Combi Vs Conventional Boiler with a tank

Soniclord

Hi,

Me and my family have rented 3 different houses and all of them have had Combi boilers which we've never had an issue with (none of this water runs cold for a few seconds when showering if someone turns tap on downstairs business lol) anyway we've looked at a few houses recently as we are moving again! And even though they're newer build houses (3 bed semi's) they all have conventional boilers in them..

Not something where used to if I'm honest and I'm a little worried as to how they work, plus the fact I'm quite sure they use much more fuel/energy than combi's than only fire up when needed!

Basically we've used a combi for all our years renting and find it very convenient (hot water on demand for a start) we are a family of 2 adults and 2 children. and if I'm honest I'm a born worrier and dont like to think about things I don't think I should have to (such as remembering to turn the water on for hot water) I know I know I sound like a lazy sod but I'm not, I'm just used to combi's.

Anyway I have a question or 2.

Does a shower (when using a conventional boiler) take hot water from the tank or is there some sort of element in showers that heats the water up before it flows through the shower? As I know with the combi if the boiler blows out (and your in the shower) the water runs stone cold..

Also how much dearer is running a conventional boiler as opposed to a combi, is it a lot more expensive? I hear it is but don't really know.

And lastly if you have the heating on when using a conventional boiler doesn't that keep the water always hot? As long as the heatings on (obviously that won't be the case in the summer months) or do you still have to heat the water separately?

Sorry for the long post.

macman

You shouldn't have to remember to turn on the DHW, a programmer or timer will do that for you.
A shower in a house with a conventional boiler (unless it's an electric shower) will get it's hot water from the hot water tank. An electric shower heats the water on demand at the shower unit.
The costs of running the 2 should not be greatly different, a properly lagged hot water tank will retain the heat for many hours.
The boiler will supply both CH and DHW, again a modern programmer will allow some flexibility. In the summer you just run it on DHW mode only.
The properties you are looking at may not be suitable for combis due to water pressure, number of bathrooms etc.

Baker89

Ok thanks for your post.

The properties we've looked at are actually smaller than houses we've rented in the past, some have a toilet downstairs and 1 in the bathroom upstairs (there is only 1 bathroom in all the houses we've looked at) but houses we've rented previously have also been like that, but all have had combi boilers.

I've also read on some other threads on here (albeit from 2009 some of them) that conventional boilers have cost people much more as opposed to combi's but I don't know if things have changed?

I honestly do believe that combi's are cheaper to run only due to the fact that with a combi the boiler only fires up when you turn the tap on (or when the heatings on) then it's off once you turn the tap off as opposed to being constantly on with a conventional boiler (well more on than off when heating water up using an immersion heater for example) perhaps these newer build houses do have better conventional boilers, as in more efficient but I'm not sure

Also an electric shower has it's own on off pull cord/switch right? The reason I ask is where we rent now has an electric shower with it's own pull cord to turn it on and off but when the boilers pilot went off one time when I was in the shower the water ran cold.. That's not right is it?

macman

Smaller houses for rental will tend to have combi's, as the initial install may be cheaper (no hot tank to plumb in). But once installed the running costs are not greatly different.
The hot water on a conventional system is not 'constantly on'. Once it's up to temp in the tank no more gas is used, and the temp is controlled by the tank stat.
The choice is determined not by budget, but by the factors already mentioned, and by lifestyle (do you want stored hot water, or hot water on demand).
A combi provides no CH at all when there is a demand for DHW.
The other advantage of a conventional system is that the tank can be fitted with an immersion heater as a backup-so boiler failure does not lead to loss of hot water.
If the shower runs cold when the boiler goes out, then it is not an electric shower-sounds more like a pumped conventional shower.

Soniclord

macman wrote: »

The choice is determined not by budget, but by the factors already mentioned, and by lifestyle (do you want stored hot water, or hot water on demand).

Personally I prefer hot water on demand, that's just because that's what i'm used to, maybe it would be easy to adjust but not sure?

macman wrote: »

A combi provides no CH at all when there is a demand for DHW.

Sorry I'm not up to date on all these abbreviations, DHW means something hot water right? I know CH is Central Heating though, just trying to get my head round these others so I know what people on here are saying, I get confused a lot of the time when I read things I don't know lol.

So basically your saying if the heating is on with a combi boiler and if someone turns the tap on the heating switches off? (temporarily though right?) whilst the sink or baths being filled up.

macman wrote: »

If the shower runs cold when the boiler goes out, then it is not an electric shower-sounds more like a pumped conventional shower.

Would it still have an on/off pull cord though to isolate it from the electrics if it needed servicing? Sorry I don't know much about these things.

manda1205

Soniclord wrote: »

So basically your saying if the heating is on with a combi boiler and if someone turns the tap on the heating switches off? (temporarily though right?) whilst the sink or baths being filled up.

Yes, but you wouldnt notice it. When we run a hot tap, obviously the boiler is heating the water for the tap, not the central heating, but in the short time of running a bath the radiators dont all go cold and the house goes cold. You dont run a bath for hours do you, so it makes no odds really, as soon as you turn the tap off the boiler will start heating the radiator water again.
Im with you ont his one, I much prefer our combi, we've had a few probs, but thats to do with our hard water, and we still had probs due to that when we had electric immersion tank.
I would think the systems where they have tanks too are more costly, how could they not be, its having to maintain the temp of the water in a tank, where as in a combi, you only heat what you're using.

