Heat only boilers and confusion

[kasser]

Trying to get to grips with all the terminology here and what can be done with what.
Heat only = open vent boiler?

I suppose nothing stops me from sealing it up and sticking an expansion vessel to it? This is the same as a system boiler then? Is it cheaper then to buy a system boiler instead of adding an expansion vessel to the heat only? Even with a system boiler you may need an extra EV anyway, so what's the advantage of picking a system boiler in the first case if you're going to add an EV to it?

Is there anything stopping me from having an open vent heating system and an unvented hot water cylinder with a heat only boiler? Or vice versa?
There's no reason I can't have an open-vent hot water cylinder with a system boiler?

If I'm right in my above thinking, a heat only boiler can be used as a system boiler with the right components, but a system boiler cannot be used as open-vent boiler due to the expansion vessel? I suppose you could, by ignoring the EV, but then you're paying more for nothing?

This is confusing me more:
https://www.vaillant.co.uk/for-installers/products/ecofit-pure-open-vent-boiler-26116.html
If you look under Specifications and DHW, it mentions a minimum pressure to operate the boiler. Why, what for?


Finally, with a cold water tank in the loft and bathroom just below, the tank is going to be less than 1 m above the shower head when taking a shower. That's 0.1 bar of pressure minus losses due to pipe length and fittings. Not possible to have a shower then? I suppose this was designed to fill a bath, so large pipes, big flow rate, low pressure?

 

[gmartine]

I'll let the others answer the rest as this was a curiosity to me and I have to pop out.

"This is confusing me more:
ecoFIT pure | Open Vent Boiler | Vaillant UK
If you look under Specifications and DHW, it mentions a minimum pressure to operate the boiler. Why, what for?"

Safety, stop it running dry.

 

[ShaunCorbs]

Heat only can be used for either open or sealed if manufacturers approve

System boiler includes expansion vessel, pump , blow off etc normally sealed

 

[EvilDrPorkChop]

The way I look at it is that on a system boiler the pump, EV, Auto Airvent and blow off are all covered under the manufactures warranty with the boiler, for however long that maybe (Usually 7+). System boilers are usually only price of a pump more (That you would usually replace on when fitting a heat only boiler anyway) so it makes more logical and cost effective sense to have a system boiler over a heat only one in most cases.

Depends on the situation, space and installation. If theres already a EV and pump in then it makes more sense to fit a heat only.

 

[Rob Foster]

Trying to get to grips with all the terminology here and what can be done with what.
Heat only = open vent boiler?

I suppose nothing stops me from sealing it up and sticking an expansion vessel to it? This is the same as a system boiler then? Is it cheaper then to buy a system boiler instead of adding an expansion vessel to the heat only? Even with a system boiler you may need an extra EV anyway, so what's the advantage of picking a system boiler in the first case if you're going to add an EV to it?

Is there anything stopping me from having an open vent heating system and an unvented hot water cylinder with a heat only boiler? Or vice versa?
There's no reason I can't have an open-vent hot water cylinder with a system boiler?

If I'm right in my above thinking, a heat only boiler can be used as a system boiler with the right components, but a system boiler cannot be used as open-vent boiler due to the expansion vessel? I suppose you could, by ignoring the EV, but then you're paying more for nothing?

This is confusing me more:
https://www.vaillant.co.uk/for-installers/products/ecofit-pure-open-vent-boiler-26116.html
If you look under Specifications and DHW, it mentions a minimum pressure to operate the boiler. Why, what for?


Finally, with a cold water tank in the loft and bathroom just below, the tank is going to be less than 1 m above the shower head when taking a shower. That's 0.1 bar of pressure minus losses due to pipe length and fittings. Not possible to have a shower then? I suppose this was designed to fill a bath, so large pipes, big flow rate, low pressure?

Quite a number of the questions you ask you have quite obviously got the general answer to already. Small houses and flats are ok for combi set ups, larger homes with more than one bog, showers etc ..no way. Then you enter system boiler land a pressurised conventional type system with out high level intermediate water storage tanks etc. but still dependant on the mains water supply ...not just pressure but volume..check your supply
then report back here with your
figures and we will advise

centralheatking

 

[Aire]

Quite a number of the questions you ask you have quite obviously got the general answer to already. Small houses and flats are ok for combi set ups, larger homes with more than one bog, showers etc ..no way. Then you enter system boiler land a pressurised conventional type system with out high level intermediate water storage tanks etc. but still dependant on the mains water supply ...not just pressure but volume..check your supply
then report back here with your
figures and we will advise

centralheatking

What's a bog got to do with whether a combi is suitable or not?

