Can the heating be automated using the temperature from TRV.

The TRV heads report to PC current temperature of each room, and also the target temperature, so theory if current is below target then I want boiler to run, the socket runs the pump for main house, so at moment the socket is timed to turn on at same time as programmer, there is no room thermostat in main house.

The granny flat has a thermostat, which turns on a different pump, but seems strange to have thermostat in the kitchen, there is no thermostat for domestic hot water.

So job one is swap all TRV's for new, as the wifi heads will not fit old TRV's I have 4 MiHome Energenie wifi heads which will go in main rooms, so office, living room and craft room, however I was going to fit the cheaper Terrier i30 heads in other rooms, as main idea is they stop over heating rather than ensuring hot enough, so can switch off rooms at times when not used.

Considering a Nest e for granny flat so we can remotely switch it on when expecting visitors.

However although I have the requirement as to if boiler/pump is required reported to PC, I can't see how to use the info to switch on the pair of sockets to control boiler/pump.

As far as I can work out I need to use IFTTT (if this then that) but as to how is another question.

Alternative method would be three programmable thermostats in parallel, so if any of three main rooms under temperature then the boiler runs, however three wifi thermostats rather expensive, so looking at hard wiring three thermostats. That may be the best method, however seems daft to require two thermostats per room, if we have a thermostat on the TRV why should I need a second in the same room?

Hive have just released smart TRVs that can trigger the boiler.

Thanks, that seems the way, and cheaper than Energenie.

Having the TRV heads control the boiler is "kind of" standard practice - I was under the impression that most, if not all, manufacturers included that ability with a radio receiver to switch the boiler as required. If they don't then I consider it an incomplete system.
Vestimi (new name for OpenTRV Ltd) say they will have a new one out to go with their recently released commercial offering. They had two versions of a boiler controller during their development and field trials stages.

For some suggestions down a different route ... well, one actually
If you replaced your DHW cylinder with a thermal store, you could control the boiler with nothing but the cylinder stat - then run both sets of heating from the store with modulating pumps (eg Grundfos Alpha). As the heating circuits are now separated from the boiler (the store acts as a large neutral point, hydraulically speaking) then you could just run the modulating pumps all the time and let the TRVs do their job - even down to zero flow rate.
You'd also get mains pressure hot water as a nice bonus An another bonus, you can get a very quiet system - none of that terrible valve noise most systems make as the TRVs close off and system pressure rises.

<rant on>AFAIK, there is not a single boiler manufacturer who makes a boiler compatible with a modern heating system without such a neutral point. Every manual I have looked at states a minimum flow rate which is typically whatever gives delta T of 20˚C at full power - and so a bypass is needed which more or less completely buggers up any idea of a condensing boiler actually condensing for much of the time. Maybe one day boiler manufacturers will get into the late 20th century, they don't seem to have set their sights on the 21st century <rant off>

This does ideally need electronically controlled TRVs as they can have an integral term to get around the (required) limitation inherent in a thermal wax head of having a significant temperature band between open and closed. In effect, in summer the room could need to be several degrees warmer before the rad went off completely, or several degrees colder in winter to get the rad on full output. A well designed electronic head should be able to apply an integral term so as to remove this limitation - integrating a different valve position for the same room temperature depending on the required heat input to maintain the temperature.
I'm currently looking at a thermal store for our house - there's room where the old cylinder used to be, but with the combi boiler (work of the devil ) in there, there's only room for a 350mm dia cylinder and there aren't many of those around. One idea I've been toying with is using the feedback from the Radbots (the name they decided to give the commercial OpenTRV heads) to control the CH flow temperature. The feedback available via radio includes valve position, so I had in mind using this to control the flow temperature - if valves are "fairly open" then higher temp needed, if they are "fairly closed" then lower temp needed, and use an electrically controlled mixing valve to get the flow temperature the algorithm comes up with. The next step being to controll the boiler to maintain the store either to satisfy the need from hot water (upper part of tank) or heating (lower part of tank - only needs to be a little over the CH flow temp needed).

