My Boiler is on its last legs - had our annual service today and th
British Gas Crook, sorry, Man said spare parts were no longer availabl etc etc
So I'm preparing for the worst. We currently have a vented(?) system cold water tank in the loft and hot water cylinder in the Airin cupboard upstairs. Boiler itself is downstairs in the kitchen. W have an ensuite with a Shower cubicle - thermostatic shower valve fe by an Aqualisa pump from a hot and cold feed from cylinder/cold tank. In the main bathroom, I have a power shower fed form the same hot an cold tanks.
Seems as if opinion is certainly skewed towards Combi systems question (finally) is....will I need to replace my Showers (v problematic) or can they run with a new combi system or similar. I' plan to do as much DIY as poss - prep work and flushing etc etc - wha do people think I should do?
Same old. Keep the old boiler until it starts going wrong. Unless it is particularly old and inefficient, it is more environmentally friendly to waste a little gas and save on a lot of manufacturing processes (with horrible PCBs etc.).
If you're happy with the shower performance and don't mind the noise/space of the pumped tanked system, keep them. There will be much less plumbing to do and your system will almost certainly have superior bath filling performance.
High flow rate combis suitable for multiple simultaneous showers are much more expensive than the simple modulating system boiler you would need to run your existing hot water system. Standard rate combis are well priced, but aren't brilliant running two showers.
Fit a high flow combi and remove the pump. Check with the mixer makers if it is a high pressure model. Some can have the cartridge replaced from high to low pressure.
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Doubles the price of smaller low priced units. Two W-B Juniors can be had for around £1,000 and will deliver approx 20 litres/min. Look around for a
20 l/min combi and see what the prices are.
But it gives you so much more and highly cost effective. One combi does one shower, one the other, with one not robbing the other, combine the two for the bath to give a high flow. One does upstairs heating and one does downstairs heating, both with their own stat/programmers. Two totally independent systems. You can have the rad temperatures low upstairs and high downstairs as well. If one combi drops out there is always heat in the house and hot water (great bonus). No large cylinder taking up space and making the place look like a school boiler room, just small neat white boxes on the wall saving space. One poster has already done this with great success.
The only disadvantage is that there are two service costs. With two boilers side by side a deal can be struck to reduce this.
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Or you could just keep the existing system and spend 500 quid on a single boiler, forget all the combi nonsense (with attendent expensive/time consuming replumbing) and have 80 litres/min.
£500 gets you from point A to point A. 80 l/min is overkill, and you will only be getting that for a few minutes before the cylinder is exhausted. Taken to extremes, the combi's will provide showers for as long as you want, all day in there with two showers going if you are that way inclined. The two combi's release valuable space and gives a natural simple zoned heating system saving money on fuel bills. No contest, the two combi's win hands down, on all points to gain zoned heating system providing two showers and bath and liberating space: Two combis win on:
Low capital cost of installation
Running cost, upstairs heating can be off most of the day.
No waiting for showers
Showers don't run out of hot water
Simple zoned heating system with independent time zones.
Different rad temperatures on different floors.
Less controls to go wrong, with accompanying down time and expense. (no zone valves and the likes)
Always heat and hot water. Two combi's means built-in redundancy.
Release valuable space for storage.
Only disadvantage is slightly more expensive on regular servicing, which is overwhelmingly offset by the above points
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Superior bath filling performance - absolutely, why anyone would ever want a combi escapes me, I can get up turn on the taps, have a piss, clean my teeth and halfway through a shave the full size bath is overflowing with steaming hot water. Wonderful. (and the tank still has enough for the old woman to have her long shower)
Using a combi on a warm day in the middle of a once in 500 years heatwave it would struggle to fill a 5 gallon bucket of bath temperature water in a similar time (despite the manufacturers claims)
A few words for combi's
"cheap s**te from europe suitable for smelly frogs" "the slowest way to run a bath - ever" "the crappiest shower you ever had" "a step back to the dark ages"
So you claim. However, claiming that capital costs are lower is simply false. The capital costs are over double.
Yes. You have to wait much longer, as you have to wait for the combi to fire up and get up to speed, unless you have one with built in storage.
Of course you can, if the boiler you choose has sufficient output (and the cylinder has sufficient input) to cover the showers, then a storage system would also not run out.
It's hardly rocket science to wire up S-Plan systems. The wiring is exceptionally simple.
It is extremely simple. If you're confused by wiring up a S-Plan system, then you should have put down the tools long ago. It is only fractionally more difficult that wiring up your iconic 2 combis.
Don't talk rot. They have crappy direct electric and gas heaters that have the efficiency of a lit fart. They have very few instantaneous gas heaters actually installed, although 24kW instantaneous electric heating is common enough, with the obvious limitations thereof.
Also, having two boilers means that your minimum modulation gets worse. In a marginal heating situation, bumping along the bottom at 4-8kW, you want the entire load on one boiler so it doesn't have to cycle unnecessarily. With 2 combis, you could have 2 boilers cycling instead of one pootling along at minimum, at much greater efficiency.
What's the make & model and is there actually anything wrong with it to warrant replacement or is it just BG "looking after their customers" by suggesting replacement?
Good point. You'd have thought a 'pro' - who claims to have installed such systems - to have known this. Perhaps some of his 'clients' might now sue him?
For what you gain it is not. Putting a new boiler on an old systems adds little value.
