What size boiler do I need?

[Colits42]

I am a newly registered gas engineer and I am getting a quote together for a job in an industrial unit. There is an old floor standing boiler, which runs 11 rads. It is roughly 21 meters to the furthest rad. The customer would like to fit a Worcester Bosch Combi boiler but I am unsure what size is required to run a system this size. Could anyone please advise on the size I would need to make the system run successfully.

Thanks

 

[gassafe]

What is the output of the existing boiler?

 

[Chalked]

What size is fitted?
Do you know how to do a whole house calculation?
Or use an app like Mr combi. To calculate room by room.

 

[Matty7]

I use Mr combi it's a great app, might be helpful for you.

 

[kozak1968]

I would be thinking about the hot water demand rather than the heating output. A 24kw combi would probably be more than enough output on the heating side but might struggle with hot water flow rate.

 

[ShaunCorbs]

I would be thinking about the hot water demand rather than the heating output. A 24kw combi would probably be more than enough output on the heating side but might struggle with hot water flow rate.

unless theres showers in the industrial unit dont think it will matter too much

 

[joni os]

Discuss with client peak demand for hot water and size accordingly. Involving client in specification will avoid disputes.

 

[IDCHAPPY]

Don't fit a Worcester..
11 rads is nowt really. Depends on DHW demand though.

 

[Colits42]

There are only two sinks being piped to the boiler and not in constant use so I am not to worried about hot water demand . I just want to have all the rads getting hot without problem as the rads are all on the same floor I dont want to get something to small and the pump cant get the water round the system properly I was thinking 30 plus kw should do it?

 

[ShaunCorbs]

There are only two sinks being piped to the boiler and not in constant use so I am not to worried about hot water demand . I just want to have all the rads getting hot without problem as the rads are all on the same floor I dont want to get something to small and the pump cant get the water round the system properly I was thinking 30 plus kw should do it?

work the heat loss of the rads but have a feeling will be less than 30kw

 

[flat Eric]

Grab a screwfix cat, look at all rads and find the nearest, add up all the btu outputs and then add 10% for the pipework. Don't over size the boiler or it will cost more to run as it wont modulate low enough ( biggest problem in domestic along with gas pipe run undersized)

 

[ShaunCorbs]

Grab a screwfix cat, look at all rads and find the nearest, add up all the btu outputs and then add 10% for the pipework. Don't over size the boiler or it will cost more to run as it wont modulate low enough ( biggest problem in domestic along with gas pipe run undersized)

slightly wrong most boilers will modulate below 15kw some below 8kw

 

[jtsplumbing]

Does the boiler that is installed cope with the heating at the moment ? What size boiler is it ? and do they intend to add on any extra radiators, just make sure that you flush system, and being as your using excising system fit a filter, Proberly a good idea to renew all the radiator valves wile system is empty.