Gas Boiler - Sealed or Open Vent?

NuttyProfessor

Hi,

I'm looking to replace my 30 year old Gas boiler. I have an open vent system with a hot water tank.

Should I leave the system as open vent or is it worth going for a sealed system? Which is best?

I've a 2 bedroom, one bathroom flat. Will be adding an ensuite.

Vaillant ecoTEC Plus is the boiler I'm looking at...

I've discounted a combi boiler as I want instant hot water with a good flow rate and all the friends I know with combi's have lot's of problems with them :rolleyes:

Canucklehead

Good afternoon: The OH handles breakdowns for all types of boilers and doesn't see a disproportionate number of combis in crisis(in fact we have had a combi for years;)) Keep in mind that a combi has all of the components needed for DHW and heating in one package where as system and open vented boilers spread the potential for failure beyond just the boiler itself if you get my drift (eg. pumps, valves, HW cylinder, F&E tank, cold water storage cistern , (expansion vessels for system boiler) etc are all separate components in an OV system)...that being said he has been installing Vaillant Ecotec Plus 400 series as well as Viessmann Vitodens 100 Compacts for those customers who wish to retain their OV systems as well as system boilers from the same manufacturers. Pros and cons of sealed vs. OV systems in terms of central heating only are detailed here with info on domestic hot water here
A good RGI will be able to advise you after conducting a site survey.

Your CH/DHW systems will only be as good as the installation and annual servicing

HTH

Canucklehead

Canucklehead

NuttyProfessor wrote: »

I've discounted a combi boiler as I want instant hot water with a good flow rate

You will get hot water on demand from a combi, flow rate will be dependent on kW rating of the combi. and mains pressure/flow.You could spring for an unvented cylinder to provide DHW at mains pressure to multiple drawoff points...this option will require adequate mains water flow/pressure also and more dosh

Canucklehead

Pssst

It is my humble opinion that far too many combis are being installed in inappropriate circumstances thus leading to customer dis-satisfaction.

Another factor to consider is your gas supply.

Now then,in the good old days,people would perhaps have a system boiler rated at maybe 50,000 btu or even a circulator for their hot water.

Nowadays,everyone seems to be having a high efficiency combi running at 100,000btu and more to try and satisfy hot water demand.

Now then, if you are in a good area,the mains pressure available (gas) might be around 32 mb. typically its less than this and this week,i have noted working pressures even on 1" services of 17mb.

In certain areas,with high demand in winter,the network simply cannot service all your high consumption gas boilers!

~I have known some streets where they almost have to take turns to run the shower!

The situation is further complicated by service renewals being done in PE pipe of typically 20mm diameter.

So then,for some people,they might have a new boiler but the network cannot feed it at certain times of the year.

Do they still make BF circulators?
If not,they should. What a great piece of kit and economical too.

Razor

I'm getting two main boiler related callouts at the moment, one is the condense pipe fiasco which is mostly down to poor installation.

The other is combis that can't achieve set temperature because the incoming main is so cold at the moment. Arguably that is mostly down to poor commissioning leading to large flow rates.

Personally I think it's horses for courses combis are great in some situations but not others.

I suppose working pressure would be dependant on the area luckily mine is fine. What do you do Pssst ID all installations?

NuttyProfessor

Thanks all.

Canucklehead are you "MikeTheboilerMan"? That site is great, I note he is not a fan of combi boilers or sealed systems...

I forgot to add that my mains pressure is not that great...

Canucklehead

NuttyProfessor wrote: »

Thanks all.

Canucklehead are you "MikeTheboilerMan"? That site is great, I note he is not a fan of combi boilers or sealed systems...

I forgot to add that my mains pressure is not that great...

Hi...it is an excellent source of info but I can't claim ownership: I'm a female fan of sealed systems;)

Canucklehead