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boiler size


 
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mon

from United Kingdom

Joined: 15 Jan 2013
Posts: 2
Location: Anglesey,
United Kingdom

PostPosted: Tue Jan 15, 2013 10:33 am Reply with quote

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.
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Agile

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Joined: 26 Jun 2004
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Location: London,
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PostPosted: Tue Jan 15, 2013 10:43 am Reply with quote

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
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oilboffin

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PostPosted: Tue Jan 15, 2013 9:58 pm Reply with quote

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

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PostPosted: Tue Jan 15, 2013 10:10 pm Reply with quote

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

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PostPosted: Tue Jan 15, 2013 10:13 pm Reply with quote

Agile wrote:
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.
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mon

from United Kingdom

Joined: 15 Jan 2013
Posts: 2
Location: Anglesey,
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PostPosted: Thu Jan 17, 2013 10:33 am Reply with quote

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.
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Agile

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PostPosted: Thu Jan 17, 2013 2:02 pm Reply with quote

dcawkwell wrote:


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.
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dcawkwell

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PostPosted: Thu Jan 17, 2013 4:11 pm Reply with quote

Agile wrote:
dcawkwell wrote:


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.

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

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

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