Are you having a laugh? You have to wait for the cold lag to empty in adraw-off in a storage system.
The boiler would have to be as big as the combined two combi's outputs, as when the stored water depletes you will be running on boiler output.
The wiring is NOT simple, especially to the uninitiated. The valves tale up space and are another thing to go wrong which is expense.
It ios NOT. see above.
You haven't a clue. You have been taking Andy Hall pills.
You still haven't a clue. Tankless on-demand (instantaneous, multi-point in the UK), is increasing market share in the USA. Want 50 litres/min for 2 hours on end? Get a Takagi multi-point at 380,00 BTU/hr.
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"No Spam" wrote in message news: snipped-for-privacy@4ax.com...
noise/space
You obviously haven't a clue what you are on about. read this.....and read it properly...
Here is a run down on combi's:
Firstly, a combi is a "combination" of the heating and water system in one case, eliminating external tanks and cylinders, and generally supply hot water at high main pressure. To confuse a little, some can run at very low pressures and even off tanks. Generally most are fed from the mains. It is generally a matter of mounting the boiler and connect up the pipes. The expert designers have done the hard work for you and put all in one case.
Types of combi:
1) The Infinitely Continuous Combi -
Heats cold mains water instantly as it runs through the combi. It never runs out of hot water. This is the most common type of combi, generally having lower flowrates than Nos 2 & 3 below. The largest flow rate instant combi is a two bathroom model, 22 litres/min ECO-Hometec. Being a condenser it is very economical too.
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Unvented Cylinder Combi -
An unvented cylinder is a similar to a conventional cylinder but run off the high-pressure cold mains. A combi with an integral unvented cylinder has approx 60 litre cylinder heated to approx 80C, with a quick recovery coil that takes all the boilers output. A fast acting cylinder thermostat ensures the boiler pumps heat into the cylinder ASAP with a recovery rate from cold around 5-8 mins (Ariston claim 8 mins). The 80C water is blended down to about 45-50C. e.g's, Ariston Genus 27 Plus, Glow Worm, Powermax, Alpha CD50.
An example being the Alpha CD50, a combination of both having a two stage flowrate, of high flowrate when using the stored water with an automatic flow regulator switching in to reduce flow to an infinately continuous flowrate of approx 13-14 litres/min.
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Heat Bank Combi -
Incoming water is instantly heated running through a plate heat exchanger (as is most instantaneous combi's) that takes its heat from a "domestic hot water only" store of water at approx 80C (instantaneous combi's take the heat from a heat-exchanger heater via the burner). A fast acting thermostat ensures the boiler pumps all of its heat into the store ASAP with a recovery rate about 5-8 mins from cold. The 80C water is blended down to about
45-50C. They are generally two stage flow rates, in that when the thermal store is exhausted it reverts to what the burner can produce, which is approx 11-12 litre/minute. e.g. Vokera & Worcester floor standing models (standard washing machine sizes).
N.B. The heat bank is a variation of a thermal store, but is "not" a thermal store in the conventional sense in that a coil carrying cold mains water runs though a store of hot water kept at about 80C. Heat-banks are far more efficient and give higher flowrates than conventional coiled thermal stores. The stainless steel plate heat-exchangers do not scale up so easily.
5) Combined Primary Storage Unit
(Not classed as a combi, but a derivative of a combi, but still a one box solution, so still in the same family)
These are a combination of a large thermal store, or heat bank, and boiler in one casing. The units are large (larger than standard washing machine size) and floor mounted. The heating is taken off the thermal store, which in many cases the DHW taken off the store using a plate heat-exchanger (heat-bank). Unlike the Heat-bank in 3) above the thermal store supplies heating "and" DHW, giving the "combined" to the title. They are available from 1 to 2.5 bathroom models. Gledhill do an excellent condensing version, the Gulfsream 2000.
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2), 3), 4) & 5) have high flowrates. No. 1 "generally" has low flowrates but there are always exceptions and some can be high - e.g. the ECO-Hometec infinitely continuous combi, actually has a very high flowrate. Nos 2), 3), 4) & 5) use stored water, but in different ways. Unlike No. 1 "some" versions will eventually run cold, but that takes quite a time, hence some are referred to as "two bathroom" models, having the ability to fill two baths with very fast recovery rates. As hot water is being drawn off the high rating burner is also reheating. Very rare do these combi's run out of hot water in average use. When taking one shower the burner may be re-heating faster than what can be drawn-off. No. 3) above uses stored water but will not run out of hot water (high and low flowrates). Most versions of No. 4) above are two stage flowrate models (high and low flowrates) and will also not run out of hot water.
There are combi models that give hot water and heating simultaneously as Combined Primary Storage Units do. Most don't as they are hot water priority.
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You're now just arguing that the extra capital cost is justified. This is very different from your original assertion that the capital cost was less.
Not only does a combi also have this cold lag (in addition to burner and primary circuit lag), but the much reduced flow rate means that the cold lag is of much greater time duration.
If you can't wire up a zone valve, you are not a competent person to do any electrics at all. It is less complicated than wiring a lighting point.
Whilst there is no doubt that it is increasing market share, it does not represent the installed base. I have no figures, but would guess that instantaneous water heating of mains water is more common in the UK than the US. It is not fair to compare the latest products in the US with UK products that were installed 20 years ago.
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