Condensing Gas Boilers

[Jeanied]

I have an old Potterton too- over 20 years old. I had the adviser come round and give me the lowdown on replacing it and Worcester Bosch were mentioned as amongst the most reliable. I run central heating and hot water on it. Since it has had its annual service I'm waiting till next spring before looking to replace it now.

[kirsty b]

I have a combi boiler that I think condenses too. Don't know anything technical about it beyond I don't have a hot water tank anymore (more space in airing cupboard), it fires up and heats the water on demand - and the water is REALLY hot

Had it a year now (housing association installed it along with new rads) and the difference is amazing. Thermostat only needs to be on a low setting for the house to be roasting, so we use it for a lower amount of time...another plus is the hot water pressure is my bathroom has massively improved, 10 minutes to run a bath instead of nearly an hour!

[Potstubsdustbins]

I have an old Potterton too- over 20 years old. I had the adviser come round and give me the lowdown on replacing it and Worcester Bosch were mentioned as amongst the most reliable. I run central heating and hot water on it. Since it has had its annual service I'm waiting till next spring before looking to replace it now.

I hope thats not a BG rip off advisor.

Colin

[pigletwillie]

Mine too is a worcester bosch and its been in for 8 years. It has just had a new expansion vessel and pressure gauge due to silting up so I have now fitted a filter.

When it comes to boilers, buy by brand. If you have never heard of it then there is a reason, spares will be hard to get hold of, reliability may be questionable and that saving you made will fly out of the window the first time it goes wrong.

As for the condensing pipes freezing up. It its installed correctly and the pipe is lagged there will not be an issue.

Most new boilers also have the ability to have solar panels connected into them to preheat your water. in the UK, solar can generate 60% plus of your annual hot water needs and the systems are cheaper to instal than solar powered electricity ones.

[Alison]

We've had our Worcester since 2007 and so it's been through a couple of very cold winters with no problems what so ever. Actually most of the moans I hear about boilers tend to be around old types and nothing on condensing ones at all so long as they're fitted properly etc etc

[Mikey]

My Parents have been looking at replacing their boiler and had BG to quote, don't ask me why I wasn;t there. £3200 for a standard gas boiler swap, which by their own omission should be completed in a day. The boiler a worcester bosch 15ri, can be purchased for £660.

No offense to your profession pots, but I'm in the wrong trade.....

[Potstubsdustbins]

Mikey 2 points.

1, look at the 3rd post down on this page. 'I hope its not BG ripoff'. British gas trade on a reputation built up years ago. Yep they really know how to over charge. But when you consider they have to pay for all that advertising, the salesman/advisor to come and con you into having their service, the sub contractors who will do all the work and then make a profit what do we expect.

2, Yes we are now very well paid I admit, we have alot of expense's which add to the bill. But it really started with the advent of compulsory registration and compulsory landlords gas safety inspections. There was at that time and still is a shortage of registered engineers ans so councils with their large housing stock started offering big money to attract engineers. 10 years ago a friend working for Nottm council was on about £900 a week and all he had to find was his tools.

Human nature then dictated that private business's jumped on the band waggon and I am as guilty as anyone else.

Colin.

[FB.]

The recent cool and dull weather has put the old boiler to the test. I'd be interested to hear anyone's comments on the heating system design and whether it's taking too long to heat up.

The lounge is about 19sq.metres. It has a radiator on the wall under the window - 170cm x 40cm x double. I estimate this is equivalent to about 2.25kW output.

The dining room is about 11sq.metres. It is connected to the lounge by double doors which we usually leave open. The dining room has a radiator on an inner wall (not an outside wall nor under a window) 110cm x 50cm x double. I estimate equivalent to about 1.75kW output.

All windows and doors are double-glazed. The house is not noticably draughty.

The boiler has six heat settings. It is set around 4. If we set much higher (say 5), when the weather hovers close to freezing all day long the boiler's constant running will occasionally trip the overheat and shut the boiler down.

Radiators are all bled in late summer every year, and usually checked again in mid-winter.

"On paper", from what I can deduce, the rads appear to be correctly sized for 21'C. The rads also get hot - too hot to touch for more than a second or two. So no problems with circulation.

The dining room is always +1 to +1.5'C warmer than the lounge despite having the two rooms connected by the open doors. This is annoying.
We wonder whether it's because the lounge radiator is heating the window and losing efficiency, whereas the dining radiator is on an internal wall and not affected by the cold air near a window.

