Boiler size?

[Scottley]

Hey peeps

I have had a look at a link posted on here for the Seduk calc. Can anyone help me out with how to use the bloomin thing?

I have a bungalow that im converting to a chalet bungalow with 4 beds and 2 baths upstairs with a main bed and ensuite downstairs. Its quite a large floor area 120mt/sq down and 86 up. I have a 250lt megaflow and all the pipework is in and run as it should be (28/22/15mm). Im a touch concerned about the boiler size. I am looking at the Worcester Bosch 40CDI but think it may be slightly oversize (as well as over priced)

Any help would be appreciated, im a firm believer in things being right and not labouring to heat the place so want it right even if it means the more expensive boiler.

Thanks

Scott

Anyone?

 

[dontknowitall]

As a guide ... rather rough and ready but it's never let me down ...

Measure each room then add all the rooms up and you'll get the size of boiler you need.

1. Height x length x width (all in metres) x 45 /1000
2. The figure for each room will give you the radiator size required in watts
3. That calculation for each room then add them all up
4. Add all the watts up and add a little for luck for the hot water and find a boiler suit. If your figure is say 21Kw then a 18/25 Kw boiler would be good.

Simples ... Eeeekk!

 

[crashndie]

hi mate with you saying you have to bath rooms i wouldnt suggest a combi boiler but rather a conventional system with a unvented cylinder the plus side of this is the boiler can be smaller size an you have shed loads of mains pressure hot water that can cope with more than 1 draw off at a time on it this system is more ecconmical to run too. a system boiler like valliant eco tec630 so theres no tanks in the loft or anythink

 

[Scottley]

Thanks guys

Dontknowitall: You were pretty close as it came to 21.15 without the heating!

How much luck would you suggest i had for the hot water? Bearing in mind its a 250lt megaflow?

Im assuming the 30kw will work ok but in your opinion do you think it will be labouring to heat the whole house or do you think i would be better off with the 40CDI?

One other probably dumb question can i use the 30cdi system boiler as a heating only boiler? The megaflo is a sytem fit so i only need a heating only boiler and the 30cdi is listed as a system boiler.

Thanks Scott

Crashndie: Your right I wouldnt consider a combi, i made the mistake of putting one in my last house with just me in it and it was awful! The megaflo is defintely the way forward for me especially with the kids . Thanks

 

[ecowarm]

do not over size the boiler its better to be sized correctly and will run at its most efficient.

 

[Rodreguez]

a system boiler is basically a HE boiler just with a pump, expansion vessel and PRV built in

 

[Scottley]

Thanks i just been googling! I think ill go for the 30CDI.

Any idea what the differnce is between the WB CDI and the RI boilers?

 

[Rodreguez]

30kw is oversized by the sounds of it go for the 24kw

wont be a prob th fit to megaflow will work fine with any DHW cylinder

 

[doitmyself]

I have had a look at a link posted on here for the Seduk calc. Can anyone help me out with how to use the bloomin thing?

I agree, the Sedbuk calculator is compicated. Use this Boiler Size Calculator instead. It will give exactly the same result as the Sedbuk one, but is easier to understand.

Having said that , when it comes to the number of walls, it means walls exposed to the weather. So a detached has two in each direction, but a semi has two, side to side and one, back to front.

I would treat it as a bungalow and then add in the radiators specified for the new upstairs rooms.

I have a 250lt megaflow

The calculator only allows 2kW for hot water, it might be better to allow an extra kW as you have a large cylinder.

There is no point in buying a boiler which is larger than your radiators can handle. So you need to work out the output of existing rads using the Stelrad Elite Catalogue and then add in the rads going into the new upstairs bedrooms.

If this is less than the calculated boiler size, you will probably need to change some of the existing rads. It does not matter if the rads add up to more than the boiler size.

 

[dontknowitall]

Re above post and outside walls, poor insulation, etc, my calculation uses 50 instead of 45 and when well insulated, internal room, etc I use 40 instead of 45. Didn't explain that early as I was trying to keep things simples.

 

[Scottley]

So the lower the number the better the insulation or internal walls?

All the upstairs will conform to new reg so good insulation, downstairs does have cavity wall but its rubbish. The lounge is the worst as its north west facing and protected by a garage on the only side that get any sun, worse still all the rads are old panels with no convectors.

