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Are you refering to the number of "why isn't my Vaillant 4** weather compensation/control/etc working" posts? If so could that be because of the larger proportion of 4** than 6** boilers in the UK, and not necessarily because they're problematical? Please don't take this the wrong way - I'm...

The Vaillant system boilers have a narrow modulation range - The 618 ecoTec plus (which doesn't appear to have a double speed pump) only modulates from 6.7 to 18kw at 80/60C and 7.1 to 19.1kw at 50/30C The ecoMax 618/2 E does have a double speed pump but has an even narrower range - 11.0 to...

That's interesting. But do you know (or have heard) what's actually wrong with them?

I take it you mean the 400 is not really good enough for use on the continent, but we buy it here because we're less discerning? What's wrong with it? I will take a look at the 618.

Are you able to point me to somewhere where I can find all boilers which come with modulating pumps, and 3rd party (separate, non-integrated) pumps? I don't recall seeing that in the few pump specs I've looked at. What controls the modulating pump? Is there a standard for this interface? No -...

I'll shortly be having a new boiler installed (probably Glow Worm Ultracom 18hxi or Vaillant Eco Tec Plus 418), together with controls and pump. 3 zones - downstairs, upstairs & HW. Probably going to stay with my existing conventional vented indirect HW cylinder. For now at least. I'm...

We're probably both thinking of the same heated debate you had a month ago on this forum about auto-bypasses :) :) Having read that (and much elsewhere) + your statement here it's still not clear to me, given that I want to have a Grundfos Alpha, whether that creates a conflict with the boiler...

Yes indeed... but isn't there a bit of a debate going on about the compatibility of variable speed pumps such as the Grundfos Aplha and auto-bypass valves?

I guess it's just bad luck if you get a power cut at the moment the last heat-requesting zone shuts down - no circulating water to carry away residual heat. How quickly do 2 port valves open or close (depending on type) when power is withdrawn? Which type of valve (open when no power or...

How does a modern low-water-content condensing boiler cope with a power cut? It's not possible for the pump to run on in order to dissapate heat - so should I expect likely need for heat exchanger replacement every time there's a power cut when the boiler is at full tilt?

I really wanted to avoid pipes going down to the floor - to achieve a neater installation. I didn't realise remote sensor valves were available. Are there alternatives to the Danfoss FHV? Are these all intended for use with under floor heating? Re: roomstat in that room: actually I'm planning...

I'm having a new boiler installed to replace my exceedingly reliable Potterton Netaheat 16/22. I've been offered this: Glow Worm Ultracom 18HXI or Vaillant Ecotec Plus 418 (+£360) Grundfos 15-60 high head pump S plan, autobypass valve Magnaclean Power flush Honeywell cylinder stat...

I am installing 2 radiators in a room and am looking at creating a zone to control these - using a 2 port motorised valve, adjustable restrictor valve to balance this circuit against the rest of the heating installation, and a room thermostat. The motivation is to be able to mount the radiators...

My current loft insulation is 40mm solid polystyrene fitted between the joists. I'm about to lay Rockwool - about 270mm - and am wondering whether to lay on top of the polysturene or discard polystyrene. If I discard the polystyrene I remove a fire risk. If I lay on top I'll get better...