New Central Heating system advice

[Madrab]

Don't take any quotes for an unvented system until it can be proven that your mains can supply a lot more than 9L/Min. Wasting your money if that is the max and don't let anyone tell you any different.

You need a proper test on the mains performed at an unfettered outlet as close to the mains entry as possible (as @muggles mentioned - say at an outside tap) that will give you an actual dynamic mains pressure and flow, you can't make any educated decisions until that is determined. Did the water supplier not give you a report as to the mains capability when it was upgraded?

 

[wwwebber]

Thanks for all the replies! Interestingly I've had another quote for an unvented cylinder this time moved to the loft, needless to say I'm more confused than ever!

Hmm, yes an unvented cylinder usually directly replaces your old hot water cylinder so that is a strange one - especially as your property needs upwards of a 210 litre cylinder which is very very heavy !!.

If you are being quoted for an unvented cylinder and nothing to help the cold water flow feeding it then beware, your flow rate is low and you will not reap the benefits. My pressure is 3 bar and flow about 12lm which is not great but is just about acceptable for a decent shower. So an accumulator may be the way to go but this needs space and money !.

So on top of a new system boiler (not in doubt) you have two options :-

1. If you have the space and money, go with unvented + accumulator, remove all pumps and tanks in the loft
2. Stick with vented and then have the hot and cold pumped around the house (including to both showers) using a twin impeller pump - I am assuming your hot and cold water tanks are big enough because you are already successfully using a pumped shower ?

I am not a plumber but I investigated pretty much ALL options when upgrading my setup so have picked up quite a lot. My setup is now sweet as a nut

 

[mecster09]

Don't take any quotes for an unvented system until it can be proven that your mains can supply a lot more than 9L/Min. Wasting your money if that is the max and don't let anyone tell you any different.

You need a proper test on the mains performed at an unfettered outlet as close to the mains entry as possible (as @muggles mentioned - say at an outside tap) that will give you an actual dynamic mains pressure and flow, you can't make any educated decisions until that is determined. Did the water supplier not give you a report as to the mains capability when it was upgraded?

So we tested the outside tap and was closer to 18 litres per minute.

 

[Madrab]

That's better but still at the lower end for unvented tho, now you want to make sure you get that 18L/min up to where the unvented is going to be with good sized supply pipework and then from the unvented to the outlets with similarly suitable sized pipework.

Simple way to look at it is, you will only get out what you put in.

You do get horizontal unvented cylinders that can be located in the loft but not sure i'd want one of them above my head TBH