Cardew

Baker89 wrote: »

Ok thanks for your post.

The properties we've looked at are actually smaller than houses we've rented in the past, some have a toilet downstairs and 1 in the bathroom upstairs (there is only 1 bathroom in all the houses we've looked at) but houses we've rented previously have also been like that, but all have had combi boilers.

I've also read on some other threads on here (albeit from 2009 some of them) that conventional boilers have cost people much more as opposed to combi's but I don't know if things have changed?

I honestly do believe that combi's are cheaper to run only due to the fact that with a combi the boiler only fires up when you turn the tap on (or when the heatings on) then it's off once you turn the tap off as opposed to being constantly on with a conventional boiler (well more on than off when heating water up using an immersion heater for example) perhaps these newer build houses do have better conventional boilers, as in more efficient but I'm not sure

Also an electric shower has it's own on off pull cord/switch right? The reason I ask is where we rent now has an electric shower with it's own pull cord to turn it on and off but when the boilers pilot went off one time when I was in the shower the water ran cold.. That's not right is it?

Taking your last point first. An electric shower operates independantly of the gas hot water supply - the mains cold water is heated in the electric shower unit.

You can have an electric 'power shower' where the hot water supply to a shower(not an electric shower) is pumped at pressure to give a high flow rate - but that wouldn't be used on a combi as they cannot supply enough hot water. So you are sure you have a combi?

If your 'electric shower' ran cold when the when the boiler pilot light went off, it doesn't sopund like it is an electric shower. It may be that you have a low pressure pump as the hot water pressure is insufficient.

Anyway, a conventional boiler running water to a hot water tank is not much more expensive than a combi and can even be cheaper.

A modern well lagged HW tank will lose about 2kWh in 24/7 with water in the tank @ 65C; so in normal use with timed hot water, a typical loss might be 1kWh(3p -4p) a day. In any case that heat is not lost as it warms the house.

In many cases, reports have shown, that depending on pipe runs etc a combi is more expensive at providing Hot water.

Soniclord

manda1205 wrote: »

I would think the systems where they have tanks too are more costly, how could they not be, its having to maintain the temp of the water in a tank, where as in a combi, you only heat what you're using.

That's exactly my level of thinking, the whole how could it not be more expensive with a conventional boiler Glad you agree with me on that point.

No offence to any other info I've used but I'm just using what I think is common sense.

I did notice in one of the houses we looked in it had a fairly small tank as well so wouldn't hold enough water to run a full bath :cool: or so it seemed by the size of it. And that wouldn't be good.

I did ask the agency if they'd ask the landlord if he would consider replacing it, but they came back to me and said no landlord in their right mind would consider replacing an energy efficient boiler considering the cost would be in excess of £1200..

Energy efficient? Not sure what planet he was on!

Wonder if they'd replace it if I said I'd pay for the combi? Hmmmm

Not sure what the cost would be to fit it though!

manda1205

Soniclord wrote: »

That's exactly my level of thinking, the whole how could it not be more expensive with a conventional boiler Glad you agree with me on that point.

No offence to any other info I've used but I'm just using what I think is common sense.

I did notice in one of the houses we looked in it had a fairly small tank as well :cool:

Yeah that's just how it seems logically to me, suppose it does depend on size of house and temp of cold water to begin with. Im happy with our combi anyway and we have definitly saved a huge amount(even with rise in oil prices) compared to using electric and coal for heating and water.

Soniclord

Cardew wrote: »

You can have an electric 'power shower' where the hot water supply to a shower(not an electric shower) is pumped at pressure to give a high flow rate - but that wouldn't be used on a combi as they cannot supply enough hot water. So you are sure you have a combi?

No offence but I'm certain we have a combi.. It's not something I wouldn't know.. Lol.

Cardew wrote: »

If your 'electric shower' ran cold when the when the boiler pilot light went off, it doesn't sound like it is an electric shower. It may be that you have a low pressure pump as the hot water pressure is insufficient.

So it would still have a on/off cord or switch if it had a low pressure pump instead?

Cardew wrote: »

In many cases, reports have shown, that depending on pipe runs etc a combi is more expensive at providing Hot water.

Perhaps but in my experience (I've never used a conventional boiler, so it's limited) I prefer combis anyway, I can say that based on the fact I'd rather have hot water instantly than have to rely on heating it up first lol.

The search for a house with a combi continues

macman

Soniclord wrote: »

Personally I prefer hot water on demand, that's just because that's what i'm used to, maybe it would be easy to adjust but not sure?



Sorry I'm not up to date on all these abbreviations, DHW means something hot water right? I know CH is Central Heating though, just trying to get my head round these others so I know what people on here are saying, I get confused a lot of the time when I read things I don't know lol.

So basically your saying if the heating is on with a combi boiler and if someone turns the tap on the heating switches off? (temporarily though right?) whilst the sink or baths being filled up.



Would it still have an on/off pull cord though to isolate it from the electrics if it needed servicing? Sorry I don't know much about these things.

DHW: Domestic Hot Water
Yes, a combi cannot supply both circuits at once. When there is a demand for hot water the diverter valve switches the flow to hot water only.
I wouldn't make a buying decision on a property based on the type of boiler that is installed, unless it's obviously wrong for the property (i.e. you wouldn't fit a combi in a house with 3 bathrooms).
All electric showers must have a isolator switch, it doesn't have to be a pull cord one unless it's inside the shower room.