Boiler/central heating - replace?

I'm moving into a new home that has an old boiler, the label on it says "Thorn EMI Heating Limited M56/76 & M80/100 gas boilers". There is a cylinder above it in the bedroom and in the attic there is a cold- water cistern and a feed-and-expansion cistern. I'm after some general advice (be gentle on my I am totally ignorant re central heating/water systems!):

  1. The timer on the system is not working - could I fit a modern thermostat and timer to the boiler?
  2. Alternatively, if the boiler is replaced would I need to replace all the radiators as well? Is there a difference between modern pipework and older (possibly over 20 years old) pipework diameter?
  3. Can the cylinder be moved into the attic? What affect would this have on the water cisterns already in the attic?
  4. If I replace the boiler, what should I replace it with? I think a combi would be out of the question as the house is a large 5- bedroomed, with a couple of bathrooms.

Thanks very much

Reply to
tvmo
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Probably, but we'd need to know a lot more about the pipework layout before being able to recommend the best solution. How many water pipes connect to the boiler, and what is their diameter? Are there any motorised valves? If so, how many and what type (2-port or 3 port)?

Not unless the current radiators are shot - which they *may* be if the system has been run for years without inhibitor, so that they have rusted inside. In this case, fitting a new boiler - which will almost certainly use a non-vented (pressurised) system - the extra pressure may just be the last straw which may cause them to start leaking. On the other hand, they may be perfectly ok.

Another consideration is that a new condensing boiler needs to run at a lower flow temperature than your existing boiler in order to maximise its efficiency. So if your existing radiators are only just adequate in terms of heat output, you may need bigger ones (or probably the same physical size but with fins on the back) to get the same heat output at a lower water temperature. On the other hand, the standard of insulation of the walls, windows and attic may well have been improved since the system was installed, making the existing rads more than adequate.

Don't worry about pipe sizes. The original system may use imperial pipe sizes - 1", 3/4", 1/2" (though probably not if it's only 20 years old) - but it's easy enough to join up to the equivalent metric sizes of 28mm, 22mm and

15mm. [1]

It *could* but you'd have to make sure that you had an adequate structure to support the weight. You'd also need to raise the cold header hank to be higher than the cylinder - for which you may or may not not have enough headroom.

There are plenty of non-combi boilers around which will suit your purpose, and give you central heating plus lashings of stored hot water. To satisfy current building regs it will have to be a high efficiency (which effectively means condensing) boiler, and you'll have to update the controls and room and cylinder thermostats to provide boiler interlock. In other words, the boiler must shut down completely and not keep keep firing to keep itself warm once both the CH and HW demands are satisfied. It also makes sense (not sure if it's mandatory?) to fit TRVs to most of the radiators.

[1] These sizes may not *look* equivalent (based on 1" = 25.4mm) but they are actually much closer than that because imperial pipes are measured on the *inside* and metric on the *outside*.
Reply to
Roger Mills

This will give you the background info:

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?title=Domestic_Hot_Water_SystemsIn general terms:

More than likely.

Unless you have a particularly unusual design then chances are what you have will be fine if not too badly corroded. Modern systems are usually designed to run slightly cooler than older ones, so you may need to swap some rads about if you find some rooms are on the cool side and balancing alone does not fix it.

It can, but the cold water cistern would need to be raised up above it on a suitable platform.

This is a deep question. Have a read of the links above to get familiar with the options.

Reply to
John Rumm

Almost certainly. There may be limitations, eg not being able to have the CH on without the HW.

You can have a combi boiler feeding eg one shower and the kitchen sink, and run a hot water cylinder off the 'radiator' half of the combi for baths etc.

Owain

Reply to
Owain

Try the BoilerChoice FAQ below. The wiki pages are good too.

Reply to
Ed Sirett

Thanks very much for taking the time to reply.

"Not unless the current radiators are shot - which they *may* be if the system has been run for years without inhibitor, so that they have rusted inside. In this case, fitting a new boiler - which will almost certainly use a non-vented (pressurised) system - the extra pressure may just be the last straw which may cause them to start leaking. On the other hand, they may be perfectly ok. " - Is there a test that can be performed to check for the integrity of the radiators/pipework?

Any recommendations on brands of boilers?

Thanks again

Reply to
tvmo

You can pressure test the whole system with air, using something like

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would, of course, have to put temporary caps on the feed and vent pipes.

If you're removing all the radiators to give them a good flush out with a hosepipe (very worthwhile if you're upgrading your system) it woudn't be too difficult to devise some connections [1] which would enable you to apply mains pressure (4 bar or so) to each rad in turn. This is well within the design spec of the rads - but higher than the running pressure of a non-vented system - and will quickly show up any weak spots.

[1] e.g.
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+
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Reply to
Roger Mills

Thanks for the reply.

