My mother has just bought a small 2 bed bungalow. It currently has a 20 year old wall-mounted gas boiler, wet plumber rads and a cylinder (Gledhill is the make of the cylinder, seems quite well insulated). There is also an electric immersion with a timer allowing usage of an Economy 7 tariff.
Any advice on how best to upgrade the system i.e. is it best to replace the system boiler and keep the cylinder or go for a combi?
What about controls? If you fit a good timer/room stat, is it worth putting TRVs on as well? I can't see the point unless you have some particularly oversized rads in certain rooms.
Would appreciate some advice before some plumber spends her pension on the wrong kit...
Tony
posted on 29-03-06
Power flush existing heating system then fit new condensing system boiler. If she can manage it don't fit a thermostat fit a chronostat this will control time and temperature and allow different temperatures at different times and also a night set back and frost protection. I prefer twin spring return motorised valves or a double pump. I also run the hot water all the time on demand by the thermostat this reduces scale build up and you never run out of hot water either.
Probably best not to go for a combi as you already have a cylinder and she will be lost without an airing cupboard I'm sure.
TRV,s a a waste of time in my opinion they jam up after a few years and mess up the themeratures of other rooms in the house. With the added danger of possibly causing condensation problems.
John Pedersen
posted on 29-03-06
Tony,
I was interested in your answer to this one ( I am about to fit a new heating system ). Would you mind expanding on this:
'I prefer twin spring return motorised valves or a double pump. I also run the hot water all the time on demand by the thermostat this reduces scale build up and you never run out of hot water either.'
for those of us less familiar with plumbing? I don't know what you mean by 'twin spring return motorised valves', and I don't understand how you apparently get on demand hot water from a system boiler. I'd appreciate if you wouldn't mind supplying a few more details here.
Thanks,
John
Tony
posted on 30-03-06
I'll try for you. From the boiler the flow of energy has to do two things , a) heat hot water and b) provide heating. To make this happen a pump moves the water in the boiler circuit round the system and to stop the hot water over heating or the boiler cycling unnecessarily a thermostat is fitted to the hot cylinder to tell it to stop firing, but as the heating may be needing to be on some way of closing off the flow to the cylinder is needed. And vica vesa. So there are various electric valves available to do this-- flow share, three way and mid position all use one actuator to do both jobs. I prefer to have a dedicated spring return motorised valve on each of (or all of) the flow pipes. Just years of hassels with the others messing people arround has led me to this place.
Now some of the heating pump manufacturers are making double pumps with one pump pumping the water round the hot water circuit and the other round the heating circuit, or both working together. Much simpler to wire up and I dont know why it wasn't thougth of decades ago.
I always make the hot water work without a clock or programmer just produce more hot water every time the temperature of the water in the cylinder falls low enough to click in the thermostat. Thus there is always a full tank of hot water and with the pre-insulated cylinders this never happens overnight only when enough hot water is drawn off to activate the thermostat. This is possibly not going to be liked by building regs but with all programmers it is possible to switch to "hot water on all the time" or "constant". The difference between my way and theirs is the heat lost by a cylinder of hot water compared to that lost by a cylinder of not quite hot water-- very little indeed. Prety much all the heat used to make hot water which isn't lost into the house goes down the drain-- here starts another story....
Nigel
posted on 30-03-06
One of the main efficiency benefits of a system boiler as opposed to a combi is that you heat the hot water in one long efficient burn and store the water in a very highly insulated tank. These lose about 1 degree over 24 hours. By leaving the boiler to heat the DHW all the time you making the boiler fire more often for shorter periods which reduces efficiency. I would therefore recommend you set your DHW to control to heat once or twice in the day to match likely demand.
Also I would advise that TRV's are a useful addition. I refurbished a vcitorian office building recently and added TRV's to all the radiators and achieved a 20% reduction in gas useage. It also improved comfort as there were less complaints about being too hot or too cold. TRV's also enable you to put less used rooms such as a spare room on a lower setting. Without a TRV the system will be entirely dependent on your room thermostat which may or may not be well located. If for example the bedroom has a south facing window and a slightly oversized radiator it will tend to overheat. A room on a north facing elevation will tend to feel cold. TRV's are very effective at balancing out all these inconsistencies
John Pedersen
posted on 30-03-06
Thanks for the additional info.
Separate motorised valves do sound like a good idea. Separate pumps too.
The system I am planning ( and hope to start installing within the next couple of weeks ) is a bit complex - a wood burner with boiler, a gas boiler, and a couple of solar panels, all linked into a Dunsley Baker neutraliser. I like the idea of all the heat producers being linked to the same point.
I'm not sure how I am going to find a controller for the system though.
The wood burner and the solar panels use thermo-siphon - the gas boiler needs a pump. I doubt I will ever need to use space heating without also wanting the hot water cylinder heated, so this may as well get its' heat via thermo-siphon from the neutralizer. I guess a second pump to run hot water through the radiators will be needed.
I am tempted to dispense with programmers, and just use a Heath Robinson switchboard to cover all the options ( or get a web-enabled programmer that will check if there will be enough sunlight to heat my water before using the gas - but then how would that work out my wood supply...? :) )
