Ideas for new heating/HW.

[nospam]

Hi,

I'm sure my heating/HW system needs upgrading so I would be grateful for some good advice on what type of system to install. My house is (currently) a 3 bed/1 bath semi with a 15 year old gas Baxi back boiler feeding a primatic cylinder. The CH system is older - I would guess at least 25 years old.

In spite of the system being old my gas bill is very reasonable at £20 per month but I hate the fact that the hot water takes over an hour to warm up (gravity fed cylinder), the boiler is noisy, and the CH takes hours to warm up the house (it does have a pump though). One radiator keeps filling up with air and I have to bleed it every few days. Another radiator gets full of "sludge" and I have had to clean it out every couple of years.

An added complication (!) is that we are going to build an extension on the house, which will add an extra bed/bathroom. The existing airing cupboard will have to be removed too.

I like the idea of a combi boiler so that we can have instant hot water (and we won't need to build a new airing cupboard), but I am worried it won't be able to cope with two bathrooms.

Can anyone suggest options that would be suitable and relative installation costs? I'm not too worried about operating costs because it'll hopefully be cheaper than now.

TIA Mark

[Christian McArdle]

Purchase costs are approximately:

Instantaneous combi - 400-700 Unvented cylinder/system - 1300 Heat bank/system - 1300 Vented cylinder/pump/system - 900

These include basic controls and zone valves. Add 200 for condensing type. Installation costs are very variable. However, the combi will be cheaper to install than the other systems. Assuming few pipework changes (i.e. boiler and cylinder in original locations), expect around 800-2000 for installation costs. Combis come cheaper.

The instantaneous combi will provide excellent showers, but poor bath filling performance. Also, you'd need a big one to get to use both showers at once (i.e. 35kW) which can affect heating performance as some types won't modulate down enough and start cycling.

The unvented cylinder and heatbank will provide oodles of mains pressure hot water, superlative for both baths and showers (and excellent for washing cars with extending foaming brushes too!) In "combi" terms, these systems are 100kW+ to the water.

If your mains water flow rate is poor, then consider the vented/pump option, which provides similar performance to a good mains storage system at the expense of the noise and reliability problems with pumps.

There are also unvented/heatbank systems integrated into the same case as the boiler. These will usually be somewhere between combi and separate storage systems in both price and performance, although there are also some very highly specified systems in this form, too.

Whatever you choose, ensure you end up with a sealed, pressurised, fully pumped system. If you don't want an airing cupboard, but plump for a storage system, consider installing the cylinder in the loft where the cold water tanks used to be. You can even install the boiler up there to free up more space. However, this can get expensive due to all the pipe and cable runs, and the loft will have to be boarded and lit, with a loft ladder and banisters. It does mean the flue goes through the roof, which can be particularly useful for condensing boilers with their plumes.

Christian.

[IMM]

installation

Here they go again, old wives tales. A large flowrate combi will fill the bath in no time at all.

Most go down to approx 7.5 kW and some to 3 kW.

[IMM]

Mark,

You would be wise to assess the Alpha CB50,

, or similar like the Worcetsrer-Bosch HighFlow, mentioned an other thread here. It will do two showers and fill a bath pronto. If you want to fill two baths at once then it will slow down, but how often do you fill two baths at once?

For an even better flow rate and cheap too for what you get, assess using two Worcester-Bosch Junior combi's.

For high flowrates it is cost effective to use two Juniors and combine the DHW outlets. Worcester-Bosch will supply a drawing on how to do it, or ask me here. Two Juniors are available for around £1000 to 1100 depending on what sized units you buy. They have 24 and 28 kW models, you could use two

24kW or two 28 kW combi's or one of each. That is cheaper than the Worcester HighFlow 18 litres/min floor mounted combi and can deliver about 21.5 litres/min and never run out of hot water. The highest flowrates of any infinitely continuous combi is 22 litres/min, which is the ECO-Hometec which costs near £2K.

Have one combi do the downstairs heating on its own programmer/timer and one do upstairs. Natural zoning, so you don't have to heat upstairs when you are not up there saving fuel. The running cost will approx the same as a condensing boiler heating the whole house. No external zone valves either, and simple wiring up too. The Juniors are simple and don't even have internal 3-way valves. Also if one goes down you will have another combi to give some heat in the house and DHW too. Combine the outlets for the DHW bath pipes and all the baths you want very quickly and no waiting. Best have the showers on separate combi's. It will do two showers no problem at all.

The Juniors are not condensing combi's, yet overall heating costs will be equivalent to a one condensing boiler as the upstairs will not be on most of the time.

A win, win, situation.

Its advantages are:

- space saving (releases an airing cupboard). Both can go in the loft, or at the back of the existing airing cupboard.

