Switch for boiler: dry switch/potential free

[chercheur]

Hello,

I'm trying to create a solution for a friend.

I have for years:
- CCU2
- HM-CC-RT-DN thermostatic valves
- a switch for my oil boiler HM-LC-Sw1-SM

I'd like to copy that solution for him with the new IP range of products.

My question is about the switch as my old model doesn't seem to exist anymore.
The HM-LC-Sw1-SM makes it possible to create a "dry" switch. It's just an open or closed contact. There is no 220 volts at its terminals.

Several questions:
- should I take an HM-LC-Sw1-FM ? (I'm not sure it just makes contact open/closed. Without 220 volts!)
- if I understand correctly this module is not compatible with the Gateway. I must take a CCU3 ?

Thank you for your help

[Roland M.]

Hello!

The HM-LC-Sw1-SM makes it possible to create a "dry" switch. It's just an open or closed contact. There is no 220 volts at its terminals.

So you are looking for potential free contact, correct?

- should I take an HM-LC-Sw1-FM ?

No, I'd not recommend the classical HM line anymore and no, this has not a potential free contact. You would have to install a additional relay (maybe a proper way to go anyway).

Take a look at the HmIP-DRSI1 (or DRSI4)!

- if I understand correctly this module is not compatible with the Gateway. I must take a CCU3 ?

Yes, classical HM has to use a CCU, HmIP can be used on both platforms, CCU and Access Point.


Roland

[chercheur]

Tx.
Indeed I'm looking for a potential free contact.

Wouldn't the HmIP-WHS2 be the right choice ?

[Roland M.]

Wouldn't the HmIP-WHS2 be the right choice ?

Certainly yes, but without knowing the actual project it's hard to tell.


Roland

[chercheur]

It is a heating project (exactly the same I'm using for 8 years now but with the new models).
The goal is to replace all thermostatic valves and the central boiler thermostat with "connected" Homematic devices.

Central control
As he doesn't need advanced functions I would stick to the Gateway (not the CCU3)

Oil boiler
Requires a potential free contact. Open or closed.
For this I would use the : HmIP-WHS2 if it fits that potential free requirement (as I think it does)
ELV confirms to me that only the HmIP-MIOB offers a potential-free switch

Thermostatic valves
Several HmIP-eTRV-B

[chercheur]

And, to be complete, the goal would be to trigger the oil boiler as soon as 1 thermostatic valve demands it.

I currently do that via a script on my CCU2.
If opened more than 20% -> trigger oil boiler switch.

Is this also possible via the Gateway ?

[petoulachi]

Hello there,

I'm having the same project in my house

Does the HmIP-WHS2 is not ok ?

Ideally, if this is direct link with the TRV it would be ideal. I do have a RaspberryMatic but love the idea that heating would work even if the raspberry is down !

for now, I do have on the CCU a program that is trigger everytime that a valve % change.
then if any of the hmip heating group's valve is > 30% OR if the total of all valves % is > 70 then it send me a Telegram message saying ON or OFF, accordingly.
All I need now is a dry contact module to connect to my boiler. WHS2 seems to be the right module ?

Merry christmas to all

[chercheur]

For this I would use the : HmIP-WHS2 if it fits that potential free requirement (as I think it does)
ELV confirms to me that only the HmIP-MIOB offers a potential-free switch

So, no, the HmIP-WHS2 is not ok

[petoulachi]

Well, it IS ok, the WHS2 is completly capable of potential free switch, I'm currently using it since tonight

Now, using only direct link could be possible but it means having a thermostat for each rooms, which I do not have. I only have one thermostat for the living room, others rooms (bedrooms and office) are handle using only TRV.

So I'm using a program on the CCU that trigger everytime a valve opening changed and switch the WHS2 accordingly. This program is a bit evolved, as it check for every room how much the valve is opened, and decided if it should start the boiler (the living room is 29%, some other rooms that are not so used are at 49%). It also add all the valve opening % and if the sum is > 70, then it start the boiler too.
I'll see in the future if I had a thermostat but it would be quite a cost for just having the heating system working without CCU, and i'm quite sure this would start the boiler everytime any valve is opened for > 1% (in fact everytime the thermostat is in heating mode).

[chercheur]

Well, it IS ok, the WHS2 is completly capable of potential free switch, I'm currently using it since tonight

So, again, nothing's better than real life experience !
Tx for the report. Great news as it is less expensive.

From what you write it seems that a CCU is mandatory to activate it.
Right ? Can't we use all independant radiator valves as thermostat ?