Ideal Logic+ 35 Vs Vogue 40kw

[hyperbole]

Another boiler suggestion post.

4 bed detached house built 20 years ago with cavity wall insulation and double glazing. 1 bathroom and separate ensuite shower. 2 adults and 1 child.

Cold water flow is 20l/m. 16 radiators but 6 are single panel. Already have Tado which supports OpenTherm.

Want to convert gravity fed system to a combi. Primarily to get rid of the airing cupboard which houses the hot water cylinder. We need this space to enlarge the bathroom. Also prefer on-demand hot water. Fully aware of the disadvantages of the combi.


Getting conflicting information from the gas engineers that came out to quote. Some quote 30kw boilers and way 35kw-40kw is overkill, some say I need to go for 35-40kw.

I am contemplating between these

Ideal Logic+ C35

DHW output 35kw
DHW flow rate 35C rise : 14.5l/m
CH output 70C min/max : 7.1kw -24.2kw
7 year warranty 10 years on heat exchanger

Ideal Logic Vogue Gen2 C40 or Vogue Max C40

DHW output 40kw
DHW flow rate 35C rise : 16.4l/m
CH output 70C min/max : 5.7kw-32.0kw
10 year warranty for Vogue and 12 for Vogue Max.

I think all 3 have stainless steel heat exchangers and support OpenTherm.


I am leaning towards the Vogues as they provide better flow rate and can modulate to lower CH output so assuming will be cheaper to run?

Are there any major disadvantages going for 40kw Vogue?
Too much for our needs ?
I am happy to pay a bit more and get a really good shower.
Is 14l/m Vs 16l/m that noticeable?
Or 7l/m Vs 8l/m when running 2 showers or taps at the same time (not very often).

Thanks in advance.

 

[hometech]

Why not start with the basics and calculate your heat demand. Look for ways in which the heat loss can be reduced (insulation) then re-calculate. Designing for maximum need (@ -2 degrees) has to be realistic...do you often have -2 where you live and for how many days each year (met office have the data).
So lets say your average working load is 20kw, min 15kw and max 25kw then a boiler that can modulate down to 15kw and max out at 25kw would be fine. So the question is not how far can it modulate, the question is how far do I need it to modulate.

Hot water then is another issue. The boiler output @ 16l/m is significant flow by any standards but can the boiler have the full 20l/min cold input at all times (priority) and can it raise this volume of cold quickly enough to give 16l/min @ say 48 degrees( to allow for mixing).
Do you believe that having 2 showers running simultaneously is simply a matter of dividing the theoretical output of the boiler by 2?

Modulation prevents the stop start but that is not what saves money. Loosing less heat is what saves money by using less gas.
Do you stop start the heating cycle as well? How much heat is used to heat the fabric of the building before heating the room?
Heat to 21 degrees for x hours per day and then allow to cool to y degrees before starting again. Do the math, which is the better option.
You also need to consider the benefits of a constant temp throughout the house (I live in a house, not a series of interconnected rooms) as this helps with humidity and you can establish comfort levels @ 18-19 degrees rather than 21-22. That reduces gas consumption.
If you want to be able to have lower temp circulating in the system, does your choice of boiler allow for the flow to be controlled? Is this on offer? If you can opt for flow temp then lower the temp and upsize the rads then leave it running 24/7.
This 24/7 works great with flow temp provided you have external temperature sensing as it needs to operate on automatic. Room thermometers won't work in this situation

 

[ShaunCorbs]

You won’t get a combi running two outlets either unvented cylinder or Viessmann 222

 

[Scott_D]

The Vogue has a stainless steel heat exchanger, logic is aluminium
Vogue has a 10L expansion vessel, logic has 8L

The vogue is a better boiler in my opinion

 

[Frelon]

The Vogue has a stainless steel heat exchanger, logic is aluminium
Vogue has a 10L expansion vessel, logic has 8L

The vogue is a better boiler in my opinion

Stainless steel heat exchanger is best if you ever consider installing a water softener in the future.

 

[hometech]

Results from temp and humidity sensors around the house. 2,500 sq feet property. No room thermostats, no heating zones. Wall radiator heating on Heating 24/7. Perfect heating and humidity.

 

[Scott_D]

Results from temp and humidity sensors around the house. 2,500 sq feet property. No room thermostats, no heating zones. Wall radiator heating on Heating 24/7. Perfect heating and humidity.

Not really relevant to the question asked though?

 

[hometech]

Not really relevant to the question asked though?

The question posed related to boiler selection
I proposed using maths to create the perfect heating profile and to use that as the start point then find a boiler to suit
I them posted a picture to demonstrate that perfect heating profiles can be achieved through maths
Which part does not related to the question?

 

[Scott_D]

The question posed related to boiler selection
I proposed using maths to create the perfect heating profile and to use that as the start point then find a boiler to suit
I them posted a picture to demonstrate that perfect heating profiles can be achieved through maths
Which part does not related to the question?

The question was about 3 specific combi boilers. You are referring to your property and how you use your heating which could be totally different

 

[hometech]

perhaps this is a perfect example of why the UK heating industry is considered the worlds most inefficient and outdated. Plumbers can't understand the vital importance of first principles and instead have fashion parades