Disadvantages of a closed system boiler on 1990s house

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I've been reading through this forum's excellent resources which have been a big help in getting to grips with understanding boilers and regulations but I would really appreciate some specific advice on the my setup.

I live in a house built in 1990 which had an Ideal Mexico 2 fitted at the same time, the house is two storey, five bedroom detached with around 13 radiators, a bathroom and a toilet, plus a kitchen sink and a utility sink. The problem is the boiler is a bit of a mess (clogged up, SGN labelled it immediately dangerous) and looks like it needs to be replaced but due to needing to comply with newer gas regulations has meant each quote so far has been with a different suggested solution. The house has 15mm gas piping (it looks like it's 22mm into the kitchen and then splits to the smaller diameter to go up to the boiler and other gas appliances) which means new piping is needed for this boiler. Am I right in saying the 22mm piping is required to the boiler to meet regulations?

The combi-boiler option looks to be out the window straight off for the size of house and potential issues with pressure in the pipes which is fine with me as it makes the choice easier!

What I'm struggling with though is the choice between an open boiler system and a closed/system boiler. The current system is an open one with a header/expansion tank in the loft and the boiler/hot water tank just below in an airing cupboard. The first engineer recommended putting a boiler in the loft (which I assume is a closed system) as that would be the easiest way to get the new piping into the house as the pipe could run up the outside of the wall and straight into the loft which sounded fine.

However the second engineer recommended staying with an open boiler system due to the age of the house as apparently it could cope with slight leaks better, the risk with fitting a closed system would be that if there were any leaks (particularly with the slightly higher pressure) then they would need to be found and repaired which could be awkward. He wanted to fit a boiler in the same spot as the existing one and feed the new 22mm pipe straight up from the kitchen as he reckoned that's where the larger piping stops.

The third engineer initially opted for the loft as well with a system boiler, when I mentioned what the second engineer had said he replied that leaks were a valid concern and pointed out that if there were any leaks in the system they wouldn't be covered in the boiler quote. He quoted for both a closed and an open system (the latter cheaper) and his choice for the pipe route was to take up the floor on the first floor hallway and put the gas pipes through there to the outside wall and down.

The fourth engineer (who I didn't speak to) has also recommended a boiler in the loft which is why I'm posting this topic to understand whether the closed system is potentially as problematic as the second engineer made out. I'm also a bit puzzled as the fourth engineer apparently said that he would look into whether there were any boilers that could take 15mm piping which I thought wasn't allowed. I've only been passed the information on as a message so it may not have been picked up properly.

Just to be clear, each of the engineers have been gas safe registered and I'm absolutely not looking for any help on doing the work myself just in case that's implied at all. As is probably clear I didn't have a clue about any of this until a couple of weeks ago (and still don't have much of a clue!), the house has been without heating now for a couple of weeks but given the high cost and complexity of fitting the new boiler I don't want to rush into anything and make a mistake.

On a slight side note, in the FAQs Worcester are placed below Viessman but reading on the forum opinions seems to be mixed on the latter due to the variation in their service agents. The first engineer quoted for a Viessman, the third engineer a Worcester. If the solution was similar would a Viessman boiler be recommended over a Worcester?

Thanks for any advice,
John
 
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Gas pipe is down to manufacturers requirements, if the new boiler will work on 15mm, so be it.

Sealed system boilers are more common so get recommended more, also easier to install, no benefits as far as I can see.
 
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A sealed system will be more likely to find leaks due to the higher pressure. They are not prone to admitting air because they are, well, sealed. If the system is truly water-tight, it should seldom need topping up. If your radiator valves are old or show any signs of past leakage you should consider replacing them.

A properly piped, serviced, clean, open-vented system should also run trouble-free for decades and does not need a pressurised expansion vessel (a part to go wrong).

If you opt for sealed, you do have a choice between a heat-only boiler and a system boiler. Heat-only has external pump and expansion vessel, filling loop & pressure gauge (if sealed) which can make maintenance easier, where as they are built in to a system boiler.

Hope that helps.
 
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Was somebody joking who said there are health-and-safety issues (fixed hand rail etc) for loft installs?

What do they propose for the condensate drain? Internal or trace heating with external?

Is the loft heated? or how do they propose keeping it above 5°C?
 
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I don't like boilers in lofts full stop, unless there's absolutely no way to get the flue out otherwise.

If the boiler can go where the old one is, consider the Intergas on an open vented system, and you may find the gas pipe is ok, or the 22mm just needs extending a tad.
 
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Part of your question can not be answered without survey on site, but for the other bits:

There are no advantages to an open vent system. "Better in dealing with leaks" is a red herring. If there are leaks, big or small, you need to solve them now; they will only get worse, not better.

Needing replacement to comply with current regs is total nonsense; whoever told you that is either completely incompetent, or a complete liar.

Dito about statements regarding the gaspipe. No such thing in the regs. The boiler needs a certain working pressure which depends on the local situation. The pipe needs to be sufficient to deliver that. If 15mm does it, then that is fine. If 22 is too small, it must be bigger. You can only decide this after measuring.

If your description is accurate, a properly sized and installed combi would work fine; it's a matter of personal preference, and a lot of installers don't like combis for anything bigger than one bathroom. That does not mean it can not be done and work fine.

Not being funny, but part of your problem is your choice of engineers. In stead of spending a lot of time learning what is needed on forums and then tell the engineer what to do, you should find a good RGI, and let him take care of the
job. Do you tell your garage how fix your car? Your tailor how to make your suit?
 
