All good info Paul, especially “Be an informed customer”!!
Phil

Yes you have picked a superb boiler. My boiler/cylinder is being replaced later this month with this same 100W combi boiler.

Thanks for your very informative video Paul. Food for thought. Cheers Nobby

Great information and sensible discussion points.
Take care.

Very informative and thought provoking. I have a Worcester Bosch which doesn't allow Opentherm. FYI, their wifi thermostat does weather compensation based on internet-provided data, rather than needing an external sensor. Viessman sounds like a candidate when this one fails and the warranty / Which awards are good confidence builders.

Thank you Paul for yet another informative video 🙂

Hi Paul, great job on your explanation and research. And that’s coming from someone retired from the industry.
And your piping skills are just fine.
The only thing I would add is to be sure to do some research on the manufacturer make sure they’ve been around for a good period of time and will be there in the future for support.

Well done 👍, Cheers….

Very interesting theme...Thank You for the video...

Good evening Paul. That was a very thorough but very clear explanation of your thought processes and reasoning. Thank you. You mentioned "Compact" boilers Oh Yes they were a nightmare, Potterton brought out Their Suprima Compact boiler and everyone wanted them..... The problem I came across was that the temperature inside the casing badly affected the solder joints on the pcb and they were forever breaking down with dry joints causing breakdowns. Potterton came out with a revised board I believe but after fitting only a few of them and having repeated problems I refused to supply and fit them. Viessman have always been the creme de la creme of boilers. As you say initially they are quite an outlay but when you factor in the guarantee of 12 years parts and labour that is longer than most more economically priced boilers will last. I know of some French or Italian boiler that would only last 6 years !!!!! Thank you as always for your excellent research and straightforward explanation of systems and their intricacies. All the best. Malc

Hi Paul, I think I'll be watching this one again in the future!!

Very interesting especially the radiator thermostats. I guess if you loose WiFi or Internet then the boiler just goes to a default value?

You made a good job on the plumbing, looks like that pipe bender has paid for itself in the end. As an aside I'm currently working on a project to replace copper pipework due to problems with the filler containing cadnium.

All the best!!

Hello, a very timely video, thank you. I have Tado X with smart valves and very happy with it. I am today having a W100 Viessmann Boiler installed but I have the W 100 B!GA version, which is heat only. What I am very disappointed about, as I like you love technology, is that the B1GA does not come with WiFi and does not work with OpenTherm. Tis is a bit of a blow to discover this. Plumbing wise its a good it for my needs with the two 22mm pipes coming out at the top of the boiler not like yours which are at the bottom  and maybe you have four 22mm pipes two for heating and two
for Hot Water. If I fitted the optional WiFi module it will only give access for my installer not for me as the customer, not what I was hoping for. I do not understand why Viessmann dont fit WiFi and OT to this version of their W100 range. Sorry about the moaning 🙂

23:17 I would no longer even consider those makes, our previous boiler was Worcester and it was a perpetual nightmare after about 4 years - the only saving grace was that it was on an extended warranty, so the dozens (literally) of parts that had to be replaced were at their cost and not mine. That said, the number of times in winter where the boiler would pack in was ludicrous and the final straw was when the main heat exchanger needed replacement at a cost of several hundred pounds... guess which part wasn't included in the extended warranty. I went for Viessmann too on the recommendation of my plumber and also have an extended warranty, it is a good boiler and went wrong once within the first couple of years - that had a bit of a drama because their engineer refused to fix the boiler because it hadn't been installed correctly; it turns out that our pipework caused a slight confusion and appeared to conform to the requirements in the manual but technically didn't. It was a bit annoying but our plumber came and sorted it out in short order so Viessmann fixed the fault - it didn't actually stop the boiler working but there was an intermittent fault that meant it had to be reset from time to time, ultimately it turned out to be something on the control board and it hasn't had a problem since.

First Paul, congratulations on your choice of replacement boiler.
  I wouldn't be so quick to interpret a boiler turning off as 'less efficient', it's the burner turning off a 1800c flame until there's enough capacity in the flow for a further burn, all gas boilers have to do this, even the 200 does so if demand falls below 1.8kW - Given your heat-losses, I expect you'll be on constant burn soon enough, meanwhile I'll have to wait on a -7...
Your point on reducing the target temperature by 2-3 degrees gets close to the 5% per degree reduction in gas consumption I'd read somewhere previously.

I can't say I'm surprised that a boiler installer will be nowhere near so accurate on heat-loss as a heat-pump installer, the lower temperature flows of heat pumps require a more accurate assessment, and they're not shy on asking to see your gas bills to verify it.

I take your point over traditional on/off control being the default on installs, partly because clients are used to them, but it also allows the boiler to be commissioned quickly, with a callback if you want to change the control - Opentherm is more popular in Europe, but it's incorporation in boilers is rarely full blown Opentherm even today.
I had looked to Opentherm for the old Buderus (part of Bosch) boiler quite a few years back, apparently they had an Opentherm interface board listed for that boiler but nobody could find one.

I was intrigued by electronic TRVs years ago as they appeared to tick a lot of boxes, but no regrets on going for the not-smart IMI Eclipse which does exactly what I ultimately needed, setting the rad flow max and self balancing across the system, the Heimeier heads maintaining the individual room temperatures with remarkable precision.
  Where I must diverge markedly from your approach is on the entire turn down turn off argument in saving gas - It takes more energy to bring a high thermal mass back up to temperature than saved - I did try it for myself when I was getting live data on consumption from the gas meter and proved that to my satisfaction.
  As has long been my habit, I still open all the doors and windows for a 5 minute a blow through, and on the monitoring system the room temps barely dip by a decimal of a degree.
The reason is simple - The walls are the greater surface of a room, and masonry is slow to release heat and even slower to absorb it.

  It is worth bearing in mind the emitter side of the equation in all of this as it's important - Quoted D50 values of radiators are only true for specific conditions - eg Room at 20, differential at 20, flow at 80 - The effective power at flow of 50 for the same room temp and differential is 30%.
  For my original on/off setup with known undersized rads of 2,682 (D50) in the Lounge, at -20 the boiler was running flat out, and getting a return in the high 30s by the time the stat shut the boiler off - With the oversized rads of 5,114, I was able to get through a -20 without the boiler screaming it's head off and nailing the target 30 return - What I was doing in effect was charging a heat battery and letting it decay.
  Roll forward to today's setup with the Viessman on continuous circulation and a -20 winter, I'd need a flow temp of 51, BUT here's the wrinkle - Continuous circulation extends the h in kWh, and I have every reason to believe the return will still be 23, just as it was in last year's -13 when the effective power of the rads was 1,452 watts - It's now a heat battery on trickle charge.

Food for thought....

Hi, yep, mingle with some installers and you find a difference between the marketing and the reality. Ask them - which one would you buy?  People might be surprised. Cheers

Hey, did you consider going up to the 200-W for it's 1:17 modulation?

viessmann, good decision. They also send you a reminder when the annual service is due, along with the installers phone number. Why didn't you lock off both ends of all the rads and crack open the highest tails instead of draining all the system. saves time and inhibitor