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We have an electric shower
And they are expensive too, OK you are not going to go out and change your shower too right now, but bills would go down if you did.
Heating water to just sit in a tank is a waste of energy,
Modern hot water tanks keep water very hot for several days. I agree it would be wasteful to have a large tank for a small flat with a single resident, but if you have a larger property and a tank suitable for the size of the household then any 'waste' would be negligible.
We’ve got a traditional system with a boiler / hot water tank / cold water tank and it’s gravity fed. So water pressure on its own both hot and cold isn’t great. However we have one pumped shower which therefore has good pressure, plus 2 electric showers. The downstairs electric shower is better then the rebel LT oarhetic electric one upstairs as it’s plumbed to mains pressure rather than the cold feed from the tank in the loft.
When we had to replace the boiler a few years ago when we had an extension we had a much bigger gas pipe out in to meet regs for a 30kw boiler (right faff that was)- but we put a boiler in that could be converted to a ‘system boiler’. I think that’s what people are referring to as unvented above.
We’d lose the cold water tank (which would free up loft space), have to fit a newer / higher pressure hot water tank and everything would broadly be on mains pressure as I understand it. I’d quite like to do that at some point as it sounds ideal.
When I lived at my parents they had a combo boiler and I wasn’t a fan. If you were in the shower and someone used a hot tap somewhere else it would go cold / lose pressure etc. So for hat reason unless it’s a small house with only a few people living there I’d avoid a combi personally.
Heating water to just sit in a tank is a waste of energy, and you have to plan more
Fair enough we have an electric shower but we've never run out of hot water - one or two hours in the morning, one or two hours in the evening and we are sorted, even when the kids were small and having baths
Get a combi. If it stops working, the boilerman fixes it.
When? Mate of mine recently had to wait 3 days to get a plumber to come round because around here they're just blocked out...and its summer! OK it wasn't a combi so he was OK, but if it were a combi he'd have been screwed for 5 days.And then there is the potential for a shortage of spare parts. A previous boiler of mine broke down many years ago and the part it needed was discontinued as it was an older model. Took a few days to source a part before it could be fixed...again lucky I didn't have a combi and still had hot water.
Heating water to just sit in a tank is a waste of energy,
No its not. You're only heating up the water you use once you've initially heated the tank. its not heating the full volume of the tank every day...rarely do we run it empty of hot water, so you're just topping it up. The tanks are super insulated. Before I replaced my tank and had the old style copper tank, foam coated with a jacket my airing cupboard was nice and toasty. Water engiergy. My current tank is so well insulated the airing cupboard is no longer warm and toasty. All the hot water pipes are lagged and you get a bit of heat from them when hot water is running through them when you're drawing hot water, but normally the airing cupboard is alot cooler than it used to be. They're extremely efficient systems.
I think the issue here is that people who don't like combi boilers are likely basing their experience on older, under powered boilers. Modern combis are reliable, chuck out lots of hot water very quickly and easily cope with a more than one hot water draw at a time.*
*all assuming that you get the right boiler for your house and demand.
I think the issue here is that people who don’t like combi boilers are likely basing their experience on older, under powered boilers. Modern combis are reliable, chuck out lots of hot water very quickly and easily cope with a more than one hot water draw at a time.
There may be an element of that, but a quick Google pulls up site after site that lists the pros and cons of combi v system boilers and they all seem to suggest that larger households are generally better off with a system boiler if no significant drop in water pressure when multiple devices being used is a requirement.
There's a load more work money for a plumber installing anything other than a combi, so expect marketing websites to sell where the profit is.
There’s a load more work money for a plumber installing anything other than a combi,
But if you already have the HW tank etc, then swapping an non Combi for a non Combi will be almost as easy as swapping a Combi for a Combi (you might have to run up the stairs to the airing cupboard a couple of times).
There’s a load more work money for a plumber installing anything other than a combi, so expect marketing websites to sell where the profit is.
Strange that many modern new builds are ditching the combi. That would not happen if combis were cheaper(and as easy to get the house to the energy level it needs to get to to pass design inspection)
There’s a load more work money for a plumber installing anything other than a combi, so expect marketing websites to sell where the profit is.
