Selection Guide
Domestic selection guide
These recommendations are based on the guidelines in BS 6700. Guidance should be sought for unusual applications, e.g.high
flow-rate showers, large baths etc.
| Hot water demand |
Bedrooms |
Indirect units |
Direct units |
| 1 Standard bath or shower |
Bedsit/1 bed
2-3 bed
3-4 bed |
120
120
150 |
150
180
210 |
| 1 Standard bath |
2-3 bed
3-4 bed |
120
120 |
210
210 |
| 1 Bath and En-suite |
2-3 bed
3-4 bed
4-5 bed |
150
150
180 |
210
210
250 |
| 2 Standard baths |
2-3 bed
3-4 bed
4-5 bed |
180
180
210 |
210
210
250 |
| 3 Bathrooms |
3-4 bed
4-5 bed
5-6 bed |
250
250
300 |
300
300
300 |
Domestic selection guide
These recommendations are based on the guidelines in BS 6700. Guidance should be sought for unusual applications, e.g.high
flow-rate showers, large baths etc.
| Typical commercial application |
Indirect units |
| Large house - 6 bed/4 bathrooms |
2 x 210 |
| Guest house - 8 bed/4 bathrooms |
2 x 300 |
| Small hotel - 8 bed/8 bathrooms |
3 x 210 |
| Sports pavillion (25 people/4 showers) |
2 x 300 |
| Sports pavillion (25 people/6 showers) |
3 x 210 |
| Student house (25 people/3 bathrooms) |
3 x 300 |
| Old peoples' home (60 beds/10 bathrooms) |
5 x 300 each supplying 2 bathrooms |
Immersion heaters
| Size |
Direct |
Indirect |
| 120 litre |
2 x 3 kW Immersion heaters |
1 x 3 kW Immersion heaters |
| 150 litre |
2 x 3 kW Immersion heaters |
1 x 3 kW Immersion heaters |
| 180/210 litre |
2 x 3 kW Immersion heaters |
1 x 3 kW Immersion heaters |
| 250/300 litres |
2 x 3 kW Immersion heaters |
2 x 3 kW Immersion heaters |
Example illustration.
A school swimming pool has 5 showers in each of two changing rooms. The shower heads are flow-restricted to 9 litres per minute
(2Ú3 of this will be hot water). Usually there are 3 one hour lessons each morning and three each afternoon. Assuming a class size
of 30 children.
Maximum demand = 10 shower heads x 9 litres/min = 90 litres/min. This is more than one
Ultrasteel can supply. At least two Ultrasteels will be needed to provide this.
Total demand = 30 children x 6 litres/minute x 5 minute shower each = 900 litres
3x300 litre units will be required.
Reheat time has to be a maximum of one hour so it is reheated in time for
the next lesson. A CUI 300 can reheat its entire contents in 60 minutes
with a boiler power of 15kW. So total boiler power required = 45kW.
If direct units were used they would have to be fitted with
immersion heaters rated at 15kW (typically 1 x 9kW + 1 x 6 kW)
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