boiler size

[mon]

hi. thinking of replacing ancient heat only boiler for a worcester green star heatslave combi oil boiler. the house heated nicely with existing size rads, i will problably replace them with same size newer ones. there is bathroom, with bath, basin, toilet, elec shower. 1 kithen sink.
total btu`s of rads: 49458 ish.
do you think a heatslave 12/18 will be big enough for system, will a 18/25 or a 25/32 be too big? thanks.

 

[Agile]

A combi is rated for hot water output.

24 kW is the normal minimum and this will supply about 8-9 li/min at 35 c temp rise.

In practice this means a combi will supply just one outlet. Fine for a small flat with one or two people not very suitable for a house with more living there in my view!

Tony

 

[oilboffin]

I think you'll need the 18/25at the very least there a very good boiler there is a lot on this island

 

[dcawkwell]

Small house the 12-18 will do nicely.
Larger house the 18-25.
Big house the 25-32

 

[dcawkwell]

A combi is rated for hot water output.

24 kW is the normal minimum and this will supply about 8-9 li/min at 35 c temp rise.

In practice this means a combi will supply just one outlet. Fine for a small flat with one or two people not very suitable for a house with more living there in my view!

Tony

This is an oil boiler. Water delivery rates are nearer 20 litres a minute.
Because they are use a heat store.

 

[mon]

Thanks to you all for your advice, from what your saying it sounds like the 18/25 should be fine? 1bathroom, abt 10 rads in total.

 

[Agile]

This is an oil boiler. Water delivery rates are nearer 20 litres a minute.
Because they are use a heat store.

Until the stored heat is depleted after a few minutes when they revert to what the boiler output can deliver.

 

[dcawkwell]

This is an oil boiler. Water delivery rates are nearer 20 litres a minute.
Because they are use a heat store.

Until the stored heat is depleted after a few minutes when they revert to what the boiler output can deliver.

Grant specs for their combi.
Average temperature draw off of 50 degree for 100 litres and 4 minute
recovery time even on the smallest boiler. Impressive.

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VTXCOMBI21*
15 litres per minute at an average temperature of 50°C
Recovery time 4 minutes approx. Based upon 100 litre draw off.

VTXCOMBI26*
17 litres per minute at an average temperature of 50°C
Recovery time 4 minutes approx. Based upon 100 litre draw off.

VTXCOMBI36*
20 litres per minute at an average temperature of 50°C
Recovery time 3 minutes approx. Based upon 100 litre draw off.
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