 

[doitmyself]

All the upstairs will conform to new reg so good insulation,

I should hope so.

downstairs does have cavity wall but its rubbish.

How do you know it is rubbish? Did you have it installed, so you can compare before and after?

all the rads are old panels with no convectors.

It could be that the rads do not give out enough heat, even with cavity wall insulation. Have you checked their output using the Stelrad link I gave and compared that with the required boiler size?

 

[Scottley]

Doitmyself:

I know the insulation isnt good as i can see it down the cavities when the roof came off. There are so many gaps its untrue, It also really cold!

I will get my other half to work out the existing rads as im flat out on the project until late. I get the plumbing done at night as its fairly quiet work.

I have some double panel rads, any idea how i can work out what BTU they are? Should i just double up the P1 figure?

 

[doitmyself]

I know the insulation isn't good as i can see it down the cavities when the roof came off. There are so many gaps its untrue, It also really cold!

Presumably you didn't have the work done, or it was done many years ago. So there is no comeback.

I would work out the boiler size assuming no cavity insulation and buy one with a max output as near to that size or very slightly over. The boiler will modulate down to the correct output. If the calc says 15 KW an 18kW is OK, but a 28kW will be a waste of money. The lower the minimum boiler output, the better

I have some double panel rads, any idea how i can work out what BTU they are? Should i just double up the P1 figure?

Get you other half to look them up in the Elite Catalogue (see link I gave).

PS We use kilowatts now; BTU are no longer used, like Fahrenheit and shillings.

 

[Scottley]

Presumably you didn't have the work done, or it was done many years ago. So there is no comeback.

I would work out the boiler size assuming no cavity insulation and buy one with a max output as near to that size or very slightly over. The boiler will modulate down to the correct output. If the calc says 15 KW an 18kW is OK, but a 28kW will be a waste of money. The lower the minimum boiler output, the better

Get you other half to look them up in the Elite Catalogue (see link I gave).

PS We use kilowatts now; BTU are no longer used, like Fahrenheit and shillings.

Lol good one

No the cavity insulation was already in when i bought the place. I couldnt see double panel no convector rads in the elite catalogue?

 

[doitmyself]

I couldnt see double panel no convector rads in the elite catalogue?

My fault. I assumed youmeant double panel with convectors. I'm not at home at the moment (dog sitting) so I don't have aces to all the info. Will post another link when I get home later today.

 

[Scottley]

Thanks fella

 

[doitmyself]

Try this one.

[DLMURL="http://www.pipecasings.co.uk/downloads/download%20files/A%20Guide%20to%20Radiator%20Sizes%20and%20Heat%20Output.pdf"]Guide to Radiator outputs[/DLMURL]

 

[Scottley]

Thanks again i cant find it on there as its an unusual size 450x2000. Im going to replace it as its tucked under a low window with a sofa infront of it at the moment. Im planning to move it to a larger wall and dividing the room anyway and the window will be changed for a bay.

I hope to work all this out tonight so i can get the boiler ordered!

 

[doitmyself]

Thanks again i cant find it on there as its an unusual size 450x2000.

The nearest size is 440mm high, which has an output of 1042 w/metre. So a 2 metre rad will give out 2084W. If we assume that output is proportional to height, your rad will produce 2084 x 450/440 = 2131W.

I think that's close enough for your needs.

 

[Scottley]

Right thanks for all your help guys. I have finally calculated it to a 30Kw boiler so will be going for a W/B 30CDI heating only.

 

[Allen]

Any idea what the differnce is between the WB CDI and the RI boilers?

Hey, Ri boiler series is part of a market-leading range of energy-saving condensing gas-fired boilers from Worcester. They can cut heating and hot water bills by between 15-20% - and they’re up to 30% cheaper to run than an WB CDI..

 

[doitmyself]

Ri boiler series ... [are] up to 30% cheaper to run than a WB CDI

Where did you get that idea from!!!

 

[tamz]

Hey, Ri boiler series is part of a market-leading range of energy-saving condensing gas-fired boilers from Worcester. They can cut heating and hot water bills by between 15-20% - and they’re up to 30% cheaper to run than an WB CDI..

The Ri is a good boiler but never believe all that you read with regards saving this or that %