we’re looking at a new boiler, which is for a commercial property for my partners new business.

we only need hot water – i.e. no central heating. The water demands are intermittent and mainly for washing several times a day. We need hot water on demand, but not massive quantities (not running a shower or multiple taps etc).

at the moment I’m leaning towards a combi boiler, which (from what I can see) should be easy to install. We’re putting it on an external wall close to the gas supply. I have routed the other pipework through to here already. We just need a plumber to install the boiler, do the flue and connect it up.

We’ve had a quote from a plumber who says a WB combi boiler will need at least one radiator to stop the thing overheating. Does anyone know if there are combi boilers out there designed for hot water only without the need for this?

The quote is also pretty high for what I reckon is 1 day’s work, but maybe i’m underestimating it! He’s quoted £500 parts/labour plus the boiler.

As an alternative we have also looked at a vented cylinder with electric immersion heater. I’m expecting this will be way more expensive to run, but possibly cheaper to install. Also with our relatively hot water needs maybe it will be cost effective afterall. Is there an easy way to estimate this?

we’re on a tight budget, and basically want the cheapest hassle free solution over a 2-3 year period

Water heater?

Just a thought….

Our office just has an electric water heater under the sink, cold feed in, hot water out.

http://www.mainheating.co.uk/324.htm

Where are you based?

Not sure what you plumber does with his boiler in summer? My combi has a switch that’s either off, HW or CH & HW. It manages to produce hot water for 6 months of the year with the CH switched off, so I can’t see why it needs a rad. But I’m not a plumber.

It’s actually a registered gas engineer you need, not a plumber. It’s perfectly legal for you to fit the water pipes to the boiler, but you need somebody on the register to do the gas (and probably the flue) and commission it.

Not sure what you plumber does with his boiler in summer? My combi has a switch that’s either off, HW or CH & HW. It manages to produce hot water for 6 months of the year with the CH switched off, so I can’t see why it needs a rad. But I’m not a plumber.

Because a hot combi will keep the pump running after hot water demand and dump the water into the heating circs to cool the appliance. Switching your boiler to water only still allows that to happen

I have seen these water heaters online but worry that they might not be man enough. We still need it to heat a decent flow rate of hot water. I’ve not used one myself, so dont know for sure if they are powerful enough?

The tech info on the site gives you a temperature at any given flow rate.

They state 10.8 @ 30Degrees and 6.5 @ 50Degrees.

The temperature is usually how much you can expect the cold water temperature to rise. Obviously the slower you run the tap, the longer the water stays in the appliance, the hotter it gets however on the water heater lit, it’s stating the temp rises as MAX, so I’m wondering if that’s the actual highest temperature you can expect at that flow rate. That’s a bit sneaky as standard practice is to list the rise in Degrees C.

A 30KW Main combi will probably do around 35Rise at about 12Litres, and may or may not work without somewhere to dissipate pump over-run heat to.

If going for a combi, I’d go for a Worcester.

Paul – that’s what I understood from what he says – empty CH pipes is not good for it. you I just wonder whethr the radiator itself is needed or if a short loop will do the trick

if we went the water heater route, can anyone advise a suitable type? this is new territory for me

thanks for your replies

You would at least need to loop the flow and return, or else the boiler will overheat after dhw demand.

Paul – that guide for the Main gas boiler says “Delta T” which i take to mean the temperature rise. I need to measure our flow rate, but I think it’s probably 10 l/min

At home we have a Worcester 30CDI which is great, and easily copes with the flow rate and gives a decent temperature. this is the benchmark for me, at least I know what it can do!

However if that’s a 30kW system, I am not sure how a 12kW electrical instant water heater will deliver enough heat. If one does exist, I’d be really happy to use it as this is much easier to install.

.. well surprise.. that ‘water’ pipes form part of a saftety device and technically not appropriate for a non ‘competant person to install..

and from the misunderstanding of what part the ch plays in the delv of the hot water by some posters above non ‘competant covers it pretty well..

half way through my competancy exams again ( every 5 years) it emphasised to me agin how much competant persons undervalue and under sell thier skill and expertise..

your not buying a chaps ‘labour’ for a day your paying for a properly qualified person to install a very expensive and potentially lethal device and to guarentee its safety..

how much would you pay your solictor/ driving instructor/ physio/ vet/ dentist hair dresser for a Full days work if they had to bring all thier equipment to your home..

Hi totalshell

I totally agree with your comments and realise the importance of gas safety and respecting somebody’s qualifications. I’m not questioning his advice about the CH heating as I can understand now why this is needed to but as it seems to be adding extra costs I’m looking for alternatives.

the price he is charging seems high compared to the boiler I had installed at home, which took 2 days to get the pipework in place. that work isn’t needed in this case. Maybe this us a fair price, I’m not sure which is why I’m asking. out of interest what would you be charging?

Do you have any experience of the electrical water heaters mentioned above?