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Do you tell your garage how fix your car? Your tailor how to make your suit?
Yes - most independent garages will choose cheap pattern parts rather than original equipment. If there is one thing that makes a car feel 'old', it is a cheap exhaust system. Sadly, once a model is out of production, the supply of original equipment dries up and even main dealers are supplied with cheap pattern parts, but they don't charge less.

I'd be torn between the choice of open-vented or sealed systems. I agree that a sealed system should be OK. If the pressure doesn't drop you know you don't have a leak and the inhibitor doesn't get diluted. But if the pressure drops and you don't have access to the filling loop or you are away, your heating stops.

With a 5-bedroom house, there will be the balance between installation costs and running costs to consider. Is it worth going for a Dutch boiler with nett efficiencies well over 100% and weather compensation or install a cheaper Grade A boiler with efficiency of 90%?
 
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Do you tell your garage how fix your car? Your tailor how to make your suit?
Yes - most independent garages will choose cheap pattern parts rather than original equipment. If there is one thing that makes a car feel 'old', it is a cheap exhaust system. Sadly, once a model is out of production, the supply of original equipment dries up and even main dealers are supplied with cheap pattern parts, but they don't charge less.

I'd be torn between the choice of open-vented or sealed systems. I agree that a sealed system should be OK. If the pressure doesn't drop you know you don't have a leak and the inhibitor doesn't get diluted. But if the pressure drops and you don't have access to the filling loop or you are away, your heating stops.

With a 5-bedroom house, there will be the balance between installation costs and running costs to consider. Is it worth going for a Dutch boiler with nett efficiencies well over 100% and weather compensation or install a cheaper Grade A boiler with efficiency of 90%?

You have a point.

I have the opinion that it's hard to find a good service these days and corners get cut.

I always find, if you want a job doing right, do it yourself!
 
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I like what Bengasman said. I'm not so keen on the advice you received from your potential fitters.
 
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Needing replacement to comply with current regs is total nonsense; whoever told you that is either completely incompetent, or a complete liar.

I never said I was told I needed a new boiler to meet regulations, the reference to regulations was for the second part of that sentence. The reason for replacement is simply that the boiler itself is not in a good state and it looks like there may be an issue with the flue as well.

Dito about statements regarding the gaspipe. No such thing in the regs. The boiler needs a certain working pressure which depends on the local situation. The pipe needs to be sufficient to deliver that. If 15mm does it, then that is fine. If 22 is too small, it must be bigger. You can only decide this after measuring.

How realistic is that only 15mm piping would be needed? Reading around it seems fairly normal to need to upgrade to 22mm and everyone who's looked at the system seems to think it needs the larger diameter piping bar the last engineer but he's no sure on that either.

Not being funny, but part of your problem is your choice of engineers. In stead of spending a lot of time learning what is needed on forums and then tell the engineer what to do, you should find a good RGI, and let him take care of the
job. Do you tell your garage how fix your car? Your tailor how to make your suit?

I disagree with you here rather strongly, all the engineers are gas safe registered and have been chosen on the recommendation of those who work with or closely related to plumbing/heating rather than just randoms out the phonebook and their advice broadly correlates with that I've found myself online and the information on this forum (errors appear more to be my use of the terminology). So I'm not convinced they're incompetent liars, I could have a nice warm house now if I'd just gone with the first quote but frankly I think I'd be the incompetent one if I just went with one quote without doing any work to find out what was actually being done and what alternatives were available. Hence it's taken several weeks to arrange different people to look over the system rather than the first four I could find.

Do I tell the garage how to fix my car? Absolutely, if there's work needing done I want to ensure it's the correct solution using suitable parts to avoid further expense and time wasted. I do use garages I trust but at the same time they may not be familiar with every quick on a particular car model and may use cheaper parts to save me money when I'd prefer spending more on a part I think is worth it.

I'm genuinely surprised at the criticism of this type of approach particularly in reference to a reasonably complex and expensive boiler install where I'd have thought common sense would be to be thorough.

John
 
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I don't like boilers in lofts full stop, unless there's absolutely no way to get the flue out otherwise.

If the boiler can go where the old one is, consider the Intergas on an open vented system, and you may find the gas pipe is ok, or the 22mm just needs extending a tad.

I've read a few comments about concerns of boilers being fitted in lofts which seem reasonable, in response to the post above the loft isn't heated at all. It only has some flooring down for storage but that's it.

The 22mm piping section appears to stop at the kitchen which is the floor below where the boiler currently is, one of the engineers wanted to try and extend that upwards but the house doesn't seem well designed for access to the gas piping hence the external piping solutions looking like they would be simpler and less disruptive to install.

John
 
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Position and flueing is the first priority, after that the RGI should be able to work out the gas pipes size, or you need another RGI if they cannot.
 
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Not a fan of fitting boilers in lofts full stop. Last resort. Regarding the pressure increase, i've had a handful of original open vented systems leaking when converting to a sealed system. To put it in to context I would say 95% of systems cope with the difference in pressure. In my opinion sealed systems are much better and it is worth the very small risk of springing leaks. Get all quotes on paper and check previous work. Go with the installer you feel will carry out the best job and not necessarily the lowest price. Consider a new pump and a Magnetic filter fitted.
 
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System boiler.
I don't mess around with anything else. Everything in one box. Job done.
You might need an addition expansion vessel for the size of house.

If there are leaks in the system they need sorting out or a new boiler
won't last five minutes open vented or not.

Running the correct gas pipe to the boiler shouldn't be a problem.
I like my boilers in the kitchen when possible.
 
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Thanks for the replies but this thread is over a year old and (thankfully) the replacement boiler has been fitted for about a year now as well. The new boiler is a non-sealed one same as the old and fitted in the same place rather than the loft, the company managed to find a fairly neat route for the new gas piping and fitted the flue through the loft without issue.

John
 
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