ᐅ Difference Between a Gas Condensing Boiler and a Gas Combi Boiler

Hello,

I hope someone here can help me. I am about to buy a small house (80m2 (860 sq ft) living area, 26m2 (280 sq ft) usable space). It is a fully renovated half-timbered house. The original construction description stated that a gas condensing boiler would be installed. However, the developer has now changed this in the description to a gas combination boiler. When I asked for clarification, he only said that a gas combination boiler is also a condensing boiler. This is not clear to me. Could someone please explain the difference and possibly give me a recommendation? I would be very grateful.

Kind regards
Osterhase74

Osterhase74 schrieb:
When I asked him, he only said that a gas combination boiler is also a condensing boiler. However, I do not understand this.

The term "combination" refers to a function, meaning that in addition to heating, hot water is produced on demand (without a hot water storage tank).
"Condensing" describes a process or condition where, besides the combustion energy (calorific value), the latent heat from condensation is also utilized (total energy = higher heating value). This explains how boiler efficiencies can exceed 1 or 100%, which would normally be impossible.
Therefore, a combination boiler can be either a condensing or a non-condensing device. A condensing boiler is always a condensing device but does not have to be a combination boiler.

Best regards

Dear €uro,

Thank you very much for your explanation – it has helped me understand the situation better. Could you possibly recommend a specific device? I would like to include more detailed specifications in the building description.

Sunny regards

Osterhase74 schrieb:
.. Can you possibly recommend a specific device? ...

That’s a bit difficult, as the heating load according to DIN 12831 (maximum power requirement for heating operation) must be calculated first.
It is important to have a wide modulation range, meaning a low minimum output to prevent excessive cycling during the prevailing partial load operation.

Examples:

Geminox THRi 0.9-9 C (1.2 - 9.8 kW at 50/30)
Elco Thision S 9.1 (1.3 – 9.9 kW at 40/30)
Viessmann Vitodens 300-W WB3E (1.9 - 11 kW at 50/30, 14 kW domestic hot water booster) from approx. Sept. 2011
Hansa Pega 25 (2.2 - 26.1 kW at 50/30)
Vaillant EcoTEC exclusiv VC 146/4-7 (2.6 - 15.2 kW at 40/30, 16 kW for domestic hot water)
Geminox THRi 2-13 C (2.7 - 14.7 kW at 50/30)
Elco Thision S 17.1 (2.7 - 18.4 kW at 40/30)
Elco Thision S 13.1 (2.8 - 14.8 kW at 40/30)
Elco Smartron 2-13 C (2.8 - 14.8 kW at 40/30)
Elco Smartron 2-17 C (2.8 - 18.9 kW at 40/30)
Remeha Quinta 10 (2.9 - 11.6 kW at 40/30) (if still available)
Paradigma Modula NT 3-10 (3.4 - 11.2 kW at 50/30)
Giersch Giegastar 11 (2.9 – 11.6 kW at 40/30) (according to Giersch "sold until 12/2010")
Sieger BK 16 W-14 (3.1 - 15.2 kW at 50/30)
Buderus Logomax Plus GB162-15 (3.1 - 15.2 kW at 50/30)
Brötje Ecotherm Plus WGB 15E (3.1 - 15.6 kW at 50/30)
Buderus Logano Plus GB202-15 or GB212-15 (approx. 3.1 - 15.2 kW at 50/30) (floor-standing boiler)
Brötje TrioCondens Baugesetzbuch 15 (3.1 - 15.6 kW at 50/30) (floor-standing boiler)
Buderus Logomax Plus GB172-14 (3.2 - 14.0 kW at 50/30, 15.1 kW for domestic hot water)
Rapido Econpact Plus Gas condensing boiler 18 (3.2 to 19.0 kW at 50/30)

Best regards.

Well, there is quite a wide range of options. Today, the developer informed me which unit they recommend: a Junkers gas condensing boiler Cerapur ECO. According to various online reviews, it seems to be a decent unit. I hope I will be satisfied with it. What can you say about the Vaillant?

Thank you for your advice & have a sunny weekend!