Hot water - on demand v cylinder

Odia1101

We are going to replace our 12 year old hot water system over the coming months and the plan to date has been to install a new high efficiency boiler and new hot water insulated cylinder. But on a recent visit to friend in Wales (same size house) they have had a new heating system installed (Baxi combi boiler - same natural gas) but it is hot water on demand - no cylinder and space back in hot press.

Seems like a great option but the Irish standard still seems to be to stick with the cylinder and store hot water as opposed to have it on demand.

I would appreciate any views please.

heinbloed

These type of boilers are called "combi-boilers". They are very common in Ireland as well. Are not against any Irish or European regulations.

Contact an energy advisor or a heating engineer before changing/replacing your existing boiler. This would avoid an unsuitable boiler, hopefully.

You start by looking at your incoming mains, if you have good mains then a combi work well, you can fit a break tank if you have bad mains but I personally don't like them with combis.

As for swapping then there's pro and cons for both, if you go with a combi then you don't have a secondary source of hot water if the boiler breaks down unless you fit a electric shower, some people can never get used to a combi and hate that they changed, you can start to hate your loved ones if they open a tap or put on the washing maching if your under the shower. On the plus they free up a lot of space, they work very well if you understand them, your not heating water you havn't used and you can run your heating circuit at lower temperatures which are better at reducing fuel costs and you don't have to worry about Legonnairs.

Have a look at zoning and other controls which can save you money which ever system you decide on.

Plombier

Gary why do you not like the break tank option ??

Plombier

Plombier wrote: »

Gary why do you not like the break tank option ??

I come across a lot that don't work as the tank is undersized and a combi is supposed to be able to give hot water all day everyday:), with a unvented cylinder installers are better at sizing the break tank as they are starting with a given amount of stored hot water.

If the break tank is larger than the required amount of hot water then a combi will work beautifully, on the other hand it's a pain in the ass to commission a 38kw combi with a just a few rads and you keep running out of hot water:mad: because of a small 60ltr tank.

Plombier

So with a properly sized tank you don't see a problem, I am interested because of your connection with boiler manufactures,
Thanks

Above is my personal opinion, below is what I'd be saying in my day job.

A combi is designed to be used with mains water, if a combi is supplied by a breaktank then any issues that may occur wouldn't be the responsibility of the manufacture and wouldn't be covered under the warranty as the boiler is fitted outside of manufacturers instructions, I would advise anybody with insufficient mains flow rate/pressure to look at stored hot water options:D

boxtysugarbulb

OP, this link might help you a little bit: http://www.miketheboilerman.com/combis.htm

JohnnieK

Odia1101 wrote: »

We are going to replace our 12 year old hot water system over the coming months and the plan to date has been to install a new high efficiency boiler and new hot water insulated cylinder. But on a recent visit to friend in Wales (same size house) they have had a new heating system installed (Baxi combi boiler - same natural gas) but it is hot water on demand - no cylinder and space back in hot press.

Seems like a great option but the Irish standard still seems to be to stick with the cylinder and store hot water as opposed to have it on demand.

I would appreciate any views please.

This is the plan for my own home.

I intend to install a Viessmann 36kW combi in my loft on the gable wall, the gas meter is below it and I dont trust the size of the pipe that connects to my existing boiler in the utility room.

My loft is large and I am also going to put in another storage tank beside the existing one and marry them together.

I will then install a Grundfos MQ3.5 booster pump on cantilever brackets on the other gable wall beside the tanks to minimize vibration noise and boost the whole house. The reason for this is my mains pressure is o.k but they have a tendency to reduce this in the warmer months and even off on some occasions. I am also going to install a Mira Jump or similar as a back up for showering in case the combi should fail.

This is just my own plan but I hope it gives you some ideas. I've had to put it on hold at the moment as my wife is fighting breast cancer at the moment so hopefully it will be something for me to look forward to in the new year.

I have installed a good few combi's lately and have more lined up too. People seem to be moving over to them in droves even though it is old technology (in the UK for years) one thing is for sure the size of the gas pipe is crucial.

JohnnieK

boxtysugarbulb wrote: »

OP, this link might help you a little bit: http://www.miketheboilerman.com/combis.htm

I have a few issues with this link.
Combi's are fine when installed correctly and i'm sure Gary71 will back me up hear the time it takes the hot water to reach the tap depends on how far the tap is away from the boiler and the flow rates and the same thing can happen to a cylinder.

Most people who work on boilers should know problems when they arise and a combi is no different. This thing "I dont know anything about that boiler" is to be honest rubbish, Any boiler has a sequence of operation and if it stops at a certain point in that sequence you should know were to start looking. And all manufacturers have good back up support and are only a call away.

antoinolachtnai

You need to be sure to make sure the plumber plumbs combis in accordance with the waterworks regulations in your area. For example see p. 39 of the waterworks regulations (http://www.dublincity.ie/SiteCollectionDocuments/Dublin_City_Council_Waterworks_Regulations.pdf .