 

[Rob Foster]

What's a bog got to do with whether a combi is suitable or not?

If you have plenty of bathrooms
..bogs ...then everytime some one goes for a dump this will
mess up,the flow to the shower
etc. chking

 

[Aire]

If you have plenty of bathrooms
..bogs ...then everytime some one goes for a dump this will
mess up,the flow to the shower
etc. chking

Well the amount of toilets a house has wouldnt influence my decision on a combis suitability. Baths, showers and flow rates are all that matters in my opinion.

 

[kasser]

Safety, stop it running dry.

But there's no DHW in heat only boilers, and especially no pressure in this context? It's just the hot water for heating running through the hot water cylinder instead of a rad... Whatever pressure you have in your rads will be the same running through the cylinder?

 

[kasser]

In what way is a system boiler dependant on mains pressure? If you fit a vented cylinder, no problem? May only be an issue if mains pressure is < 1bar; you can't pressurise your heating system then?

 

[Rob Foster]

In what way is a system boiler dependant on mains pressure? If you fit a vented cylinder, no problem? May only be an issue if mains pressure is < 1bar; you can't pressurise your heating system then?

So if there is a shortage of incoming mains water ...where does it come from really
chking

 

[Riley]

This is such a weird thread

 

[Rob Foster]

Well the amount of toilets a house has wouldnt influence my decision on a combis suitability. Baths, showers and flow rates are all that matters in my opinion.

of course it does it affects the total demand for the property
esp at peak times when kids come back from school or in the morning when everybody is bathing or showering...intermediate high level,storage was the nirmal forva very good reason ...off to
Bristol have a good rest of day
chking

 

[kasser]

So if there is a shortage of incoming mains water ...where does it come from really
chking

This problem would apply to all 3 types of boilers.

 

[Last Plumber]

Edit:

 

[Aire]

This problem would apply to all 3 types of boilers.

Low mains pressure would only affect combis and system boilers. If you have low mains pressure on a gravity hot and open vented system then there will no issues.

 

[kasser]

Can't you have an open-vented cylinder with a system boiler?

 

[Aire]

Can't you have an open-vented cylinder with a system boiler?

Yes

 

[Aire]

Can't you have an open-vented cylinder with a system boiler?

Any boiler will work with a gravity hot water system. You could have a combi and an open vented cylinder if you feel the need.

 

[Riley]

It’s all about everything that goes With it. It’s heavily impacted by system capabilities ie
flow/pressure, age of system ie is it a fragile old system that may not deal with pressure you can make a heating/hot water creation to suit

 

[Last Plumber]

Heat only = open vent boiler?

Normally meaning a regular Boiler as in not much else apart from Heat ex, Burner and controls. Connections on top to vent heat ex.

I suppose nothing stops me from sealing it up and sticking an expansion vessel to it?

No, as long as you include all the correct and necessary safety features too.

This is the same as a system boiler then?

No. It would be a regular Boiler on a sealed system.

Is it cheaper then to buy a system boiler instead of adding an expansion vessel to the heat only?

By the time you have added all the components and piped and wired them up it is cheaper to buy a system Boiler probably but there are other reasons for that decision beside the costs.

Even with a system boiler you may need an extra EV anyway, so what's the advantage of picking a system boiler in the first case if you're going to add an EV to it?

It depends on what you're doing, there is more to it than the EV, you would need to pipe it correctly and add the necessaries in the correct places. If you are installing a new system and want it sealed there is little point in buying a regular Boiler when the system Boiler is ready to go. In my opinion.

Is there anything stopping me from having an open vent heating system and an unvented hot water cylinder with a heat only boiler?

No.

Or vice versa?

No.

There's no reason I can't have an open-vent hot water cylinder with a system boiler?

No.

If I'm right in my above thinking, a heat only boiler can be used as a system boiler with the right components,

You can use a regular Boiler on a sealed system with all the correct components and the necessaries in the right place, yes.

but a system boiler cannot be used as open-vent boiler due to the expansion vessel?

No it can't but not because of the EV. The connections are on the bottom of a system Boiler and it is piped differently internally due to layout of the other internal components. The appliance will not naturally vent as a result of this.

