Drayton Wiser Home Assistant Integration

Third party integrations
3731

I’m another ‘It depends’ believer.
My experience:-

We had a new gas boiler fitted 18 months ago to replace an original 25 year old unit.
It’s a Heat only boiler, not a combi.
Since all new installs have to be a condensing type, that alone should provide some improvement in efficiency.

I tried changing the system setup to get the best efficiency.
At the time, the house was not occupied during the day so it was set up to be off between 9 to 3pm.
This also sort of lead to installing the Wiser system.

Low temperature, low flow just did not work for this house.

The radiators are piped in micro-bore, some 8mm, some 10mm.
The radiators did not provide enough heat output using low water temperature. (60C I think).
The rooms could not achieve their target temperatures at times.
Low flow also increased the boiler cycling activity as it could not modulate to a sufficiently low output.
(Boiler cycling results in poor efficiency).

Boiler cycling will also happen if you have micro-zoning. Radiators demand heat at random times. A radiator is likely rated at 2 or 3kW so the boiler shoves out 20kW -or whatever it’s rated at- for a short time and then has to throttle back or cycle off/on. Just think. If a room is up to temperature, it may only need a few hundred watts or so to keep there. OpenTherm may help here.
The good news under these conditions is, the return temperature is nearly always below 55C so the boiler condensing feature is always active.

Conclusion:
Low flow, low temperature needs big bore piping and huge radiators.
A boiler with a large modulation ratio (10:1 ?) is good.
Don’t over-size the boiler - it will likely result in more cycling than necessary.
With a room heating controller set to ‘Gas’, it is on a 10 minute heating cycle. Best to select ‘Oil’, which is on a 20 minute cycle, potentially doubling the gas valve MTBF.
The original CH system boiler was set at 70C, which is probably what the CH system was designed for.
It is also what it has ended up being set to without making major changes to the rest of the system.
OpenTherm would probably not have helped one jot here.

A new house design is whole different story.

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3732

Just spoke to Veismann tech support.

They confirmed all their combi boilers:

  1. Speak opentherm (but couldn’t confirm to Wiser specificall) so this info could only come if somebody here has Veismann and its worked.

  2. Can do 2 flow temps for ufh and radiators using a heating mixer extension. They said if using a manifold mixing valve the boiler would only do the highest flow temp, but if using their own mixer it could heat to lower flow temp channel only if that was the only one being used at that time.

I did smile as their support wasn’t as great as Wiser or other companies, just like Urban Plumber said it would be.

They didn’t fill me with confidence, but their boilers do seem to have features many others don’t including:

  1. the heating mixer extension for 2 channels

  2. combi 46L storage boiler removing need for a separate cylinder and heat geeks say it can supply about 7 showers at the same tim with such a small storage section as it uses heating plates instead of smaller coils.

Then the other issue is that I’ve never met anyone thats had these, and I guess most installers wouldn’t know how to use them properly?

Regardless, Wiser and Heatmesier both told me their underfloor heating solutions are only on/off and modulate via opentherm.

Does anyone here have experience with Veismann or do you recommend Baxi/Main or another opentherm one?

Thanks

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3733

See my linked post for some experience with a Viessmann Vitodens 100-W and a Wiser on OpenTherm, I was perfectly happy with how it worked, my only grumble was that the Viessmann was fairly limited in the data points it supplied (setpoint, flow temp, modulation % IIRC, but not return temp for example). The opentherm gateway was only there for inspection and overriding Wiser occasionally (I can’t remember what hacking I was doing), but it worked fine without it too.

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3734

Admin - sorry for this long post and topic has perhaps also steered slightly away from Wiser specifically, but hoping its still relevant to most here as more about wiser heating zone integration with the opentherm boilers and heating theories.

…So the story continues…

I had a long 2 hour session with my local heat geek. Turns out his boss Andrew is also the guy that originally trained Adam from Heat Geeks - he showed me snapshots of Adam saying that.

They want to put a Veismann 200W-32kw Combi boiler due to lack of space for cylinder or even a combi storage unit like 222W.

ZONING

The alarming thing is they want me to get rid of all zoning completely. No Heatmeiser for UFH. No Wiser for TRVs.

They want me to forget about the room zoning and the floor zoning too, and just treat the house as one envelope.

The ViCare app from Veismann will let me control the heating directly from the Veismann without asking 3rd party apps to do this - which will remove need for opentherm modulation as it does all the modulation automatically + greater data.

The boiler will allow me to (if I want) have 2 zones in the house. The UFH zone and radiator zone which I can turn off/on if needed.

As nobody is at home during day 80% of the time, I might turn off the rad circuit until evening - but they are against this.

However, their plan is to keep both on 247 with a setback at night and only turn off if going away.

The system only measures the weather temp externally, then calculates how much to modulate the boiler from 32Kw down to 1.x?W as required to keep the heat at the desired eg. 20C temp internally.

It uses the temp of the outgoing water vs return water temp to calculate how much heat loss is happening I think?

UFH SPACING

Although they wanted me to do a heat loss calculation at £400 this would only serve to tell me how wide the UFH pipes should be and size of radiators (which I’m not changing). As such its pointless for me. The ideal UFH pipe spacing they wanted was 100MM or 125MM to increase the surface area and allow lower water temp to flow through. (My builder is moaning as he only wants 150MM for bending issues so a bit of a conflict there - I’ve asked him to do counterflow layout instead of serpentine but i’ll need a laying plan to guide him i think).

On the heat loss issue they said its not a major issue if I don’t do that with them as the boiler will gather the data and after 12 months be able to confirm the ‘exact’ heat loss rather than the ‘estimates’ they would do.

PROBLEM

The only thing thats not making sense to me and I couldn’t get a straight answer is how their system will know when the ideal temp internally has been reached without room stats - as House A could have great insulation and House B crap insulation.

