System Boiler Size

[DP]

Hi,

I'm planning for a 250 Litre unvented system (megaflow most likely) and a system boiler (Worcester most likely) to go with this. I'm struggling to obtain hard stats on how I should size my boiler and was wondering if you can help.
I will have 14 radiators in total. It's a 4 bedroom house and some of these radiators are on the larger side. I could provide the BTU's if that is required.

I'm interested in your thoughts and also any comments you have on the brands I have selected.
Thanks in advance.

Your cylinder has a heat demand, about 24kw (can be found in cylinder spec), which gets the cylinder to 75% heat in about 20 minutes. For myself or my customers, that would be the Absolute minimum boiler size. Putting a smaller output boiler means water would take longer to heat with no CH demand. Put the heating on, water would take even longer to heat

My advise would be give Heatrae Sadia a bell and seek advise there

 

[DP]

Although HW cylinders now expect around 20KW so they heat up quickly, there is no real need to add this to the central heating requirement.

Hmmm

So what would you allow if the boiler was fitted with weather comp, so the HW and CH can never be heated at the same time? (Bit difficult heating a cylinder to 60C when the flow temperature is 40C.)

One would pick a boiler that has two inputs, one for heating and another for hot water.

 

[D_Hailsham]

One would pick a boiler that has two inputs, one for heating and another for hot water.

Don't you mean two outputs (temperatures)?

That sounds like boiler with weather comp control for the CH.

 

[shambolic]

No he means two inputs which can give two outputs depending which input is calling for heat.
Like a Vogue.
Input one from hw can be set to 80 ( have it on for 30-40 min).
Then input two for ufloor or rads set for an output of 50.

 

[Dan Robinson]

No - he means inputs. Let the boiler decide then how best to operate.

Most do in some form or another.

 

[D_Hailsham]

No he means two inputs which can give two outputs depending which input is calling for heat.
Like a Vogue.

Interesting. I see that it only works when an outside sensor is fitted (so weather comp) and with S Plan only. CH and HW times would have to be mutually exclusive.

Incidentally, I hope Ideal's quality control of the manufacturing process is better than of the publishing process. This is just one appalling example from the Vogue System Boiler Installation Manual. The book is full of similar mistakes.

 

[Dan Robinson]

There are various ways to control it.

I have my boiler set up for hot water priority and OT controlled heating.

 

[Dan Robinson]

I don't have an Ideal though.

 

[DP]

One would pick a boiler that has two inputs, one for heating and another for hot water.

Don't you mean two outputs (temperatures)?

That sounds like boiler with weather comp control for the CH.

No, twin inputs. One input to say HW demand is required so boiler runs at higher temperature, other for ch saying compensated output temperature required.

 

[DP]

No he means two inputs which can give two outputs depending which input is calling for heat.
Like a Vogue.

Interesting. I see that it only works when an outside sensor is fitted (so weather comp) and with S Plan only. CH and HW times would have to be mutually exclusive.

Incidentally, I hope Ideal's quality control of the manufacturing process is better than of the publishing process. This is just one appalling example from the Vogue System Boiler Installation Manual. The book is full of similar mistakes.

View attachment 91635

DH, if you are an installer, I suggest you fit a logic or a vogue. Cracking boiler operation, features and thought that has gone into it. What if there are a few errors in the MIs, does that mean the appliance is not worth consideration?

 

[D_Hailsham]

What if there are a few errors in the MIs, does that mean the appliance is not worth consideration?

But it's not just a few errors; there are hundreds of them. Almost every page has one or more similar errors. What is worse, similar errors occur in other Ideal manuals. If Ideal care so little about the quality of their documentation that they, apparently, leave it to a illiterate school leaver to typeset, what will a customer (who will see the manual as it is left with him) think about the quality of the product?

 

[Dan Robinson]

How do you know the printed manuals are the same as the online PDF's?

 

[Agile]

I have to say that its pretty poor for a UK based manufacturer not to produce manuals with many spelling and grammatical mistakes.

We can understand why that happens with Italian or German boilers and with Chinese made anything.

The odd thing is that the overseas boiler makers don't even use their UK offices to advice and proof read their manuals.

Tony

 

[shambolic]

It's a fault with the online formatting depending on what your viewing it on and how it converts to PDF. I've seen it when checking stuff in a Cust house then next time I check its fine then bad then fine. Bit random but the printed books are fine.

 

[Dan Robinson]

Although I could never fit an Ideal, my experience of their manuals is one of the better ones.