1 horse power is approximately 750 watts = 0.75 kW. So 50kW = 66 horse power (an interestingly enough, an actual horse is capable of significantly more than 1 horse power for short bursts).

However, if you're running steam calcs in horse power then you're either a masochist who enjoys excruciating unit conversions in Imperial, or aren't familiar whatsoever in metric. Seriously, the Imperial units for thermodynamic work are painful. Do yourself a favour and do thermodynamic calcs in metric.

Boiler capacity is typically listed in kg/hr of steam at a particular service pressure. This equates to a

*full load* power. The boiler only boils off what it needs to in order to maintain the setpoint pressure. So if you can only condense 15kW of steam at your load, the boiler can only boil off that amount too.

There is also the whole condensate removal and return process which is critical to the performance of a steam system. I won't even begin to start that here.

So, typical process to size a boiler is as follows:

- Work out your
*connected loads . *Bear in mind that with saturated steam, temperature is proportional to pressure (which is actually the reason why steam is so bloody useful). So, you need to keep in mind not just the kW of your load, but also the pressure. Lower pressure steam needs larger pipework (lower density, kinda like high voltage electricity) and visa versa, so forgetting to understand your delivery pressure will screw you.
- Work out the sequencing of your connected loads. It is very rare for everything to be running full load simultaneously.
- Convert all kW values to pressure and mass flow rate (otherwise you can't size pipework)
- Determine your
*peak, average and minimum demand *in kg/hr at boiler discharge pressure.
- Boilers have to be sized on worst case, ie peak demand +10%. Accidentally blowing out your boiler will be a rude expensive shock. If your peak is significantly higher than average, you may wish to revisit step 2.