Conflicting advice from different gas engineers, confused!

[jmonkmalvern]

Hi,

I'm posting here really for a second opinion as we're a bit confused right now! I'll try and be brief. We're renovating a house which we've completely stripped back, as part of the renovations we had a local gas engineer company come out and run new pipework for our gas supply, hot and cold and flow and return to the location where the boiler will be re-installed downstairs kitchen and where our rads wil go upstairs. Downstairs heating is through an UFH system which is installed and ready to be connected up.

We've just had a different gas enginner company come out to re-fit the boiler (a Worcester Bosch 30i Combi) and he's noticed the orignal company used 15mm copper pipe for the upstairs rads. His opinion is the "back bone" should have been in 22mm with 15mm coming off this for each rad. I don't belive he was touting for work and his comments seemed genuine, his reasoning (forgive me on my limited knowledge) was that the boiler wouldn't be able to cope with powering the UFH downstairs and the upstairs rads if they were both on high at the same time. The system would work using 15mm but long term could develop problems. The company that originally completed the pipework have said that because the property is small and the rads are small that it should be fine as the UFH has a separate pump and the boiler will just be powering the 3 rads.

A few points:

• The run from the boiler location to the furtherest rad is about 15m. The pipework run is very straight with only a couple of bends.
  
• The upstairs rads are: 1 x 2,792 BTU's (818 Watts), 1 x 4,725 BTU's (1,385 Watts) & 2510 BTU's (736 Watts)
• The UFH system is split up into 2 zones (21m2 & 13m2).

Is there a right or wrong answer to this or it just the personal preference of the engineer?

Any adivce would be appreciated.

Thanks,

James

 

[Razor900]

As you say some will always use 22mm, some will use 15mm and some will run it in 10mm speedfit from a manifold under the boiler!.

That's a small rad load it will work fine with the 15mm.

 

[jmonkmalvern]

As you say some will always use 22mm, some will use 15mm and some will run it in 10mm speedfit from a manifold under the boiler!.

That's a small rad load it will work fine with the 15mm.

Thanks for the quick reply, appreciated! So you don't think having those rads and the UFH system running at the same time would be an issue? The second guy seemed to imply this whereas the first guy said it wouldn't make a difference as it runs from a separate pump?

 

[polesapart]

Won't be a problem.

 

[Madrab]

Can I presume that it is 22mm out of the boiler up to where the UFH is and then splits, then 15mm up to the rads? As suggested if it's just for 3 smallish rads then it should be fine

 

[jmonkmalvern]

Won't be a problem.

okay that's good to know thanks.

 

[dilalio]

It's a small load and on a sealed system.
What is the total KW load for heating? Work that out (likely @12KW) and you'll know that all is fine.

 

[jmonkmalvern]

Can I presume that it is 22mm out of the boiler up to where the UFH is and then splits, then 15mm up to the rads? As suggested if it's just for 3 smallish rads then it should be fine

I presume this is what the plan is (boiler sat in a box at the moment), the manifold for the UFH system is installed below the intended boiler location on the same wall so it will only have a very short distance to travel to that. Good to know that it's okay for the 3 small rads,

I'm still a bit confused why the second guy is so adament it won't work with 15mm. He's stil going on about it now and is saying he's spoken to Worcester Bosch and they've confirmed it shoud be 22mm?

 

[jmonkmalvern]

It's a small load and on a sealed system.
What is the total KW load for heating? Work that out (likely @12KW) and you'll know that all is fine.

Sounds like a good idea, how is this usually calculated?

 

[Madrab]

How large are the rads ... sizes ... type? How far away are they (how long are the pipe runs)?

 

[jmonkmalvern]

How large are the rads ... sizes ... type? How far away are they (how long are the pipe runs)?

I guess you mean their output and not physical size? If so they're:
1 x 2,792 BTU's (818 Watts), 1 x 4,725 BTU's (1,385 Watts) & 1 x 2510 BTU's (736 Watts)
The first 2 rads are horizontal double column traditional style, the second one is a flat panel heated towel rail.

The pipe run is approximately 3m to the first rad (the branch to this rad is probably about 500mm), then another 4m to the next rad with another 500mm branch then another 10m to the final rad. It's a pretty small, 2 bed Vicotorian terrace so the rooms are quite small.

Manifold for UFH is under the boiller so the pipe run to this would be minimal.

Read more: https://www.diynot.com/diy/threads/...-gas-engineers-confused.558623/#ixzz6fY7Yo3sZ

 

[durhamplumber]

Is there a right or wrong answer to this or it just the personal preference of the engineer?

The norm usually is a backbone of 22mm but as said will make no difference in your property.And considering that many new builds are still mainly 10mm.

 

[jmonkmalvern]

The norm usually is a backbone of 22mm but as said will make no difference in your property.And considering that many new builds are still mainly 10mm.

Thanks for the clarification that makes sense.