No idea which system to choose. HELP!!!!!!!

[triedandtested]

This question has probably been asked a hundred times.

Which would you install in your home?
Combi boiler or unvented hot water system.

We are going to replace the whole system boiler and rads. Its a 4 bed house with two reception rooms, dining, kitchen, cloaks, en-suite and main bath.

Completely in a pickle as we have been getting different advise from different people.

The current situation is that the system is 16 years old. The house is generally on the cold side. The heating system is very noisy when on. There are 6 of us living here. If we go out as a family we always run out of hot water. Currently two power showers and traditional hot water tank. I must assume that its too small.

Been told that a megaflow unvented system is what we need with a very large tank. This plumber not keen on combis.

Also told that Ethos combi 54 is the boiler to have as it has a flow rate of 25litres/min. This plumber does not seem keen on the unvented system.

and I have read that you can have a combi with a hot water tank?????

Now we don't know where we stand?

All we want is to be warm in Winter. Be able to have hot water when going out. Run two showers at the same time if needed. Have hot water available at three outlets at the same time. Not have to wait 2 hours for the bath to fill with hot water. No loss in water pressure.

We have had a couple of combis in the past and never got on with them. Yet friends of ours have always had combis and think they are great.

I would appreciate some guidance.

 

[gas4you]

To make the most of an unvented cylinder you need to have your incoming mains tested for pressure and flow rate. This needs to be at leats 3 bar and around 20 litres / min. You will also need to have a 22mm cold mains supply to it, right the way back to your outside stop cock. If you don't have any of these then you will probably not get the performance you state you expect.

Upgrading if required will be costly. Even if you go for a powerful storage combi you will not get out what isn't going in.

The mains unvented route is usually deemed the best following the above guidelines and I would think that a 170 litre or there abouts would suffice your needs.

A powerful combi will have the disadvantage of requiring a large (possibly 28mm) gas pipe installed to it depending on how far the gas pipe run is.

As a rule if cost is no problem with your size property I would go with the un-vented, but not the megaflo.

 

[Dan Robinson]

Run two showers at the same time if needed. Have hot water available at three outlets at the same time

The holy grail eh!

The best way to achieve this reliably is with a break tank and unvented cylinder with a 3 or 4 bar pump set.

Not cheap though.

Where is the current boiler and cyliner?

A good system boiler and unvented cylinder is one solution. The Atmos Multi is another. Either can be run from the mains or a break system.

A combi will never satisfy your multiple draw offs. The Ethos might - but that needs a monster gas pipe, and I have heard rumours about their Customer service - they are just rumours. Although I picked one to pieces not too long ago and was not that impressed by the mechanical bits inside - same diverter block as a keston C36 as I recall.


Your budget will dictate you final system. Some people want what they simply can't afford - so be dilligant.

 

[triedandtested]

Thanks for the replies so far. I have a few questions and answers for you.

Current boiler in the garage, cylinder (900mm, 117 Litres) in cupboard next to bathroom upstairs.

Can I measure the flow rate by running tap and checking how much water comes out? How do you measure the pressure (bar)?

Why not a megaflow?

What would you class as a good unvented system?

Why would a break tank be required if the cylinder size of 170 litres is installed?

 

[Dan Robinson]

MEgaflo - made by Heatre Sadia, owned by Baxi = cr#p.

Break tank system has powerful pumps with both high pressure and flow. Your question there is somewhat irrellevant.

Oso, Tribune, Ultra Steel are all good makes of cylinder - there are others.

Pressure is measured in bars - you'll need test guage which can be fitted to the washing machine service valve. Flow can be done with a bucket and stopwatch - although both tests are only indicators and pressure can change.

With the info you gave I would think about an unvented system with the cylinder where the current one is, large cold wate sorage in the loft (current is likely to be inadequate) with a booster pump in the loft or by the cylinder depending on space. Down side to pumps of course is the noise, and I would feed the lavatories separeely so that pumps aren't turned on in the night if someone is caught short.

The boiler can be left as is and changed later as a separate project.

Ideally the tank is changed to unvented, you get a dry loft, there are no pumps, and you are run straight from the mains, but chances are the pipe leading through your airing cupboard is too small; and the pressure and flow would be too low.

 

[JohnD]

you say the heating system is very noisy when on. What sort of noise? Bangs, clonks, gurgles, hissing, bubbling, whooshing, whining?

How big is your hot water cylinder, and have you got room for a bigger one?

Is the cylinder heated using pumped supply from the boiler, or is it gravity flow? How long does the cylinder take to get hot again after you've run a bath?

You say the house seems cold. Does the boiler run all the time in cold weather, or does it heat up the radiators, then go off until the radiators have cooled a bit? Give me an example of a radiator size and the room size it heats.

Are the radiators fully hot all the way to the top and bottom, or do they have cold sections?

Whe you are heating the house in cold weather, do you leave internal doors open or closed?

Since the house was built, have you added cavity Wall insulation or improved the loft insulation? How thick is the loft insulation?

Questions, questions

 

[triedandtested]

you say the heating system is very noisy when on. What sort of noise? Bangs, clonks, gurgles, hissing, bubbling, whooshing, whining?

Hot water on by itself makea a noise which is a cross between clonking and gurgling.

How big is your hot water cylinder, and have you got room for a bigger one?

Cylinder 117 litres and yes room for a taller and slightly wider one.

