Sealed system, have I got this right?

[bolst3r]

I need a new boiler, but it turns out my header tank is fed from the water softener and, as usual, there is no viable way to get a hard water feed up to the loft.

However...

My main feed comes into the utility room and splits, one side goes to the water softener, and one side goes to the drinking tap in the kitchen. Someone suggested swapping to a sealed system as the boiler is also in the utility room so I can easily connect it to the main feed (I believe this is a sealed system) and is compatible with my megaflow?

Now this is where I got confused, one person said I would also need an expansion vessel in-line, whilst another person said certain Bosch/Worcester had everything they needed internally, so it was just a case of directly connecting the main feed in.

I don't really have space for an external expansion vessel so happy to go for a slightly different boiler, if they do actually exist?

 

[muggles]

Heat Only boilers on sealed systems need external expansion vessels

System & Combi boilers have internal expansion vessels.

There are some boiler manufacturers who are quite happy with softened water in the system

 

[bolst3r]

Heat Only boilers on sealed systems need external expansion vessels

System & Combi boilers have internal expansion vessels.

There are some boiler manufacturers who are quite happy with softened water in the system

Thanks for the response.

I think I understand. I currently have a Promax SL, which i'm assuming is a heat only boiler, however because i'm on an unvented system it's been suggested I could swap to a System boiler to get around the softened water issue.

Another solution is to use a heat only boiler but if I do this, i'll need an external expansion vessel.

So both solutions are correct, just coming at it from different directions? Would there be a reason to not go for the System boiler as this would be preferred?

Just out of interest which boilers are ok with softened water? Would is be a problem having this circulating in my heating system? I have some older cast iron rads and would hate for them to dissolve.

 

[Mottie]

I don't really have space for an external expansion vessel

They’re not that big - not much bigger than a couple of gallons of oil. Are you sure you don’t have room for that in your utility room?

 

[bolst3r]

They’re not that big - not much bigger than a couple of gallons of oil. Are you sure you don’t have room for that in your utility room?

if we had to force it in we could, but we're pretty tight on space so if there is an viable alternative we would prefer that route. To me a system boiler makes sense...?

I've just looked on screwfix, I can see there are about 265mm x 235mm, so there's an outside possibility it could go above the cabinet that houses the boiler, wouldn't look great though.

Is there a reason to opt for the heat only over a system boiler? The purchase/install price appears quite similar.

 

[Mottie]

Is there a reason to opt for the heat only over a system boiler? The purchase/install price appears quite similar.

From what I understand, with the system boiler the expansion vessel, pump and maybe a few more bits are inside the boiler housing. If they go wrong, they may be more difficult to replace and there is usually very little option to use generic parts. With heat only, it’s all outside. You may find that the boiler is bigger to accommodate that but I’m not 100% on that.

 

[polesapart]

There are also flat expansion vessels, and they don't have to fitted right next to the boiler.

 

[bolst3r]

There are also flat expansion vessels, and they don't have to fitted right next to the boiler.

this is interesting. I have a cupboard that houses a water softener on the floor, so maybe when I fit a reaplcement Duoflow there will be sufficient space to fit an expansion vessel

 

[Mottie]

If you don’t know about boilers etc, why not get a heating engineer round, tell him you want a heat only boiler with a sealed system and let them tell you where things will fit?

 

[bolst3r]

If you don’t know about boilers etc, why not get a heating engineer round, tell him you want a heat only boiler with a sealed system and let them tell you where things will fit?

I did, I had two around to quote, and both have suggested quite different solutions so i'm trying to learn the difference and ultimately end up going with the best person/solution.

In the past I've used a heating engineer that looks to have made things easy for themselves which has caused me a bit of grief (whole house fit out, and didn't push hard water to the heating header tank, even though they actually installed the softner at the same time)

So sorry for all the questions, just trying to cover myself and avoid issues like before

 

[Mottie]

In the past I've used a heating engineer that looks to have made things easy for themselves which has caused me a bit of grief

Yes, have it fitted where it’s convenient for you. I have my boiler fitted out of the way in the loft and a few on here have said that could be a problem for the engineer that has to service or repair it. My loft has a ladder, is boarded out and has good lighting up there. Someone on here even said that they don’t touch boilers that are fitted in lofts. As far as I’m concerned, it's up there for my convenience, 365 days of the year, not for their convenience on the couple of hours a year they come to service it!

 

[muggles]

Thanks for the response.

I think I understand. I currently have a Promax SL, which i'm assuming is a heat only boiler, however because i'm on an unvented system it's been suggested I could swap to a System boiler to get around the softened water issue.

Another solution is to use a heat only boiler but if I do this, i'll need an external expansion vessel.

So both solutions are correct, just coming at it from different directions? Would there be a reason to not go for the System boiler as this would be preferred?

Just out of interest which boilers are ok with softened water? Would is be a problem having this circulating in my heating system? I have some older cast iron rads and would hate for them to dissolve.

Yes, your existing boiler is heat only (also sometimes referred to as Regular). System boilers tend to be physically a bit larger depending on which brand you choose, and generally need to be fitted on sealed systems whereas heat only boilers can go on your existing open-vented system.

Presumably your existing system has had softened water in it for years if there's softened water to the header tank, so it's a bit late to start worrying about that now from the point of view of your radiators. Intergas definitely allow softened water, I think Viessmann do too but always worth checking with them directly.