TL;DR: How do I make the thermostat send a ‘heat’ request to the boiler without making the boiler use way too much gas?
Hi all,
I have a question about automating central heating. My current setup:
Ground floor:
- Main thermostat linked to boiler (Honeywell T6 on WiFi through Honeywell integration)
- One radiator with Sonoff TRV-ZB, zigbee
- Three radiators with non-smart knobs that are usually open
- The main room has a Sonoff Presence sensor
First floor:
- Three rooms that can be occupied with Sonoff TRV-ZBs.
- Two of three rooms have Sonoff Presence sensors
All rooms that can be heated smartly are controlled through a blueprint once shared here called ‘Advanced heating control V5’.
I have a helper called ‘Comfort Temp’ which is a slider that controls the setpoint on the main thermostat and the TRV of an occupied room.
So the obvious question is: is there any good way to get the main thermostat to send a heating request to the boiler?
I’ve seen something about a WiFi module that you can put in between the main thermostat and the boiler that offers more control (Nodo OpenTherm Gateway, OTGW). Does anyone have experience with this? Or do I solve this with more TRVs on my ground floor? I’ve heard about central heating systems not enjoying a fully thermostatic valved circuit. More TRVs also means I have to replace the valves on a couple of radiators.
Any advice would be greatly appreciated!
Just to make sure: You have zero buffer tank between your pipes and the boiler?
Just chiming in to say I think this guy’s got the right idea. I realize what community this is posted in, but sometimes when you’re really into your hammer everything starts to look a little too much like a nail. If you have room for it (sounds like a pretty big house) a buffer tank would make a huge difference
‘Big’ is relative. It’s a house in between two left and one right in a block of four. It’s big enough for two people, but it’s not huge.
I’m not sure I understand the function of the buffer mentioned. Is it a heated buffer that can pump around hot water without having to expend gas to heat? How does that differ from the expansion vat I have? Is that just to soak up excess pressure?
Sorry about all the questions, I’m just not sure about all of this stuff.
In most hydronic heating systems I’ve worked on, there’s an insulated tank of hot water either somewhere in between the boiler and radiators or built into the boiler directly. The thermostats talk to valves that send the water to radiators in the rooms that need it. The boiler just keeps that water at a set temperature.
In larger buildings with really long runs, sometimes there are valves to bypass certain radiators and/or multiple tanks located around the building. I can’t say without more information about your home, but it might make sense to have one near the area you’re trying to heat most.
No storage tank at all and thermostats that fire up your boiler directly sounds very unusual and inefficient. The expansion tank you have is just meant to stabilize pressure, it doesn’t have enough volume to do much for temperature
Ah no there is one of those expansion vats in between. It’s not huge but it doesn’t need to be.
Okay. Shame. Because basically that’s what would help you most.
English is not my first language and although I can kinda get my point across, technical jargon is a bit of a blind spot. So just to clarify: I have a little vat of say 10 liters connected to the heating pipes. It’s next to the boiler. It contains a rubber membrane in the middle to expand if pressure builds. Is this the type of buffer you’re referring to?
No worries. And while English is not my first language either,I think you were right with the term expansion tank - these are sadly only meant for keeping the pressure stable, not really “buffering”.
A buffer tank is large (often 500+x l) and well isolated. A bit more modern heating systems use them to, well, basically buffer things- the water in it is heated up (with the actual heating system running under ideal operational parameters and while it takes long its needed less frequently) and then the house getting its heating demand out of that. This is basically the ideal solution for your issue.
But sadly its often not feasible installation wise - while they are not that expensive they need a lot of room, a floor that can actually bear the weight and of course someone who install them.
But maybs speak to a professional about it if you own the place - it might be cheaper in the long run if you combine the costs of the alternatives, and these days they have creative solutions sometimes.