Is the cylinder heated using pumped supply from the boiler, or is it gravity flow? How long does the cylinder take to get hot again after you've run a bath?

Gravity flow. Takes approx 1 hour but shorter with emersion.

You say the house seems cold. Does the boiler run all the time in cold weather, or does it heat up the radiators, then go off until the radiators have cooled a bit? Give me an example of a radiator size and the room size it heats.

House 16 yrs old. Boiler runs all the time in cold weather at weekends. During week 6.30-8.30am and 5.00 to 10.00 pm. Its on all the time no individual regulators on radiators. Front room 14x12. Rad 1800x450 double,single fin.

Are the radiators fully hot all the way to the top and bottom, or do they have cold sections?

Some colds sections can be at top, middle and bottom. Rads are bled approx every month in colder months.

Whe you are heating the house in cold weather, do you leave internal doors open or closed?

We try and keep the doors closed. However with 4 kids thats not always practical
Since the house was built, have you added cavity Wall insulation or improved the loft insulation? How thick is the loft insulation?

We have only been in the house 12 months. No cavity wall insulation to our knowledge. Loft insulation increased to 8 inch.

Questions, questions

Hope I have answered them correctly.
The two power showers make a lot of noise. Pumps situated in cylinder cupboard.

People seem to have an opinion on which makes of boiler not to fit. I would like to know which make of boiler they would fit.

I seem to get the idea of the quality of what goes in to the system reflects on the quality of what you get out. I'm still not sure what would be classed as a quality system.

I get the feeling that a combi boiler is not the way to go.

Any ideas on how to find a engineer to install this system that would know what they are doing. Not sure of anybody at the moment. The closest anybody gets to measuring the pressure is turning on the cold water tap for 5 secs and going that looks ok.

I get the feeling that maybe these engineers are not as thorough as they could be. I do not want to spend 1000's on the job for them to turn around and say well I installed it as the manual said, therefore its nothing I have done. I want somebody who knows what they are doing from the start and can highlight the potential problems. I think its called planning. Does that type of enginner exist. I believe so from reading this forum. But I could do with finding one.

 

[JohnD]

a few suggestions:

The radiator size you mention sounds OK.

You really ought to have TRVs fitted and they will save you money.

You do not mention a room stat but I hope you have one.

If your boiler is running constantly in cold weather it might be undersized for your house. I used to have an undersized boiler until I improved the insulation, then it became more than big enough.

Your loft insulation sounds fine.

Gurgling, clonking, cold sections, regular bleeding. Sounds like gas and sediment due to corrosion. Giving the system a chemical clean, and preferably fitting a Magnaclean, is easy and probably a DIY job. This will improve the efficiency; cut the noise, clear the cold spots, make the house warmer. It will need cleaning anyway if you are going to buy a new boiler (or the new boiler will get clogged up and the pump will fail early) so you may as well do it and get the benefit while you're deciding what else to do. It might take you an afternoon to drain, fit the Magnaclean, and refill with cleaner, then after a couple of weeks, another afternoon to drain, rinse and fill with inhibitor. In between you can open the Magnaclean and marvel at the amount of old sediment you can take out of it.

BTW it is much easier, cheaper and better to clean the system before it gets a blockage, rather than after. If it is really bad and you are short of time but not money, you might need a Power Flush which costs hundreds of pounds but is done in a day.

Cavity insulation only costs a few hundred pounds but makes an amazing difference in keeping your house warm.

Slow reheat of cylinder will be because it is gravity feed. You might get a small improvement by improving insulation of pipes, but a modern cylinder, fully pumped, goes to hot in 20mins. It would be possible to change to fully pumped without buying a new boiler or cylinder.

I am just a householder, not a plumber or heating engineer but have done some of these things. I happen to like stored hot water, not combis, especially if you have a house with several people who may use several hot taps at the same time.

 

[simond]

Measure the water flow.

Investigate how to raise it if you want three showers simultaneously and you have less than 30l/m.

If upgrading the water main is difficult or unlikely to deliver the flow rate my advice would be to forget break tanks and pumps and fit an accumulator. We fit 100s of them in the South East and unlike break tanks there is no noise, no loss of water in a power outage, no power consumption, no dead flies in the tank that you wash your teeth in, no problems of water stagnation, I could elaborate but have done so elsewhere......

 

[triedandtested]

We are intending to replace the boiler, cylinder and all rads. TRV's are essential.

What on earth is an accumlator. whats its purpose.
Maybe you can post a link to where you wax lyrical about the item

Please can anybody advise which make of boiler to consider and which size. Close to dismissing combi as system

 

[Dan Robinson]

An accumulator builds up pressure from the mains and holds it. It does the same as a break tank and pump in a different, and as Simon says, silent way. Although (as I understand it) it is dependant on having good mains pressure to begin with.

Either way I would look at this:

http://www.atmos.uk.com/core_files/productDoc(83).pdf


I have one at home and we have fitted many over the years with no realiabilty issues. They work as a Megaflo, but are much more efficient and burn naff all gas when compared to similarly performing appliances.

They will work from the mains, tanks (with pumps) or an accumulator - in fact you;'ll see an accumulator a few pages in.

 

[triedandtested]

What about the folowing makes of boiler

Vaillant, Worcester, Veissman, Kidd

Are they any good

 

[gas4you]

All 3 are probably the best on the UK market at present and I would put them in the order you have listed. The Veissman in 3rd, only due to their rubbish after sales service should you ever need it.