JG pipe on system boiler?

[Luggsey]

I'm going to be piping up a new external Grant Vortex oil combi boiler soon and have just looked at the tank, sealed type, which has a 28mm pipe for the boiler. It's a big 5 bed house with loads of underfloor heating so I'm assuming I need to use the 28mm pipe as on the tank.
Question is I have seen jobs where copper is used from the boiler to inside the house and then run in jg 28mm pipe to the tank.
Is there a regulation distance that I must use copper as I seem to remember 1m being mentioned?
Cherrs all.
Paul.

 

[ShaunCorbs]

1m normally but more the better normally a length of pipe eg 3m

 

[Luggsey]

1m normally but more the better normally a length of pipe eg 3m

I can easily make it 2m by coming in the wall and up to ceiling height.
Cheers.

 

[SJB060685]

I was always told a minimum of two metres after boiler but like Shaun says the more the better.
The next part I'm not sure I get you. Are you saying the primaries from existing boiler are 28mm? The manual will state the minimum recommended size for the output. How many UFH circuits and radiator circuits are there? Have you done your mass flow rate calculations?

 

[Luggsey]

I was always told a minimum of two metres after boiler but like Shaun says the more the better.
The next part I'm not sure I get you. Are you saying the primaries from existing boiler are 28mm? The manual will state the minimum recommended size for the output. How many UFH circuits and radiator circuits are there? Have you done your mass flow rate calculations?

I had Grant specify the boiler based on demand but I was questioning is 28mm pipe usual for this size Installation?
I have to be honest and say I normally see 22mm used but this is a pretty big house so I assume it can't cause a problem using 28mm?

 

[SJB060685]

If you know your circuit loads you can start to calculate your mass flow rates, which will result finding your required pipe sizes, these calculations can also be used to size LLH and distribution headers. If Grant specify 28mm for the output then you fit to that. Increasing the size when not needed extends installation costs.

 

[ShaunCorbs]

What’s the Kw of the boiler ?

 

[Luggsey]

What’s the Kw of the boiler ?

Without going over the house to check I'm pretty sure its 36KW.
Grant did say the 25KW would manage buf it would have been close to its limit so I went for the next one up. I am told if it's too big and fires to often it's not a problem to reduce its output but I doubt it will be oversized as the house has a high output UFH system over 150m2 using 900m of pipe. The expansion tank I worked out is pretty big!

 

[SJB060685]

My design guide suggests 28mm will supply up to 40kw on 28mm at delta t 20 and .9m/s target volocity.
Just out of curiosity do you know the required inputs for each of the zones?

 

[Luggsey]

My design guide suggests 28mm will supply up to 40kw on 28mm at delta t 20 and .9m/s target volocity.
Just out of curiosity do you know the required inputs for each of the zones?

Do you mean UFH zones?

 

[SJB060685]

I mean the load requirements for each UFH zone and any radiator zones. Are you tapping in to an old system or has it been designed from scratch?

 

[Luggsey]

I mean the load requirements for each UFH zone and any radiator zones. Are you tapping in to an old system or has it been designed from scratch?

It's all brand new, I supplied all the UFH specs to Grant at the time, Family bereavement means it was well over a year ago I did so so I dont have figures in my head? I can say its 900m of 16mm pipe and 6 small rads upstairs. I was surprised when I looked closely into UFH specs to find out the 'usual' design temprature when its below zero outside was to low for my disabled Mum! I went with a Swedish brand by LK with 150mm pipe spacing for high output. I think from memory its 14 zones.

 

[SJB060685]

Ok. I take it the boiler is a Grant Vortexblue? Manual says 28mm required for primaries as I said above.

 

[ShaunCorbs]

28mm for me upto the distro point then 22mm to each manifold

if you can post up the kw requirements for each loop / manifold set

as a rough work out gives me around 14kw for the ufh around 21 dc at -5

that’s for a min of 100mm slab insulation
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Also I wouldn’t want a combi on a 5 bed house heat only and unvented cylinder

unless your planning on adding a cylinder?

 

[SJB060685]

Also I wouldn’t want a combi on a 5 bed house heat only and unvented cylinder

unless your planning on adding a cylinder?

I personally don't like combis, would much rather a system boiler and unvented but I think its too late for that if he's already done the first fix.
He could add a cylinder at a later date but it will probably require quite a bit of alterations

 

[Luggsey]

It's an un vented system, advanced appliances 300l tank with solar and solid fuel coils, 2x immersions.
System boiler of course. I'm up as far as getting the concrete pad fitted outside for the boiler and want to get pipe and liners sorted out for the wall holes.
Thanks for on going help.
🙂

 

[SimonG]

Your first post says it's a combi boiler???

 

[Luggsey]

Your first post says it's a combi boiler???

Sorry my existing Grant boiler here is combi, the new one is system.
Its definitely 22mm pipes on it.
Is there any problem with bringing the oil feed pipe into the back of the boiler and flex piping it to the front? The only floor knockouts are at the back?
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Is it necessary to have a cold supply to a system boiler or can it be filled via external tap and hose pipe?
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To add, is it better to use one hole through the wall for pipework, the boiler has a 4" knockout at the right height and I have a 4" cutter....

 

[SJB060685]

You could bring the oil line through a punch out at the back but I put a rubber grommet in to sleeve it as always but make sure any fittings are are accessible.
You need a cold supply to the filling loop, I would not fill via a hose pipe.
There's no reason you can't use your 4" drill bit to make a hole for pipe work, again make sure its sleeved and pipework insulated, you will also need anti freeze and the frost stat wired in correctly.

 

[Luggsey]

You could bring the oil line through a punch out at the back but I put a rubber grommet in to sleeve it as always but make sure any fittings are are accessible.
You need a cold supply to the filling loop, I would not fill via a hose pipe.
There's no reason you can't use your 4" drill bit to make a hole for pipe work, again make sure its sleeved and pipework insulated, you will also need anti freeze and the frost stat wired in correctly.

Thanks for that, one hole in the wall will be easier, I'll link in a cold supply as well then. I was concerned about it freezing but I suppose it wont in the boiler enclosure?
Is sentinel 500 ok for antifreeze?

 

[SJB060685]

As long as any pipework exposed to the outside elements are sleeved it should be fine, bare in mind you're only going to have maybe a foot or so coming through wall and back into boiler.
If sentinel 500 is an antifreeze then yes, providing you does it right.

 

[EvilDrPorkChop]

I didn't think you could use JG Speedfit on a oil fired system if it was sealed? Only OV.