System design help

[soul2soul]

Hi All,

Need advice on what to do with our hot water system.

Current set up is a system boiler (Potterton Suprema 60he), copper hot water tank in the bathroom & cold water tank in the loft. Stuart Turner twin 2 bar pump connected to shower in the bathroom.

The shower is great at the moment but the hot water tank only holds 110 ltrs or water so it does not last long so we need a better solution. There is no space to fit a bigger tank in the bathroom so we have decided to fit a new tank in the 3rd bedroom (1st floor) where space is not an issue.

Our dilema is whether to switch over to a mains pressured unvented system or just fit a bigger copper tank in the new location. We plan to go into the loft in the future so getting rid of the tanks up there would be a bonus.

Ourt concern with the megaflo or similar is what sort of pressure from the shower we can expect compared to the current set up which are really happy with.

We renewed the water mains coming into the property to 32mm poly last year & have 22mm copper going upstairs to the water tank & 15mm plastic then copper to the kitchen sink & outside tap. Static pressure varies between 3.25 & 3.75 bar at the outside tap. The flow rate at this tap is about 16lts per minute.

Can we expect the shower to be as good as it is now or will it be worse? Noneone seems able to give us a guranteed answer on this.

Thanks

 

[gas4you]

Pressure will probably just be ok on a megaflo but I would hope to see at least 20 l/m out of the hot tap.

What is the flow rate out of a cold mains tap?

If you stayed with a copper cylinder, go for a fast recovery version, they are smaller but give more HW due to re-heating it faster.

 

[soul2soul]

Thanks for the quick response. The outside tap has a flow rate of about 16ltr a min but I assume that there will be more than this going to the megaflo as the pipes to that will be 22mm as opposed to 15mm to the outside tap?

 

[Agile]

Not necessarily!

For a start turn on the kitchen cold and the garden tap together and measure flow rate at each without touching anything until you have finished.

Then turn off garden tap and measure flow rate at kitchen tap AND the pressure at garden tap with kitchen tap running.

Tony

 

[soul2soul]

Thanks - will do the suggested tests & post the results when I get home.

 

[soul2soul]

Hi,

Done the tests this evening.

Combined flow rate of outside & kitchen tap is 15 1/2 ltrs per min.
Flow rate of klitchen tap by itself is 10 ltrs per min with the pressure at the outside tap being 1.5 bar. The pressure went up to over 5 bar when i turned off the kitchen tap if that helps.

Thanks

 

[Agile]

That seems pretty good.

The last test is to measure the current shower flow rate.

If its about 10 li/min or less then it will be fine with an unvented.

If a bit more then you can extrapolate!

Tony

 

[soul2soul]

Sorry been away for a few days so have not been able to reply.

The current shower with pump provides more than 17ltr a min.

Any recomemndations on who to use in South West London to fit an unvented system?

 

[Gasguru]

The current shower with pump provides more than 17ltr a min.

Thats just plain greedy A shower flowrate of 10 to 12 litres is perfectly adequate. Even the water regulations require notification to the water company once 12 litres is exceeded.

Have you checked the cylinder is actually being heated to 60 centigrade ie the cylinder thermostat operates correctly. Have you checked the correct quantity of water is heated in the cylinder ie is the thermostat located approximately 1/3 up the cylinder side and is the timeclock allowing sufficient time for full heating.