Is it ok to have unvented cylinder in loft

[hztm2008]

Would really appreciate some advice. We currently have warm air heating with prismatic water cylinder in an airing cupboard in the bathroom. We are looking to re-fit the bathroom and the plumber has suggested replacing the prismatic cylinder with an unvented water cylinder in the loft - this would then allow the airing cupboard to be removed to make way for a shower cubicle and would provide a good water feed for the shower. I am a little concerned about having this in the loft - is this a good idea and are these units safe?

We have posted before on this forum when we were considering changing the warm air to a wet system. Whilst we received lots of helpful info, there was lots of conflicting ideas on the system we should go for and we ended up keeping the warm air. The plumber has suggested the other option would be to change to a wet system with combi boiler (we have 4 bed 70's detached house with one bathroom, cloakroom, kitchen and utility room) but I think the advice on here before was that combi boilers are not too good in this type of property.

So, just wondering whether to go with the unvented in the loft or keep the old prismatic and stick with an electric shower over the bath.

Thanks for any help.

 

[Dan Robinson]

You are on the practical limit for a combi.

A cylinder in the loft is fine as long as the weight can be supported and the safety requirements met.

 

[OwainDIYer]

You can, if you want, run a hot water cylinder off a combi boiler. It's plumbed in as an additional radiator circuit with its own zone valve and timeswitch.

So you could have the shower off the combi mains pressure hot water output, but use the cylinder (open vented or unvented) for the bath etc.

Showers are usually of short duration so having the entire boiler output diverted to the shower won't affect the general house heating.

 

[dcawkwell]

Hi delivery combi will be fine and remove all the old tanks and nasty warm air unit.

 

[JohnD]

if you go for an unvented cylinder or a combi, remember that water output through (all) the taps will be limited by what comes into your house through the main.

Run your kitchen cold tap into a bucket, time it to full, calculate how many litres per minute you get.

An unvented is fantastic if you are lucky enough to have 20 lpm

 

[hztm2008]

Many thanks to everyone for the info.

I have to say that a combi boiler does sound very appealing - one unit in the utility room and no water in the loft. However, I am worried that you do not really know how well it will perform until it is installed and, the external water pressure could change over time and there would be nothing I could do about it. Also, if it breaks down I have no other source of water. I know people who love them and people who wish they had not had them installed. I am not too keen on an unvented cylinder in the loft but do not have anywhere else to put it.

At present we just have an electric shower over the bath and we could keep this arrangement with the warm air heating and existing old cylinder. I am just worried that it is a little dangerous climbing in and out of what will be a shiny new bath.

Thanks again for the advice.

 

[Dan Robinson]

Most of your concerns about a combi are just as valid for an unvented cylinder.

Be careful using a kitchen tap as a reference. Some taps are very restrictive. Some might be plumbed onto small supplies or flexible hoses and will give false readings.

 

[CBF]

As Dan has pointed out with regard to kitchen taps, i had one that was showing 11 trs/min out of the sink taps, however the outside tap was overflowing my flow cup & that shows 25 ltrs/min

 

[DP]

My recommendation would be the unvented cylinder. This must be located as mentioned by few lads here already, where heavier weight can be supported, safety components plumbed correctly and lastly, the cold feeds are balanced feeds

You then have a belt and braces job, where if he boiler wa to pack up, you will still have hot water. You could fit a cylinder with solar coiled for future expansion

Limiting factor will be the WAU which will not have the cloute for rapid heating of hot water. You will also need pumped supply to cylinder which is unlikely at present it b a prismatic cylinder

WAU maintained correctly does heat he house rapidly.

 

[Dan Robinson]

Also avoid those internal air bubbles if going ion the loft. They deplete their air quicker than normal and it is a PITA to recharge it all the time if in the loft. An external expansion vessel just needs its annual service along with the boiler.