Hi everyone, my apartment has an independent heating system with a gas boiler. Four radiators are connected to this boiler. Currently, the system is managed (in winter) by an on/off room thermostat that allows me to set the heating on and off times and a set temperature. I’d like to upgrade this system. My idea is to:
install smart thermostatic valves on the radiators,
replace the current thermostat with a relay, and install a temperature sensor in the main room. What do you think?
This is fine and is in effect my setup as I use a Hive Thermostat with TRV’s on each radiator. The TRV’s control the temperature on the Hive Thermostat which acts as a relay for the boiler.
You can use a relay instead of the Hive Thermostat but if my HA server is ever down, I just rely on the Hive Thermostat to turn the boiler on / off and use the TRV’s manually.
I’m missing a step. The valves close the radiator in the room when the temperature is reached, but then who sends the signal to turn off the boiler?
Where in the world are you?
You mentioned “apartment”. Do you have your own boiler?
How many other apartments are in the building?
Does the boiler also produce hot water?
Is the boiler supplying hot water heat or steam?
If steam, is it a two pipe or one pipe steam system?
I have a property, 2 family, 3 floors, one pipe steam. I ran a 150 family hi-rise that used 2 pipe steam. Being responsible for either, I’ve seen modifications made without consultation or permission have had negative impacts on other residents (if not the heating system overall).
You would use a ‘Helper’ which see’s which TRV’s need heat and if any do then set the boiler on, if they all don’t then off.
Private boiler, used for both hot water and heating (no steam). Is there any integration on HA to manage the boiler?
There are integrations for boilers although it would depend on the type of boiler you have. If your boiler supports OpenTherm then you should look for something that utilizes that.
I have a simple boiler for Hot Water (no cylinder / tank) and Heating, so just use the Hive thermostat to tell the boiler when to provide heat to the central radiators. This could have been done by a simple relay but as mentioned I get some redundancy if HA goes down.
My boiler doesn’t support the Opentherm protocol. Will there be a card in HA that can let me choose the ignition schedule, temperature, etc.?
The Hive Thermostat provides a climate entity so can use any card that supports the climate entity.
If you opt for a relay then you can use jcwillox/hass-template-climate: 
Templatable Climate Device for Home Assistant, Supports Running Actions On Service Calls.
HA has Schedule - Home Assistant which can be used for scheduling.
Another thing to consider: is your boiler controlled by a thermostat that just switches ON/OFF or is it a system that has different states depending on the requested temperature and the current one. (modulating)
If just ON/OFF, it might be easy to control your boiler with a relay on ESPhome and use an automation in HA to control all the boiler and the TRV’s.
Simple on/off thermostat. So can you confirm that I could use a Sonoff-type relay on the thermostat’s current contacts and a TRV on each radiator? And could I use “scheduler” in HA?
If you are 100% sure about the ON/OFF, then it’s just like a switch that is controlled by a temperature sensor and a dial knob.
In that case, there should be only 2 wires to your boiler which are shorted when heat is requested.
Then, any relay will do to imitate shorting those 2 wires and of course that relay has to be controlled by HA so be aware of the integration to get it into HA.
Regarding the scheduler: have a look at 🔥 Advanced Heating Control
So I’m installing a TRVs on all four radiators, a relay in place of the current thermostat. When all four TRVs are closed, do I turn off the boiler with the relay?
I wouldn’t install a relay, there is no need for it. If you have a simple heater that will react to ‘hey we want warm water over here’ by one of the TRV’s, then no need to turn it off via a relay: simply closing the TRV will stop the request for hot water.
Are you talking about replacing the functions of something like this:
What is the brand and type of heater that you have?
Simply put yes.
What I do is set the Hive Thermostat Temperature to a low value (12c) which turns the boiler off and if any TRV needs heat I set the temperature of the Hive Thermostat to a high value (30c) which basically makes the Hive Thermostat an ON / OFF switch.
If HA ever goes down, I can set a schedule on the Hive Thermostat along with a temperature which will control how the boiler provides heat - not as efficient as when HA is running since the TRV’s don’t communicate with the Hive Thermostat directly (I’m not using the Hive App as I prefer the local control).
Energas Damona Plus (Filebin | xeoou1z9bt8nh23j)
VIMAR 16577 (Cronotermostato grigio - 16577)
Flow rate with thermostatic valves closed
The boiler is equipped with an automatic bypass,
which protects the primary condensing heat exchanger.
In the event of an excessive reduction or complete cessation of water circulation
in the heating system due to the closing of thermostatic valves or valves
on the circuit elements, the bypass
ensures minimal water circulation
inside the primary condensing heat exchanger.
The bypass is calibrated for a differential pressure
of approximately 0.3 - 0.4 bar.
I found this in the manual, maybe that’s why you say it’s not necessary? But maybe it’s better to put the relay in anyway?
You would still want the relay as you should trigger the boiler to provide Heated water when the TRV’s need it. If you don’t, then you will be setting your boiler to provide heated water to the radiators 24/7. In essence you will be wasting gas / electricity by heating the water when it isn’t necessary.
1 Like
Ok so with the picture you sent, it becomes more clear.
The function of your thermostat (Vimar) is to tell the heater that you need heated water. It will measure the temperature and as long as the built-in thermometer is not reaching the desired temperature, it will ask for more heat.
In a normal situation the valves on your radiator are simply (partially) open to let that heat flow through them.
Your TRV’s will do the same thing, however they physically control the valves of the radiators. Where they report to, is what the relay is for.
What SJ20035 has is a replacement for the (wired) thermostat (Vimar) which tells the boiler to start providing heat.
A relay is indeed the best way to go, it will be HA that fully manages your heating system then.
So, to summarize, I could install a relay on the contacts of the current thermostat (such as the SONOFF ZBMINIR2) and install TRVs on each radiator. Then I’d like to create a configuration like this:
- heating on from 6:00 PM to 10:00 PM
- temperature on each TRV about 20 degrees
Then the TRVs will automatically close when the temperature is reached, while the heating system will be active within the range indicated above.
What do you think? Is this a good configuration?