Options for boiler update

Biggish_who

ThisIsWeird said:

Biggish_who said:

Yes if I thought I had a good enough gas pipe for a 30kw combi boiler, I'd probably be okay with the HW flow on that. But I don't think I will, based on what BG engineer has told me.
A new gas supply from the meter is virtually impossible due to layout, etc.  

I have a 30kW combi in a 3-bed, 3-bathroom house, and the flow is superb for showers. 

Painfully slow process for baths, tho' - so we only shower.

Ah that's a shame. I do like a bath a couple of times a week, so stories like this put me off Combis & make me want to keep the cylinder! 

FreeBear

ThisIsWeird said: I have a 30kW combi in a 3-bed, 3-bathroom house, and the flow is superb for showers. 

Painfully slow process for baths, tho' - so we only shower.

Only have an electric shower - Temperature is good, but flow isn't brilliant. Get about 10l/min mains water and can fill a bath in 8-10 minutes. Have the DHW temperature set to ~45°C, so don't need to add any extra cold water. Loving the (almost) instant hot water that a combi provides, so I'd be reluctant to go back to tanks and the hassle of waiting for the stuff to heat up.

Biggish_who

See people have very mixed views on Combis! Some love it, and some hate it!

I'm perfectly happy to press the 'boost' button and hour in advance to make sure the HW tank is full enough to have a bath.

But with my current tank I just leave the HW on constant, there's always hot water to hand. It doesn't seem to cost me much in gas, and the only time it's a problem is when I want a piping hot bath, which seems to take more than my current tank can store! 

ThisIsWeird

FreeBear said:

Get about 10l/min mains water and can fill a bath in 8-10 minutes. Have the DHW temperature set to ~45°C, so don't need to add any extra cold water. Loving the (almost) instant hot water that a combi provides, so I'd be reluctant to go back to tanks and the hassle of waiting for the stuff to heat up.

In theory, these figures are not at all bad. At that flow rate, a bath-fill of over ~100litres (20+ gallons) in 10 minutes is totally achievable.

Can't remember the last time I filled a bath - it would have been well over a decade ago when kids were small. I recall it being painful, but I'm almost certainly doing it a memory-blurred disservice.

Belenus

Biggish_who said:

FreeBear said:

Biggish_who said: I'm still not sold on a combi due as I've heard lots about the low HW flow & not being ideal for 2 bathroom properties! 

I switched from a gravity fed DHW system to a combi in 2023. Hot water at mains pressure was a revelation, and no more waiting for a tank to heat up. I only have the one bathroom, so the setup suits me. If you're wanting a system boiler, at a minimum, you'd probably want a 180l DHW tank at a minimum.

An alternative would be the Viessmann 111-W which has a built-in 46l tank to supply that initial burst of hot water. But at just over £2K, not a particularly cheap boiler (although it will modulate down to ~3.2kW).

Also 180L sounds like a lot for the tank.

Bear in mind I currently only have an 85L tank, and apart from not quite being enough for a piping hot bath, it's never been an issue any other time.

What temperature do you have set for your hot water?

If less than the maximum, then consider changing it to maximum an hour or so before your bath and turning it down again afterwards.

That might give you a hotter bath as well as avoiding the above mentioned issue of scalding hot water at taps.

Biggish_who

Belenus said:

Biggish_who said:

FreeBear said:

Biggish_who said: I'm still not sold on a combi due as I've heard lots about the low HW flow & not being ideal for 2 bathroom properties! 

I switched from a gravity fed DHW system to a combi in 2023. Hot water at mains pressure was a revelation, and no more waiting for a tank to heat up. I only have the one bathroom, so the setup suits me. If you're wanting a system boiler, at a minimum, you'd probably want a 180l DHW tank at a minimum.

An alternative would be the Viessmann 111-W which has a built-in 46l tank to supply that initial burst of hot water. But at just over £2K, not a particularly cheap boiler (although it will modulate down to ~3.2kW).

Also 180L sounds like a lot for the tank.

Bear in mind I currently only have an 85L tank, and apart from not quite being enough for a piping hot bath, it's never been an issue any other time.

What temperature do you have set for your hot water?

If less than the maximum, then consider changing it to maximum an hour or so before your bath and turning it down again afterwards.

That might give you a hotter bath as well as avoiding the above mentioned issue of scalding hot water at taps.

Well there are no temperatures displayed anywhere on the boiler, just a dial with + and - on. So I have it about 3/4 of the way. 

I will try putting it to maximum before my next bath.... Assuming that is safe, and not going to cause anything to overheat! 

Biggish_who

Update: Ah, ok, so it turns out the temperature dial extends further than I thought, past the scale printed above it!

I also didn't know I could press a button which shows the selected temperature on the digital display. 

Although I thought I had it 3/4 of the way up, it was actually only set to 51° so I've turned it up to 60 for now and see how that goes for my next bath. 

The most it will go to is 65° so I can go up slightly more if the bath still isn't hot enough for me! 

Grandad2b

Replaced our 40 year old system boiler (they all were back then) with a 30kW combi in the summer. Heating is absolutely fine and I've reduced the rad temp to 55˚ which is apparently more economical. It's more difficult getting used to DHW flowing backwards as it were, the shower (previously pumped) was right next to the HW cylinder whereas the boiler is at the other end of the pipework but I'm sure we'll get there eventually. Savings? Too early for anything other than general impressions but in Dec 23 we used 1212kWh, last year was 890. 

Bear in mind this was a VERY OLD boiler with pilot light and gravity circulating DHW; the pilot light alone was using nearly 3kWh daily.

ETA We lost the airing cupboard of course (well the heat source); that's been replaced with a 80W greenhouse heater. So leccy use will be slightly up.