Finally, with a cold water tank in the loft and bathroom just below, the tank is going to be less than 1 m above the shower head when taking a shower. That's 0.1 bar of pressure minus losses due to pipe length and fittings. Not possible to have a shower then? I suppose this was designed to fill a bath, so large pipes, big flow rate, low pressure?

Sounds like it!

If you don't mind me asking, have you served an apprenticeship of any kind and if so what in?
Was it a Gas qualification (I can see you are GSR) or have you done some Plumbing & Heating Qualifications too?

 

[kasser]

Nice one Last Plumber, thanks.
Clearly, I haven't served any apprenticeship and I'm no plumber. I do gas but as this includes heating, I thought I'd better get to grips with this. I deal with combis and haven't come across situations like here yet.

 

[Riley]

I am in no way criticising but how can you just do combis?? Do you literally just do straight swaps??

 

[Last Plumber]

Nice one Last Plumber, thanks.
Clearly, I haven't served any apprenticeship and I'm no plumber. I do gas but as this includes heating, I thought I'd better get to grips with this. I deal with combis and haven't come across situations like here yet.

Well it is good to see that you are trying to educate yourself but I have to admit that your questions give some cause for concern.

Things do seem to have turned completely around over the years. It used to be at least 5 years before you came out of your time, even then you knew very little compared to older more experienced folk. In those days Gas was only viewed as one of the fuels we worked with and the Plumbing and Heating systems were the main issue. It looks now as though Gas as the main thing they teach and the rest 'might' follow dependent upon the needs and responsibility of the individual concerned?

I am by no means having a go at you personally you understand, it just bothers me that you asked these questions when you are already working on Boilers and installing Heating systems by yourself?

I do think it is good that you have an inquiring mind and obviously give the subject some thought before you do something but you could land yourself in it quite easily if something goes wrong.

Does that not worry you?

 

[kasser]

I don't do "just" combis. I'm a newbie and as combis are by far the most popular type of boilers, I haven't come across the other types yet. I'm not ruling them out, which is why I'm trying to learn about them. And I wouldn't install one of these by myself in the beginning.
However, I've heard there are many engineers doing just combis.

The gas course is just gas, it's all about safety and it's all about learning, retaining facts rather than understanding. The chapter on boilers was among the shortest. Indeed it looks like they expect the rest to follow, especially on the heating side.

It's fair enough to have some concern but it should be at the industry as a whole. In my short time, I've done some LL cert and I've seen some shocking things that have been passed by engineers.

 

[Last Plumber]

It's fair enough to have some concern but it should be at the industry as a whole.

Indeed it is at the industry, not you personally.
Carry on learning! I am sure the folk on here will help all they can.

 

[Riley]

As we said fella we weren’t having a go and we all have to learn somewhere Do you have any guys with experience that you can call upon

 

[kasser]

Yes, fortunately I know some people who can help.

 

[Riley]

Thats what you need mate. Also I know it’s a bit of a backwards way of doing it But try registering with your local college on an introduction to a Plumbing and you can learn all about the background to the systems

 

[Allgoode]

There's never a daft question as far as i'm concerned.

Better to ask and be wiser/safer for it instead of just plowing on ahead without a scooby and making needless mistake's or worse injuring yourself or others.

(Been there and got tee-shirt from it, came off a lot lighter in the pocket so always aware now.
Also some customer's are sneaky bar-stewards and can cause mysterious leaks/damage so a few phot's if working somewhere new is always a good move.)

Every day is a school day as far as i'm concerned & as long as you keep an inquisitive mind and are switched on there is always something new to learn.

Cheer's,

Andy

 

[Allgoode]

Forgot to add, if you can look inside a "heat only" boiler beside a "system boiler" you will immediately see the piping difference's and logic to the layout which helps to put the theory in context.

Old scrappy or removed boilers can let you tinker to your hearts content without worry about damage or if you have some spare bits leftover when you are learning.

 

[kasser]

Youtube is pretty good too.

 

[Millsy 82]

I personally only fit a system boiler if I lack space to fit an external pump expansion vessel etc. In the future it's generally easier and cheaper to replace external parts. On oil I would fit a system boiler as Grant's are awkward and have 2.5 bar pressure reliefs.

Yes you can fit most heat only boilers to most vented/unvented cylinders etc.

 

[chris watkins]

Youtube is pretty good too.

I can highly recommend the Domestic Heating Design Guide if you want to get up to speed with heating it will be the best £28 you will spend.
https://www.cibse.org/knowledge/knowledge-items/detail?id=a0q20000008I7odAAC