Suggest gas combi boiler

[Depo]

Hi guys,


I`m looking for ultimate gas combi boiler, for underfloor heating, but struggling to find such. Can you advise? Must have following spec:


1. 24-30kw - 1 bed flat.
2. Stainless steel heat exchanger
3. Minimum of 12.3L/min at 35 degrees
4. Modulation 1:6
5. Minimum efficiency of 89%
6. No more than 40dB when burning at max
7. Consumes no more than 87w when burning at max and no more than 5w when idle
9. Brass/copper instead of plastics inside
10. Does have optional 7 day timer.


Thanks 🙂

 

[Rickster123]

28-30kw for a 1 bed flat?

Welcome to the forum by the way!

 

[ShaunCorbs]

and underfloor heating in a one bed flat lol first time ive heard of underfloor going in a flat

 

[Depo]

Because I don`t want to shower(at 40 degrees), then somebody starts washing dishes in kitchen and flow/pressure drops. Or washing machine starts running. I prefer to have guaranteed flow.

 

[Depo]

and underfloor heating in a one bed flat lol first time ive heard of underfloor going in a flat

Why not? Radiators don`t look good, take up space, don`t heat efficiently. Also the kid and cat can enjoy warm floor(and me walking bare feet). And UFH cuts my gas bills. BTW its got high ceiling, not rabbit box newbuild, bigger than average.

 

[Ray Stafford]

Because I don`t want to shower(at 40 degrees), then somebody starts washing dishes in kitchen and flow/pressure drops. Or washing machine starts running. I prefer to have guaranteed flow.

Then dont buy a combi.

 

[ShaunCorbs]

Because I don`t want to shower(at 40 degrees), then somebody starts washing dishes in kitchen and flow/pressure drops. Or washing machine starts running. I prefer to have guaranteed flow.

kw doesnt = more pressure and if you want decent flow unvented system is what you want

 

[Depo]

Vaillant boiler for example:

At 42 degrees it provides 7.8L/min, but at 35 9.4L/min. It makes me think that getting higher kw boiler will give me more water at 42 degrees.

 

[Depo]

Then dont buy a combi.

I meant flow at specific temperature.

 

[rpm]

and underfloor heating in a one bed flat lol first time ive heard of underfloor going in a flat

There are some big flats around mate.

 

[Ray Stafford]

I meant flow at specific temperature.

You won't get that with a combi if someone opens another outlet.

 

[Depo]

rpm, why not? I explained reasons in my post above.

 

[ShaunCorbs]

Vaillant boiler for example:

At 42 degrees it provides 7.8L/min, but at 35 9.4L/min. It makes me think that getting higher kw boiler will give me more water at 42 degrees.

nope it slows the flow down to heat the water (so more heat = heating the water faster = slightly better flow rate) but if your incoming water flow rate is low your hot water flow will be less

and them figures are at about 15-20 lpm (main pressure about 1.5 bar)

 

[snowhead]

Hi guys,


I'm looking for ultimate gas combi boiler, for underfloor heating, but struggling to find such.


9. Brass/copper instead of plastics inside

I doubt there is such a thing made anywhere in the World.

Everyone uses plastics.

 

[wattsie1987]

Is this guy for real?!!? Would you like a high gloss or matt finish on it?

 

[rpm]

rpm, why not? I explained reasons in my post above.

Think you misunderstood my post, I`m replying (with the quote) to another post and saying there are some massive flats with massive floorspace around.

 

[Ray Stafford]

Vaillant boiler for example:

At 42 degrees it provides 7.8L/min, but at 35 9.4L/min. It makes me think that getting higher kw boiler will give me more water at 42 degrees.

You are correct. By increasing the kw rating, you will either get more flow for the same temp, or a higher temp for the same flow. At the extreme top end of the combi market - around 40kw - 42kw, this is enough to support two concurrent outlets at very moderate flow rates. (say a basin tap).

But to get a constant temp and flow whilst running multiple outlets anything more than that, you will need either stored hot water, or a dedicated water heater from the light commercial sector.

 

[Depo]

What I`m trying to achieve - if I shower and somebody opens a kitchen tap, water flow doesn`t drop in shower and still keeps running at xxL/min at xx degrees.

 

[Depo]

I doubt there is such a thing made anywhere in the World.

Everyone uses plastics.

Vaillant Ecotec Pro and Ecotec Plus are like that - one has more metalic parts, hence its cheaper. I didn`t mean zero plastic parts.

 

[Depo]

Is this guy for real?!!? Would you like a high gloss or matt finish on it?

Don`t care, can be pink, it will be hidden in kitchen cupboard.

 

[Depo]

Thank you very much Ray, your post was excellent.

 

[snowhead]

What I`m trying to achieve - if I shower and somebody opens a kitchen tap, water flow doesn`t drop in shower and still keeps running at xxL/min at xx degrees.

The only way you'll get close to that is by having a boost pump just for the water inlet to the Combi.
Even then it won't be guaranteed.

 

[wattsie1987]

What I`m trying to achieve - if I shower and somebody opens a kitchen tap, water flow doesn`t drop in shower and still keeps running at xxL/min at xx degrees.

Flow restrictors are the only way to achieve this. ecotec plus and pro use the same internal components plastic to metal wise. They are my boiler of choice though.

 

[Depo]

As per Ray`s post, its not a problem with amount of water supply to the boiler, but kw of boiler itself - ability to heat XX L water at xx degrees per min.

 

[ShaunCorbs]

What I`m trying to achieve - if I shower and somebody opens a kitchen tap, water flow doesn`t drop in shower and still keeps running at xxL/min at xx degrees.

unvented system