Combi boiler - 3 different solutions quoted.

[Jay1988]

Anyone a bit better researched fancy offering some opinion on this. I'll lay out my understanding:

All 3 gas reg number, all 3 good reviews on google, yelp, checkatrade.

Situation 40 year old boiler, looking to get rid of tanks and go to combi. Currently the 22mm supply pipe is reduced to 15mm somewhere, this then feeds the current boiler. Boiler and supply are on opposite ends of the house, supply front, boiler back in the kitchen. 6.5m-7m straight run.

Would like gas hobs as part of the works.

Quote 1: Guy says no idea where it's reducing, so he'll run 22mm up to the loft, then down to the kitchen. This is good for the 27w baxi platinum he quoted, and the rings.

Quote 2: Same mention of no idea where it's reducing 22>15mm. So he wants to run 28mm to the loft, then down to the kitchen to cover rings and a 30kw baxi 830.

Quote 3: "i've done a house 1 road down same design, the 22 runs to the kitchen, so we'll rid of the 15 and run 22 off the 22 to the new boiler, tap off that for the rings" only installs glowworm boilers.

Now I didn't really like how all 3 pulled the specs out of the air on the spot, when it's my basic understanding that run lengths, bends and elbows etc make a big difference if sticking to 22mm (assume thats a big reason quote 2 returned 28mm).

All 3 were in the range 2.7(22mm)-2.9k(28mm)

Both new pipe installers wanted to run gas pipe up the front of the house, which isn't the dream.

Can any one educate me and provide some thoughts on a direction here, it'd obviously be easier if the 22mm is in the kitchen, and has the capacity to do a 30kw boiler + a gas hob.... But nobodys filled me with confidence!

 

[bernardgreen]

Situation 40 year old boiler, looking to get rid of tanks and go to combi.

What advantage will a combi give you ? Will it provide the same hot water service that you have now ? Will the advantage of "no tanks"

be greater than the disadvantage of reduced hot water flow that you get from a tank of hot water.

oth new pipe installers wanted to run gas pipe up the front of the house, which isn't the dream.

It is a dream for metal thieves, if you are lucky they will turn off the gas at the meter before ripping the pipe off the wall.

Now I didn't really like how all 3 pulled the specs out of the air on the spot,

All they want to do is get a figure so they can sign you up for the installation.

Remember that combi boilers were invented for installing in flats and ultra compact houses where there is no space for tanks or cylinders

 

[Madrab]

Without being onsite it's difficult to suggest what may be correct.

Is the meter outside and does the supply pipe come through the wall? Do you have wooden or concrete floors?

 

[Jay1988]

What advantage will a combi give you ? Will it provide the same hot water service that you have now ? Will the advantage of "no tanks"

be greater than the disadvantage of reduced hot water flow that you get from a tank of hot water.


Remember that combi boilers were invented for installing in flats and ultra compact houses where there is no space for tanks or cylinders

It's a 2 up 2 down house, current storage cupboards wise outside the kitchen is : 1 x built in wardrobe in master bedroom, 1 x small cupboard in spare bedroom.

The gain of a cupboard is pretty big. If you ignore the built in wardrobe, moving from 1 to 2 cupboards is easy maths.

So I was pretty convinced on a combi, especially with the likewise of baxi offering 7-10 year warranties.

The pipework solution was more the concern. As you rightly point out, I'd rather not display some copper on the wall. Especially if I've already got 22mm in the kitchen, thats potentially just been converted to 15 under the kitchen floor...

 

[Jay1988]

Without being onsite it's difficult to suggest what may be correct.

Is the meter outside and does the supply pipe come through the wall? Do you have wooden or concrete floors?

It's outside, there's a utility outside room off the porch, so the route would be supply room > porch > living room > into kitchen.

supply goes straight down into the supply rooms concrete floor, so currently goes via concrete floors. Porch floor is concrete, living room floor is concrete, then we hit the kitchen. all fairly small rooms though so 6.5-7m if the pipes a straight run.