So in a nutshell:

  1. I can replace the boiler for a modern one without changing the pipework [1]
  2. I can replace the radiators for modern ones without changing the pipework [1]
  3. I can have the cylinder in the attic as long as the water cistern is above it and the supporting structure is adequate

Is a system where you can heat up particular zones quite easy (and affordable) to achieve, e.g. where you can heat up the downstairs during the day, whereas the upstairs remains cool?

Really appreciate all the advise thus far, thanks.

[1] This is on the provision that the pipework is pressure tested and found to be sound
Reply to
tvmo

That's about it. But you may not *need* to change either - you can increase the efficiency quite a lot just by updating the controls.

Zoning is easy (and relatively cheap) to achieve in *principle* - simply by adding motorised zone valves, each controlled by a timer/thermostat - and tied together to operate the boiler and pump whenever one or more zones are demanding heat.

In practice, the ease or otherwise depends on how the system is currently configured. If there are already separate upstairs and downstairs circuits, it's dead easy. If (as often happens when the downstairs floors are solid) there is only one circuit running between the floors, with pipes going up to the upstairs rads and down to the downstairs rads (like my house!) it's much more difficult to achieve zoning. The only realistic choice then is between no zoning, and one zone per *room* - which gets pretty messy and expensive.

Reply to
Roger Mills

That's brilliant, thanks very much for the advice.

Now the hard bit, does anyone know a good plumber in the Bridgend area, South Wales?!?!!!!!

Reply to
tvmo

And that the existing pipework has sufficient controls eg radiator valves to meet Part L of the building regs.

Owain

Reply to
Owain

Rad valves only in the sleeping areas to meet Part L.

Reply to
Doctor Drivel

Thanks guys.

Any advice on what brand/type of boiler I should go for?

Is there any type of radiator that is better than another, i.e. high- efficiency, low ongoing costs?

I've got 13 rooms in the house, can anyone give me a rough estimation on how much this is likely to cost?

Any advice on how to get the best price and advice out of a plumber?

Cheers

Reply to
tvmo

Not from me ..gas? oil? nucleasr fission :-)?

No. All the heat that goes in comes out. Soemwhere. That's the odd things about radiators. All one can say is that of your CH pipes go OUTSIDE teh insulation - i.e. through a cold roof - the bigger teh radiator the lower the tempearture they need to run at and the less losses you will get.

If your boiler works better at low temperatures alos, thenuse larger rads also.

A fair bit. Id say between 5 and 7k but thats a guess only.

Ignore the advice, and get him to sign a written contract. ;-)

Reply to
The Natural Philosopher

Can we just recap a little? What is your rationale for convincing yourself that you need to spend *anything*? How old is the existing boiler? Is it reliable? Can spare parts be obtained when necessary?

Is there anything wrong with the existing radiators? Are they adequate? [In other words, have you calculated the heat losses for each room, and compared them with the rated outputs of the relevant radiators?]

Why employ a plumber - this is a D-I-Y ng!? If you want to employ someone to do whatever needs doing, at least educate yourself sufficiently to be able to do it yourself - then you can discuss things on equal terms and not be confounded with BS.

Reply to
Roger Mills

The boiler is at least 24 years old. Not sure if it reliable (I haven't moved in yet), but I know it is very expensive to run. Parts are not available, I've tried.

"Is there anything wrong with the existing radiators?" - I don't know I haven't moved in yet "Are they adequate? [In other words, have you calculated the heat losses for each room, and compared them with the rated outputs of the relevant radiators?]" - I don't know I haven't moved in yet, plus I wouldn't have a clue on what to do anyway

"Why employ a plumber - this is a D-I-Y ng!?" - Is changing a boiler a DIY-thing, I wouldn't have thought so? Good idea if you have enough time as well.

"If you want to employ someone to do whatever needs doing, at least educate yourself sufficiently to be able to do it yourself - then you can discuss things on equal terms and not be confounded with BS" - why do you think I've subscribed to this group? I'm open to suggestions, are there any good books about installing a central heating system?

Thanks

Reply to
tvmo

Fair comment!

Have you looked at the FAQs suggested by Ed the other day? They are a good starting place - namely:

The FAQ for uk.diy is at

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fitting FAQ
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CH FAQ
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a Boiler FAQ
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Reply to
Roger Mills

I did look over the articles but, and I may be being a bit thick here, I didn't see the practical issues discussed re installing a complete central heating system. Bar the pipework (hopefully!), that is the task I will be undertaking.

Thanks.

Reply to
tvmo

The boiler choice FAQ is specifically written to answer some of the questions you are raising.

The wiki.diyfaq.org.uk has a few pages such as

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Reply to
Ed Sirett

Are sealed systems better than open systems?

Reply to
tvmo

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