Boiler Quotes - Help Me Choose!

MarkyMarkD

Hillfly wrote:

We have a 4 bed detached house and run a Worcester Bosch condensing combi boiler.
The hot water pressurte is great - so much so that we got rid of our pathetic electric shower and now use one that runs direct form the hot water system.
I guess it depends on the water pressure in your area but also i think you need to make sure you get a model of boiler that can cope with the demand you require. I'm sure any decent installer would advise you on this.

Yes, I do wonder whether my parents have just been sold a woefully under-specced boiler for their large house. But, the level of flow you want for your bath is the same whether you have one bedroom or five, surely?

mleonard79

Yeah Markymark it might well be the case they'be been sold something inadequate for their size of house. Not sure how that would affect the pressure though either. I'll keep you posted on what its like when the new system goes in. Thanks.

Michelle

ahll

The one down thing I have noticed about a combi boiler is that it takes a lot longer than conversional to fill a bath. I assume this is because it is heating the water as it goes.It can be annoying though but now I go off and do something while the bath is running.

MarkyMarkD

That's exactly what I'm talking about, ahll. It takes forever because the hot water pressure is rubbish.

moneysavingplumber

With combis there will usually be an increase in pressure, but a decrease in flow-rate, so showers are usually better provided they are of a type that don't use a vast volume of water, but bath filling times are usually decreased, as the average flow rate through a combi is 9-12 litres/min, and a conventional gravity system with sufficient head will deliver around 20 litres/min through 22mm pipe work.

One of the biggest problems with even high-flow combis like the Worcesters is when used with multiple bathrooms, or houses where there are large simultaneous draw-offs of hot water, they are not usually suitable in these circumstances.

It's worth making sure it's right for you before committing to changing over to a combi.

When changing from older conventional systems to modern condensing boilers, if there is any evidence of sludging in the system (i.e. low cold spots in the radiators) then it is now very advisable to renew as much of the system as possible, especially sludged radiators, as the smaller heat exchangers in these boilers are very prone to limescale formation when there is any impedance to the flow through the waterways, i.e. sludge in the system elsewhere.

MarkyMarkD

Thanks for the technical expertise, moneysavingplumber.

In my non-technical mind, pressure and flow rate are the same thing - I definitely meant flow rate, when I said pressure.

I would view a reduction in flow rate of over 50% as appalling - it already takes long enough to fill a bath.

The other problem with my parents' system is that the boiler doesn't seem to fire up very readily - so it can take ages until the first hot water flows. Admittedly first hot water can take a while in our house too, as some of the pipe runs are very long.

kenshaz

Building companies never install Combi Boiler into their new developments,they will not cope with the multi take -off ponts and ensuite bath-rooms of modern housing,if you want access to constant volume of hot water at a good flow,header tanks and indirect cylinders,if you want economy and sparse supply install a Combi

moneysavingplumber

MarkyMarkD wrote:

Admittedly first hot water can take a while in our house too, as some of the pipe runs are very long.

Long legs of pipe work can be a problem but in larger properties this is usually remedied with a secondary loop incorporating a bronze pump and pipe 'stat which ensure the water is hot close to the main point of use.

flossy_splodge

Can I be very cheeky and but in on this fascinating conversation please. I have just had a couple of quotes for a new boiler and absolutely NONE of this was mentioned by either company! Eek! How on earth do I figure out what I need if I can't depend on professional advice. I have an average sized 3/4 bed detached house which retains its warmth quite well. My existing boiler is VERY old and tempermental and it costs a fortune in heating oil. (No gas available in area). At present there is only me here but I will be selling soon and do not want to install a duff system that might cause a knowledgable buyer to back away. Any comments appreciated.:o

moneysavingplumber

Hi flossy_splodge,

One of the most important things if you are planning to sell is that the boiler is correctly notified to building control, which will need to be done by the installer via Corgi, and you will receive a certificate through the post a few weeks after the installation, and the buyers' solicitors will almost certainly ask to see this while the purchase goes through.

It is very difficult to speculate on what type of boiler or system your house will need, but it will certainly need to be a condensing boiler. If a 'regular' boiler is installed then it will have to be sized using the 'whole house' method, check it out here http://www.est.org.uk/housingbuildings/calculators/boilersizing/
, if a combi is being installedthen sizing will be based on required hot water output.

If you currently have a conventional (i.e. non-combi) then I would be inclined to stick with the type that you have. The things the quotes should include are everything mentioned in the above thread, most important are timer and room thermostat, thermostatic radiator valves on all but the radiator nearest the room thermostat, an automatic by-pass, to flush and treat the system with cleanser and protector and to balance the system for optimum performance.