Combi versus vented/unvented system

[lagransiete]

Hi
Currently i have vented system with Ideal classic boiler which is working well.Fairly soon i will have to either relocate that boiler due to building works being carried out, or replace with either a system or combi, the latter of which could be fir where my cylinder is at the moment in the bathroom above the kitchen.I live in a small 3 bed chalet bungalow so a boiler would be ok for the point of view of general usage.Although i do have two bathrooms one has an electric shower and in any case there are only two of us here. Problem is I use to have one ( Alpha)in a previous house which gave me loads of problems I had to have the diverter valve replaced 3 times , a major electronic part once and some washers too.Limescale is a problem here without a doubt and deposits were found within the boiler.After 6 years use we found the system had a high amount of acid and needed flushing out with inhibitor added/We did that shortly before we moved so we dont know what state its in now.One annoying thing we found was that the water kept veering from cold to hot and back whilst taking a shower.A friend of mine, who has a Worcester Bosch, told me of similar problems which he knew others experienced too.Anyway reliabilty and costly repairs being an issue I am reluctant to go back to a combi but I could be convinced if there was one out there which could give reasonable lifespan with few problems.
As for the vented system which i have now , the HW takes about a minute to reach the taps, which is too slow .Someone suggested there may be dead legs in the circuit and suggested installing a secondary circuit to compensate for that and keeping the Ideal, which, as i said , works well.
Not sure of the benefits of an unvented system other than greater water pressure on the HW.I know it is more costly, requiring a new special cylinder and requires decent cold water pressure which `i think i have. Being as I eventually intend to change our second bathroom downstairs into a wet room, then its something i could think about in the future should i opt for a system boiler
I would be grateful for any advice. thanks

 

[petej]

If you are happy with your present system and the hot water cylinder and cold water tank is in good condition why not replace the Clasic with a new conventional condensing boiler.
It should be cheaper to buy and install, the hot water pressure will be the same and there is less to go wrong in them.
The water in the c/h system and boiler just circulates so after initial filling the system you do not keep running fresh water (limescale) through the small water ways as you do in a combi boiler.

You probably have an immersion heater in your cylinder so have a back-up if the boiler does break down.

Personally I like the Ideal Clasic and would move it if it was my own house (I am gas safe reg) but if you have to pay to have it moved it may not be worth it.

It may not be legal either as boilers fitted now have to be condensing (unless it is virtually impossible to install one ) but I am not sure about re fitting an old one.

Also you may need a new flue if the wall is a different thickness. Are these still available ?

 

[lagransiete]

If you are happy with your present system and the hot water cylinder and cold water tank is in good condition why not replace the Clasic with a new conventional condensing boiler.
It should be cheaper to buy and install, the hot water pressure will be the same and there is less to go wrong in them.
The water in the c/h system and boiler just circulates so after initial filling the system you do not keep running fresh water (limescale) through the small water ways as you do in a combi boiler.

You probably have an immersion heater in your cylinder so have a back-up if the boiler does break down.

Personally I like the Ideal Clasic and would move it if it was my own house (I am gas safe reg) but if you have to pay to have it moved it may not be worth it.

It may not be legal either as boilers fitted now have to be condensing (unless it is virtually impossible to install one ) but I am not sure about re fitting an old one.

Also you may need a new flue if the wall is a different thickness. Are these still available ?

Main problem we have at the moment is the fact the hot water takes nigh on a minute to arrive to the kitchen taps where its mostly used( our shower upstairs is electric).We are on a metre so a lot of water gets wasted.Someone suggested a well lagged secondary circuit idea to compensate for that , but then someone else then said it was only worth doing with pipe runs in excess of 10 mtrs. I remain The boiler, cylinder and kitchen sink are all very close to one another(boiler in kitchen, cylinder in upstairs bathroom).
Because of the extension we are having built, the old or new system boiler will have to go to a new adjoining (and rather offset)garage with all the extra pipework that entails.Combi no doubt would be the simplest and cheapest solution as it could go where the cylinder now is , but i just dont trust them.I would need some convincing i think so for now its down to a system boiler.
I have no idea what condition the cylinder is or water tank and would have to rely on the advice of the engineer.This is a very hard water area so its quite likely that I would need a new cylinder as well, which then takes me to the unvented option i guess, plus plenty of limescale inhibitor and one of those electronic descalers.
So much to think about thanks

 

[petej]

Sorry but I am having trouble understanding why your hot water takes so long at the moment.
Quote
hot water takes nigh on a minute to arrive to the kitchen taps where its mostly used

The boiler, cylinder and kitchen sink are all very close to one another(boiler in kitchen, cylinder in upstairs bathroom)

Normally water coming from a cylinder is all ready hot when you turn on the tap, With most combi's it is cold and so takes slightly longer to build up this heat and give you hot water.

