My Central Heating Solution using Thermal Actuators

This does seem like exactly how I implemented my setup originally. Nothing was hardwired, it was able to be returned to standard in seconds. I’ve since now decided to do a permanent installation as I’ve got a new house and the ability to do what I want :wink:

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It’s due to you posting this in the first place that put the idea in my head to start with.

I’ve just been looking for a 'ready made" solution that would look okay if I installed it for someone.

I really liked what you’d created :slight_smile:

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This is what our boiler is doing from it´s temperature treshold. Since the manifold is a very short but closed to the boiler, the temperature loss is close to zero, when no actuatores are open.

Do you have two boilers, one for heating and one for warm tap water? I only got one, so unless either a room or someone using hot tap water, our boiler will be on standby.

No, just the one. A combi boiler. Whenever a hot water tap is opened, the boiler will switch to hot water and go back to heating when closed. I have the heating schedules in the mornings set for heating before the bathroom is used. During the rest of the day, hot water doesn’t influence the central heating much at all.

Not all boilers can cope with that set up. Most modern ones can and even then most need to be told to expect it.

Same as ours then.
I still dont see the need to switch in the actuators.

It’s not a major issue.

If…

Your particular setup has a blender between the boiler and the UFH manifold, which is there to return the (~60°C) flow back to the boiler if the UFH return flow is up to target (never more than 40°C).

Then in theory it’s not a big deal to have the boiler on and not signal any heat demand.

However, if your system doesn’t have a blender, (which if you’ve only got UFH) and your boiler is set to limit the flow to 40°C, then it would be ‘nice’ for your boiler to know that none of the zones are calling for heat.
However, this assumes that you have a locked open loop / bypass so that the water can return.

The actuators in the WTA really come into play when there are multiple manifolds, with multiple UFH manifold pumps and 2 port isolation valves.

If you consider how this wet schematic might be wired to maximize water flow, so that it is routed where it is needed.

The picture is exactly how our heating system is made. Only changes are.
The Hot Water Tank, the Pump Pack and the valves are all build inside the boiler. And then our system is having 13 zones and no Raditors, it´s all floorheating.
Our boiler covers both hot tap water and floor heating, so it´s split up into two different sections each having an independ thermostat. But I guess thats quite normal, and your picture is just a principal drawing.

This is why I failed to understand the need for the actuator switch. The switch wouldnt make any change, as the room thermostats is controling the acutators for each zone/room.

So the picture doesn’t represent your installation then :wink:

I was only trying to get across how the actuators in WTA would make a difference in a system, that WASN’T like how yours is installed. :slight_smile:

The basic principle is…

Room thermostat triggers a 2 port valve / WTA

Microswitches in 2 port valves / WTA call for heat from the heat source, WHEN (and only when) the valve is fully open.

(Obviously this is only a simplified explanation, I’m happy to provide a schematic if you’re interested, but as you understand your own setup, do you want to know???)

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As a principal matter, it does :slight_smile:

Not really… Just trying to understand the need of the switch… Perhaps it was something I didn´t know and missed :wink:

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To be honest I always expected the return pipe would show a differential to the in pipe and was hoping to use this differential to work out if the heating was actually working hard or not. So if there was a large differential then the heating is working hard, putting a load of heat into the house and when it was a small differential the heating was fully up to temp.

However, hard data on my system said otherwise. I realise this is just my heating and systems may vary depending on flow rate and how good the radiators are, how many there are etc. But the graph below of heating in/out pipe was NOT what I expected.

Imgur

You can see there is seldom more than a 2*C differential and the out pipe comes up to temp and cools almost exactly tracking the in pipe. I think this just because the loop flow rate is high.

That’s a pretty efficient system you’ve got there then.

I monitor the gas consumption into the boiler, which gives me a pretty good idea of how are the system is working.

I think it’s the opposite, it’s more or less the original 1970s heating that might have had the burner replaced once, but the heat exchanger is still the rusty old cast iron thing in the garage and several of the radiators are so full of gunk they don’t heat at all :slight_smile:

It’s being upgraded to a condensing gas boiler in the old “hot press” with a few radiators being replaced in the next couple of months, will be interesting to see how this graph changes when i connect it up once the plumbers and spark leave :wink:

Anyway, I wanted to thank the OP for this post as it’s pretty much exactly what I’m after. The only difference will be the temp probes as I prefer the Dallas OneWire DS18B20 probes. They are more compact and I have found them easier to deal with and accurate enough. They do require soldering as they are just TO92 package and need a pull up resistor soldered in.

