Starting out with central heating / radiator control

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matthijskooijman
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Starting out with central heating / radiator control

Post by matthijskooijman »

Hi folks,

I'm brand new to this board and to domotica in general and looking around to create a control system for my central heating system. In particular, I'm interested in creating multiple (probably 2 or 3) zones. I work from my home office on the first floor, so the single thermostat on the ground floor we have now is not sufficient.

I've read up on this forum and other places a bit, and it seems that FHT, Max! and (Danfoss) Z-Wave are the most commonly used systems for heating control. I do have some questions, hopefully someone can provide some insights here.

Using the Max! system, there is no direct control over the heating boiler, it only controls the radiator valves. However, as far as I understand, leaving the boiler on 24/7 will not help to save energy (probably use more energy than my current single-thermostat setup?). Is this understanding correct? If so, how would you recommend to interface with my boiler to turn on only when there is heat demand? I can imagine a small software solution here: Have a PC talk to the Max! Cube to find out if there is heat demand and then toggle a simple relais to turn the boiler on. However, doesn't such a software solution prevent the system from working autonomously at all, when the PC / software is broken for whatever reason?

Using the FHT system, I've found the FHT8W relais, which switches on the boiler when any thermostat signals a heat demand. However, this device seems very big and expensive (€90) for just a remote controllable relais (especially since it only needs to short a 24V signal for my boiler, I think). Are there extra hidden features here? Also, it seems that using the FHT8W will degrade to on/off switching of the boiler instead of modulating (though the modulation protocol of my Nefit Ecomline seems to be unknown as of yet, so I might need to fall back to on/off anyway).

Looking at pricing, the Max! system seems interesting. It is also easy to hack on, because of the (cheap) ethernet-enabled cube. The FHT system is slightly more expensive, but does seem more mature. However, it seems that the (only) radiator valve actuator they have (FHT-8V) does not have a manual override knob, it can only be remote controlled. Is that correct?

So far, some of my questions and thoughts. I welcome both answers and other ideas!
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Re: Starting out with central heating / radiator control

Post by Bwired »

regarding Max valvues
Yes you are right, max controls the valvues, but the guys who are working on the Max protocol already have a way to control the Hvac.
I control the hvac with the proliphx IP thermostat. All is coming together in my domotica systems, so i can now heat up just one room or whatever I want.
I can do it automatic or when somebody set the temp on the valvue manually.
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jrkalf
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Re: Starting out with central heating / radiator control

Post by jrkalf »

Martijn,

sorry to be a late addition to your post. Most things you think about FHT are correct.
The FHT8w relais is nothing but a on/off switch which switches the boiler system on for 15 minutes at a time. (yes, it's that stupid/simple).
With one addition, if you buy the pre-built one, it comes with a FS20 transmitter built-in you can use to transmit to an additional device, or simply to log when it's on/off.

You're probably mistaken thinking that the FHT8v is controlled by a computer only. It 90% of all setups done by domotica implementers I've seen it's not directly controlled by a FHZpc or CUL/CUNO device. In nearly all cases a FHT80b-2 or -3 devices (nowadays they only supply the -3; Newest version) are used for primary room control and a computer based system to direct the FHT80b devices or purely for logging purposes.

This FHT80b device is a basic thermostat which communicates with one or multiple FHT8v devices and/or FHT80-TF devices. (actuators and window/door sensors). This will allow you to have a temperature override per room. If you want single actuator overrides on the actuator itself, it's going to be hard. You'd have to remove the batteries from an actuator and use the manual gear open or close the actuator.

FS20/FHT have their flaws in communications protocol which, I'm not sure, Max! will probably have as well. Except for the pairing system most of the system is transmit and receive unidirectional. transmitters transmit, receivers receive. Nearly never bi-directional. (except for the FHT80b device).
---

if you have any questions, you can ask any question you have. I've got a setup running at the moment and I'm pretty happy with it.
So is KidE and Kroonen from this forum. RDNZL has just started testing with it as well if I'm correct, and he's implemented FHT support into DomotiGa(.nl).
If you can't fix it with a hammer, you've got an electrical problem!

Fibaro HC2, various z-wave switching, alerting, detection modules.
ELV FHT80b heating system.
matthijskooijman
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Re: Starting out with central heating / radiator control

Post by matthijskooijman »

jrkalf, thanks for your clarifications on the FHT system, I think I have a decent picture now.

However, I'm inclined to have a closer look at the MAX system, since it offers an override on individual actuators and (AFAICS) allows radiator actuators to work without a separate room thermostat. I'm interested in this since most of my rooms only have a single radiator and aren't used enough to warrant both a radiator knob and a separate wall thermostat, being able to use just a knob sounds like a feature. I'm aware that having a temperature sensor inside the knob isn't ideal, but I most of these rooms are only heated every now and then, so I guess that'll work out.
Bwired wrote:regarding Max valvues
Yes you are right, max controls the valvues, but the guys who are working on the Max protocol already have a way to control the Hvac.
What guys are these and what way is this? Do you have any link, documentation, etc.?
Bwired wrote: I control the hvac with the proliphx IP thermostat. All is coming together in my domotica systems, so i can now heat up just one room or whatever I want.
I can do it automatic or when somebody set the temp on the valvue manually.
So you have a central system that monitors the MAX system and then controls the IP thermostat as a sort of expensive on/off switch for your HVAC?


Furthermore, what temperature sensors does the MAX system expose through the Cube? If I read the other threads correctly, only the temperature values from the wall thermostat are known on the gateway and the radiator knobs only send their setpoint? That would be a pity, since having those extra temperature sensors would be great for logging :-)

And, thinking about how the wall thermostats work: Can the wall thermostat actually control the valves directly, or does it just propagate the temperature setpoint to the knobs (in other words, does the temperature measured on the thermostat actually influence the valves, or is it just informational)?
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Re: Starting out with central heating / radiator control

Post by Bwired »

in every room we have a temp sensor, so we know the temperature in every room.
In somebody turns the knob on a valvue i can put on the heating only just for that room, or i dont do it because the temp is already above x degrees.
The guys are a lot of domotica freaks who are already able the put the hvac on with their domoticasystem.
Also we can control the MAX valvues the same way, this al together makes almost everything possible regarding heating.
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Re: Starting out with central heating / radiator control

Post by KidE »

you could also take a look at the new and revised FS20/FHT devices from EQ-3/ELV called Homematic.

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The new thing about these elements is that they are Using a BidCos bidirectional protocol.
I've been using FHT's for about 2 years now and i'm more than happy with it. My new ones will be Homematic for sure.
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