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Discuss New heating system: 4 bed,2 bathroom, UFH/radiator mix in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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Hi
We are getting new heating installed.
Likely go with Viessmann - looking for set and forget, high efficiency, high comfort level, weather comp heating with high modulation ability x20 levels from 1.6kW to 35kW
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Question is, what to choose: system boiler + unvented cylinder (180 litre), or the 111-W combi, with 46 litre internal hot water storage..
This will run 90 sq m UFH (maybe polypipe tray system above insulated suspended floor) to ground floor, and 6x radiators to first floor - 4 bedrooms + bathroom.

My gut feeling is that a system boiler gives advantages:
- 180 litres of pressurised indirect hot water at the ready when a power cut occurs.
- immersion heater in event that a boiler fault arises temporarily.
- an immersion heater to use 'free' electric from possible future solar PV (the price will come down, right?)
- a better match for the size of home, even if, usually, it will only be 2 occupants..
26kW or 35kW .. 50 sq m Gr floor extension will be well insulated modern design, insulated EPS block+beam floor, this is on the cold east/NE of building.. 20 sq m 1st floor extension will be well insulated design, this on the north of the building. Old roof will get a very thorough insulation fitted, with ventilated warm roof ridge/eaves.
Plan to use triple glazing to replace old failing DB glazing.

What do you think?
Thanks.
NB. Why don't online heat loss calc tools include options for triple glazing?
 
System and unvented best with div cons

Needs sizing right
 
System and unvented best with div cons

Needs sizing right

1 vote of system + unvented [why that choice here?]

All I know about divicons is that they cost a lot. What will a divicons do for us?
UFH zones downstairs usefully separates upstairs radiators from downstairs UFH.. What more does a divicon provide for?

Sizing is a worthy topic in heating systems, yet, if the cost of the boiler is not so much more than a likely sufficient 1 size smaller, these Viessmans, with 20x modulation from only 1.6kW, make considerable difference to efficiency in spite of over-sizing..
 
Because your getting a new system installed and you have more than one bathroom / likelyhood of more than one outlet being used at the same time )

No requirement for a pump and mixer at each manifold on the underfloor but

Also depending on min zone kw usage I would suggest either a llh/ plate or cct set up due to the low demand with one zone open

Also I would check my min load figure as that seems very low normally Viessmann's have a low of around the 4kw mark
 
+ 1 , for the System boiler and a 200 , sorry but yes the divicons are a fortune , I did the 200 course ( again lol) down in Telford again a fortnight ago . The divicons are superb and the savings with WC are incredible. But you have to balance the savings with the inital cost of the installation, and thats where it gets tricky.
I would have a word with Viessmann tech on your plans , they wont charge you and are very helpful.
 
Thanks for the input. Viessmann are helpful, but they tend to push domestic queries to registered local engineers.. It can be difficult to pin them down to explain why a technical aspect is relevant and how..
Local engineers are, hopefully, busy getting on with installs to earn a crust.. Not much time for explaining stuff.

My feedback to Viessmann is to provide case studies on the website - not so that someone like me gets daft ideas on DIY gas installs, but that potential customers learn what they want and why - how a Viessmann product differs from a different product.. Less time for installers to attempt explaining and persuading people like me!
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So, what does a divicon do? How will that provide us with savings?
 
Because your getting a new system installed and you have more than one bathroom / likelyhood of more than one outlet being used at the same time )

No requirement for a pump and mixer at each manifold on the underfloor but

Also depending on min zone kw usage I would suggest either a llh/ plate or cct set up due to the low demand with one zone open

Also I would check my min load figure as that seems very low normally Viessmann's have a low of around the 4kw mark
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Thank you. Wow. Lots of information here. Thx.
Water pressure/flow volume is borderline for 2 simultaneous showers. Had been told that 2 options are for a pumped/pressured unit pre-cylinder.. OR, to add an accumulator vessel that will gather peak of water pressure and improve the thresholds..

How does a divicon change the equation?

UFH: 1 manifold, correct? I am not entirely clear on relation between Viessmann Sub-Mounting kit and the polypipe manifold..

