Drayton Wiser operating questions

[Mister Banks]

My suggestion is a compromise to having nearly every room in a zone of its own.

 

[harrythefurrysquid]

In your first example I have a similar situation. I have 2 lounges joined by double doors which are open during the day but closed after about 19:00. The rooms have 3 radiators in total with the main lounge having 2 rads controlled by Wiser TRV's and a Wiser room stat.

Sounds like your main decision is whether to treat the lounges as one room or not.

If you treat them as one room, the valves will all actuate together (as far as I can see, anyway). You can use a room stat if the TRVs aren't doing a good enough job measuring, but you could also just offset the set point to compensate. This is basically the "one zone" solution, but it's a bit sub-optimal because you're relying on air circulation to even out any cold spots. In some ways it's not as good as having old-style TRVs.

If you treat them as separate rooms on one schedule, then IMHO it's more a decision of whether to use Comfort Mode or not. If you use Comfort Mode, you need those rooms to be heating at more-or-less the same rate. If they don't, then you're probably going to have the boiler slightly ineffectually trying to warm an interconnected space from only the coldest room for at least an hour (in my experience, anyway). But if you turn off Comfort Mode and just use schedules, you won't have that problem: All the rads will come on together but Wiser will still have the fine control to heat the colder room more aggressively and you shouldn't get cold spots. Maybe that's why Comfort Mode is off by default.


Re the bathrooms that sounds fine. I only have a towel rail and it has an old wax TRV on it that I leave wide open. That's my bypass circuit (though I suspect Wiser means you don't need a bypass circuit anymore).

 

[Mister Banks]

I dont use comfort mode so thats one thing I dont need to account for. I could try these rooms allocated as one room with the room stat in control and see how the system performs although I dont have any issues as they are, they both have the same schedule and temp setpoints and both heat roughly at the same rate.

 

[e9508686]

This thread is very interesting and has asked some of the question this mind field introduces.

I've been doing my best to swat up on this as possible but I have no idea if I'm right or not...

According to my boiler documentation, my ideal instinct 30 boiler is capable of modulating:

6.1 to 24.2kW (20,700 to 82,600 Btu/h)

According to ideal, my boiler does support OpenTherm (although I do need to install an OpenTherm harness).

So if I use Drayton wiser this modulation can be utilised. Side question: if you don't use Opentherm and instead just have an on/off setup on the boiler, will it always run at 24.2kW?

The thing is, as an example a standard size radiator might have a BTU rating of maybe 6000BTU. But the minimum modulation of the boiler is 20,700BTU. So as far as I can work out, you're basically wasting 4kW out the flue. If instead you turned on three radiators that would be 18,000BTU and the boiler would still be able to supply the heat for those with the minimum modulation using roughly the same amount of energy?

At the same time, turning on 10 radiators or the whole house is going to use a lot more than 6kW. So with that in mind I guess you should still just heat some rooms but maybe 3 or 4 radiators at a time rather than one at a time.

This obviously depends on the lowest modulation supported by your boiler.

There is another side to this where having one room cold next to a room you are trying to heat could result in using more energy than just heating both rooms. It would be awesome if the system could automatically run a bunch of tests to be able to suggest changes like this but for now this is something we would have to try and analyse manually. I'm not really too worried about this though because we all have this to consider even before introducing smart TRVs or OpenTherm.

So with regards to what I was suggesting about modulation, is that actually correct?

 

[harrythefurrysquid]

Side question: if you don't use Opentherm and instead just have an on/off setup on the boiler, will it always run at 24.2kW?

It'll still use TPI (Time Proportional Integral) to cycle the boiler for progressively shorter periods to avoid overshooting the set point, but the boiler will fire up at the same temperature every time and then modulate down based on return flow temperature using the boiler's own logic. The flow temperature is typically configurable so you could manually setup your boiler not to use full power if you know that's not really required for your house. When using Opentherm it will fire up at lower temperatures rather than relying only on the boiler's return temperature modulation, and in my experience will make greater use of the pump to make the most of warm water in the pipes - which isn't an option for on/off control.

Opentherm is very easy to install if your boiler supports it: it's just two wires which aren't polarity-sensitive.

So with that in mind I guess you should still just heat some rooms but maybe 3 or 4 radiators at a time rather than one at a time.

In general you want to be using as many radiators as possible when you want to change the temperature of the property, so that you can run the water at lower temperature and still get reasonable kW output. If you have interconnected rooms (open plan, or doors left open) you probably want them at the same temperature and ideally the radiators would heat at the same rate.

Once you're up to temperature, Wiser is pretty good at opening TRVs selectively to just put (say) 10% heat into a specific room. This is where having Opentherm is particularly beneficial as obviously it's preferable not to fire the boiler at 70 degrees just to warm a single rad up to 35.