Without this information, it all seems theoretical to me although the return water temp could perhaps help somewhere but only to confirm how much heat is lost rather than how much retained in the rooms and if its the ideal temp or not.

In addition different rooms could have different insulation = different end result competely.

This is really concerning me, so I might layout the heatmeiser wiring at a minimum, incase I decide to zone again in the future. Will also lay out extra radiator piping will developing, incase rads are needed in future (although hopefully not).

Is anyone that has experience with Weather Comp (and even Veismann 200W perhaps) able to advise me on the question which remains unanswered on 0 internal stats?

Thanks

ps. They said although it sounds crazy, even ‘skill builder’ from youtube who was always disagreeing with heat geeks Adam about this has now agreed this approach and that this is better than zoning floors/turning off etc. Not been able to check this incase anyone has seen it?

3735

James - so this means that the Wiser hub can’t speak opentherm directly to a boiler for modulation without this gateway device??

3736

I would go with the advice. I’ve been watching them for a while now and also the recent skill builder videos and if I was installing a new gas system I would be doing this. Instead of having an internal thermostat, weather comp can be used purely along with balancing to achieve constant stable temps. It might take a little adjustment in the first few weeks to dial in the correct weather comp curve but then it should be pretty set and forget. The only thing that you might end up adding if you find a few radiator rooms get too warm such as bedrooms is you might add a few manual TRVs just to act as temperature limiters but most of this can be achieved through balancing anyway.

3737

The way I read this post is that he only inserted the gateway in order to inspect what was being reported by the boiler ( IE just to get the data out to openhab). Correct if wrong.

3738

Re: the skillbuilder episode I think they’re talking about is regarding the guy that had a terribly installed heat pump. Heat geek replaced they system and now the owner is really impressed and loves it, having absolutely hated it before. I think this turned skillbuilders thinking having seen how steady state heating worked with his heat pump after heat geek redid the install.

3739

thanks Tombadog. Very helpful.

When calculating flow temp from external weather, doesn’t the boiler need to take into account the level of insulation in house/effect of the flow boiler flow?

It can’t be the same flow temp for a highly insulated house to one that is basically made of straw? Without knowing the internal temp, boiler can’t calculate the insulation quality - unless return flow temp is enough to calc this?

I asked this question to another heat geek and he said you have to have a sensor both inside and out to make the weather compensation work - so now 2 different approaches from 2 heat geeks unless i’ve misunderstood something?

3740

This document from viessmann I just found has some more info. Basically, the installer will set a weather compensation curve based on either a heat loss calculation or very good guess based on experience. This can then be adjusted in the first weeks of operation. You can also add a internal sensor and use a feature called room influence to also feed in your desired indoor temp but this isn’t necessarily needed hence the 2 different opinions. You could always try without and then add one if you feel it’s needed - I imagine (but don’t know) it’s wireless.

3741

My Ideal OpenTherm combi boiler works just fine in OpenTherm mode.
It’s my Wiser HUB that leaves a lot to be desired.
As people have already said in this thread and Wiser themselves have also, Wiser has a poor implementation of the OpenTherm standard.
However the Wiser integration does work on a basic level and does recognise the boiler as OpenTherm with flow temperatures and modulation info etc. See a lot further up in this thread, it has been discussed before and limitations noted.

Maybe this detailed subject should be discussed in a separate thread?

3742

Based on the comments do you now see that room zoning isn’t always, if ever, a good idea.

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3743

I really think it depends on your circumstances and house construction. We have good internal insulation. I can easily maintain a 10C offset between rooms that are not used and rooms that are used, so in my case room zoning makes total sense.

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3744

I feel my fav term in architecture meetings is also applicable here “It depends” :slight_smile:

3745

just a quick question on wiser trv’s. can you choose which ones have the ability to turn boiler on and boost heating even if its off atm in schedule?

thank

3746

Not sure I understand the question …

but if a itrv is low in the schedule, you can always boost the rad and that will trigger for heat from the boiler… I havent tried setting the trv to off and seeing if you can still call for heat though, it might still work.

whats the usecase?

3747

sorry let me rephrase.

  1. trv is off in the schedule as nobody expected to be home.
  2. user comes to room unexpectedly and decides they need heat.
  3. If they press the boost button on TRV, would this trigger boiler to turn on?
  4. Also - Is there a setting in Wiser to select which TRV’s can trigger boiler or not? I know Hive have this setting for their TRVs.

Thanks

3748

So when you say off, do you mean “off” or like at a low temp?

For my house we have the away mode set to 12c (our off). IN our case the rad is set to 12c by the schedule and YES, by twisting it (shows red) , it will boost the rad for 30mins. You can also boost the rad for more than 30mins in the integration/climate card.

I havent tried if the rad is “Off”, easy to test though

I dont think Wiser allows you to set which TRVs can trigger the heat or not, but within this integration we have something not available in native wiser called “PassiveMode”
See In Built Automations · asantaga/wiserHomeAssistantPlatform Wiki · GitHub , this may be what you are looking for.

Another approach is to put normal TRVs on them , they only get hot when other rads in the house call for heat…

hope this helps

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3749

You can lock individual TRV’s so that fiddling with the controls on them doesn’t do anything. This can be done in the Wiser app or in this Home Assistant integration.

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3750

The answer to point 3 is yes but heating just one room is very inefficient and costly. Most gas boilers cant modulate low enough to efficiently heat one room.

The answer to point 4 is no, Wiser doesnt have this as an option however i believe that the Wiser HA integration has a “passive mode” where the TRV can be set to not call for heat. Personally i do this in my Wiser setup but i just have manual TRV’s for this function which are a lot cheaper than Wiser TRV’s.

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