What boiler is best for the job

[RedArrow]

210l Santon Premier Plus Systemfit Indirect Unvented hot water cylinder and a Valiant ecoTec plus 630 system boiler.

What makes you think you need a 28kW or 30kW boiler?

The truth is I don't really know, I just wanted to make sure I got enough power. I always think it's better to look at it than look for it.

Let me give you some more info.

Full renovation of a mid terrace with 10' high ceilings. All ground floors have been lifted and insulated with celotex. Both front and back external walls have been insulated. There is 150mm of rockwool below all upstairs floors. Loft has been insulated with 125mm of clelotex. Biggest heatloss currently is the original sash windows. We plan to restore those and add secondary glazing before winter kicks in. There will be a full bathroom with power shower and 2 ensuites with power showers.

 

[D_Hailsham]

What makes you think you need a 28kW or 30kW boiler?

The truth is I don't really know, I just wanted to make sure I got enough power. I always think it's better to look at it than look for it.

I suggest you use the Whole House Boiler Calculator.

Even with the minimal insulation I doubt if you will need as much as 30kW.

The Santon cylinder you propose to use can only use 18kW, but there's no need to allow that much on top of the heating as you only need the full heating output when the outside temperature is -3C. Allow 3-4kW extra for the cylinder (the calculator allows 2kW) and you should be fine.

I hope you have had the incoming cold water flow rate and dynamic pressure measured. You need a minimum of 20 litres/min @1.5 bar.

 

[RedArrow]

What makes you think you need a 28kW or 30kW boiler?

The truth is I don't really know, I just wanted to make sure I got enough power. I always think it's better to look at it than look for it.

I suggest you use the Whole House Boiler Calculator.

Even with the minimal insulation I doubt if you will need as much as 30kW.

The Santon cylinder you propose to use can only use 18kW, but there's no need to allow that much on top of the heating as you only need the full heating output when the outside temperature is -3C. Allow 3-4kW extra for the cylinder (the calculator allows 2kW) and you should be fine.

I hope you have had the incoming cold water flow rate and dynamic pressure measured. You need a minimum of 20 litres/min @1.5 bar.

Using the link you gave I get:

29.68kw when i say 3 floors

21.05kw when I say 2 floors

 

[D_Hailsham]

Using the link you gave I get:

29.68kw when i say 3 floors

21.05kw when I say 2 floors

That is a lot for a mid terrace. Did you put in 0 for the number of front to back walls and 2 for side to side?

I assume those figures are based on minimal insulation. What happens if you assume it has been improved?

Why the two versions? Are you turning the loft into habitable accommodation?

Here are the U values used in the calculator:

Window U-values

Double glazed wood/plastic 3.0
Double glazed metal frames 4.2
Single glazed wood/plastic 4.7
Single glazed metal frames 5.8

Wall U-values

Filled cavity wall 0.45
Unfilled cavity wall 1.6
Solid wall 220mm 2.1

Roof U-values

Pitched < 50mm insulation 2.6
Pitched 50-75mm insulation 0.99
Pitched > 75mm insulation 0.44
Flat uninsulated 2.0
Flat 50mm insulation 0.54

Current Building Regs require a U value of 0.3 for an externally clad solid wall, which is better than the 0.45 allowed for a filled cavity.

 

[Dan Robinson]

Personally I think the whole house thing is a load of crap.

Alec, I asked about cascading them for big properties. Not the op.


There is a 3 day veissmann training thing on the 19th. Text me your email and I'll forward you the details.

 

[RedArrow]

Using the link you gave I get:

29.68kw when i say 3 floors

21.05kw when I say 2 floors

That is a lot for a mid terrace. Did you put in 0 for the number of front to back walls and 2 for side to side?

I assume those figures are based on minimal insulation. What happens if you assume it has been improved?

Why the two versions? Are you turning the loft into habitable accommodation?

