Why do I have so many thermostats?

[therafox]

Hey folks, I just recently moved to the UK and the way heating systems work here is new to me - apologies if this is a dumb question.

In my current flat, I have an immersion heater which consists of an unvented indirect cylinder (TI120P4) for both hot water and underfloor heating. This is connected to a Danfoss TP9000 which is right next to it.

My ultimate goal is to replace this with something smarter (Hive or Nest). If I understand correctly, the TP9000 is the "brains" behind the heating - based on the temperature and current time, it controls two motorized valves (one for hot water, other one for heating) that are part of the cylinder. If I were to install a smart thermostat, I'd remove the TP9000 and wire the new one to control these two valves based on a wireless temperature sensor I'd put in my room.

This is just my understanding - if I got anything wrong so far, please correct me!

Now, here's what confuses me: in addition to the TP9000, I have three more Emmeti CS11 thermostats - one in my bedroom, one in the living room and one in the hallway. And I also have a Danfoss TS2 in my bathroom. How do these relate to the TP9000? I'm assuming they are feeding the current and target temperature of each room, but I'm not sure I understand how exactly the TP9000 works with this? Specifically, if I understand this heating system, there's only one on/off switch for the heating in the whole flat - it can't actually control the heating in e.g. my bedroom separately. Is it just doing something simple like "turn on heating if at least one room is below target"? Or am I missing something here? What confuses me specifically is that, with Nest or Hive, I'd only have one thermostat, so I'd basically need to get rid of all three Emmeti, correct?

Thanks in advance for helping me understand how this system works!

 

[Bodd]

Hello Fox
Welcome to the UK

If you have underfloor heating: you would have a stat for each zone.

You may have:
Zone 1 = Hall
Zone 2 = Bedroom
Zone 3 = living room

The Emmeti CS11 I think is Thermostatic progamer for that individual room.
The TP 9000 would be I thing general master programmer that would also control the Hot water.
And so on

You have control of each zone.si if you have a spare room, you may want to close the door and not heat thst room to save energy and money.

the kitchen may be warm enough due to cooking so you may not want that on.

in the summer you may only want the bathroom on first thing in the morning.

Where did you move from?

 

[Bodd]

As for replacing with Hive , Someone clever will turn up soon and point you in right direction.

Good luck.

 

[ericmark]

The smart thermostat, Hive, Nest, Honeywell Evohome, Drayton Wiser, are all except Nest designed to link to TRV heads. And except for Hive can connect to boiler either On/Off or to ebus using OpenTherm.

EPH do an OpenTherm system using master and slave thermostats, I seem to remember up to 10.

The problem is unless using OpenTherm then the boiler modulated using the return temperature of the water. Still needs a master thermostat to tell it to turn off on warm days, but the smart thermostat can do the reverse to what you want making the system less efficient due to switching On/Off instead of up down.

Mothers house I tried fitting wifi linked TRV heads which worked well, but as to how UFH links in I don't know, I would guess the EPH system with master/slave. But much depends on boiler.

 

[therafox]

Thank you both - this is super useful. If I understood correctly, every room has a separate motorized valve somewhere in the floor, in addition to the two "master" valves. These valves are controlled by the Emmeti CS11 thermostats while the TP9000 is only time-based, for the system as a whole.

With this in mind, it seems I need a smart heating system that supports three zones. It seems Genius Hub and Honeywell both allow for this, but they're quite expensive. EPH's website is a bit harder to navigate, so not sure what exactly I'd need.

I wonder if I can just get two Hive thermostats, one to replace the TP9000 and one to replace a single CS11 in my bedroom. Then I'd effectively merge the living room and hallway zones into one and have a separate control for my bedroom (which would have to be colder than the living room). Presumably, I'd need to keep the existing CS11 themostats in the living room and bathroom at max temperature, to ensure the valves are always open. Would this work?

The problem is unless using OpenTherm then the boiler modulated using the return temperature of the water. Still needs a master thermostat to tell it to turn off on warm days, but the smart thermostat can do the reverse to what you want making the system less efficient due to switching On/Off instead of up down.

I think this master thermostat is not connected to the TP9000, but is actually separate and I suspect this is it:

Is this what you were referring to?

 

[ianmcd]

That is your HW thermostat that controls the HW temp in the cylinder, what actually heats everything ? do you have a gas or oil boiler, or is that cactually a thermal store , post a full pic of that cylinder

 

[therafox]

It's on a water cylinder from Kingspan, which I believe heats both hot water and underfloor heating in the apartment. There's no other boiler and no gas in the apartment.

 

[ianmcd]

That is why I asked post a full size pic of what you have, you dont have what you posted a link for

 

[dilalio]

I have an immersion heater which consists of an unvented indirect cylinder

You have a direct cylinder/thermal store.

 

[therafox]

Apologies, was a bit hard to get the angle in a photo, but I managed to do it:

You have a direct cylinder/thermal store.

Can you explain the difference? I thought it's indirect because it also receives heat from an external source (there's hot water in the building).

 

[ericmark]

no gas in the apartment

Then all I said was useless.
Can't work out quite why you have in immersion heater unless heating turned off in summer, but it seems you have a building hot water supply, and so well beyond my ken.

 

[ianmcd]

You have a direct cylinder/thermal store.

Not often I disagree with @dilalio but in my humble opinion you have an indirect hot water cylinder and you are supplied on a district heating system, hence the energy meters and the two expansion vessels, this doesnt make any difference to how your thermostats get wired , but the immersion heater that you thought heats things up is simply an emergency backup, for each thermostat there will be an individual zone valve, so for each one you will need a single channel hive and receiver, so will start to get expensive, you can change all or some zones with hive units, dont see any point in changing the bathroom one for example

 

[ianmcd]

And you need to turn that thermostat up to that mark that someone has made, it has to be at that setting to prevent the formation of legionella

 

[therafox]

for each thermostat there will be an individual zone valve, so for each one you will need a single channel hive and receiver, so will start to get expensive, you can change all or some zones with hive units, dont see any point in changing the bathroom one for example

My main problem with this is, if I don't change the "master" TP9000 thermostat in the utility room and only change the ones in my rooms, Hive wouldn't be able to turn the whole system on/off, only individual rooms, which is way less power efficient (the system could be on with all valves closed). But if I do replace that with a Hive, I have an additional "master" thermostat I need to place somewhere. If I e.g. place it in my living room, I'd have two thermostats in the same room, one which controls the room zone and one which controls the whole flat. This is why I'm curious if it's a good idea to just set the living room and bathroom/hallway stats to a high temperature, keeping them always on - and have a Hive that turns off heating globally when they are warm enough.

And you need to turn that thermostat up to that mark that someone has made, it has to be at that setting to prevent the formation of legionella

Well, this was potentially life-saving information that I never would've thought to ask. Thanks!

Is there a reason this isn't simply always set to a high temperature then? I find it odd it's even possible to have it lower than the temperature needed to kill legionella!

 

[ianmcd]

you are over complicating things, the TP9000 is replaced by a dual channel hive and the others with a single channel hive for each channel