- never without heat in the house,

- high flowrates (will do two showers and fill a bath in few minutes,

- No waiting for a cylinder to re-heat

- Natural zoning, one does upstairs and one does down

- hardly any electrical control work (running a wire to a programmers/stat and power to each,

- simple no brainer installation,

- minimal components used.

- less piping used

- cheap to run overall as upstairs would be off most of the time

- etc.

[Owain]

Mark wrote | In spite of the system being old my gas bill is very reasonable | at £20 per month but I hate the fact that the hot water takes | over an hour to warm up (gravity fed cylinder), the boiler is | noisy, and the CH takes hours to warm up the house (it does | have a pump though). One radiator keeps filling up with | air and I have to bleed it every few days. | Another radiator gets full of "sludge" and I have had to clean | it out every couple of years.

1. Flush the system out thoroughly (Andy Hall has posted instructions on how to do this - Google. Note warnings about sludgy water and carpets.) and use inhibitor.

1. Convert the HW primary to fully pumped and update controls. This will speed up hot water drastically.

2. *If* the Baxi boiler and your pipework allows it, convert the primary/radiators to a sealed system with a pressure vessel. (Watch out for any leaks in the radiator piping.)

The above 2 or 3 steps should all improve the existing system and will be needed before you fit a new boiler anyway.

| An added complication (!) is that we are going to build an extension | on the house, which will add an extra bed/bathroom. The existing | airing cupboard will have to be removed too. | I like the idea of a combi boiler so that we can have instant hot | water (and we won't need to build a new airing cupboard), but I am | worried it won't be able to cope with two bathrooms.

It's quite possible to have a combi run a hot water cylinder off its radiator circuit, so you could have instant mains pressure shower in one bathroom and the other bathroom off a cylinder. As Christian said, a pressurised system cylinder could go up in the loft. (A storage system can also give you an electric immersion system as back-up hot water if the boiler fails.)

Owain

[Andy Hall]

These seem to be your recommended products of the month along with the upstairs downstairs combi solution.

For those group participants who are planning slightly longer term projects, it would be a great help if you could post your one-size-fits-all recommendations for May, June and July as soon as you have looked at the manufacturer web sites.

This would enable people to plan for the May solution if they are buying then and avoid buying the April solution which clearly won't work after the 30th of this month.

.andy

To email, substitute .nospam with .gl

[PoP]

You are taking the p!ss and I claim my five pounds! ;)

PoP

[IMM]

Recommended solutions to the OPs needs.

< snip drivel >

[IMM]

< snip drivel >

[John Rumm]

With such a recommendation the original poster can probably at least work out which solutions to avoid now... he might also want to check the "Combi-Boiler Choice- ?Alpha any good" thread from a couple of days ago to see the shortcomings and oversights in this so called "win win" solution!

[IMM]

< snip drivel >

[Mike Tomlinson]

In article , Andy Hall writes

He'll be telling the OP to put Cataclean in his fuel tank next...

[IMM]

Another troll. Go back to local.yorkshire please.

[nospam]

I'm not sure what this means. Can you please explain?

Sounds good!

Thanks, Mark

[nospam]

I didn't think I could use inhibitor on a system with a Primatic cylinder. Is that right? (There's only one header tank).

Is it worth updating an ancient system? Or could it be cheaper in the end to throw it all away and start afresh? The radiators are all ancient - what's the chance that the pipework is alright? Also bear in mind that I am adding a new bathroom and two more rooms.

I was hoping that boilers don't fail that often :-)

Thanks, Mark

[IMM]

See my post on this.

[IMM]

You can. You have to put the inhibitor into the system on rad side.

Best rip the lot out as little of it is salvageable. It may take more time connecting onto the old stuff.

[Neil Jones]

extension

They probably don't, but you can bet it would be at the most inconvenient time...

[IMM]

Is there ever a convenient time.

[Christian McArdle]

To heat water quickly, you need lots of power. However, when heating the house, you need much less after the house is up to temperature (until the radiators heat up, it will use everything you can throw at it).

There are two ways of reducing the power when the house is warm. Traditionally, a boiler thermostat was used which turned off the burner when the water was too hot and turn the burner back on when it had cooled a bit. However, it is more efficient to have a variable (modulating) burner that simply turns down the heat rather than cutting the power.

Unfortunately, boilers only have a defined range that they can turn down to. Think of a gas hob. The big burner can only turn down so much, whilst the little milk pan burner can turn really low. The same effect happens with some boilers. If you get one that is too big, you may find it can't turn down enough. If this happens, it reverts to the turning on/off cycling approach, which is less efficient and can be distracting if the ignition is loud. Luckily, however, some designs of burner have large modulating ranges and can turn very low AND have a very high heat, too. So, if you decide to go for a high power instantaneous combi (i.e. 35kW), then one of the important parameters to compare is the lowest burner temperature. 3kW would be excellent, 12kW might not be acceptable, particularly in a small house or flat.

Christian.