Combi boiler filling loop placement and other peripherals

[Del-inquent]

Are there any requirements on where the filling loop is fitted? I'm looking at having our standard boiler replaced with a combi. The current pipe layout has the pipes exit the top of the boiler. Water inlet is immediately below the boiler, Ideally I'd like the loop to be fitted from immediately below, going up the left hand side of the boiler and going into the pipes above. Are there any other peripheral elements I need to consider that will have to be fitted in the change from standard to combi?

I'll be getting it fitted by a gas certified plumber but need to plan the layout of the kitchen in the meantime and no plumber seems to want to come and discuss it, been bad enough trying to get quotes!

[Nickfromwales]

A lot of modern boilers have an inbuilt filling loop at the connection manifold. What boiler are you looking to install?

 

https://youtu.be/XUTakE3Eut4?si=qWBdb7PKmyK_6uVp

 

Just a random grab of da ‘net, but these are commonplace nowadays. 

[stu w]

As above , just purchase the internal filling link with your boiler 

Edited May 28 by stu w

[JohnMo]

32 minutes ago, Del-inquent said:

standard boiler replaced with a combi

Hope your ready for the drop in hot water flow. Isn't this a degrade. Make sure you get one with a good hot water flow, some are absolutely rubbish flow rates. Choose wisely, not any old one will do.

 

You will need cold water inlet control group, basically a small expansion vessel and over pressure relief, and a condensate drain.

 

Some reading of how to improve performance. The cylinder referred to in the document looks like this.Combi-SuperFlow-White-Paper-v1-2-4.pdfCanetis-SuperFlow-Product-Sheet-WE-050318.pdf

[Del-inquent]

17 hours ago, Nickfromwales said:

A lot of modern boilers have an inbuilt filling loop at the connection manifold. What boiler are you looking to install?

 

https://youtu.be/XUTakE3Eut4?si=qWBdb7PKmyK_6uVp

 

Just a random grab of da ‘net, but these are commonplace nowadays. 

No decisions made yet on which one, that's another question I was going to pose a little later down the line!

[Del-inquent]

16 hours ago, JohnMo said:

Hope your ready for the drop in hot water flow. Isn't this a degrade. Make sure you get one with a good hot water flow, some are absolutely rubbish flow rates. Choose wisely, not any old one will do.

 

You will need cold water inlet control group, basically a small expansion vessel and over pressure relief, and a condensate drain.

 

Some reading of how to improve performance. The cylinder referred to in the document looks like this.Combi-SuperFlow-White-Paper-v1-2-4.pdfCanetis-SuperFlow-Product-Sheet-WE-050318.pdf

Compared to the system in place, a candle with a saucepan of water held over it would be an upgrade... We currently bathe using a bucket and a yoghurt pot as a ladle (not joking) 😅

It's a small chalet bungalow, effectively has a head height of 18 inches, we need to move the bathroom upstairs which will mean not possible to have header tank (no access to the tiny loft space) and there is no space to put an unvented cylinder without losing one of the habitable rooms. At the moment there is a tiny HWC in a cupboard. It needs replacing, the pipework goes through the kitchen because of the design of the place... overall a combi solves so many problems and after months with a bucket and yoghurt pot... 

I don't mind paying for a decent combi. I looked into the superflow, got many mixed reviews on them. I'm all ears on recommendations for a decent combi. 

 

[JohnMo]

1 hour ago, Del-inquent said:

ears on recommendations for a decent combi. 

Basically you need a powerful boiler BUT it needs to modulate down well for heating so sub 6kW at mine modulation, is ideal but the lower the better. Atag, Viessmann would be my go to boilers. I have used a superflow with A series Atag combi and they are excellent but you need two things to make them work well, remove cold inlet restriction, that is fitted to all UK boilers. Have a boiler that specifically takes pre heated water (most don't) so it can modulate effectively. Have run 3 showers from my Atag combi and superflow setup at the same time, no effect switching on a cold water tap either.

 

What ever you get make sure you don't flood the place with thermostats as all you will do is make the CH ineffective and make the boiler short cycle. If you can run as a single zone on WC. Both the manufacturers mentioned do that out the box.

Edited May 29 by JohnMo

[sharpener]

1 hour ago, Del-inquent said:

there is no space to put an unvented cylinder without losing one of the habitable rooms

 

You can get horizontal cylinders specifically designed to go in the eaves space.

[Del-inquent]

5 hours ago, sharpener said:

 

You can get horizontal cylinders specifically designed to go in the eaves space.

 When I say it’s small…

 

already looked at them, the only place one will fit will be permanently inaccessible once the works are finished. 