Here are the U values used in the calculator:

Window U-values

Double glazed wood/plastic 3.0
Double glazed metal frames 4.2
Single glazed wood/plastic 4.7
Single glazed metal frames 5.8

Wall U-values

Filled cavity wall 0.45
Unfilled cavity wall 1.6
Solid wall 220mm 2.1

Roof U-values

Pitched < 50mm insulation 2.6
Pitched 50-75mm insulation 0.99
Pitched > 75mm insulation 0.44
Flat uninsulated 2.0
Flat 50mm insulation 0.54

Current Building Regs require a U value of 0.3 for an externally clad solid wall, which is better than the 0.45 allowed for a filled cavity.

The loft has always been habitable space since the house was built. I have put a new slate roof on with 125mm celotex for insulation in the roof.

No I put 9m for length times 2 walls and 6m width times 2 walls and those were the figures it gave me so I had thought maybe the correct number would be somewhere between 21-30kw?

 

[D_Hailsham]

No I put 9m for length times 2 walls and 6m width times 2 walls and those were the figures it gave me so I had thought maybe the correct number would be somewhere between 21-30kw?

That is why you have such a high result!

You only need to count walls which are exposed to the outside temperature. (See the note in RH column) If it is a mid terrace, they are the front and back walls, so the number of length walls, ie party walls, are set to 0.

As for the other factors, I think you can use the "filled cavity" and "insulation over 75cm". It's the window factor which is the problem. I have no idea what effect secondary glazing will have. Have the suppliers of the SG units told you what U value will be achieved?

If the loft is used, you have three floors.

 

[RedArrow]

No I put 9m for length times 2 walls and 6m width times 2 walls and those were the figures it gave me so I had thought maybe the correct number would be somewhere between 21-30kw?

That is why you have such a high result!

You only need to count walls which are exposed to the outside temperature. (See the note in RH column) If it is a mid terrace, they are the front and back walls, so the number of length walls, ie party walls, are set to 0.

As for the other factors, I think you can use the "filled cavity" and "insulation over 75cm". It's the window factor which is the problem. I have no idea what effect secondary glazing will have. Have the suppliers of the SG units told you what U value will be achieved?

If the loft is used, you have three floors.

Thanks for clearing that up. Now it makes a big difference.

Down to 10.9kw.

One other thing "Allowance for Domestic Hot Water"? What goes here?

 

[Dan Robinson]

So you need a 12 or 18kW boiler.

Job done.

 

[RedArrow]

So you need a 12 or 18kW boiler.

Job done.

Thanks Dan

Ok great let's say 18kw boiler. Any type you would recommend?
Also I was thinking on the 210L santon premier plus hot cylinder but I'm getting conflicting replies on that. I have room for a larger tank, would I need anything larger? I was going with 50ls per person and 50ls over as my guide.


Ok great let's say 18kw boiler. Any type you would recommend?

What hot cylinder would you team up with it?

Thanks

 

[Dan Robinson]

Intergas 18ov

Albion cylinder. Or RM Stelflow. No point paying Santon or mega flow prices.

Decent installer will be able to install an s plan that will give you weather compensation on the heating. .

 

[RedArrow]

Intergas 18ov

Albion cylinder. Or RM Stelflow. No point paying Santon or mega flow prices.

Decent installer will be able to install an s plan that will give you weather compensation on the heating. .

Off to google some of these now.

Would 210L be OK for the cylinder size?

 

[oph]

Personally I think the whole house thing is a load of crap.

Agreed dano. The thing is whole house sizing dosent take into consideration room type usage. More used as bedrooms and less than reception rooms means less kW is required overall.

Far too hit and miss

 

[Richardthe3rd]

Personally I think the whole house thing is a load of crap.

Agreed dano. The thing is whole house sizing dosent take into consideration room type usage. More used as bedrooms and less than reception rooms means less kW is required overall.

Far too hit and miss

I also agree, it's a load of cr.p, when you consider how easy it is to do a complete & comprehensive Heat Loss calculation, where Party Wall are considered on their own.

 

[jeff the gasman]

210l Santon Premier Plus Systemfit Indirect Unvented hot water cylinder and a Valiant ecoTec plus 630 system boiler.

My builder has told me I don't need a system boiler with the Santon cylinder as the cylinder includes everything. He told me I need a heat only boiler such as the ecoTec plus 428.

What advice would you give me

For a start I would tell your builder to shut his cake hole and stick to throwing cement at bricks. Flicking idiot. (the builder that is).

Plus a very big 1 from me