I currently have a two bedroom house that has a central heating system and seperate immersion heater for the hot water. The central heating system is rubbish, it eats gas and the radiators barely get hot, and some of them hardly warm up at all. Recently the pump has started making a noise too, sounds like a cavitaing noise, or it could simply be on its last legs. The pump is under the fitted kitchen, which is not good....
The CH system runs through the immersion heater, and is supposed to heat the water in there up - I guess that if it was working properly it might do, but at the moment it just warms the water enough to have a wash in.
I don't know whether to get rid of the lot and have a combi boiler fitted or replace the existing boiler and pump in the hope that it would heat the hot water in the immersion tank enough. I am tempted to maybe go for the latter, but the downside to this being that when the CH is switched off in the summer I won't have any hot water.
The other thing is, I have recently been asking around for prices on a combi fitted and have been appalled to the point of disgusted at the prices that the plumbers charge, I know that they make a lot of money, but the prices have been ridiculous. If anyone could PLEASE recommend me a reasonable plumber/heating engineer in the West Yorkshire area I would be eternally grateful.
Any plumbers in this area reading this please feel free to contact me on
Well, you could start by having someone investigate what's wrong with your current system. It could be something quite trivial. It would have been interesting if you said what model/age your boiler is -- might have got some hints on replacement verses repair. The problem may not be in the boiler anyway, in which case just replacing it won't fix the problem either.
BTW, central heating boilers are quite capable of heating a hot water cylinder without also heating the house (unless wrongly plumbed or faulty).
Thanks for this info - the boiler is a Glow-Worm Space-saver Balanced Flue Boiler. It looks quite old and looked old when I moved in here 10 years ago. I havent been able to afford to do anything with it until now.
Get a CORGI engineer to come along and check it -- I presume you haven't had it serviced for 10 years, and that alone might be what's wrong with it. Unless the engineer thinks it's beyond economic repair, get the engineer to service it and explain the controls (timeswitch, thermostats, heating/hot water control) to you. It might be that it would benefit from having more modern controls fitted.
I used to have one of these in a previous house and yes it is. These are around 20 years old and were never a quality product in the first place.
Some types of boiler have four pipes, with two (usually larger) going to the HW cylinder and two for the heating. The HW circuit works by convection (commonly known as "gravity") - i.e. it naturally circulates by water heated by the boiler rising and on being cooled by the cold water in the cylinder, falling. This tends to heat the water quite slowly. The heating circuit runs from a second pair of pipes and has a pump to circulate the water.
The second arrangement is known as fully pumped and has a single pair of pipes from the boiler. I am pretty sure that this is what you will have. There should be a diverter valve somewhere or other (typically in the cupboard where the HW cylinder is), and the pump will circulate the boiler water to either the cylinder, the radiators or sometimes both in some designs
The valve should be something like this
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that in almost all cases, the water in the boiler circuit (primary) is kept separate from the hot water that you use by there being a coil in the hot water cylinder. There is a cylinder type called a Primatic, where the CH is filled from the HW side, but these are unusual. If you go into your loft, and you have a large and a small tank, you don't have one of these.
Given that nothing has been done to this system for ten years, and possibly the ten years before that, it is quite likely that it is full of sludge as a result of corrosion of the radiators. It is also possible that the diverter valve (assuming there is one) is stuck and not operating. This can be the explanation of poor performance. Typically when sludged, the radiators will remain cold at the bottom.
It may be possible to rescue the radiators by having the system thoroughly cleaned. This can be done as a DIY job by draining and flushing the system at each radiator, or by renting a power flushing machine. Alternatively, if you haven't done plumbing work before, getting a reputable heating engineer would be a better bet. Beware here. There are outfits who specialise in this work and are rippers off par excellence. £500+ for a clean is not unusual. British Gas are cream of the cake with prices around £800 not being unknown.
The boiler might still be servicable. The cylinder could be OK, but won't be high performance. If you are in a hard water area, it is probably scaled up and not performing well.
Given the age of everything and lack of maintenance, it may well prove more economic to take everything out and fit new things. You may need new radiators anyway if there are signs of any leaks from pin holes etc.