I typically place them in random places behind cupboards or the sofa as far away from heat sources like TVs and radiators where they will give a good representative temps.

Something I have learn time and time again is to not focus on the accuracy of the temperature probes. Invariably if you move them around you will get different readings, this is normal. I instead accept the temps I am given and work on how the room feels at that temperature. If the probe turns out to be in a cooler area of the room then I might want it’s target to be 20C but if a probe turns out to be in a warmer part of the room I might set the target to 21C there.

Indeed, it shows the return temperature of the heating pipes is way too high. Ideally, in modern systems, you would want this temperature to be between 30 and 40 degrees C.
To let the heater work most efficient, you want the water returning to take up as much heat as possible, and that is virtually nothing in the case there is only a 2 degree difference.
Which basically means you are just throwing away a lot of heat. So this could cause a relatively high energy bill as well.

Emmm. Where would that heat go exactly? If you think it through energy in, energy out, the only loss will be in the boiler out and return pipes as they are currently outside the house.

What it might say is that the radiators are not transferring the heat to the rooms very quickly or my circulation rate is too high.

But lets put some numbers on it. I’ll pull a figure out of the air and say the heating loop contains a total of 50 litres of water. To lower 1 gram (1 ml) of water by 1C you need to lose 4.184 Joules of energy.

To lower 50 litres (50 kilos) of water by 1C you need to lose 208.4 kJ. To lower it by 2C thus you need to lose 416kJ.

If it takes water 40 seconds to circulate the heating loop (again guessed, but a flow rate of 75 lpm), then the heating loop is releasing an average of 10kW of heat along the loop. Given that I only have 4 radiators on and they are often rated to 2kW at 60C it’s working fine (with my guesstimated numbers of course) accounting for 2kW in total lost from piping.

Having taken the 416kJ of energy out of the water in 40 seconds the boiler only has to add 416kJ of energy back in as it passes the heat exchanger. Obviously the heating needs to apply much more than that or the system would never heat up. So if it’s a 30kW boiler that sounds about right that it can go fro 20C to 60C or higher quite rapidly.

Going the other way and slowing the flow rate down would result in cooler radiators later in the loop and much higher boiler temperature as it would heat the water flowing slower through it more and at worst trip the internal cut out to prevent boiling in the exchanger.

So the boiler should be balanced such that the in and out pipes are quite close in temp. the balance is between flow rate and boiler power output, along with the radiator sizes and count. My boiler achieves it’s loop temperature easily and then cycles itself with it’s loop thermostat to maintain that. Isn’t that how it’s meant to work?

Depending on how you look at efficiency having the whole loop at operating temperature is fastest way to heat the place in a balanced fashion. With a lower flow rate the last radiator in the loop would get cooler water, trying to heat that room would cause wasted heat in other parts of the house.

Another way to look at heating efficiency is that, assuming the boiler and all pipe work is inside the house (not so in my case although my probes are on the pipes as they enter the house) then it can only be 100% efficient at providing heat from burning whatever to the house. The savings only come from getting that heating to where and when you need it and not waste it elsewhere.

The energy would just go out the chimney then.

So ideally you would like all heat loss to be through the radiators. And radiators shouldn’t be put in series (so in a single loop), normally they are placed in parallel, so that when you close one radiator, all other still get the warm water. (And you don’t damage the pump of your boiler)

The boiler can then just throttle down depending on the requested heating.

At least that’s how it works here in the Netherlands, so I’m not sure we are talking about the same system.

Yes, heating systems vary quite a bit. Mine is a 1970s UK based oil fired system. It has on or off. On is both burner and pump on a single relay. It has radiators in parallel on the single loop with one “locked on” radiator often called the “feed radiator”. The boiler is just a kerosene flame thrower and a large heat exchanger which it blasts a flame into. The flame is forced to rise through a matrix of pipes and baffles and eventually up the chimney. The pump circulates the water through this and round the radiators. A thermostat stuck into the side of the heat exchanger switching in and out the flame while leaving the pump running.

It also has an exchanger coil in a copper hot tank for hot water heating which will have an impact on the loop too.

The inefficiencies in this older system is in the direct and open flame system and it being outside in the garage.

I am upgrading to a condensing gas boiler inside the house soon, so it will be interesting to see how it does with these sensors.

Hi Stuart.
How do you monitor the gas consumption? Does your boiler have a special sensor?

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