later on in the year im going to replace my old potterton boiler with a newer more efficient worcester bosch one as i have a mate who works there and he gets a good discount!!

at the moment i have a boiler and a big hot water tank taking up space in the airing cupboard.

i was thinking of getting a boiler which gives me instant hot water so i can get rid of the hot water tank and the power shower i have too.

would it work out better in the long run(money saving wise) to go this way or should i just stick? to a boiler that will work with the water tank??

oh and what are the names of the types of boilers im on about?

cheers

steve

oh and what are the names of the types of boilers im on about?

Combi

Can't comment on if it would be the best for you though.

Get a traditinonal typr condensing boiler, NOT a Combi and keep the water tank.

The tank does take up a bit of space but if you have a tank you can shower and run a washing machine and a dishwasher and flush the lavatory at the same time, combis, unless they're considerably over specified for the nominal load of the house tend to suffer from spiking in water temperature if multiple water outlets are used sinumtaneously.

If the system is set up and controlled correctly there's minimal additional running costs for the condensing boiner & hot water tank setup. This is what I did 5 years or so ago and have never loked back. Mu last house had a Worcester Bosch combi and it was an absolute nightmare.

I also agree with the above. With a combi boiler the hot water goes to the neares point that needs it, so if you are in the shower and someone runs a tap downstairs then the shower will run cold.

cheers for the replies.

i currently have a potterton envoy and its running 7 rads, some of which we think are not big enough for the rooms.(some are only 50cm in width and single row?)

we currently have the hotwater set to come on twice a day for an hour and this gives us ample hot water although we do occasionally run out.

the cupboard the tank and boiler are in is next to the bathroom and i wanted to put anew boiler in the loft and get rid of the water tank so i can incorporate the cupboard into the bathroom when i renovate that sometime this year.

i also want to put some bigger rads in the bedrooms and i think the current boiler would struggle to heat them.

also i would like to get rid of the electric power shower as me and the wife use it everyday and i cant see it being that economical.(9.5kw i think)

Get a new twin coil tank and the boiler as suggested above… then bung some solar hot water tubes on yer roof! Mucho hot water for little cost 😉 You can build your own solar panel using some single glazing, some wood, an old radiator and some matt black paint to make it very cheap (though not as efficient as the evacuated tube type solar installations).

Get rid of the power shower and just plumb your shower straight into the hot water system. Job done!

We don't have that… yet – if I get around to fitting a hot water tank that is the long term plan. But we have a Woscester High Flow condensing boiler with a mini built in tank. It's rather good, and will run both showers at the same time fine. It is about the size of a fridge mind, not one of these poxy wall mounted jobs!

What the above said regarding combi's. They're not for everyone, derive the popular belief they are the thing to have nowadays.
I've got a potterton combi, came with the house, would not consider one again!
I've fitted a few unvented cylinders recently and been really's really impressed with them. Mains pressure hot water throughout the house, Very high flow rates and the tank can reheat in 15-20 mins with the right boiler combination.
Last one was a 250l tank, paired to a weedy 12kw boiler. Customer plans to upgrade it soon anyway, but it still heats use tank fully in under an hour! 4 bed house with 2 bathrooms.

I have a boosted combi same as RobS. It provides a much grater flow of hot water than you can get from a tank system but I doubt it is very efficient.

I would always go for this type of boiler myself. Never run out of hot water and I can get ten times the flow of an electric shower from it.

We've moved from a house with a combi to one with a tank and are going to go back to a combi.

My mind was made up the first time I went for a later morning shower after bathing the kids earlier that morning…

I've got a traditional open vented system and recently added a pump to the gravity fed shower. Nice and powerful and unaffected by taps being opened/closed in the house.

I wouldnt recommend this type of boiler

According to the woman on the BBC news a couple of weeks ago (when talking about the proposed boiler scrappage scheme) 2/3rds of your gas usage is taken up with heating your water when running a tank system as opposed to an on-demand combi 😯
I'm assumin gshe was referring to an older G-rated model though.

I've just converted from an old tank system to a modern combi & i can't believe the difference it has made.

Read about the boilers, what you can get regarding the scrapage scheme etc in yesterday's Guardian (money section). I got a Worcester Bosch fitted about 2 years ago, the gas bills have gone down by about %30.

