Worcester Condensing Boiler

The_Latman

Hey Folks,

Looking for some advice on a condensing boiler. Its around a year old at most. I moved into a 20 year old house which has this Worcester a+ energy rated boiler. I recently found out that my gas bill had leapt up by around £245 since November when I last submitted a meter reading.

My boiler was set around the 3/4 mark on the front dial when we moved in. Ive turned that down as I read that these boilers are supposed to work really well on lower settings, however had to turn it back up over the weekend due to the extreme cold outside and the fact that the house wasn't really getting anywhere near the thermostat setting.

The rads are getting hot to touch and I was just wondering about any general advice on these kinds of boilers. I had read a couple of things:

1. Condensing boilers work extremely efficiently at low settings, so keep the boiler set low.
2. British Gas recommend turning the boiler to full over the winter and allowing the thermostat to control it.
3. Should CH and HW programs be on at the same time?

The boiler was serviced in October and we had Hive fitted then as well. The heating has been on this morning since 6:30 and its supposed to reach 21, yet has slowly increased to 18.8 from around 15 degrees. I turned the boiler knob down to half with my bills in mind!

If I turn it right up it does seem to get to temp quickly, yet takes forever at the lower setting despite being "extremely energy efficient".

Any help much appreciated!

Lat

Cardew

Welcome to the forum.


As a general principle condensing boilers work more efficiently at lower water temperatures; this is because the lower water return temperature enables them to stay in condensing mode for longer.


However the gain in efficiency is not that great, and certainly not enough to justify you setting the water temperature too low - which you are obviously doing.


You should turn the water temperature on the boiler up so that the house heats up in the time you consider acceptable. Don't forget that the output of the boiler modulates(turns down) to maintain the correct temperature.


Both water and heating can be on at the same time, assuming it is not a combi boiler there is a valve that diverts the boiler hot water to either radiators, hot water tank or both.


It might be an idea to prioritise central heating timing so the house warms up quickly - the domestic hot water can be set for a time before you need heating e.g. very early morning.

The_Latman

Thanks Cardew,

I knew I could run the CH and HW together, but had read somewhere that it was a bad idea to do so, so many conflicting posts out there!

I think I will turn it back up again, the house is just too 'fresh' when the setting is as low as it is. Ive adjusted the thermostat so that its a lower temp (unless we need it higher of course.)

Regarding the modulation of the water temp, is that something the boiler will do itself, or does it rely on the room thermostat to keep in check?

Thanks,

Lat

macman

A modern digital programmer will usually have an optimiser mode on it, so the boiler can 'learn' the correct switch on time in order to get the house to the required temp by the 'on' time set on the programmer. So, if you require it at 18C by 7.30am, it will remember that, based on previous days, it needs to switch on at maybe 6.30am in order to achieve that. It adjusts that timing based on the most recent cycle. Warm up times are longer at present because we've had some of the coldest nights of the winter so far. Since heat loss is greater on cold mornings, due to the greater differential temp, you need to set the output temp higher to achieve warm up in an acceptable period.
There is no mystery or problem about running CH and DHW at the same time: the more hot water you heat, for either purpose, the more gas you will burn.

matelodave

It dpends how your heating system is configured but a lot of systems wont heat the house and hot water at the same time - the hot water from the boiler goes through a diverter valve and one might have priority over the other.

So to maximise the amount of house heating you should time the hot water to heat ready for your morning ablutions with the heating coming on about half to an hour before you get up. With a properly insulated tank you might get away with just heating the water for an hour or two a day - it depends how profligate you are with hot water.

If you are out all day then shut the heating off or down about half an hour before you leave the house as the place will still be warm enough whilst you get ready. Likewise set the heating to come on before you get home so the place is warm and then down about half to an hour before you go to bed. The ideal control is a programmable thermostat which allows different temperatures at different times of the day and on different days of the week if you want

As said above the although the boiler might be more efficient running at lower temperatures, it won't necessarily heat the house and the savings are negligible. Lukewarm rads will only do that if they are very large and on all the time and the house is extremely well insulated.

The boiler should be set quite high at this time of the year to ensure that the house heats up in a reasonable time especially if you only heat it when you get up and come home from work - once the house is up to temperature then the room stat and any trvs will control the house temperature and the boiler will look after itself.

The_Latman

OK, thanks for that guys. In my old house it was a very, very old boiler but I had the daily programmable timer. Wasnt able to set temps or anything with the timer, not without using the old wheel style thermostat.. I was running HW and CH together so may explain the high gas bills whilst there as well.

I do tend to only have the heating on for a couple of hours in the morning until the family leave, Im a field engineer and work from home but dont mind wearing extra layers instead of burning gas anyway.

This newer house is supposedly a lot more energy and heat efficient so I will look at my programming again. Ive got Hive from British Gas so have a lot more flexibility for programs.

Thanks all,

Lat

Cardew

The_Latman wrote: »

Regarding the modulation of the water temp, is that something the boiler will do itself, or does it rely on the room thermostat to keep in check?

Thanks,

Lat

The water temperature doesn't 'modulate' it is the output of the boiler that modulates to maintain the water at the required temperature. e.g. if you have the water temperature for the CH set to, say, 70C it might need an output of 20kW to get the house up to a temperature of 20C as the radiators will initially be dissipating a lot of heat. After the rooms are up to temperature it will modulate the output down to say 8kW to maintain that 70C. The thermostat will also switch the boiler on at say 19.5C and off at 20.5C.


There is nothing wrong with having water and CH on together. However, as I said in my first post, you are better heating the water before(or well after) you first switch on CH in morning so all power of the boiler is input to CH.