[Del-inquent]

5 hours ago, JohnMo said:

Basically you need a powerful boiler BUT it needs to modulate down well for heating so sub 6kW at mine modulation, is ideal but the lower the better. Atag, Viessmann would be my go to boilers. I have used a superflow with A series Atag combi and they are excellent but you need two things to make them work well, remove cold inlet restriction, that is fitted to all UK boilers. Have a boiler that specifically takes pre heated water (most don't) so it can modulate effectively. Have run 3 showers from my Atag combi and superflow setup at the same time, no effect switching on a cold water tap either.

 

What ever you get make sure you don't flood the place with thermostats as all you will do is make the CH ineffective and make the boiler short cycle. If you can run as a single zone on WC. Both the manufacturers mentioned do that out the box.

How far from the boiler can the super flow be? Boiler position in a corner of the kitchen (less than ideal but making best use of space available and it’s where the current one is)

[JohnMo]

15 minutes ago, Del-inquent said:

How far from the boiler can the super flow be? Boiler position in a corner of the kitchen (less than ideal but making best use of space available and it’s where the current one is)

Need to be as close as possible realistically.

[Nickfromwales]

Why bother? A combi on it's own is fine, and effective?

 

[JohnMo]

1 minute ago, Nickfromwales said:

Why bother? A combi on it's own is fine, and effective?

 

Higher flow rate than you would otherwise get from a combi, due to a lower dT required to be added to the warm instead of cold water, especially in winter. Consistent output flow rate winter and summer. In fact our hot water flow hasn't changed since we installed an unvented cylinder for the ASHP compared to the combi and pre heat.

 

Simple additions, big performance improvement. What's not to like.

[sharpener]

20 hours ago, Del-inquent said:

It's a small chalet bungalow

 

10 hours ago, JohnMo said:

Simple additions, big performance improvement. What's not to like.

 

Expense. Complication. OP has a small property and is desperately short of space.

[Del-inquent]

1 hour ago, sharpener said:

 

 

a small property and is desperately short of space.

Probably the most accurate description of our property going 🤣

Whoever designed the place should have their pencils and rulers taken away. If I had the funds I'd bulldoze it and start again. The current header tank is tiny and has actually had the sides cut to get it to fit in the tiny eaves, and the overflow tank is screwed to the wall of the bedroom, which is obviously a delight in itself. A combi really would solve a whole lot of problems, even if it introduced other, hopefully less frustrating ones.

[JohnMo]

2 hours ago, sharpener said:

Expense. Complication.

Overall less expense than a UVC and boiler combination. No servicing required unike an UVC, pretty simple to install overall.

 

If OP doesn't have space leave it out. But for anyone with a Combi boiler great performance for nor money, and easier cheaper than an UCV

[JohnMo]

Or the other alternative is a combi storage boiler such as a Viessmann 111-W it has the cylinder built in to give the same effect in a compact package, 25kW boiler will modulate down to 3kW. Will 20l/min DHW flow rate.

 

Install is the same as a standard combi, no complications.

 

Edited May 30 by JohnMo

[Nickfromwales]

14 hours ago, JohnMo said:

Higher flow rate than you would otherwise get from a combi, due to a lower dT required to be added to the warm instead of cold water, especially in winter. Consistent output flow rate winter and summer. In fact our hot water flow hasn't changed since we installed an unvented cylinder for the ASHP compared to the combi and pre heat.

 

Simple additions, big performance improvement. What's not to like.

If you've got one bath / shower then a massive output combi is a complete waste of money / effort afaic? Plus the storage boilers are physically bigger, and stick out a lot more than a regular combi.

 

A 37/40kW combi will scream DHW out, but all of these things are cold mains dependant so that is the real question here. If cold water cannot get in, DHW will not get out, simples.

[Nickfromwales]

14 hours ago, JohnMo said:

What's not to like.

Keeping a preheated tank warm 24/7/365 for no real benefit, my 2 cents. Burner lighting, pumps cycling, diverter valves moving about etc unnecessarily.

 

PS I am a huge fan of heat-store combis, and have fitted loads of Vaillant 937(now 938)'s in the past. Fabulous things. Just this family doesn't need one IMHO.

[sharpener]

4 hours ago, Del-inquent said:

The current header tank is tiny and has actually had the sides cut to get it to fit in the tiny eaves, and the overflow tank is screwed to the wall of the bedroom, which is obviously a delight in itself.

 

When we moved in there was a Fortic combined HW and header tank in a cupboard in the bedroom (with a noisy pump), cos it was directly above the Baxi Bermuda gas fire/back boiler and had gravity circulation. Fortunately there was room for a UVC in the bathroom when we had it all re-plumbed.

 

Fire went as spares to a friend, quiet replacement pump is going to be part of HP system in our present house, old pump has replaced an even noisier one on the UFH. As my grandfather would say "nothing wasted where they keep pigs..."