection is used to fire the boiler. The stats' own contacts are used to operate the CH zone pumps. You always have HW with CH in this case, as you currently have, but the wiring is minimal and your zones have full smart control. Its an option.
My recommendation? Get 2 smart stats, and get a mechanical cylinder stat. Connect all 3 to the first relay lex box I posted, the NRG one. Each zone will be independent, HW will fire the boiler according to the cylinder stat. If you want timing of the HW, use the respective smart stats receiver relay. This relay box is part of Nest, it's the optional ext. kit in tado, it's the 2 channel wireless receiver of Hive. Youll need 2 Nest kits, expensive, or 2 tado or hive stats with one of their ext kits/ 2 channel receivers respectively.
Sorry about the long winded reply, but It's important to paint a complete picture of options. It'd be easier if we were chatting in the pub with a beermat and a biro, but here we just have words.0 -
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