EDIT: Here's a schematic of the system as installed in the flat. The TMV on the boiler loop is to control the return temperature into the boiler so it doesn't condense and rot itself to bits before I work out exactly what to fit in it's place.

Oh yes, personally I would not consider anything like Hive - but then I value privacy and security
Like most of the "smart" stuff, Hive is built upon connecting you to outside servers - and some functions don't work without that. Can't say for Hive specifically how much is dependent on an external server - it varies from system to system. It also means you are at the mercy of the vendor as to how long it works, and in some cases whether it suddenly changes how it works
Of course, Nest is even worse - being owned by Google who have a business predicated on invading your privacy (second only to FaecesBook). Note that Google bought Revolv a few years ago - and then shut down the servers, turning Revolve Hubs into ornaments.
Microsoft kicked Zune users in the privates a few years ago, they've recently told users of it's ebooks service that it's being shut down - and users that have purchased ebooks will lose access to many (most ?) of them.

Personally, I'd look very carefully at what you are getting into before going with any of these systems. in particular, what is the product (with Nest, you are the product ), and how much the device is dependent on external connectivity (both for routine operation and setting up).

I have fitted Nest Gen 3 and have tied the four existing electronic heads to it, although boiler called 18-25 I would say in real terms it's not modulating, at the moment waiting for plumber to complete fitting valves.

The main problem is to change plumbing other than adding motorised valves means ripping up floors, so want at least one Winter in house to see what is really required.

Last house was well insulated, and we found temperature was slow to change, turn heating off at night, and 8 hours latter even on coldest days temperature only dropped 4°C so the main thing was to ensure home never got too hot, as once too hot, took ages to cool again.

I looked at Hive, but it would not work, as the relay contacts are internally connected to line, and I need out from common and in at N/O and N/C contacts and it can't be configured that way. Nest allows me to configure as I want.

The house has had a garage converted to granny flat, and plaster board and false ceilings hide the original pipe work, the circulation pump for house was on a 13A plug, the programmer had a supply, and then two wires to boiler room/kitchen in flat. It was impossible with hard wiring to select between room heating and DHW or just DHW without going out side and walking around the house and into flat and plugging in or unplugging the pump.

So Nest heat link now in granny flat, and the original feed wires work the thermostat in the main house hall. I have programmable thermostats down stairs now, except for kitchen, want to fit some upstairs, the EQ-3 Bluetooth Smart Radiator Thermostat (UK) 142461D0 at £15 each seems best option, although they will work with phone, unlike the Energenie they can also be manually set, and main thing is to reduce temperature of up-stairs rooms, think I need 5 if doing kitchen as well.

The flat will have thermostat set to stop frost damage only most of the time, standard TRV good enough.

However I have a problem, if all TRV close, then pump could cavitate, not sure if a by-pass valve will work with pump on the return? Can't turn DHW off, as that's how boiler cools down, so boilers OK, but that does not help protect the pump.

SimonH2 said:

<rant on>AFAIK, there is not a single boiler manufacturer who makes a boiler compatible with a modern heating system without such a neutral point. Every manual I have looked at states a minimum flow rate which is typically whatever gives delta T of 20˚C at full power - and so a bypass is needed which more or less completely buggers up any idea of a condensing boiler actually condensing for much of the time. Maybe one day boiler manufacturers will get into the late 20th century, they don't seem to have set their sights on the 21st century <rant off>

Click to expand...

Well said

A good valid and accurate "rant".

Yes good rant, also noted most combi boilers are selected to heat the DHW rather than the central heating, this house is half again size of last house, boiler 25 kW where last house was 28 kW, there is no way the house even needs 25 kW, a 2 kW fan heater set to 1 KW is enough to heat every room, so 8 main rooms so around 10 kW would be ample. This house oil so only modulates to 18 kW but last house gas modulated to 8 kW but even heart of winter boiler would cycle, so 8 kW more than required.