All the system boilers I have fitted are basically a conventional boiler with extras built in to them a pump,expansion vessel and motorised valves depending on the model . and they have still requires a hot water cylinder.

I think unvented cylinders are great for the extra pressure but they are quite expensive to buy and have a lot more to go wrong with them and if the pressure from your existing cold water tank is adequate now I would opt for an ordinary maybe Hi recovery cylinder if I was replacing it.

I think if you went for a pumped loop on your hot water system It would be expensive to run, and not suitable for a combi boiler. A pumped loop is more suitable for a large hotel to get hot water to all the taps fast.

Just a thought, even though the hot water cylinder is near the kitchen tap does the hot pipe go directly to the tap from the cylinder and does your kitchen tap have a good flow of water through it, some of the new small bore taps are rubbish on low pressure gravity systems.

 

[lagransiete]

Sorry but I am having trouble understanding why your hot water takes so long at the moment.
Quote
hot water takes nigh on a minute to arrive to the kitchen taps where its mostly used

The boiler, cylinder and kitchen sink are all very close to one another(boiler in kitchen, cylinder in upstairs bathroom)

Normally water coming from a cylinder is all ready hot when you turn on the tap, With most combi's it is cold and so takes slightly longer to build up this heat and give you hot water.

All the system boilers I have fitted are basically a conventional boiler with extras built in to them a pump,expansion vessel and motorised valves depending on the model . and they have still requires a hot water cylinder.

I think unvented cylinders are great for the extra pressure but they are quite expensive to buy and have a lot more to go wrong with them and if the pressure from your existing cold water tank is adequate now I would opt for an ordinary maybe Hi recovery cylinder if I was replacing it.

I think if you went for a pumped loop on your hot water system It would be expensive to run, and not suitable for a combi boiler. A pumped loop is more suitable for a large hotel to get hot water to all the taps fast.

Just a thought, even though the hot water cylinder is near the kitchen tap does the hot pipe go directly to the tap from the cylinder and does your kitchen tap have a good flow of water through it, some of the new small bore taps are rubbish on low pressure gravity systems.

when the tap is left off for some time like overnight , if I then turn it on, it takes nearly a minute before the really hot water arrives ( its starts warming up after about 35 secs).I could understand it if we lived in large house with lots of pipe work and dead legs, but this is a chalet bungalow where cylinder boiler and taps are in close proximity.

I have no idea where the pipes go first from the cylinder as its all under floorboards and behind cupboards but i could time the bath sink taps upstairs see if they warm up quicker.
The flow is obviously slower than the cold water but seems reasonable to me.I'll time the water uspstairs now.
Edit -water took 30 secs to get upstairs but i would have to try again tomorrow morning to get a more accurate estimation

edit it definitely warms up quicker upstairs

 

[PlumbingExpert]

i would go for a combi, if you want to keep up to date. I kept them semerate, and am regretting it now, as it failed in 2 years!

 

[Kenny]

sounds like you have a plumbing system that has been altered over the years, look at the pipework it may be a better idea to re-pipe parts of the system to give a more direct flow of water thus reducing the time it takes to reach the outlet,keep it simple with the boiler, in my experience combi's are problematic if it is still ok to re situate an existing boiler do that, as your ideal boiler was a good boiler with not many parts in it to go wrong, when I was still a heating enginneer and still living in the UK (5 years ago) combi's were the biggest culprits when it came to breaking down.
Do yourself a favour and keep it simple, less parts = less breakdowns

 

[jonspa]

If you have room for and unvented system and the budget go for it everytime, cant beat mains pressure hot and cold water.

Combis are good, certainly for heating only what you use, but if water pressure into the property is low, it wont be good coming out of the boiler. and you cant put a shower booster pump unto a supply from a combi.

have a look at mrcentralheating.co.uk very keen prices, dont get ripped by a high st national merchant.