We moved into our house 7 months ago. It has a gloworm back boiler a
the moment (it's old but not sure how old). Having a new centra heating system and all new rads and pipework. It's a fairly larg detached house, 2 double bedrooms and 1 large double bedroom, bathroom and a downstairs wc. We have 10 rads at the moment but wil need 11. The immersion and water tank are in the bathroom but if w keep them we would create more room in the bathroom and move th immersion to one of the bedrooms and the water tank to the loft. I'v spent ages on the internet looking at different boilers and systems bu cannot decide. We've had quotes for combi's, unvented cylinders an heat only boilers, the quotes being from £2500 to £6000 from variou plumbers, the combi being the cheapest. We've decided which plumber w are having (has a very good reputation). Would like advice on wha people think would be best system and which boiler to have
We moved into our house 7 months ago. It has a gloworm back boiler a
the moment (it's old but not sure how old). Having a new centra heating system and all new rads and pipework. It's a fairly larg detached house, 2 double bedrooms and 1 large double bedroom, bathroom and a downstairs wc. We have 10 rads at the moment but wil need 11. The immersion and water tank are in the bathroom but if w keep them we would create more room in the bathroom and move th immersion to one of the bedrooms and the water tank to the loft. I'v spent ages on the internet looking at different boilers and systems bu cannot decide. We've had quotes for combi's, unvented cylinders an heat only boilers, the quotes being from £2500 to £6000 from variou plumbers, the combi being the cheapest. We've decided which plumber w are having (has a very good reputation). Would like advice on wha people think would be best system and which boiler to have
We need more information about your expected water usage. In particular, we need to know:
How many people live there?
How many teenage daughters? (better not publish your address though!)
Does anyone in the house prefer baths?
Does anyone like having long showers?
Are you likely to add an additional bathroom, in a loft conversion/extension, say?
What is the maximum flow from your kitchen tap? (measure with bucket and timer)
Is your electricity supply reliable?
Is cost a major factor?
There are several possible solutions. The answers to the above questions will determine the best solution for you. Some possible suggestions are:
Instantaneous combi. The cheapest solution will provide unlimited length showers of good quality. Requires about 20lpm from the mains water supply. Bath filling will be slow. Temperature regulation will be poor, but not a problem if the shower mixer is chosen carefully. It will be the most energy efficient, assuming similar boiler types.
Unvented cylinder. This will be the most expensive solution. It will provide oodles of hot water at mains pressure, enough to drive the largest and most obscene panel shower with body jets. It will require yearly maintenance to ensure continued safety. It will fill a bath as rapidly as the water can enter your house down the supply pipe.
Heat bank. This will cost a fraction less than the unvented cylinder. Purchase costs are similar, but installation is simpler. It will also provide mains pressure hot water, but flow rates might be slightly limited if your mains water supply is really strong. It will still fill a bath in 3 minutes, so this isn't a problem. It is inherently safer than an unvented cylinder, reducing the need for maintenance, but might be slightly less energy efficient, as the condensing boiler may need to run at a higher temperature. Some installers will not have heard of them, and so may refuse to fit them. The hot water is never stored in this type of system, meaning that the hot tap provides drinking water (unless you have a water softener). This can be useful when filling kettles/saucepans, if you're not a patient type.
Conventional gravity system. This will be cheaper than the mains pressure options. It is a good system when the mains water supply is poor. When pump assisted, it can provide excellent shower and bath filling performance, as the expense of noise and pump maintenance implications. It requires a large cold cistern in the loft, which can be problematic if it is decided to have a loft conversion, or the loft space is not suitable for other reasons.
Some combi boilers work on the principle of (2) and (3) above, but with small stores. They can be useful in some situations, particularly when space is limited. However, they can be expensive, often more so than the full sized discrete systems they emulate.
There are 2 of us (at the moment) in the property. Shower mainly, occasional baths. Fairly long showers. If we added anything it would be an ensuite shower. Flow is approx 21 lp
There are 2 of us, no children (at the moment). Mainly shower, occasional baths. Fairly long showers. Would maybe add an ensuite shower, but that wouldn't be yet. Flow from tap approx 21 lpm. Electricity supply has been reliable so far. We would fit the rads and pipework ourselves and get the plumber to d the boiler. Around £1500 (maybe a little bit more) to spend on boile inc fitting.
OK, if you're happy doing the radiators, you'd be happy fitting a heat bank. It is plumbed in just like a radiator, but with additional mains cold in and hot water out. It is much more suited to quick DIY installations than a mains pressure cylinder, which has to have all sorts of additional safety equipment, pressure relief runs etc.
So, I would narrow your choices to a high flow combi and a heat bank system. Something like:
Worcester Bosch HE35+ for 1140 inc VAT. (instant combi)
or
DPS Pandora + Worcester Bosch HE28 for around 1500 inc VAT total.
You'll need to budget a few hundred to get a CORGI round to install the gas/flue, if you're not happy to describe yourself as competent for these tasks. You'll need more if it requires a new gas run.
Note that you won't get the full benefit of the heat bank at only 21lpm, although it will still be noticeably quicker than the combi and less prone to temperature fluctuation. However, you may find that after rejigging, the total throughput of water in the house actually exceeds 21lpm anyway. Kitchen taps often aren't as wide bored as they used to be and you can find the bathroom taps, with their twin wider passages can pass more water.
If you are replumbing the house, consider replacing all cold water pipework with 22mm bore (except runs to toilets and basins). Provided pressure is high enough, I'd then use 15mm for hot water pipework between tank and kitchen and either 15mm or 22mm from tank to bathroom, remembering that there will be more wastage and longer lead times if 22mm is used, although it might marginally increase flow rate.
It is what I paid for exactly that system. The boiler has since dropped around 20 quid. I got the impression that I could have got the Pandora cheaper if I improved my non-existent negotiating skills.
"Christian McArdle" wrote in message news:41e254a7$0$19160$ snipped-for-privacy@reading.news.pipex.net...
Not true - misinformation. Old wives tales. Some models fill baths as fast as a conventional cylinder.
Not true - misinformation. Old wives tales. On some models it is very good. This section is misleading as it is so sparse.
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.
Not so. They are reduced in pressure, whiuch can restrict the flowrate.
Nor so. This can be much more expensive than a combi system as a tank is in the loft, cylinder, etc, complete with a large amount of pipe and fittings
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