Oversized Boilers????

[bengasman]

I'm looking into getting a new boiler - Combi replacement for an old standard model.

Now I have spoken to one chappie who says that it is too high and would thus be inefficient?

Nonsense, he hasn't got a clue.

Can anyone explain in simple terms about how a bigger boiler is not efficient?

Thanks in advance.

There is only a marginal difference that is so small that in real life it is impossible to notice.
The only thing is that if you have an exceptionally strong boiler on a really small set of rads, it might run a bit rough.

 

[mysteryman]

5 TIMES seems to be overlooking the fact that you want a combi, so don't worry about that.

Reducing the maximum output of a modulating boiler does not reduce the minimum output: that stays the same.

Take my advice about the Vitodens 200-W combi with weather compensation. As of next month they will have anti-short-cycling control as well as their considerable other benefits.

 

[bluey831]

Right - I'm getting the picture - hazily!!

I'm narrowing down my boilers to either a WB30CDI or WB37CDI
or Vaillient831 or Vaillant837.

Fully take on board what has been said about the Veissman and the Avanta but the idea of looking into the pros and cons of these makes me want to put my head in oven - except it aint a gas oven so I'm stumped on that one too!!!

My gut is for the Vaillant837. The only problem is that it can only modulate down to 12kw - higher than any of the other three.

My understanding is that it will only be inefficient at the point when the return requires less than 12Kw - at that point it will cycle on and off. HOWEVER - the time between it dropping below a 12Kw need and the boiler being shut off because the room thermosat has reached its level cannot be very long - presumably??? In that case, presumably the amount of on/off cycling would be very little and thus the inefficiency would be hardly measurable.

Please - someone just tell me I got this right!!!!

 

[bengasman]

Forget about the efficiency, there is no discernible difference between the different models as long as the install is done right.
Picking the right installer is far more important than choosing the boiler.

 

[bluey831]

Gotcha on that one Bengasman. I have had the 'companies' in and pretty sure I'm going to wide berth them. BG done the usual £3.5K - the others were about £2.3k. Got all the speel about the one man band not being there afterwards but they would be - 24/7.

Therefore, I am going to get some quotes from approved Vaillant or WB rgi's. They should be cheaper and if they are approved they should do a decent job. Will they be there afterwards on Christmas eve etc??? - well that will remain to be seen. However, as a precaution I can keep a minimum Homecare contract as a backup if I sense there is a need.

Then again ... the best laid plans an all that ....

 

[bengasman]

You don't need home care with a WB or Viessmann, they come with a full 5 year all in warrantee.

 

[bluey831]

Agreed. WB said that they expect the installer to deal with any issues in the first three years and they deal with any in the last two years. All full parts and labour.

Therefore, that does depend on how easily it would be to get the installer to come back and deal with the issue - especially if it was at a bad time in winter etc.

Hence my thought of just having a minimum Homecare contract as a backup.

 

[onlyfitidealboilers]

its not the installers issue to come back and look at a fault with the boiler say a year down the line, its not his fault the boiler manufacture design a crap boiler..

maybe if he gets paid thats another matter.