But they aren’t doing that - they are saying that smaller properties with fewer people / situations where consistently high water pressure isn’t a requirement then a combi is a good option. They aren’t saying they aren’t good, they are saying that for SOME users a system boiler is a better option, for others a combi.
We're in a 4 bedroom house, built in 1997, still on the original system boiler. I too, don't get the "hard work" comment, the water heating comes on, on a timer(!) twice a day, an hour each time. We've never run out of hot water, but there's only 2 of us (sometimes a house full, though).
The dear wife has been hankering after a new boiler, so it looks like I'll be coughing up. It'll be a system boiler for us again.
Heating water to just sit in a tank is a waste of energy,
heating water extremely quickly is a waste of energy too. Overall it nets out, which is why there isn't any environmental pressure to/from one of the solutions.
Its worth noting that the flow rate on a combi boiler is pretty poor. If someone in your house likes baths, a good tanked system will typically fill it much quicker.
Well I’ve certainly not experienced any of the problems people are talking about with combi boilers. As long as you spec the big enough boiler for your house and have enough flow, a shower will not go cold if someone else turns a tap on.
In our current house our system boiler looses about 10 deg of heat every 6 hrs or so.
As a family our hot water requirement varies day to day, sometimes we heating water just for the sake of it, others say waiting for water to heat up
Couple things about combi boilers.
Firstly there are only two types of combi boilers; ones that are broken and ones that aren’t broken... yet. One combi I had the manufacturer had an eight year lifespan (this was back in the 90’s, pilot light, etc.). And they never breakdown in the summer. One of mine went dec 29th and it was -10 outside. Another (a Worcester) took three weeks to fix (to be fair, that was the plumbers, not the manufacturer) in January. So I’m a little biased. Combi’s have more internal moving parts (hot water priority) so something else to fail.
Secondly: yes standing losses are less and you only heat the water you use. Distribution losses however you also need to factor in. Unless your in a Passivhaus chances the house designer hasn’t even given the boiler location (verses where your hot water outlets are) any thought. Boilers tend to be located for convenience of getting a flue out, not where water is required. A hot water cylinder is easier to locate centrally. If it’s in the wrong place you’ve a big slug of (cold) water to get through the pipes before hot starts to come through (true in a cylinder set up to though). HW cylinders can come with immersion back up (I always spec them with, and that’s on non-domestic).
Thirdly: in a combi all water is heated instantaneously. This means that you are ruled by the laws of thermodynamics. An electric shower (which most people moan about being ‘underpowered’ is approx 10kW (direct electric, no trans losses). Mass flow = heat/(Cp. delta T). What’s your shower flow rate? 6 l/min minimum. If you like a lot of flow, double that (worse if you’ve multiple heads/jets). How much output does your boiler have? 28kW min, maybe as much as 40. A system boiler is what, 10-15? And an hour or two to hit HW storage temp... so, yes you will need to upsize your gas pipe (from the meter). From memory, 50kW gives 0.3l/s at 50 deg C, a bath tap is 0.2 l/s iirc. Which is why combis are better suited to flats than houses. How many bedrooms/en-suites? How many simultaneous showers/other water outlets in use? How big is your boiler again? This is why house combis are bigger as they are semi storage (usually a small internal HW tank).
Forthly: decarbonisation of heating. It’s coming. Gas is dirty, from 2025 it’ll be illegal to put Nat gas fired boilers into new build homes (Scotland anyways) and net zero is 2045. Decarb presently means electrification and you’ll be back to HW storage tanks...
We have a conventional boiler and tank, have no idea whether it's vented or not. It's been in the house for nearly 30 years long before we bought the place.
Having a tank of hot water was good for us before the kids became teenagers. Between the two of them they can empty the tank when taking showers.
We have investigated updating the whole system, to see what our options are. Most quotes have come in to replace the whole system with a combi setup. Since I'm working from home I don't really want that kind of disruption.
We are constantly bombarded with offers on this government boiler replacement scheme, I don't know anyone who's done that. Anyone on here have any experience?
Well, I am quite heartened (is that a word) by this thread.
I thought it was just me being my usual indecisive self, but it appears that the choice is actually quite a difficult one & comes down to a lot of different factors.
asbrooks
We are constantly bombarded with offers on this government boiler replacement scheme, I don’t know anyone who’s done that. Anyone on here have any experience?
