Baxi 105e Instant-end of service life advice please.

[FlatMax]

Hi everybody.

 

Our 2002 Baxi 105e instant has been (and still is) a cracking good boiler, but of late it is becoming increasingly unreliable with niggly random issues mainly around control items. I've done numerous jobs on the water set over the years, including swapping out the PCB, thermistors, and other bits which are still readily available just about anywhere.

 

The latest iteration of what can be described as 'random' faulting, is that the boiler locks out when you shower whilst the system is calling for heat; you are then left with the flashing 50C LED and DHW symbol, and the pump running continuously. Powering off for half an hour and reconnecting sees the boiler run its usual ignition check and hey presto, all back to normal! Central heating functions as normal, and DHW as well, just not both together.

 

I'm guessing the overheating is something to do with the diverter valve (the DHW diaphram is new) but my wife has pointed out that the boiler is probably at the end of its service life, is less efficient and more polluting than a replacement, and she would be stuck if I wasn't around when these things happen. All this is very true, so I'm looking for a replacement.

 

The Baxi Duo Tec 28 is the replacement I'd go for, as it sits on the same jig and has the same pipework/flue configuration. I'm not looking for big efficiency savings here, just another boiler that will last 15-20 years and be more reliable going forward. Parts are also readily available for this model and it has a seven year manufacturing warranty. Do members think this is a good combi boiler or are there others out there that are significantly better? 

 

Any advice would be gratefully received. 

[JohnMo]

1 hour ago, FlatMax said:

I'm not looking for big efficiency savings here

Why not when it's easy to do, actual boiler efficiency has little to do with boiler model more to do with how it's plumbed in and controlled. You could probably save a good 20% on heating costs. And get way better hot water performance.

 

So choose your combi of choice, but make sure it's controlled via opentherm, not on off thermostats. But ideally has plenty of turndown so min output is low.

1 hour ago, FlatMax said:

Baxi Duo Tec 28 i

Not the best boiler out there, pretty poor turndown, with a min output of about 10kW, so boiler will cycle a lot at mild temperatures. The best will turn down to under 2kW.

 

Can only run at a set flow temp. So not the most efficient by a long way.

 

Hot water flow rate is 11.5L minute. Just looked at my old boiler and it did 15L minute at the same 35 Deg temp rise. And had a turn down to half the one you are looking at.

 

I would look at other makes and models.

[marshian]

I did the sane thing many years ago - had a glow worm boiler that had given sterling service so chose another glow worm the same KW rating - it was a big mistake!!!!

 

I didn’t take into account insulation improvements to the house, SUDG, CWI improved Loft insulation etc

 

boiler was massively oversized - couldn’t do DHWP, had a terrible modulation level 24 KW max 10 kW min and as a result cycled like a twat in shoulder seasons and wasn’t that great in the winter either

 

find a better boiler as @JohnMo says - preferably with same pipework configuration and flue position and get some real benefits and savings with a better modulation

[FlatMax]

7 hours ago, JohnMo said:

Not the best boiler out there, pretty poor turndown, with a min output of about 10kW, so boiler will cycle a lot at mild temperatures. The best will turn down to under 2kW.

I hadn't even considered this; thanks for the insight. Here in South Devon we don't get much below 10 celsius ambient during the coldest months, so I can keep the house at 20C with a flow temp of 55C no problem. We have twenty rads in total (thirty five panels if you count the double rads) spread over three floors and 2,500 sq ft floor area. Building was new in 2003, so half decent insulation.

 

What would you consider is a good turndown ratio for a modern condensing combi? Our old Baxi has a ratio of 3:1 which oddly, is the same as the latest Duo Tec 28! 

 

Thanks again.