I have had people round from two different heating installers. They gave me conflicting advice and I need help to sort out which one, if any, was giving the best advice.
I live in a bungalow with a 15 year old 20 kW boiler, 8 radiators and an Elson? hot water system. This system has worked well but I want a new boiler before the old one gives up on me.
Company no. 1 said I need an 18kW boiler feeding a new indirect combination tank in the loft.
Company no. 2 said I need a 24kW combi boiler and no tank.
I use the shower every day and the bath very occasionally. People have told me that combi boilers take ages to fill baths. I do not want to wait 10-15 minutes for a bath to fill in case I forget it and wander off to do something else, but a little longer than my present system, 3-5 minutes would be ok.
Does anyone have experience of these systems and does one of them seem better than the other or should I go for something else?
My preference would be for a combi, but it's largely a personal preference thing - both have advantages and disadvantages.
A 24kw combi will be ample for the radiators and for showering purposes. Hot water flow will be slower - you'll probably notice it in the kitchen too. You'll get a higher flow from a higher power boiler - for about an extra =A375 you could get a 28kw boiler which would give a better flow rate, and hence fill the bath quicker. Any combi (except a storage combi) is goint to fill a bath more slowly than at present, so it might be worth buying a =A310 bath alarm if you go down this route - they beep when the bath reaches the required depth.
It might also be worth going back to each company and discussing the other option with them - they may be able to give more info on the pros and cons in your particular case and explain why they are recommending one rather than the other.
You might find it helpful to google back on this group since this question comes up pretty frequently. It also tends to start a holy war on frequent occations with pro and anti combi supporters championing their own pet solution.
Have a look at Ed's boiler choice FAQ (Ed is a professional gas fitter and well respected contributor to this group):
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I use the shower every day and the bath very occasionally. People have told
a 24kW combi will be in the 15 minute time frame during the winter (when the incoming mains water takes more heating), especially if you like a decent quantity of water in the bath. To get adequate bath filling performance, I would personally not considder a combi with less power than 35kW.
There are things you ought to check, like make sure you are getting a good enough flow rate from the cold main (use a bucket and a stop watch to check). If you can't get at least 15 litres per min then forget going the combi route.
To form a more complete picture it would help if we knew:
How do you like your shower? Plenty of power, or a nice gentle rain effect, or multiple body jets etc? What is your hot water useage pattern? How many others in the house?
My preference would be for a combi, but it's largely a personal preference thing - both have advantages and disadvantages.
A 24kw combi will be ample for the radiators and for showering purposes. Hot water flow will be slower - you'll probably notice it in the kitchen too. You'll get a higher flow from a higher power boiler - for about an extra £75 you could get a 28kw boiler which would give a better flow rate, and hence fill the bath quicker. Any combi (except a storage combi) is goint to fill a bath more slowly than at present,
See above also. And why would anyone with half a brain spend a fortune on an additional multi point to do the job a storage tank does for a fraction of the cost - and far more reliably?
I often wonder what world he exists in given he always seems to manage the most expensive 'solution' to the most simple of problems - like how to fill a domestic bath quickly. It's only been a problem since people have been conned into thinking an instant water heater of modest price is the answer.
There also seems to be a school of thought that a multipoint will be "cheaper" than a conventional system. But given the cost of labour it really makes next to no difference either way and it doesn't seem to save the fuel bills either.
"Vented HW cylinder. This is still the norm for most houses. With a modern cylinder and correct controls there should be no problem with running a bath every 15-20 minutes. Cylinders are now required to have a good level of insulation (not the old jacket insulation). New replacement cylinders will be able to heat the whole cylinder from cold in around 20-25minute,"
20 to 25 minutes? Only a quick recovery cylinder can do this. The normal art L is rated at 30 minutes warm up is all criteria is met in boiler temperatures, flow, etc. A quick recovery with a condensing boiler can reheat in 10 to 15 minutes depending on boiler size. They also enhance efficiency. There is no mention of quick recovery cyldiners in this FAQ.
"Unvented HW cylinder: Offers HW at mains pressure together with excellent flow. These are expensive and can only be installed by qualified people. To justify the expense you really need to have an excellent water main at least 25mm diameter plastic pipe. Results will be adequate but probably not worth the cost if used with an ordinary lead or 20mm plastic incomers. "
The all important annual service is omitted. It will cost £60-100 a year to have serviced
"Thermal store: Offers most of the advantages of the Unvented cylinders, costs are similar but may be diy installed. The flowrate is still pretty good (around 20 litres/min). Can be used to integrate other sources of heat (solid fuel, solar) or facilitate underfloor heating."
No mention of the heat bank variant of the thermal store, which can give flowrates of 40 litres/min or more.
"Normal combi boiler: Heats water only when it is needed. Instant availability (after the HW has drawn through and the boiler settled down - about 10-40 seconds). Never runs out. Simplified installation. Rather limited flow rate. "
Know as an "infinitely continuous" combi, not a normal combi. Some models have very high flowrates that fill baths very fast indeed (MAN made in Germany), although these are not available in the local plumbers shop.
"Small storage combi: As above but holds a store of HW to give a prompter response and improved flow rates for a while until the stored HW has run out. "
These are to elimnate the combi lag at the taps, giving faster hot water.
"Large storage combi: Washing machine sized floor standing combi boiler. Contains pretty much all of the benefits of a HW cylinder whilst still having a simplified installation. Saves the space that a HW cylinder would take. There are multiple decisions to be made based on trades-off between size, cost, flow rate, warm up times etc."
Some are larger than washing machines sizes. Some can supply three baths (Gledhill Gulfstream), ACV Heatmaster.
No mention of high flowrate wall mounted combis like the Alpha CD50, which is a mix of the infinitely continuous combi and a stored water combi. It is a two stage flowrate and never runs out of hot water.
No mention of high flowrate multi-point water heaters like the Rinnai and Andrews, which can also be fitted outside saving much space inside a house.
Overall 5/10 for this FAQ section. This is misleading and omitting information gives a distorted ill-informed view. I would not recommend people take this FAQ seriously.
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