35 kW heat output HE boiler on 22 mm heating circuits?

[doitall]

I think you need to trust the engineer that probably knows the boiler. or Not.

Assuming you are not talking about the combi, then it has 4 connections 2 x ¾" for the heating and 2 x ¾" for the cylinder.

If it's just 2 pipes going to a zone valve (Y plan) then 28mm + depending on heating requirements.

Put it in writing what the engineer said and hand a copy to the installer, saying you hold them responsible for any addition costs if it doesn't work.

 

[ALEC1]

Ron does the house really have a 35kw heat loss. how big is it, how many radiators?

 

[mickyg]

a) its unlikely you need 35kw
b) its quite possible to get up to around 40-45kw through 22mm tube, it all depends on the circuit, length, speed of the water, delta T required and so on.
Easy way to get to the bottom of it or at least have a laugh is ask both guys to provide the reference material or calculations they have done to come to their conclusion

 

[Agile]

Or asking the question another way, who chose 35 kW ?

If the installer does not know how to wire up the boiler and cylinder I have little faith in his ability to size the boiler correctly.

Obviously with a 35 kW boiler its a very large 10 bedroom property!

Although with only a 250 li cylinder there are only 5-6 people living there!

Very odd indeed!

Tony Glazier

 

[Agile]

Or asking the question another way, who chose 35 kW ?

If the installer does not know how to wire up the boiler and cylinder I have little faith in his ability to size the boiler correctly.

Obviously with a 35 kW boiler its a very large 10 bedroom property!

Although with only a 250 li cylinder there are only 5-6 people living there!

Very odd indeed!

Tony Glazier

 

[Dan Robinson]

10 bedrooms?! I know you are on the short side but.... ?


But I agree. I am working non some pretty big pads at the moment and 35kW is an immense amount of heat when you think about it.


Place we started yesterday.... 6500 square feet, the newly dug basement is like a fricking cathedral. 55kw.

I have to stand on a ladder to reach the ceiling ffs.


I would be very surprised if less than 90% of the posters coming on here with pre- installed, or plans to install a boiler have the correct size.



So, OP, unless your house is half the size and with a basement the size of a modest Anglican chapel, and a 46" plasma instead of a cinema, I would double check your specifications.


*edit* we fitted a 300 litre cylinder here.

 

[sherbert]

Or asking the question another way, who chose 35 kW ?

If the installer does not know how to wire up the boiler and cylinder I have little faith in his ability to size the boiler correctly.

Obviously with a 35 kW boiler its a very large 10 bedroom property!

Although with only a 250 li cylinder there are only 5-6 people living there!

Very odd indeed!

Tony Glazier

Agile

So are you saying that heating engineers that do not wire up there sysetms are incompetent ............. !!

You question if they cant do the wiring then they cant size the boiler correctly yet come on here asking questions about if to use 22mm or 28mm pipework

Hmmmm ... Pot and kettle springs to mind

 

[rontheman]

All

Thanks for your feedback. House is c 3000sq feet with high celings and high heat loss through the walls, 3 bathrooms, 5 bedrooms, and a need to have the house somewhat warmer than average.

Boiler already installed so committed to it. 2 circuits, one for hw and the other for the rads + underfloor heating for ground floor.

The installing engineers position is that they are not qualified electricians (!) and that their consents do not cover electrics. Their view is it is the job of the electrical contractors to sort out the wiring. (And, yes, it sounds like bs to me as well as raising some doubts overall). I asked them if that meant that every job they do necessitated calling in electricians, and they hummed and harred! Hmmmmmmm!!!!

 

[JohnD]

is this relevant? but...

My old mum had a large house with a 30kW boiler. The boiler was tapped at 28mm, the heating circuits came out at 28mm, into 28mm pump, out at 28mm, then went off tee 22mm to upstairs rads and 22mm to downstairs.

It could have been (but wasn't) zoned.

Seems to me that saved having lots of 28mm pipe in the house.

 

[Agile]

That is the normal way to do it John.

It sounds as if the new OP has employed builders who are subcontracting!

I do realise that some boiler installers dont feel confident with doing the wiring.

Not many electricians are very experienced at wiring heating systems. Virtually none are qualified for unvented cylinders.

But if you cannot do wiring then you cannot install an unvented cylinder as the interlocks rely on the wiring.

I suspect you will find that the installation of your unvented cylinder will be partly ( or wholly ) by someone who is not qualified to install them. Make sure they complete the Benchmark Certificate with their details. Same for the gas boiler!

I still say its over sized. And the cylinder undersized if the house is occupied as a five bedroom house could be.

Tony