Some expert advice needed - Back Boiler

[Paul591]

Hi All,

We are looking at purchasing a three bedroom semi, late 1970s construction that has a back boiler heating system.

It has a hideos gas fire front, and with efficiency in mind, we would be looking to replace it. However, I have heard horror stories of huge sums of money, and entire water and gas pipework needing to be replaced to cope with the 1 bar pressure.

Bottom line, is it feasable to replace a back boiler with a newer system - if so, when getting quotes, what are the things I am looking for that will need doing. Ie, does the boiler have to be relocated to the kitchen etc?

Many thanks for any help!

Cheers
Paul Lofthouse
Nottingham

 

[leakylea]

the tradesman who calls to price the job will have all the expertise to correctly advise you on the requirements to get the system up to the current regulations and industry standards, with an imput by yourself really to state what type and style controls you want and what style of boiler you will get best value from.it is adviseable to replace as much of a systewm as you can afford,if not fittted already it is required to install thermostatic radiator valves,to at least all bedroom radiators during a boiler exchange.
Nowhere,more than plumbing is the term you get what you pay for more true
A new combi can be as cheap as 399, not flushed no trv's, few controls, plastic pipe the total will be around £1500
A system with a quality boiler, correctly flushed or completely repiped with all the correct valves and controls that meets all the manufactures requirements for warranties etc can be £4,000 plus
On a basic semi detached having a combi put in i would advise a total rip out and repiped in new copper the amount of alterations from your existing back boiler set up would take longer than the repipe.

 

[Bernie2]

Hi Paul,

I am not trying to frighten you, but it is better to have your pipework renewed as its nearly 40 years old and whilst the pipe itself may be okay what about the joints, they are the weakest points?

The system you have in now, probably works at atmospheric pressure and so the joints will not be overly strained. But putting in a new combi system and turning an old open vent system into a sealed system is asking 40 year old joints to take nearly 3 times the pressures they are accustomed too.

Another reason is that where as in an open vent system the boiling point of water would be 100Centigrade, in a sealed system with as much as 3 times atmospheric pressure the boiling point changes quite a lot.
The problem is steam, starts to form at about 100C in the atmosphere, in a pressurised system the water temperature can be well above what it would at atmospheric pressure, and if a joint where to break open, all the water in the system would immediately turn to steam.

The problem with this of course, is that it would then want to occupy a space nearly 1000 times bigger than the water. In other words you would get a big bang.

If you look at a combi system its got all kinds of safe guards on to prevent that from happening. And certainly its a very rare thing to happen, I can't recall one happening. But its possible. So its best to renew the pipework as well as the boiler. The boilers on the market today, come in all sizes and shapes and can be virtually fitted anywhere. The constraints of course are usually cash.

Hope this is helpful.

 

[Deleted member 2053]

Steam actually produces 1600 times the volume of hot water and it will split new pipework just as happily as it will split old pipework. There is absolutely no need to fit a pressurised system unless you are planning to change to a combi. You can have an open vent system boiler fitted which will still use the same header tank in the loft and the pressures will be the same. You are going to be relocating the boiler so yes you will need the water pipework extended and it is likely that the gas will have to be repiped from the meter as newer boilers are more critical about gas pressre at point of use. I have changed old systems to pressurised and have yet to have a leak that was not of my own making. Sometimes customers wanty some rads changed as they want a newer style and in fact these new convecting rads (the ones with fins inside) are more comfortable to live with when the heating is running. But if the old ones survive a proper acid powerflush and have no obvious surface rusting they are unlikely to start leaking after you change your boiler. Unless of course your plumber leaves his pipework full of flux.

 

[Bernie2]

Hi Paul again!

I am sorry if I appeared to be putting you off installing a combi boiler, but I always feel its better if people know the dangers about what can happen if things go wrong and why its important to inspect the system.

If of course, after you have considered the points being made, then great go ahead do it.

The point I was really trying to make was about one of the weakest links in the system, namely the joints. You could always' pressure test the system, which is usually to 1.5 times the maximum expected working pressure of the system if your unsure.
We don't really know what sort of jointing was used in the system? In point we don't even know whether its in copper or iron.

You also have to remember we don't know much about your system other than its open vented, indirect and has a back boiler unit.

We don't for instance know, if the pipes run under floor boards, what expansion and contraction has done to them over the years. Where they properly fitted in the BS recommended way to allow them to move freely or where they fitted in cut notches and constantly allowed to rub against the joist's? Has this worn the pipe wall thin?

We don't know how many times the system has been filled and refilled introducing corrosive new water into the system, or if it has or hasn't had suitable inhibitors included. We don't know if there are or have been leaking glands or some way that could cause air entrainment into the system promoting internal corrosion. We don't know the speed of the pump for the system or whether its been exceeding the recommended maximum flow rates and causing internal pitting and wear to the pipe work or radiators.

We don't know if installing a combi might leave lots of dead legs in the circuit.

There are so many variables that it becomes a bit difficult to give you clear answers.

The thing is if the system looks okay you can always chance it and see. If it doesn't pan out and you start getting leaks or noises then you have lost nothing, you can then either re pipe or part re pipe it.

As to the gas supply, well it depends what you have already got on the gas pipe work. You may have the correct size gas pipe already, for a direct modern replacement. You could inspect the supply pipe and work it out from its size, length and resistances and appliances fitted or expected to be fitted.
As to its condition, obviously a standard gas test will tell you, but then I assume its been fitted correctly.
But you would want a Gasafe registered person for that.

However if you install a combi its better that you have a direct separate gas supply straight from the meter.
　
Sorry its a bit, bits and pieces, its more to promote thought than an exact series of standards to be observed. If something occurs to you then look up the applicable standard.

I mean most of what I mention can be found just by looking, you don't have to be skilled to notice a pipe has got a thin wall or its been rubbing like mad or even that the joints have been leaking. You can tell all that just by looking at it.

Bernie2　


　
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[dontknowitall]

If I knew a few years ago what I know now, I'd have never gone to the first plumber to give me a quote on heating. (Luckily he was fantastic, but it could have been a very expensive mistake.)

I'd get in three quotes, even though this might mean phoning around 15 plumbers! When you get them to your house (not before!), ask them all three questions:

1. What are the regulations
2. How many systems have they fitted
3. How long have they been trading

**Generally** the newer people will know the regulations better while the more experienced people will know how to do the job better and quicker (usually). You must be careful that you're not going to get it in the neck (e.g. HIPS pack when you sell or CO poisoning from poor ventilation) if something is installed incorrectly.

Boring as they are, these things are seemingly more important these days than the price and whether the flamin' heating system works or not. If it doesn't work, you've at least got the Sales of Goods Act and Trading Standards behind you!

Hopefully from the above posts you'll see there's a fair amount of stuff involved.

Good luck!

 

[Mike Jackson]

If someone stood and asked me those three questions I'd be straight back out the door. Sounds the sort of thing that people who stand over your shoulder and question everything you are doing would ask.

When you contact a heating engineer be straight about what you want. Explain that you're not sure of the best system for your circumstances and you need advice and a quote. Don't initially get more than 2 or 3 round as we speak in plumbers merchants and if you start contacting loads of plumbers you get tagged as an awkward customer and the prices will go up.

If possible find an engineer by personal recommendation or go to The Chartered Institute of Plumbing and Heating Engineering and find registered plumbers in your area. All CIPHE members follow a code of conduct and membership is limited to those with proven qualifications/experience.

Mike

 

[dontknowitall]

Point taken Mike. I guess I must have had too much sauce last night when I posted that!! Your post is much more sensible.