Swapping a Glow-worm 18hxi for a combo boiler

[Frank Nicklin]

I'm re-modelling my bathroom to remove the hot water cylinder. I currently have a single pipe 'S' Plan system running on gravity feed hot water and pumped CH. I installed the CH system back in 1986 when money was tight.

The original Glow-Worm boiler was replaced about 8 years ago with a Glow-worm 18hxi condensing boiler and works extremely well. Radiators heat up well, no obvious signs of starved rads. When I piped it originally, I sized the pipes as 22mm to the first few radiators dropping to 15mm I think then back to 22 on the last run from the last radiator. The boiler never cycles or locks out. The pump is running on mid speed.

I've been quoted for a new combi boiler. The plumber knows the system is single pipe but did have a few concerns about return temperature. Is this a problem if the current boiler copes well.

 

[Aire]

Not a problem. It will work, just not as efficiently as a 2 pipe system. But If you can upgrade it then that would be better.

 

[Frank Nicklin]

I could but I put all pipes under the floorboards when I installed it. Empty house and all that. To do it now would mean every room being ripped up. Thanks for your advice.

 

[Aire]

I could but I put all pipes under the floorboards when I installed it. Empty house and all that. To do it now would mean every room being ripped up. Thanks for your advice.

To be fair it sounds worse than it is. Obviously much easier in an empiter house but you only need a few floorboards up in each room.

 

[Frank Nicklin]

Yes, but I have hardwood flooring down, its all fixed with the skirting removed and replaced over the top of the flooring. Would be a nightmare to undo.

 

[Harvest Fields]

Are you Gas safe registered?

 

[Frank Nicklin]

No I’m not. I fitted the original boiler and plumbed it in except the gas and electrics. It was commissioned and tested by a then Corgi engineer. The replacement was fitted by a Corgi Engineer and the new one now will be fitted by a Gas Safe Engineer as well as the removal of the cylinder. I know my limits.

 

[richard978]

No I’m not. I fitted the original boiler and plumbed it in except the gas and electrics. It was commissioned and tested by a then Corgi engineer. The replacement was fitted by a Corgi Engineer and the new one now will be fitted by a Gas Safe Engineer as well as the removal of the cylinder. I know my limits.

What on earth made you go for single pipe, the new boiler will work but you may have problems balancing the system.

What size pipe have you used and how many radiators.

 

[Old Account]

No I’m not. I fitted the original boiler and plumbed it in except the gas and electrics. It was commissioned and tested by a then Corgi engineer. The replacement was fitted by a Corgi Engineer and the new one now will be fitted by a Gas Safe Engineer as well as the removal of the cylinder. I know my limits.

I was under the impression that non registered engineers can’t fit flues either.

 

[Harvest Fields]

Evening Ron. It’s been a while. Mwahhh wa wa wa wahhhhh

 

[Old Account]

Evening Ron. It’s been a while. Mwahhh wa wa wa wahhhhh

Good evening mate 🙂 How are you doing

 

[Frank Nicklin]

The original boiler was balance flue. In my OP you will see I mention pipe size. There are 11 rads. All reach temperature and have TRVs although I removed the heads on the downstairs rads because that’s where the roomstat is. Probably a mistake to fit them on those rads.

 

[Harvest Fields]

Special trv for one pipe.

 

[Frank Nicklin]

Yeah didn’t realise at the time however the ones I have don’t seems to impede flow as I say all rads reach a good temperature. I will probably replace the upstairs with one pipe trvs and just lockshielda downstairs.

 

[Frank Nicklin]

Well, I'm pleased to say we have a functioning new Combiner's Boiler on our single pipe system and efficient it is too. The Nest stat is connected using OpenTherm, the house temperature appears more stable than before, hopefully because of the OpenTherm function, i.e. less peaks and troughs in the temperature gradient. Hot water is great as is our new shower. All in all a successful install. I've attached a couple of pics showing the before and after bathroom refurb. Think I did OK for a DIY'er. Oh and ignore the protective cover on the shower base its gone now and aligned properly.