Exactly what wombat said. Absolutely do not get a combi unless you really need the space. Condensing boiler plus decent tank like a Megaflow is the way to go

wow some conflicting advice here then!!

any ideas what rating my old potterton envoy is then??

tell me more about these hi flow tanks as my hot water pressure is very poor?

Band B I think

Hi flow tanks are properly known as unvented. As far as the end user is concerned, it's the same as a normal cylinder, just running at mains pressure. It's obviously more complicated than that though underneath.
Main thing is that not all houses are suitable for one, you need decent mains pressure and flow to start with. Absolute minimum of 2 bar pressure, ideally 3 plus. Secondly, flow rate in excess of 20 litres per min, ideally 25-30 plus. Good pressure doesn't mean good flow and vice versa. Check flow approximately using a big bucket or flexi tub. To check pressure, use a mains pressure guage on an outside tap or washing machine tap. Just make sure it's mains and not cold from the header tank in the loft. You'll get a guage from b and q or screwfix for 10-15 quid.
Personally, i'd always go unvented, but don't have good enough pressure here.

not sure about pressure but my main pressure is so powerful that i can only open the main stop cock under the sink about an eighth of a turn bfore the water pressure from the taps is to much??

that is not pressure you are adjusting, but flow rate.

as an example set your mains cold water tap to drip and then try to stop the flow of water. water will spray everywhere and you will not be able to stop it. you still have high pressure even with a drip, but poor flow. therefore even if your stopcock is only letting by a drio, there is still pressure, but little flow.

not sure about pressure but my main pressure is so powerful that i can only open the main stop cock under the sink about an eighth of a turn bfore the water pressure from the taps is to much??

If space is a concern, then you could consider a thermal store boiler such as a Powrmax. This is basically a cylinder with a boiler stuck on top. We've had them in the past & they have worked fine. I think you can get upto 185l of storage & condensing.

I would not get a combi unless there was really limited space for a large unvented hotwater cylinder. 'instant' hot water from a combi depends very much on where it is in relation to the tap you've turned on.

Old gravity fed systems only have about 6 feet of GPE before your shower head. That's why they dribble at you. If your mains pressure is good then you'll get better results from either a combi or an unvented system.

The unvented system will deliver hot water at a constant temperature. The combi can be affected by changes in the water pressure. Having said that you do need pressure balancing on your hot/cold supply to avoid freezing/scalding with the unvented system if someone turns a tap on.

We got a new boiler & cylinder set up when we moved in. Worcester+megaflow. It is great. Big volume. And fast reheating. It never seems to run out of hot water at times of high demand.

I seam to remember back in my days in house bashing an NHBC standard regarding the use of combi boilers in dwellings with more than one bathroom which I think went along the lines of if you do it make sure that the manufacturer has varified the design.

The general rule is that for a small house with one bathroom a combi is suitable but a larger house (ie a family home) with more than one should have a HW tank for above mentioned reasons.

Do get a digital temperature gauge though – they make a huge difference to how well you can control the central heating – an extra £80 or so well spent IMO.

'spose it depends on your circumstances, I'm moving to a combi, even if it's just for the hot water & keep the other one for the heating

We've got 3 teenage girls who all want a shower in the morning, guess who's last in the queue & gets a cold shower?

We have a Atmos combi which is a similar system to RobS and TJ I think for a two bathroom house. I don't know anything about the technical stuff but it is about the size of a fridge as well. It provides us with mains pressure hot water, if two showers are running then the second floor shower loses some pressure but no heat. It does have a huge shower head though and the shower is still more than adequate. The first floor bathroom has a momentary loss of pressure but that is all. It has a smaller shower head but still pretty big. Hot water is pumped round the system at peak times so hot water is instantaneous then, but there is a wait at other times.

We are very happy with it.

