unvented systems with 15mm mains inlet

[a1topdog]

I want to get gas central heating installed (currently have electric) and planned to have an unvented , indirect system.

The problem is I only have a 15mm mains water and all of the cylinders I have seen (megaflo , ariston etc) require a 22mm mains connection.

Should I pay to have a new 22mm mains laid or is there another way around this problem. (I don't fancy having my drive dug up!!)

(I have arranged a pressure and flow rate check , but it hasn't been done yet)

 

[breezer]

they may use a "mole" to lay new pipe.

hole at each end put in "mole" and it (hopefully) pops up at other end, aparently its quicker / easier than digging whole trench

 

[oilman]

You need to know the flow rate from the mains. You can use a 15mm supply, but you won't be able to get the quoted performance. Baths will be slow to fill, and if people are having showers and washing up at the same time, you may notice a drop after a while. You must be rich if you can afford an unvented cylinder, would you like me to quote a nice rich-man's price?

 

[Bahco]

IThe problem is I only have a 15mm mains water and all of the cylinders I have seen (megaflo , ariston etc) require a 22mm mains connection.

Should I pay to have a new 22mm mains laid or is there another way around this problem. (I don't fancy having my drive dug up!!)

)

You don't need to change your mains supply to connect to a 22mm pipe
Provided your pressure / flow is satisfactory you only need to take a cold supply from your existing rising main be it 15mm or 22 mm

 

[a1topdog]

Thanks for your answers. I am aware I can increase the 15mm to 22mm , but its the loss of performance I worried about.

I wasn't sure at what point between the mains inlet and the cylinder to get the pipe increased. It seem like a bit of a juggling act between increasing flow rate but losing pressure.

The cylinder would be located on the first floor , but the ground floor would have mains cold water connections to the kitchen , loo , dishwasher and washing machine.

At what point in the supply would you advise making the pipe size increase?

(ps - I ain't rich - I just want a decent system put in right at the first attempt!!)

 

[oilman]

You need to increase the size just before the combination valve, but it doesn't matter, the registered installer will do it, you are not allowed to. You also have to inform building control before it's installed, and they WILL want the paperwork once it's done.

The pipe size change will have no effect on flow rate or pressure as the pressure is controlled by a pressure regulating valve.

(ps - I ain't rich -........

You must be if you're having one of these. Did you know they should have an annual service too?

 

[a1topdog]

Did you know they should have an annual service too?

No I didn't - I don't fancy open wallet surgery once a year

Help me out here then - what system would you recommend for me - I've
currently got a 3bed , 1 bath , 1 shower but will be extending to 5 bed with an additional bath and shower. A combination of baths and showers will be being used at the same time.

 

[2scoops0406]

Again, only from experience, the performance of my megaflo fed from a 15mm main was "satisfactory", but then it was only a 2 bed semi. What I was told was it wasn't the pressure that was so important, but the flow rate, which will obviously be greatly helped by a large main.

 

[oilman]

You have to go a long way to beat a normal hot water tank. You can have a sealed heating system , which has some benefits, but it needs checking every year. In the end, there's no free lunches.

 

[bripl]

try a thermal store like boilermate made by glenhill mains pressure hw no need for annual service or to inform building control or special certs for installation. albion do one as well maybe the better option

 

[oilman]

A thermal store will not get over the problem of a limited water supply, and will not provide water for multiple bathrooms,...but then have the latest pseudo-high-tech solution and have something to moan about for ever after.

 

[bripl]

oilman i beg to differ,if the water pressure is adequate at say 2/3 bar it will deliver hot water to multiple outlets at better flow rates than a conventional sys or high output combi as for new tech i installed boilermates approx 15/20 years ago and still going strong with minimal maintenace.the original poster needs someone to do a site visit to determine the best cost effective sys suitable for THEIR needs.talking as someone who has lived with a combi[never again]megaflow[too much maintenance/expense] tanks/pumps[too noisy/constant filling]albion[five years/not a penny].i the same as you can only express an opinion from personal experience

 

[oilman]

At last, someone with som experience of thermal stores. Sorry about the post, but I have asked earlier about thermal stores, and found little response so I thought the inflammatory approach might work. I have had to deal with only a few thermal stores, as everyone is Megaflo mad round here.

However,.........in this case even if there is 2-3bar pressure, its the flow rate that fills baths, and I'd be surprised if you could do 2 at a time from a 15mm main in a reasonable time. Alright you might have difficulties trying to do it from a standard HW vented tank too, but would the thermal store be any better?

It's better that you can put it on the ground floor and still have hot water upstairs, but you are still dependant on electricity to get hot water if it one of the Gledhill products with a plate heat exchanger.

 

[2scoops0406]

Ok, don't know, but is the largest domestic main you can have 32mm? If so, can you connect this without reducing to a domestic unvented tank? If not, how come on the continent, you seem to get mega powerful showers, whereas our often seem a cr@p bit in comparison?

 

[oilman]

Ok, don't know, but is the largest domestic main you can have 32mm? If so, can you connect this without reducing to a domestic unvented tank?

Domestic tanks have valves which take 22mm pipes, so there's a reduction somewhere. If you use 32mm fittings, you'd have a big bill.