Boiler size

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you could get a couple of domestic boilers and cascade them. I know some on here have suggested 40kW which I think is a reasonable number if the cylinders are new.

Given the use these might get and depending if you live in a hard water area you might want to get something slightly larger to cope with the build up of scale which will compromise your efficiency.
 
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Refurbishing a 9 bedroom bed & breakfast, bedrooms have a bath/shower in each, central heating uses two C55 Keston boilers, hot water will be three 300 litre unvented cylinders supplied via their own boiler/s.

Could you please give me a rough idea on the size of boiler to supply these cylinders?,would like to heat them within 30 minutes.

Thanks.

Lets call it a 10 bedroom for simplicity and that may have excluded the owner/staff bedroom anyway.

If they are all double there will potentially be 20 people living there. Using the rule of thumb of 50 li of hot per person that will need 1000 litres of stored water. You apparently have 900 li which is fine.

What would surprise me is if you really have a dynamic supply flow rate of 100 li/min @ 1.5 Bar which would be needed to operate that system. But you did not ask about that so we can leave that big problem out of the equation.

That stored water should be adequate to reheat at a leisurely rate. As the cylinder coils probaby do not absorb more that a maximum of 10 kW each then a 28 kW boiler would therefore be totally adequate.

Not only is it not possible to reheat the cylinders in 30 minutes but its not required with normal water usage in a B&B. I dont know quite why but the actual HW usage in hotels is far below what would normally be expected.

However, I can so no reason why the two Kestons should not be able to manage the HW as well as the CH. Its normal to reheat water before the CH comes on in the morning and to keep it topping up as required during the day.

It is not relevant what current gas assessments someone holds. It is what knowledge and experience he has. A domestic qualification can enable installation of any number of boilers up to 60 kW output each operated together.

When asking for advice its always best to listen politely to all the advice given. Its usually pretty obvious who is giving good advice!

Tony Glazier
 
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Agile";p="2053464 said:
That stored water should be adequate to reheat at a leisurely rate. As the cylinder coils probaby do not absorb more that a maximum of 10 kW each then a 28 kW boiler would therefore be totally adequate.

It is not relevant what current gas assessments someone holds. It is what knowledge and experience he has. A domestic qualification can enable installation of any number of boilers up to 60 kW output each operated together.

When asking for advice its always best to listen politely to all the advice given. Its usually pretty obvious who is giving good advice!

Tony Glazier[/quote

having listened politely to your advice you seem to have made some fundemental errors in it.

firstly the building regulations dictate the time the cylinder shuld take to reheat,last time i read them it certainly didnt quote a "leisurely rate".

secondly domestic boiler qualification has been 70KW for the last 7-10years.

both trivial points, but basic problems from someone who prides himself on being above the rest of us gas herberts.

Personally my advice would be to instruct a mechanical consultant/engineer/specialist to carryout a survey and design the system from that, rather than asking varying plumbers what they think.

Best solution for you is rip them out, dependent upon incoming main size etc i'd be advising you to instal 3 X rinnai HDC1500's with a buffer vessel. this will give you 50l/m no problems.(hot water)
 
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gasafengineer

1.It is not relevant what current gas assessments someone holds. It is what knowledge and experience he has.

2.A domestic qualification can enable installation of any number of boilers up to 60 kW output each operated together.

3.Its usually pretty obvious who is giving good advice!

1.Not in a court of law.

2.Input rating of 70kw are referred to in the gas industry regards dom/com certification , now if you would like to explain how to calculate rated input from appliance output i'm all ears , unless of course you are familiar with the appliances to be installed (efficiency). :D

3.Well it ain't you or bennyboy is it. :LOL:
 
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no, dont ignore folk its more fun to see what they have to say.
 
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I assume there is enough flow of water to supply these 3 unvented tanks?

If not it won't matter how many cylinders you have.

Most of the coils in unvented cylinders are in the 20-25kw region.

So you can't throw any more heat at a particular cylinder than that.

Although I would be cascading hot water and central heating boilers
in case of failure.
 

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