Please define: "llh / plate or cct set up" (what are they? ..and.. ) in relation to low demand..
I Just checked and a 200-W modulates down to 1.6kW - this, not the price tag, attracts me to the boiler.. The 100-W would be fine, but Viessmann have further developed things.

What reason for preferring the system boiler?

Thanks
 
Thanks for the input. Viessmann are helpful, but they tend to push domestic queries to registered local engineers.. It can be difficult to pin them down to explain why a technical aspect is relevant and how..
Local engineers are, hopefully, busy getting on with installs to earn a crust.. Not much time for explaining stuff.

My feedback to Viessmann is to provide case studies on the website - not so that someone like me gets daft ideas on DIY gas installs, but that potential customers learn what they want and why - how a Viessmann product differs from a different product.. Less time for installers to attempt explaining and persuading people like me!
--
So, what does a divicon do? How will that provide us with savings?

A divicon is basically a mixer , it regulates the flow temp by mixing it with the return temp , but its all controlled through the boiler , where the WC control s the heating through the preset curve and slope ( basically the flow leaving the boiler )
I have recently bought another house and basically are in the same boat as you , even I arent sure what to do lol .
 
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Thank you. Wow. Lots of information here. Thx.
Water pressure/flow volume is borderline for 2 simultaneous showers. Had been told that 2 options are for a pumped/pressured unit pre-cylinder.. OR, to add an accumulator vessel that will gather peak of water pressure and improve the thresholds..

How does a divicon change the equation?

UFH: 1 manifold, correct? I am not entirely clear on relation between Viessmann Sub-Mounting kit and the polypipe manifold..

Please define: "llh / plate or cct set up" (what are they? ..and.. ) in relation to low demand..
I Just checked and a 200-W modulates down to 1.6kW - this, not the price tag, attracts me to the boiler.. The 100-W would be fine, but Viessmann have further developed things.

What reason for preferring the system boiler?

Thanks

Need to get the static and dynamic pressure and flow tested asap

Simply the sub mount is a div con

My figures were for the 100 but good choice the 200 is the best boiler top of the top

Either system boiler or 4 pipe boiler (with hw prioritie) both are good set us
 
I see it now.. The combi 111-W has modulation ratio of max 1:6, ie. 26kW boiler can run as low as ~4.4
Not quite the same as a 200-w with 1:19 max ratio.

And I have this feeling the installer wants to fit that one, either because it will be a nice simple install, or, because the current boiler discount on that model is better than on the 200-w

May be I am out of order to say the latter.

Sub mount is a div con .. Got you. Costly stuff. Viessmann technical describe it as plug and play for UFH in combo with the boiler controller.

Static and dynamic pressure and flow tested..
Water?
Well, pressure looks to be ~3.2 bar. Flow I think was around 15 litres..
But that was via 15mm pipes, 10m of pipe away from 25mm main reduced to 22mm..
 
Your the customer aslong as it doesn't harm or effect the system in a bad way you can have what you want

Yep plug and play with a few pipes :D

Yes sounds like it's just enough for an unvented

Where's the plan/location for the new kit / boiler / unvented ?
 
Plan is that the garage will be 'carved up' - 6' taken from rear to help create a utility room, front for bikes/storage - garage door gone, replaced with insulated wall and modern insulated hinged doors or door+half.. Good for big items when required.
On side of garage next to house are gas, electric and water main.. Nearest front will go boiler next to cylinder.. Down pipe outside for condensate and pressure release.. Flu can go directly through wall at front.. Pipes can go up to 1st floor void easily, and to understair cupboard for possible UFH manifold.

Downside of cylinder+system boiler is more space taken, but I like the upsides.. And when price of solarPV comes down or power cuts get to be a thing, then we can push cheap/free elecric in to hot water cylinder via immersion.
Water pressure.. We'll have to see what 22mm delivers, but it ought be sufficient.. Worst comes to worst can add a pressurised tank to incoming water..
Be interesting to know what the new heating bills will be.. I fancy it will be a serious change from huge old house bills. We'll see.
 
Yea so plenty of room for say an 200-300l accumulator worst case
 

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