Then the choices are replacement with a similar system (new boiler and cylinder) or going for a combi boiler.
If the size of the existing boiler suggests that you have a one bath or one bath and a shower not used together household, then a mid range combi of 15 litres/minute HW rate may be enough for your needs. There are larger models available for if you use bath and shower concurrently, but these are usually physically quite a bit larger, so if you have a space constraint you may have to site somewhere else. Also, before going for a combi, do check the cold mains supply rate. Using a container of known size, time how long it takes to fill at the kitchen cold tap. If the flow rate is less than about 20 litres/min, a combi will be disappointing. Keep in mind also, that even a 15lpm one will normally take longer to fill the bath than your present system.
This gives a rough idea of the issues. You really need to invite some heating engineers along to quote for fixing/replacing as appropriate.
I am using exactly the same boiler in my 3-bed semi and it works fine with separate water and CH as per normal installation.
Indeed they are an old model now and I have an eye on replacing it in the foreseeable future but providing it is suitable maintained there is absolutely no reason why it should not do all you require.
It could simply be the pump or a clogged up system I guess. I agree the danger with some plumbers ( BG included ) is that they wil condemn it on sight. Best rely on the personal recommendation fo a friend or colleague.
Andrew Gabriel and Andy Hall have given comprehensive answers on which I can't improve - but I will add a couple of additional comments.
First on terminolgy - because it helps to use correct descriptions when discussing things with plumbers. An immersion heater is an electrical heating element, fitted to a hot water cylinder, to heat the water inside the cylinder. You may or may not have an immersion heater - but even if you have, it's not really what we're discussing here. What you have *definitely* got is an indirect hot cylinder, which has a coil of pipe inside - through which hot water from the boiler passes in order to heat your domestic hot water, without actually mixing with it.
When everything is working properly, the water from your boiler heats both the domestic hot water and the radiators. It is perfectly feasible to heat
*just* the hot water in summer when the radiators are not needed. There should be settings on your programmer to permit this.
Now for something you may be able to do in the short term to help the immediate problem. In the attic you should have two tanks - a big one and a little one. The little one is the so-called fill and expansion tank for the primary circuit - that's the water which circulates from the boiler through the radiators and through the heating coil in the hot water cylinder. It is disctinctly possible that this small tank has run dry - starving the primary circuit of water, and causing poor circulation/cavitation, etc. It is supposed to be topped up automatically by a ball valve. But, because the ball valve only has to operate occasionally, it is quite common for it to stick shut - and to fail to open even when the water level drops.
So, find the small tank, and make sure that there's a few inches of water in it - freeing up the ball valve, if necessary. Then bleed all the radiators and anything else which is bleedable in your system. You may find that things then improve considerably.
Even if this does make things better, you should still get the system checked by an expert - and the boiler serviced - as soon as possible.
Wow, thanks for all the useful info guys, I am amazed at how quick and comprehensively you answered.
I am going to attempt to drain the CH system so I can take a look at various things such as whether their is sludge in the radiators. I know that there are two valves at the bottom of the radiators that I can turn off in order to remove the radiator, but it seems that when I try to undo the big nut holding the radiator to the valve it twists the valve and loosens the compression joint underneath it causing leaks, so it might be easier to drain the whole lot and start from there.
So the question is - how do I drain it? I am presuming that there is some kind of drain point somewhere, most likely at the lowest point of the circuit. The pumb is underneath the kitchen floor and this would be the lowest point, would it be a good place to look? Also - will there be some kind of connection for a hose or something?
I would suggest that you ought to check the F&E tank - and make sure that there is water in the system - *before* resorting to draining it. That may be all you need to do in the short term.
With regard to draining radiators, if you remove the plastic knobs or caps from the valves, you can usually grab the valve body with *light pressure* from a Mole wrench used from above (so that the end of the spindle disappears into the jaws) - in order to support it whilst undoing the union nut, so as not to strain the pipework.
It sounds as if you have wooden suspended floors downstairs - in which case a lot of the pipework will under the floor. If you're lucky you might find a drain tap with a discharge pipe going out through an airbrick. That would enable you to drain the whole system if you really want to - but I don't think I'd be doing that at this time of year unless absolutely necessary.
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