Cylinder replacement - no boiler

[whiskyfrank]

May sound a silly question but I have a very old direct cylinder on an emersion, in a bedroom that needs replacing.

The heating is electric as we have no gas and is fine.

Can I replace this with a direct unvented cylinder in the utility downstairs?

I have showers upstairs and downstairs so need hot water to both as well as taps etc. Will this work pressure wise for hot water supply? ive been told we have 2 bar dynamic water pressure in.

 

[cross thread]

You may have 2 bar but at what litres per minute

 

[whiskyfrank]

im fraid i have no idea

 

[ChrisJP]

Easy enough to measure it - run you kitchen cold tap into a litre measuring jug and time how long it takes to fill

 

[oldbuffer]

1. 2 bar dynamic pressure is at the lower limit for an unvented cylinder. Worth checking you do get this pressure, and at different times of the day.
2. You need a flow of at least 20 litres per minute (cold main, "open pipe" flow).
3. You would almost certainly need some pipework changes. Probably from 15 mm to 22 mm from kitchen to bathroom, particularly if you use a bath as well as a shower.
4. An unvented cylinder must have an overflow (well, pressure / temperature relief pipe) to outside.
5. You need to consider the electrical supply. Normally unvented direct cylinders have two immersion heaters. The lower one is expected to run off an "economy" electricity tariff, the upper one off normal rate electricity. Each requires a dedicated 15 amp supply directly back to the consumer unit.
6. An unvented cylinder requires an annual service.
7. Installation and service may only be done by someone with a current "G3" accreditation. Some gas engineers have this via Gas Safe, but not all gas engineers are G3 registered. There are other accreditation schemes, such as NAPIT.
8. The installation must be registered with your local Building Control department. This registration is normally done by the installing engineer provided they are G3 registered.

 

[ChrisJP]

All of which would persuade me to fit a vented cylinder vented to a header tank in the loft, as presumably the existing cylinder is, if I needed to renew the cylinder. Much less hassle and passively safe so needs no annual inspection

 

[Madrab]

How are you with the pressure/flow from your current HW cylinder?

 

[whiskyfrank]

Pressure is very good on the vented cylinder now.

Id like to move the cylinder downstairs to the utility which is where the supply is now mainly as i need the room upstairs to fit a bigger bathroom

 

[ChrisJP]

If the HW cylinder continues to be vented and supplied by a cold water storage tank (which normally will be in the loft) then moving the cylinder downstairs will make no difference to the HW pressure. This is governed by the head difference between the cold water storage tank and the shower head/HW outlet - the cylinder can be thought of as just a bulge in the pipework.
If you go to an unvented HW cylinder, then the HW pressure will be entirely dependent on your mains pressure and flowrate - it doesn't make any difference where the cylinder is located.

 

[whiskyfrank]

that makes sense thanks for that