However my [rant on] is the wireless thermostat, unless tied to TRV the wall thermostat is not to control room temperature, but to switch off boiler as summer approaches, it stops the boiler cycling off/on to test if required, the wall thermostat should be mounted in a room kept cool, so it can turn off when room around 17°C to 18°C so house is not heated when likely a warm day, and really one want a high hysteresis so once a warm day is detected it will not turn back on too soon, the room should have no outside doors, or alternative heating, and on the ground floor if possible. OK many houses you can set A1 and in spite of having an outside door one uses the hall, the TRV controls each room temperature, the wall thermostat just stops cycling as summer approaches. With a wireless thermostat one also needs a fail safe, the Honeywell Y6630D is an example of a wireless thermostat with a fail safe, the Horstmann HRFS1 is an example of a wireless thermostat without a fail safe. i.e. if the battery becomes depleted the heating can stick in the on mode. But as you go to thermostats with fail safe, one also goes to thermostats with anti-hysteresis software, so the thermostat starts to switch boiler off/on before the set temperature using a mark/space ratio, however for a thermostat in a hall you don't want anti-hysteresis software, the old thermostat with the little heater inside and the neutral not connected is ideal in the hall, in winter it should never turn off, all control is with the TRV's. You can't buy a wireless thermostat without anti-hysteresis software that has a fail safe. Only option is hard wired.[rant off]

Not sure if you call my thermostat in this house hard wired or wireless? There is a pair of wires from heat link to thermostat, it seems reading about the thermostat the pair carry more than just power, it was selected because of existing wiring, it was easiest way to link main house to flat so the heating could be controlled without walking outside, and down a set of steps into the flat, likely not best wall thermostat, but better than lifting floor and dropping ceiling to thread wires. So fitted Nest Gen 3, not to get control with phone, but so did not need to rip up floor.

Out of interest this is the control panel on phone, the "Flat Heating" was a temporary measure it was a wireless 13A socket which I plugged the pump into, now no longer required, there are two radiators in the living room, so two TRV heads clearly set to same program, kitchen and shower/toilet do not have electronic heads, all other rooms on that floor do. I was going to call it ground floor, but it's only half a ground floor, the other half has the flat below it, house built on the side of a hill. I can walk out of patio doors in living room and look down onto top of apple tree.

ericmark said:

I looked at Hive, but it would not work, as the relay contacts are internally connected to line, and I need out from common and in at N/O and N/C contacts and it can't be configured that way.

Click to expand...

Add a relay - stat turns relay on/off, relay has whatever contacts you need.

However I have a problem, if all TRV close, then pump could cavitate, not sure if a by-pass valve will work with pump on the return? Can't turn DHW off, as that's how boiler cools down, so boilers OK, but that does not help protect the pump.

Click to expand...

In your case, might be able to use modulating pump as the gravity loop for DHW should protect the boiler. Noted on the Grundfos site that it said minimum 1 bar inlet pressure for 82°C flow - but return from rads should be quite cool. A bypass & standard pump might work as long as it's set to a low enough pressure to maintain positive head at the pump inlet. On the other hand, swapping the pump is probably less work than altering the pipes for a bypass valve
Would it be practical to move the pumps to the flow side ?
BTW, is your boiler condensing or not ?

Not seen any drains outside, so assume not condensing, but instructions say it is. At 18 - 25 kW can't really see condensing working, says it switches off at 81C and back on at 55C that seems to hot for condensing.

ericmark said:

... most combi boilers are selected to heat the DHW rather than the central heating ...

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I'd change that to "almost all" are selected for hot water demand. In the flat, the boiler is nearly 30kW and only ranges down to 9kW. In the depths of the Dec 2010 cold spell (not getting above freezing during the day) I measured* the heat demand for the flat and it was only 2kW. Even with such a grossly oversized boiler (needing a permanently open bypass to cope with TRVs), the DHW flow rate was "not impressive" - as in, hoping the bath would not go cold faster than it's filling

* Ran the system from the immersion heater in the thermal store, let everything settle for a day, then read the meter, and read again a day later, then do "units / time" to get average heating load.