I've not even heard about that. Any info or links?
Having a tank of hot water was good for us before the kids became teenagers. Between the two of them they can empty the tank when taking showers.
So is it the case that a modern system boiler could not be set to automatically reheat the hot water tank if it drops below a certain temperature instead of just heating for an hour a day or something?
Or is it that they do reheat automatically, but not fast enough?
Or is it that they do reheat automatically, but not fast enough?
Ours reheats fast enough to allow for the four of us to have showers at the same time one after the other (ie, two showers used concurrently twice). It sometimes doesn't quite manage to keep up when one of our daughters has a shower bath (she fills the bath whilst showering then sits in the bath when it is full to the brim). But it is a massive bath (enough for me to lay out flat in it) and it also has very steep sides so the volume of water required to fill it is huge.
The advantage of having a HW cylinder is if you have (or add solar PV) you can heat your HW directly from that, effectively for free. More and more new builds seem to come with solar PV built into the roof.
The issue is whether a decent make of combi can ever compete with (or get close to) an unvented system in terms of shower pressure etc.
Easily and indeed much better - you just need a boiler with the capacity. Ours is the best shower I have ever used - run off a combi
So is it the case that a modern system boiler could not be set to automatically reheat the hot water tank if it drops below a certain temperature instead of just heating for an hour a day or something?
Yep, just stick a thermostat on the tank and leave the HW timed to be switched on all day (or 24/7) but the boiler will only heat the tank when the thermostat swithes on. Pretty sure that's the standard set up for any modern system with a HW tank (as in having a thermostat on the tank).
We drop the HW tank thermostat temp down in summer as the incoming cold isn't that cold so we don't need the hot water to be so hot for showers etc. In winter I stick it up an extra 5-10 deg so the HW tank lasts longer.
@stumpy01 It's called the ECO3 scheme.
I believe, or though I'm struggling to actually find anyone who's taken advantage of the scheme. I'm naturally skeptical when it comes to free stuff, but you can get a replacement boiler if it's more than 5 years old. All the mail I get through the door states that you don't have to be on benefits to benefit from the scheme. Apparently the government are throwing money at it to due to its climate commitments.
I can only find something from my local council. As with anything that nearly free with the government they don't really advertise or everyone would jump on it.
but you can get a replacement boiler if it’s more than 5 years old.
Our must be getting on for 30 years old, model came out in 1988.
Easily and indeed much better – you just need a boiler with the capacity.
With an unvented cylinder the hot water is at incoming mains pressure - AFAIA it's not possible for a combi to be better than the mains pressure.
With an unvented cylinder the hot water is at incoming mains pressure – AFAIA it’s not possible for a combi to be better than the mains pressure.
My thoughts exactly - and I struggle to believe that the most powerful domestic combi boilers can heat water at mains pressure and deliver it to multiple heads simultaneously at that pressure.
With an unvented cylinder the hot water is at incoming mains pressure – AFAIA it’s not possible for a combi to be better than the mains pressure.
We got a Worchester 8000 Life 40 combi installed on the cheap last year through one of the council/power company schemes.
It's flow rate is apparently 16L/min. The flow out of our bath taps is ~15L/min and it comes out hot. Perhaps we don't have the best mains pressure but is fine for me.
I noticed after a bathroom refit that shower head is limited to 9l/m and detaching that and running cold water full on gave me 15l/m (bucket test).
As there are two of us, it wasn't hard to calc that a 40kw combi would be fine. Filling bath at the same time ia going to slower than a cylinder, but we know we always have hot water (unless combi is broken)
Bigger house, more people,more showers etc and the calcs would be different.
My combis the size of a washing machine.
It's also oil fired so not a fair comparison.
Strange that many modern new builds are ditching the combi. That would not happen if combis were cheaper(and as easy to get the house to the energy level it needs to get to to pass design inspection)
Not really, as you say it's all about making the EPC score. Your standard fitted PV panels are also all but useless to your average 9-5 family so the power may as well go somewhere useful.
The biggest thing about combi's is the environmental issue, they're not compatible with storage systems so if you're looking to the future the best bet is a tanked system. But don't be under any illusion that the boiler is somehow different, it's not, it works exactly the same and has the same chance of breaking down, it's only the controls that are different.