 

[oldbutnotdead]

You're correct about elbow/bends, run lengths etc as well as the loads of connected devices contributing to required pipe sizes- if you are bored you can google the figures and do the sums yourself. People who do these sums every day tend to be able to quite accurately gauge pipe size needed from a quick look at the place. I'm no expert (so I'd be doing the sums) but by the sound of it your existing 22mm if it really does go to the kitchen where the boiler will be would be fine on a 7m run.
BUT if the gas pipe is buried directly in concrete and not ducted then you may find engineers refusing to use it (since it wouldn't comply to current standards).
The loft option- 28mm would definitely be fine unless it needed lots of bends, 22mm might be marginal again depending on the route. Yes it'll look a bit pants, what ya gonna do?
As above on the combi route- infinite hot water is nice but the bath probably won't fill as quickly as it does now & you may find the shower uninspiring (depends on how its plumbed now & how much drop you have between hot water header tank & shower)

 

[Jay1988]

You're correct about elbow/bends, run lengths etc as well as the loads of connected devices contributing to required pipe sizes- if you are bored you can google the figures and do the sums yourself. People who do these sums every day tend to be able to quite accurately gauge pipe size needed from a quick look at the place. I'm no expert (so I'd be doing the sums) but by the sound of it your existing 22mm if it really does go to the kitchen where the boiler will be would be fine on a 7m run.
BUT if the gas pipe is buried directly in concrete and not ducted then you may find engineers refusing to use it (since it wouldn't comply to current standards).
The loft option- 28mm would definitely be fine unless it needed lots of bends, 22mm might be marginal again depending on the route. Yes it'll look a bit pants, what ya gonna do?
As above on the combi route- infinite hot water is nice but the bath probably won't fill as quickly as it does now & you may find the shower uninspiring (depends on how its plumbed now & how much drop you have between hot water header tank & shower)

If I'm bored.... or stressed they half arsing and it's not being done right!

Pipe is buried in the concrete, nobody offered that was against standards angle.

a 22mm run via the loft would 100% be longer than the route that's in the floor at the moment, that was the most confusing thing about his quote.

the current bath filling time is around 20-30mins, with the time to heat tank more like 1hr-1hr20. If I ended up with worse than this I'd be shocked. I currently have a boiler from when the house was built in 1978(W2000). It doesn't do anything in a hurry, I think people have been offering 30kw boilers to increase the flow rate for showering, with these models offering 11l / min. Which sounds plausibly better than my 7.5kw shower can put out now. Bathrooms getting left until the kitchens done anyway, so that's future mes problem.

Checking http://www.gb-gas.co.uk/clc/pipesize/GAS PIPE SIZING 2016 WEB.htm

It looks like the run length can be up to 9.2m, if it only had 90dgeree bends at start and below the boiler, a straight run in between. Which it could be, but I doubt my fellow mans ability to deliver such perfections.

 

[oldbutnotdead]

Ah, if you're on an electric shower now you'll definitely notice an improvement. Tank reheat time isn't outrageous (are you still on gravity hot water/pumped rads?) but bath fill time is v poor (my old gravity system filled the bath in about 10 mins).
If the boiler is going in the kitchen then you might want to get it put in before you do the kitchen up- easier to hide it with a cupboard, easier for the fitters as well. Just make sure you know where new stuff is going so they don't stick a load of pipework where you don't want it.
That's a bonnie calculator, think I'll save that link

 

[Jay1988]

Ah, if you're on an electric shower now you'll definitely notice an improvement. Tank reheat time isn't outrageous (are you still on gravity hot water/pumped rads?) but bath fill time is v poor (my old gravity system filled the bath in about 10 mins).
If the boiler is going in the kitchen then you might want to get it put in before you do the kitchen up- easier to hide it with a cupboard, easier for the fitters as well. Just make sure you know where new stuff is going so they don't stick a load of pipework where you don't want it.
That's a bonnie calculator, think I'll save that link

Yeah gravity fed and a pump that looks like it belongs in a museum. So the move to a 30kw combi, from my 70s tank system should be quite the treat!

And yeah boilers going in first, then sparky, them 2 can make a mess of things before plasterer comes in. Then finally kitchen, micro managing all of it made me realise why people like to pay for all in one packages!

 

[oldbutnotdead]

Good luck with it all- especially managing it. One thing to watch with good trades is that they're really really quick- so if there's anything they need to know about or be aware of stick Post-It notes on the walls or whatever- otherwise you'll be out front having a fag, suddenly remember you had to mention x before they did the rad in the front room, come back in and find they've done it already.

Make sure there's a usable FCU near where the boiler is going, yes of course you could use a 13A socket but lots of fitters won't- not sure if its a regs thing or a manufacturers' instructions thing or what but the ones I've dealt with don't like it.