Shall I convert vented to unvented?

[andy.budgell]

I have a fairly typical vented central heating system with F&E tank in loft, and indirect HW cylinder which has a 42 gallon cold water tank in the loft.

The hot water cylinder, CH pump and 3 way valve are in the airing cupboard on the landing.

The boiler is in the garage (which in partially integral to the house) and the 2 primaries go up into the house and along under the upstairs floor into the airing cupboard. I have 8 rads and power shower – which is fed from the surrey flange on the HW cylinder up into the loft and down into the bathroom.

I am in the process of making the loft space useable. The only option for stairs up into the loft is through the airing cupboard (alarm bells). This means I have to move both the hot water cylinder, pump, valve, and associated pipework BACK into some of the wardrobe space of the bedroom behind the airing cupboard. The stairs would then go OVER the cylinder etc. The space is there to do that and it is the only option.

I will also have to move both tanks in loft to somewhere under the eaves laterally about 1.5 metres.

So, I can do all this moving around of my current system (or pay someone to do it). Or I can get an unvented HW cylinder put in the garage – cos its too big for the airing cupboard, and at the same time convert the CH to sealed by use of expansion vessel etc. Then I would be free of both loft tanks AND the cylinder and pump etc in the wardrobe space.

I don’t know what to do. My first estimate from SGS in Salisbury was £3429 to convert to sealed. Seems a lot of money considering its 2.5 days work, and surely no more than £1000 for parts.

Any ideas anyone? The garage gets freezing in the winter, I assume that would affect the efficiency of the new cylinder?

 

[DP]

You have not stated make and model of boiler, so it is difficult to say if you will be able to convert the open vented heating system to sealed. It would not make any difference to unvented system if the boiler was open vented.

Putting the cylinder in the garage would be good.

You cannot use a Y plan on unvented system. If you wish to retain the Y plan, you will need to fit a 2 port to the flow to the cylinder as well.

Do talk to building control as they will require plans for UV cylinder installation.

Power shower would have to go as the cylinder will have sufficient pressure (mains permitting). Check shower as it may not be suitable for UV system.

Make sure balanced feed is provided as some installers 'forget' to do this.

 

[andy.budgell]

The boiler is a Baxi Solo, about 5 years old. The estimate that I have had assumes the current boiler will be used.

What about the estimate? Is that about right, I know its hard without seeing site.

What do you mean about wishing to retain the Y-Plan? Sorry you've lost me.

 

[giblets]

Excuse my ignorance DP, but why can't you use a Y-plan on an unvented system?

 

[DP]

3 way valve (most likley) is a Y plan. Regardless, a three port valve will need additional 2 port valve connected to it.

 

[andy.budgell]

Before this post gets bogged down with Y-plans.......

£3.5k seems a lot to spend. Is this viable?

Or do I keep my existing vented?

Would I also need a separate feed for any normal mixer shower so that I dont get scalded when the wife turns the cold tap on?

 

[gas4you]

All unvented cylinders have a pressure reducung valve, or balancing valve, in the cold supply. This reduces the cold mains to around 3 bar. if fitted correctly all the colds for the bath and showers should be taken after this valve, so when another tap is turned on the valve opens instantly to let more water through to keep the outlets balanced, preventing the issue you describe. To make this work correctly you need at least 3 bar cold mains pressure, ideally around 20 litres/min flow and a 22mm cold supply to the cylinder.

There would be a lot of pipe work changes to do this properly.

What make and size cylinder have you been quoted for?

 

[andy.budgell]

Cant remember size or name, I'm sure it began with A.
I have a 3 bed 1 bathroom house, so I imagine its failry average.
£3.5k?

 

[john90]

Andy, why not get a couple more quotes. This will give you a better idea if it's a fair price and make sure the installers have their unvented ticket.

 

[andy.budgell]

Thanks for the info everyone.

Thanks for info gas4you regarding balancing valve. Are you saying the there needs to be a new cold water feed to bathroom?

 

[gas4you]

Yes if you don't have 22mm mains supply to it already and you need to check what size your incoming main is to your internal stop tap as well in a perfect world

 

[andy.budgell]

The cold water supply around the house is currently 15mm. This gets reduced from the 25mm cold coming into the house.

Could this explain the cold water "noise" when anyone uses a cold water tap or toilet refills etc?

Would a self employed plumber be a better option than a company? How much do self employed plumbers charge per day?

 

[gas4you]

25mm outside is ok, but 15mm everywhere internal is not for unvented. Don't know how much anyone charges in your area. Get 3 quotes from various recommended sources. Make sure whoever is quoting has a vaild unvented ticket