Seems to be a big swing against combis, I don't see why. You'll get a combi to fit in a kitchen wall cabinet, freeing up space somewhere else in the house. All the gubbins is there at hand, so relatively simple to diagnose problems when they occur. No header tanks to worry about, don't usually have to wire in remote stats and valves. Simple to put a single wireless programmer/stat somewhere. Who actually runs two baths simultaneously anyway. A high flow rate combi will easily give an excellent shower, if your mains pressure is anywhere decent. What's not to like? Good to have an electric or gas fire and an electric shower in the house as backups though, slightly better backup for a tanked system would be to add an immersion heater to that.

thanks for all the replies,

seems like a big divide on what would be best.

to be honest i dont want to spend much as we would like to move in about 4 or 5 years time.

i think i will get my local plumber around and he can advise on what will be best for me!!

just out of interest would a newer condensing boiler and a hot water tank just slot into the original postitions in my airing cupboard and would they be any more efficent than the 15 year old potterton boiler and the tank i have now??

whilst the potterton is a good unit if you go for the newer boilers then they are a lot more energy efficient due to strict energy requirements. We seem to be putting a lot of Glow Worm units in at the moment like the Ultracom. So you have an electric shower or is it running from the tank at present? Just stay away from Nibe…

Don't always trust the plumber. I don't feel we were very well advised on its position. It was installed in the airing cupboard next to our bedroom. Great, we thought, warm towels. However even though it is supposedly a quiet boiler it wakes us up all the time. Wish we'd kept it downstairs in the utility.

Remember also that combis will fire up any time the hot tap is turned on. If I'm up early for work and want a shower/shave, on comes the boiler which promptly wakes the wife and kids up.

Knowing you've always got hot water is good tho'

…and we've soundproofed the airing cupboard…not very well, obviously 🙁

I've just fitted a Glow Worm SXI which is a combi with a hot water storage tank also built in, you can go for 110Lts or 170Lts. Dogs do dars in my opinion. Best of both worlds. Instant hot water within 5 secs for a tap 3 mts away. Also top of the Sedbuk energy rating guide. Not the cheapest but as hopefully it's one of those things you go for every x amount of years.
Andy

Thats the Ultracom isn't it? That's what we've put into a lot of our sites and the verdict is that people are very happy with it.

mastiles_fanylion – Member

The general rule is that for a small house with one bathroom a combi is suitable but a larger house (ie a family home) with more than one should have a HW tank for above mentioned reasons.

I have to say for me its the opposite – you just need a combi with either the boost (heat bank) facility or a high power or both ( which I have) That way you never run out of hot water and we get full mains pressure and flow ( very high – painful in the shower) of very hot water. Its the best I have ever used but I haven't used the unvented cylinder systems)

disadvantage is the size of the thing and the cost. Advantage no cylinder and unlimited hot water.

We are running two bathrooms off it. If one bathroom has the hot tap full on the furthest away one only gets a small amount of hot water – this is not an issue for us and if it was could be easily cured by putting a flow limiter in each bathroom to make them share the flow.- we would still have more flow of hotter water than I have seen before from this and the same would apply to a non vented system anyway.

We have just had a new combi installed. Running a shower and a cold tap and there is no difference.

Running the shower and dishwasher/washing machine etc and there is a slight drop in pressure, and the temp rises slightly.

Will try runnning shower + shower/bath tonight to see what happens. I'm pretty convinced it will be ok… and thats a 35kw boiler.

If you have a tank surely it runs cold quite quickly if its a family home etc? ie 4 baths in a row.

Hot water on demnad is much nicer!

Our combi as been installed in a converted cellar, miles from the bedrooms and so far you cant hear a noise. Although when it does fire up it does make a fair amount of noise. I am surprised just how little heat the boiler itself produces. Its in a small probably 2.5 x 1.5 m2 room and it doesnt get hot at all. I guess thats efficiency of modern boilers

at the moment we only use the bath to give our 2 young uns a quick bath 2 or 3 times a week.

otherwise we use the electric shower.

i dont think we have run out of hot water from the tank apart from once when we had a big party and were doing lots of washing up.

we have the hot water set to come on twice a day for an hour at a time.

hot water pressure is non existant at the moment??

i would like to put bigger radiators in the 3 bedrooms at the same time too.

what do you think.

We stuck with the tank when we had our boiler replaced. Our plumber summed it up very simply. If you even have a power cut or problems with the gas supply, then you've got a tank of hot water ready & waiting

If you're running out of hot water with a cylinder, then the cylinder is undersized. Standard gravity cylinder is 120 litres ish. Most common unvented cylinder is around 210, but they go from 90 to 300 in off the shelf sizes. A very good one will still have got water in it 3 or even 4 days after switching the heating off because the insulation is so good.

as i said we have only run out of water once??

"otherwise we use the electric shower."

Electric showers cost a fortune to run!