Combi Replacement Advice

[Doctor Drivel]

Glowworm is a piece of junk, the old ones lasted, new ones should go straight to scrapyard without stopping to be hung on customer’s wall.
Veismann appears to be good, but rare and may have issues finding approved engineers or parts.
Vaillant is good though not as good as they used to be partially due to absorbing second raters like glowworm and heatline
Worcester Bosch is decent boiler and their customer care is generally considered to be the best of all makes, also offer 5 year warranty.

Atmos are excellent, but a bit pricey. Buderus 600 range are v good and a part of Worcester-Bosch group, so service and parts is guaranteed.

Best get a boiler with integrated weather compensation. The upper middle range Vaillants are about the same price as the Ethos, but with far inferior flowrates

 

[scholesy]

I'm not a 100% sure exactly how weather compensation works. Is it of value if I never have the heating turned on in the warmer months, it usually gets switched on Nov - March.

Thanks for all the suggestions so far they've been very helpful.

i plan to do the work in the summer. I was going to drain down system and put new radiators in before the boiler is changed. Would it also be advisable to change the current copper piping as well? These were installed with the current boiler 12yrs ago. Or would you just leave them, (assuming their size is sufficient of course)?

 

[ChrisR]

I'm not a 100% sure exactly how weather compensation works.

Neither is anyone else, because the manufacturer's don't say much about what they've implemented. They claim to keep the boiler in condensing (higher efficiency) operation for more of the time, but information about the weather is neither necessary nor sufficient to do that.

Full control systems aren't simple; Joe public's (including majority of plumbers') eyes would glaze over before the end of two sentences. Maybe that's why the mfrs don't try to explain, or maybe it's because their "system" is just to turn the boiler up a bit when it's cold, and down a bit when it's hot.

Beware plumbers trying to sound as though they know more than they do, and be careful with manufacturers' claims. Mrfs might claim 15% extra but over what? How much of that would you achieve yourself if you adjusted your boiler twice a year?
Some of the most evangelical promoters of "weather comp" (they love abbrevations like that) are some of the most ignorant to55ers I've come across

Changing your pipes is unlikely to be necessary, because flow rates with condensing boilers are lower. If you're changing your rads, then you would gain if you increased the sizes to suit lower radiator temperatures.
DO pay attention to the insulation on the pipework though. especially under suspended floors. You can easily lose 15% under there. Hairfelt lagging is near useless, and 9mm lengths slit and slipped on are also inadequate.

 

[Doctor Drivel]

I'm not a 100% sure exactly how weather compensation works. Is it of value if I never have the heating turned on in the warmer months, it usually gets switched on Nov - March.

Thanks for all the suggestions so far they've been very helpful.

i plan to do the work in the summer. I was going to drain down system and put new radiators in before the boiler is changed. Would it also be advisable to change the current copper piping as well? These were installed with the current boiler 12yrs ago. Or would you just leave them, (assuming their size is sufficient of course)?

ChrisR is right that plumbers guess at what it is, without understanding it, you only have to read what is written here. Weather compensation is feed-forward control, as opposed to all others which is feed-back - anticipating the coming temperature drop or rise in the building as the outside temperatures change, and acting in advance.

The radiator temperature rises and drops to the outside temperature. It is crassly foolish not to fit the outside temperature compensation for what it gives when the extra is so small. It improves economy and comfort conditions.

 

[scholesy]

Part of the work I had planned for the Summer included insulating (thermal and acoustic), the walls and floor. I hadn't thought of insulating the radiator pipes, (although it seems very obvious now), so thanks for the info. Whats the best material for doing this.

Also sound advice on getting bigger rads. Is their a type\make of radiator that outperforms others. My knowledge on this is zero. Thanks.

Sounds like 'weather comp' is a grey area. I am usually quite stingy with my heating settings anyway having it come on/off a few times throughout the evening, saving longer spells only for the coldest nights. But as has been mentioned it does seem like i'd be daft not to include it for the extra little cost of it.

 

[Doctor Drivel]

I'm not a 100% sure exactly how weather compensation works.

Neither is anyone else, because the manufacturer's don't say much about what they've implemented. They claim to keep the boiler in condensing (higher efficiency) operation for more of the time, but information about the weather is neither necessary nor sufficient to do that.

See my other post on how weather compensation works. It does lower the flow temop for far longer. ..and it works on all the house, not just the temperature in one room as OpenTherm does. (although 4 tenmp sensors can average the temp using OpenTherm. Have weather compensation and local trimming via TRVs and bingo.

Full control systems aren't simple; Joe public's (including majority of plumbers') eyes would glaze over before the end of two sentences. Maybe that's why the mfrs don't try to explain, or maybe it's because their "system" is just to turn the boiler up a bit when it's cold, and down a bit when it's hot.

They get too many phone calls to their tech dept from dumbos who don't know heating never mind how to set up weather compensation. It will cost them with extra tech staff. One BIASI model comes with compensation, but they will not sell the outside sensor. BIASI come out with tripe that it is not work connecting.

Beware plumbers trying to sound as though they know more than they do, and be careful with manufacturers' claims. Mrfs might claim 15% extra but over what?

....than without it.

How much of that would you achieve yourself if you adjusted your boiler twice a year?

Nowhere near.

Changing your pipes is unlikely to be necessary, because flow rates with condensing boilers are lower.

They are? New on me.... You are confusing with temperatures.

If you're changing your rads, then you would gain if you increased the sizes to suit lower radiator temperatures.

Correct. Engineer the system into lower temperature, assisted by weather compensation. But do not change the rads if they are OK. Compensation can make up for larger rads.

DO pay attention to the insulation on the pipework though. especially under suspended floors. You can easily lose 15% under there. Hairfelt lagging is near useless, and 9mm lengths slit and slipped on are also inadequate.

Too true.

 

[Doctor Drivel]

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