Any combi boiler that can heat hot water and radiators at the same time?

[eveares]

Hi all.

Does anyone know if there are any combi boiler that can heat both the hot water and the radiators at the same time? I know most don't, but was wondering if there was any exceptions?

I can't see why this would not be physically possible as you could have a diverter valve in the boiler what has three positions (HW Only, CH Only and HW & CH), a bit like a 3 port valve in a conventional system.

What's the hold back, the kW output of the gas burner not being enough?

Regards: Elliott.

 

[kidgreen61]

No

 

[muggles]

No, there aren't. You'd just end up with poor hot water performance. What's the issue, why do you want to be able to do this?

 

[CountryFan]

As per @muggles its to do with poor water performance and combi’s are hot water priority. What are you trying to achieve?

 

[foxhole]

Hi all.

Does anyone know if there are any combi boiler that can heat both the hot water and the radiators at the same time? I know most don't, but was wondering if there was any exceptions?

I can't see why this would not be physically possible as you could have a diverter valve in the boiler what has three positions (HW Only, CH Only and HW & CH), a bit like a 3 port valve in a conventional system.

What's the hold back, the kW output of the gas burner not being enough?

Regards: Elliott.

Water temp and heating temperature different .

 

[Why Not Indeed]

CH should be a closed loop, don't want to be mixing fresh water in to it all the time, and vice versa.

 

[dilalio]

CH should be a closed loop, don't want to be mixing fresh water in to it all the time, and vice versa.

Eh?

 

[eveares]

CH should be a closed loop, don't want to be mixing fresh water in to it all the time, and vice versa.

As far as I know, even combi boilers when heating the hot water to the taps, still use a secondary heat exchanger for the hot water to the taps.

In other words, the hot water being drawn from the taps does not pass through the primary heat exchanger above the gas burner, which is shared with the CH loop that has the corrosion inhibitor in.

 

[eveares]

As per @muggles its to do with poor water performance and combi’s are hot water priority. What are you trying to achieve?

Was just looking at a 3 bed semi detached house that has no central heating what's so ever and was wondering what would be better for a new system?

Combi boiler or a System Boiler with a unvented HW cylinder?

 

[dilalio]

Was just looking at a 3 bed semi detached house that has no central heating what's so ever and was wondering what would be better for a new system?

Combi boiler or a System Boiler with a unvented HW cylinder?

Cylinder always better.
If you can spare the room.
Future non-gas replacements will require a cylinder so worth bearing that in mind.

 

[dilalio]

I'm in the process of ripping out regular boiler with gravity HW and solar cylinder to replace with a combi.

I think customer is mad but that's what they want. They're extending out the side, the back and in the loft but still no room for a cylinder

 

[Madrab]

Combi boiler or a System Boiler with a unvented HW cylinder?

Depends on the property - how many bathrooms and how you want the system to perform, what you expect.

It will also be dictated by the mains water performance.

 

[dilalio]

It will also be dictated by the mains water performance.

Which affects both a combi and a UV

 

[eveares]

Depends on the property - how many bathrooms and how you want the system to perform, what you expect.

It will also be dictated by the mains water performance.

I have not even viewed the property yet, assuming I even get it. It's a 3 bed, semi detached, one bathroom + downstairs WC house in the north west.

I have a Vaillant 937 storage combi boiler atm, which is fine for the most part; but like all combi's, it becomes an issue when it breaks down on the rare occasions. Flow rate is not as high as my previous place (see below), but decent-ish.

My previous place (my childhood home) had a large unvented Heatrae Sadia MegaFlow tank, which was great, but it was a 5 bed detached house with 3 showers, utility room and 7 hot taps.

 

[Madrab]

As suggested the mians flow and pressure is key to either solution. if the mains is suitable though then tThe biggest impact with using a combi is using more than 1 hot water (HW) outlet at the same time - most combi's even the large on3e will struggle to supply more than 1 full flow HW tap at the same time, in mostly all scenario's regardless of cold water supply.

A separate unvented cylinder will always out perform a combi, if the mains supply can sustain it. Even a properly plumbed and designed vented HW cylinder system can out perform a combi too.