Gas condensing combi boiler Viessmann Vitodens 50 or 100w

[stanmore]

Hi I am looking to replace a 10 year old Combi boiler and have had three companies quote, the boiler will be sited in the same location, be mains gas and is for a small 2 bed/1 bath terrace occupied by a single person. The boiler is in the roof space with good access and head height with a flue vented through the roof. All three companies have suggested Viessman Vitodens with 2 recommending the 50w 29kw and the other the 100w 30kw. The installation will include a magnaclean and a scale inhibitor with RF control. The company quoting on the 100 has suggested that they will only undertake a water flush and will not install an inhibitor, as this is their experience with Viessmann, and they are no longer on the recommended list of installers hence can not obtain the extended 10 year warranty. The two companies suggesting the 50 are recommending a chemical flush and will add inhibator and have stated that they can obtain the 10 year warranty. The quotes range from £2,100 - £2,500 with all 3 including a hopewell RF thermostat and controller. Is the 100w worth the extra cost above the 50 w and why do all companies recommend a Honeywell controller? Any advice is gratefully received

 

[muggles]

What's the thinking behind replacing the existing boiler? A new one won't be any more efficient, assuming you're not significantly upgrading the controls. No idea why the companies are suggesting a Honeywell thermostat, both boilers are OpenTherm compatible and would be much better off fitted with an OpenTherm-compliant room thermostat. That way you might squeeze a tiny bit more efficiency out, although your new install is unlikely to ever pay for itself.

 

[stanmore]

Hi Muggles thank you for your response, the existing boiler a Baxi has failed twice recently with the heating engineer making a temporary repair but suggesting that a repair will cost circa £300 with him also quoting for a replacement. Hence this is one of the options to repair and hope it lasts a further 5 years or so. I will raise the question around the Open Therm but I would also like to know the benefits of the 100w over the 50w to see if it's worth the extra. Thanks

 

[stanmore]

Hi I checked the quotes and the companies are all suggesting Honeywell T3R controllers which don't appear to be OpenTherm controllers but the T4R is, should I be requesting this type of controller or a Viessmann specific? Thanks

 

[stanmore]

The existing boiler is a Baxi Duo-Tec HE 28 with a Salus RT500RF controllable

 

[ianmcd]

Definately get rid of the Salus , they are total Shoite, as for the boiler , personally I wouldnt have either but we all have our own preferances