There is another side to this where having one room cold next to a room you are trying to heat could result in using more energy than just heating both rooms. It would be awesome if the system could automatically run a bunch of tests to be able to suggest changes like this

Consider the Heat Geek advice (intended for Heat Pumps, but somewhat applicable here) and don't setup adjacent rooms at wildly different temperatures as you'll effectively end up trying to use one rad to heat two rooms which will cause the boiler to fire more often.

 

[e9508686]

Thanks Harry. Really useful information.

Regarding the flow rate temperature and hot water temperature, what happens with that when you connect Opentherm? I read somewhere that the knobs on the boiler itself which control these temperatures effectively become redundant once you connect Opentherm. Is that true? If so, do you then have control on that through the wiser app?

Interesting regarding how a boiler will fire up at full temperature and then monitor the flow rate to work out what to modulate down to. I didn't know that. Learning a lot about this.

I think it's mad how people have these smart heating systems setup but don't even question these sorts of things. For example if you don't have opentherm and therefore you're not running the boiler at a lower modulation, and you are just setting the heating on in Room A for an hour then Room B for an hour etc. They have no idea that this is inefficient with regards to having one room warm at a time, blasting the boiler at higher temperatures (rather than using opentherm) and using more energy overall.

I rang Drayton earlier to ask about Opentherm. I had a bunch of questions and the engineer on the phone didn't know any of it. He said that people never ring and ask about Opentherm. I know Tado removed support for it too for the same reason. I have no idea what the actual savings could be using opentherm Vs not but from what people say in this thread, it sounds like a no brainer.

Does anyone have any experience using the under floor heating unit for Drayton wiser? I currently have my radiators on one thermostat and my UFH on another. I was asking Drayton if I needed to have the Kit 3 (which supports 3 channels) and the guy said you can just use kit 1...is that right? As far as I know, I just have a single zone UFH (although I'm only basing that on the fact I have only 1 thermostat - how else would I tell?). The single zone consists of a large open plan room, a utility room and a cloakroom. In addition to the UFH, there is a radiator in each of those three rooms. Will the Wiser system correctly fire things up to use the UFH and radiators in the most efficient way to heat these rooms to my desired temperatures? Obviously UFH takes hours to get going compared to radiators so unsure how it would map them out together. Also there would only be a wall thermostat in the main open plan room but in the utility room and cloakroom the smart TVRs would be monitoring the temperature for the radiators and UFH (I'm confused if that's going to work efficiently in the wiser app). Does anyone know?

I almost never have the UFH switches on as I feel it uses some much energy. I wonder if OpenTherm would make it more efficient.

 

[Mister Banks]

Are you asking how Wiser controls both heating and DHW with Opentherm? If so then the answer is it doesn't as Wiser only supports Opentherm with combi boilers.

 

[harrythefurrysquid]

Regarding the flow rate temperature and hot water temperature, what happens with that when you connect Opentherm? I read somewhere that the knobs on the boiler itself which control these temperatures effectively become redundant once you connect Opentherm. Is that true? If so, do you then have control on that through the wiser app?

As far as I can tell, the set point you configure on the boiler is still used based on how I've seen it work. Wiser will call for 100% heat when there is a significant difference between the current and desired temperature (2+ degrees) and I believe this will result in the flow temperature that you've configured. The return flow temperature modulation may also continue to work as before - or it might depend on the boiler manufacturer.

Unfortunately many boilers in the UK do not support Opentherm (e.g. Vailant, Worcester Bosch), so it's relatively uncommon. I had to buy an adapter from the Netherlands to add support to my Greenstar 30i. It's a shame support is not mandated.

As MB says, Kit 1 is the only version that officially supports Opentherm, and it's intended for a Combi and single plumbing zone (which can then become multi-zone through the use of TRVs). Sounds like your setup is more complicated - you at least need to find out if you have a separate hot water cylinder and any zone valves. My only experience is with Kit 1 as an informed consumer - I'm not a plumber or heating engineer.

Once you've figured out the basic configuration of your heating system, I suggest maybe have that conversation with Drayton again but without the Opentherm complication. It's not the end of the world if it turns out you can only do Kit 2 or Kit 3 - the TPI on/off modulation will still give you fine control when combined with smart UFH and radiator valves.

 

[e9508686]

I just mean, on a combi boiler, you can select the hot water temperature and flow rate temperature with the two knobs on the front. But I thought one of the things Opentherm did was automatically adjust the flow rate temperature to more efficiently heat the radiators - but sounds like that's not true and instead it's just the modulation which is different. So sounds like the knobs still work as normal.

