Move or Replace Hot Water Cylinder in a pressurised system?

[doitall]

Drivel, or is that DrDrivel.

What anything delivers is reliant on the mains.

300 Ltrs of stored water at 60C can deliver 60+ Ltrs/min at 45c when you include the cold for dilution.

Where does that leave your Combi can.

 

[GeorgeBramwell]

Drivel, or is that DrDrivel.

It is not drivel. You didn't know and cannot add up. Have you no shame?

What anything delivers is reliant on the mains.

Yep. That is why I asked what the DHW deliver was on the unvented cylinder?

300 Ltrs of stored water at 60C can deliver 60+ Ltrs/min at 45c when you include the cold for dilution.

Where does that leave your Combi can.

60 litres/min? What cold mains in house does that? Get real. If you get 30 litres/min from the mains pipe you are doing very well. The only way to get 60 litres/min is to have a cold water accumulator.

In a 4 shower setup, the high flow combi wins hands down it will deliver the DHW in the morning instantly as long as all 4 showers are not on at the same time - which is the same as an unvented cylinder (dependent on the cold mains). You will find it is rare that all 4 would ever be on at the same time. No waiting for reheats with a combi, so a higher throughput of people in the showers. A 300 litre cylinder is rare in a house, usually 200-250, even with two bathrooms.

 

[doitall]

A 200Ltr cylinder will fill 4 baths easy.

And stop talking showers, The OP has said Bathrooms, so budget from both.

So that will be 4 Combi's, an industrial gas meter, and a 50mm steel gas pipe.

 

[GeorgeBramwell]

A 200Ltr cylinder will fill 4 baths easy.

And stop talking showers, The OP has said Bathrooms, so budget from both.

So that will be 4 Combi's, an industrial gas meter, and a 50mm steel gas pipe.

200 litres cylinder will fill 4 baths? You need to do some sums. OK let's say he has 4 bathrooms at 100 litres a bath. Your 200 litre cylinder will deliver about 190 because of the dead spot at the bottom. You would fill two immediately, well at 25 litres/min in 4 mins. Two baths at once is 8 mins. Then you have to wait 30-45 minutes for another two baths as the cylinder reheats, while two baths are ready and vacant but cannot be used as there is no DHW.

Now a W-B Highflow 550. will fill 2 baths simultaneously in about 8 minutes. 7 minutes to reheat and still DHW available at kitchen tap while reheating, and two more baths directly after. No contest over an unvented cylinder, it wins hands down in DHW delivery.

Say, W-B Highflow 550. It will fill 2 baths simultaneously in about 8 minutes. And two showers are wanted. The two showers can be had simultaneously, immediately after the baths have filled. Four people in the morning can have baths and showers with minimal inconvenience. In reality as people do not shower and bath "exactly" at the same, there will be none.

An ATAG 25 litre/min combi, will fill 4 baths simultaneously in 12.12 minutes. Or two simultaneously in 8 minutes and another two simultaneously directly after and no waiting at all for any cylinder reheating. No contest over an unvented cylinder, it wins hands down in DHW delivery.

Use some common sense and some sums.