Recommend a system boiler & control

[dreadpirate57]

I’m struggling to choose my system boiler and controls, between all of the different brands, smart thermostats and technologies, I’m confused.

Physical set up is as follows:

System boiler and 210l Indirect unvented gledhill hot water cylinder

12 radiators across 3 bedrooms and one bathroom, 3 - 4 sinks

50 sqm of wet ufh in one open plan kitchen (one thermostat zone), supplied by continal. Calculated at 4.4kw. Salus wiring centre.

My plumber has setup with 3 2 port zone valves, one for ch, one for cylinder, and one for ufh. He’s on the old school side, so not too famililar with the newer smart elements of heating systems.

I’d like homekit compatibility and for the system to be efficient, perhaps making use of opentherm / weather compensation.

Does anyone have a similar setup and could you provide any recommendations on system boilers and controls?

So far ive looked at Viessmenn Vitodens 100-W B1HF 25kW System and Worcester Bosch Greenstar 4000. It looks like bosch easycontrol won’t work however, due to the addition of ufh.

Initially I was looking at tado but its unclear if it would work in the above arrangement.

Any advice / recommendations would be very much appreciated.

[JohnMo]

If you have wired a d set up as S/Y plan, you are stuck with one flow temp.  WC will not work correctly as you need a high temp to heat the cylinder.  You need to change the wiring to X plan or priority hot water. This switches the boiler to 2 different flow temp setting.

 

Your UFH will have a mixer valve as the flow temp will be different from radiators, so on a fix temperature.

 

Not really of smart thermostats, so will leave that for others to comment. Most are just dumb on/off units with WiFi.

 

If it was my house.

X plan on boiler, using only boiler controller to do WC. Heat pump cylinder so I could do DHW as low temperatures. No zones.

 

Viessmann boilers are good, but need to be plumbed and wired as per their instructions, to get the best out of them.

[dreadpirate57]

Thanks John,

 

We have not yet wired up from an electrical perspective, but the zone valves and first fix plumbing and cylinder are all piped up. 

 

Am I too late? 

 

I'd ask my plumber but he has a tendency to overreact.

 

Cheers.

[JohnMo]

Have read up, other good boilers are Intergas, Atag, both do weather compensation out the box.

 

https://theintergasshop.co.uk/content/189-why-hot-water-priority-pdhw-is-the-reason-s-and-y-plan-should-be-banned

 

 

[marshian]

9 hours ago, JohnMo said:

If it was my house.

X plan on boiler, using only boiler controller to do WC. Heat pump cylinder so I could do DHW as low temperatures. No zones.

 

Viessmann boilers are good, but need to be plumbed and wired as per their instructions, to get the best out of them.

 

^ WHS - I'd use Viessmann controls with a Viessman boiler and Valliant controls with Valliant Boiler WC and X Plan - I'd avoid third party controls on boilers where manufacturers have really good controls (they just aren't going to be optimised because they are cover multiple boilers)

 

However the most important thing for me is sizing the boiler properly to the heat loss of the property and making sure it modulates down as low as possible to minimise cycling and cover the autum spring months with low temp and low boiler output levels.

 

I'm not sure if many manufacturers have caught up with the modulation ratios that Viessmann are capable of - a few are getting close