I don't have a hot water cylinder - it's a combi. I just wasn't certain if my UFH has any separation between the rooms or if it's just one big section (most likely the latter). I will have to ring Drayton to ask - I just felt like the support I got before was pretty rubbish so don't have much faith they'll be able to give me definitive answers.

 

[e9508686]

Oh I did have another question - sorry

What's the deal with weather compensation? As far as I can tell, that's part of opentherm rather than wiser? But I guess wiser tells the boiler to switch heating on via opentherm and then it can use the temperature sensor to determine how intensely to hear the room etc?

 

[harrythefurrysquid]

I just mean, on a combi boiler, you can select the hot water temperature and flow rate temperature with the two knobs on the front. But I thought one of the things Opentherm did was automatically adjust the flow rate temperature to more efficiently heat the radiators - but sounds like that's not true and instead it's just the modulation which is different. So sounds like the knobs still work as normal.

Opentherm will control the flow temperature, but in my experience the "maximum" temperature is what I set on the boiler control panel. Other boilers might behave differently. It's possible that Opentherm simply communicates the percentage demand rather than an absolute number, or maybe the boiler just caps it.

Kit 1 should be good for a combi. You should still check to see if you have any sort of zone valve. If you have only one thermstat then possibly you don't, but potentially there could be a temperature sensor embedded in the floor.

What's the deal with weather compensation?

You can have weather compensation without a smart thermostat if you have a sensor plugged into the boiler. My understanding is that it adjusts the flow temperature based on the outside temperature, and you fiddle with the heating curve parameter until it gives you what you want. Apparently works fairly well though it can't compensate for wind effects.

Wiser does incorporate weather compensation in its Eco mode and Comfort mode. Eco mode keeps track of how fast rooms tend to cool, and turns off the heating early in those rooms if it predicts that the room will not get too cool by the scheduled time. Comfort mode does the opposite: it turns the heating on by predicting how long rooms take to heat up, and trying to hit the desired temperature at the requested time. Both modes compensate for the weather (outside temperature) based on information from the internet.

Weather compensation doesn't have any depedency on Opentherm.

But I guess wiser tells the boiler to switch heating on via opentherm and then it can use the temperature sensor to determine how intensely to hear the room etc?

Wiser measures the temperature using room stats and thermometers in the TRVs (not with fantastic accuracy in the latter case, unfortunately). It can individually control the valves and will fire up the boiler as needed. Again Opentherm is not required for this - but does allow a bit more efficiency if it's available.

 

[e9508686]

Really appreciate all these responses - really helpful and you're certainly filling in all the gaps which I wasn't sure of.

Just to be clear, currently I have two wireless thermostats - one for the radiators and one for the UFH (the level of configuration on them is awful).

I've attached what I think is a photo of the UFH manifold - I don't know if that indicates if I have more than one UFH zone? As I said previously, I have no reason to think I have more than one zone but wasn't sure if if was normal for an UFH system to just be configured as a single zone even when it spans across multiple rooms.

I've also attached a photo of the two Salus wireless transmitters which actually look like they're all connected together inside that Danfoss connector box so it probably is just all running under one channel.

I wonder if this is getting more complicated though, because, without looking at it in too much detail at midnight on a Friday night, if I have my two thermostats connected to the DanFoss connector box and that being the single "thermostat" connection to the boiler, I can't just switch that out with my Drayton Wiser hub/open therm connection because then the UFH wouldn't be connected either (assuming I'm not moving that over to Drayton Wiser initially). Maybe I would have to do it all in one go.

On second thought... surely the UFH is on a separate channel, it's not like if the UFH comes on then the radiators comes on and vice versa so they must have different pipes going to and from the boiler? I clearly have no idea what I'm talking about but I'm trying

 

[harrythefurrysquid]

Definitely sounds like a two zone system, which is what I figured you'd have for UFH. You probably need advice from a professional installer - or maybe someone on here has more direct experience.

 

[e9508686]

According to Wiser website:

Do I need an extra heating channel to use UFH with Wiser?​

There is no requirement to have an extra channel on the Wiser Hub to support UFH.
The UFH control strip has a boiler output which can be wired to the boiler to ensure it fires when a UFH channel needs hot water, you can also on commissioning tell the Hub to activate either Channel 1 or 3 (hub type depending) when the UFH requires the boiler to fire.

I'll get Drayton to confirm all of this but this looks promising

 

[Mister Banks]

The problem with finding the Wiser information is that there are multiple different versions of documentation. For example I have found 3 user guides, one has 44 pages, one has 61 pages and the last has 66 pages. All versions show the older app version. I wish Drayton would have somewhere on the internet where all documentation is accessible.

If you need to contact Drayton for info I find emailing support is best as they seem to know much more than the call handlers who i think are just for basic install and operating issues.