No way on earth would you get a condensing combi that actually provided DHW and could work in condensing mode when heating that flat.

I do have an idea which involves splitting the main and condensing heat exchangers (hydraulically, only needs tee'ing into the link pipe internally) so the pump can pump round the main heat exchanger, but only that actual flow from the system goes through the condensing heat exchanger. I just need to put a drawing together and contact the various technical departments and ask "which of your boilers is suitable for this ?" - to which I expect the answer will be (to all intents) "are you having a laugh ?"

ericmark said:

Not seen any drains outside, so assume not condensing, but instructions say it is.

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Could have an internal drain - anyone with any sense will keep the drain internal if they can, avoids all those "boiler packs up in cold weather - get the hair dryer out" frozen pipe problems. Indication would be a (typically) 21mm (3.4" in old money) drain pipe coming out from the boiler. On wall hung boilers, it's typically at the bottom. But when I was looking at floor standing ones at church, the manual I was looking at showed it coming out higher up - condenser heat exchanger just "tacked on top" of an old non-condensing model.
When I bought the house next door to the flat the boiler wasn't working - cold weather, external drain First thing I did was move the drain to the kitchen sink drain. And when I was helping a friend do up his house, some clueless f**kwit had just put the drain outside the garage where it would be slowly eating away at the foundations Changed that to go into the kitchen sink drain.

says it switches off at 81C and back on at 55C that seems to hot for condensing.

Click to expand...

AIUI about 54˚C is the limit - for gas. Oil may be a degree or two different. I agree, at those temperatures it isn't going to be condensing at all.

I am told very few oil boilers are condensing. But in the kitchen, so it could use internal drain. Boiler a Greenstar Utility 18-25 and the installation instructions I down loaded say it's a condensing boiler, but maybe I have wrong instructions?

I know what you mean with hair drier, and also over time the U bend seems to fill with rubbish with gas boilers, I would once a year empty it, once it caught me out once.

Problem is this house does seem to have been owned by some one clueless. Old house even a month before we left, sale all agreed, I was still doing maintenance on it, this house it looks as if for last 5 years nothing has been done. They swapped a window where we noted a crack in double glazed pane, but it was cracked again before we moved in.

Decking all rotten, steps loose, and in some places rotten, the main house consumer unit is trapped between original ceiling and new false ceiling with a small hole just big enough to put hand in and turn off power. The motorised valve for house was plugged into a socket in the flat, no control at all. So would not be surprised to find condensate going into main drain.

Yeah, I know what you mean about inheriting someone else's "clever ideas" - I've got similar issues here, but when I looked at the place I could see that there was a lot to correct.
As to the boiler, it might be (a smaller model) the one I was looking at - the pictures look vaguely familiar. If you look at the diagram on page 7 of the manual, the condensate outlet is item 22, part way up the rear right hand corner.

My parents had a breakdown due to clogged trap. On their boiler, the trap was in a "very awkward" position, especially with the boiler mounted fairly low on the wall. The BG engineers had never cleaned it, and over time it had virtually clogged with aluminium oxides from the corroding heat exchanger that had previously been replaced. Come that very long and cold spell at the end of 2010, the condensate production exceeded what could flow through the trap for long enough for it to back up and trip the boiler out. Dad, being one to "say what he meant", had some quite strong words to say to BG about the lack of maintenance on this item

Sorry. Going back to the original post, why don’t you just use evoHome? You get the TRVs and multiple zoning options with relay boxes?

If you want to plug it into other systems, just run it with homebridge.io - we have Nest with Tado TRVs and use HomeBridge to connect it all to the rest of the HomeKit enabled stuff.