If we turn down the dining room radiator flow, it takes even longer for the house to warm up from the heating being off overnight; the heat-up rate for the lounge and dining room is about 2'C per hour. Earlier today, for example the max/min thermometer in the dining room said that the house cooled to 18'C during the daytime (lounge 17'C) while we were out, and it took two hours - perhaps three hours - for the lounge to reach 21'C.
In fact, the hallway and cloakroom pretty much attain the same temperature as the lounge.

The boiler does not burn gas constantly while trying to warm the house - it spends about one-third to one-half of its time heating and then one-half to two-thirds of the time the hot water is being circulated.

So, is the lounge "coldness" an under-sized radiator, or due to the rad's position under a window; where the chill from the window is neutralising a lot of the rad's heat?

[Potstubsdustbins]

If you use imperial it will be much easier for me.

Info I need. Height, width and length of both rooms as individuals. Number of outside walls in each room, if an internal wall is unheated on the other side count that as half an outside wall. Wall construction. Are the spaces above heated or not. Are your radiators finned.

Colin

[FB.]

Lounge: 18ft x 12ft x 7.5ft.
Two outside walls - 18ft and 12ft.
Radiator 6ft x 1.3ft x double (approx 7500BTU)

Diner: 12ft x 10ft x 7.5ft.
Two outside walls - 12ft and 10ft.
Radiator 3.5ft x 1.6ft x double (approx 6500BTU).

Internal walls backing-onto both the lounge and diner rooms are heated (hallway adjacent to lounge and kitchen adjacent to diner).

Walls regular cavity type (bricks, then cavity, then concrete blocks). Internally there is plasterboard on frames attached to the blocks (dry lined?).

Radiators have fins between the back and front sections.

Partial heating used upstairs - bathroom and ensuite radiators, plus heat drifts up the open stairwell from the hallway and cloakroom radiators.
We tend not to use bedroom radiators as it gets too hot - especially around 6am when the heating is working hard to get the downstairs up to 20'C or so for breakfast time.
The upstairs is usually 15-18'C, which we find most comfortable for sleeping.

Loft has the usual about 5-6 inches of insulation, but this has been turned into a virtual insulated cavity due to the loft being almost entirely boarded.

[Potstubsdustbins]

FB thats better I was brought up in imperial so it helps me see things that are not always obvious to me in metric.

The system was installed by a plumber not a domestric heating engineer. Thats why there is only one rad in your lounge. As a rule of thumb when a room goes over 12ft x 12ft you split the heating load to supply two radiators. This will ensure a faster heat up and better circulation of the warm air.

By my calculations your lounge requires a minimum of 10,300 Btus. Your rad is under size at approx 7500 Btus.

Your diner is better 6500 btus required rad 5900 Btus. From what you say I would think that this rad is on a side wall and the joining doors are at a right angle to it. Therefore the warm air will find it difficult to circulate into the lounge as the natural air current will be in a circle between the two side walls.

The lounge rad though being on a wall opposite the joining doors will to some extent lose some heat to the dining room.

Hope this helps explain things Colin

[Aberdeenplotter]

FB,

we are in the throes of getting prices to replace an old combi boiler for which spares may not now be available according to British Gas and have been quoted £1920 + vat for a straight replacement with a worcester 34cdi classic. Still waiting for other quotes.

Worscester Bosch offer a 6 year warranty on that boiler and you can buy an extra year's protection for £45. Importantly as well, if you use an installer on Worcester Bosch's panel of recommended installlers and that installer goes bust, Worscester Bosch underwrite the obligations of the installer. Details on the Worcester Bosch web site.

[FB.]

The system was installed by a plumber not a domestric heating engineer. Thats why there is only one rad in your lounge. As a rule of thumb when a room goes over 12ft x 12ft you split the heating load to supply two radiators. This will ensure a faster heat up and better circulation of the warm air.

By my calculations your lounge requires a minimum of 10,300 Btus. Your rad is under size at approx 7500 Btus.

From what you say I would think that this rad is on a side wall and the joining doors are at a right angle to it. Therefore the warm air will find it difficult to circulate into the lounge as the natural air current will be in a circle between the two side walls.

Thanks, Colin.
I had always suspected that the lounge needed a second radiator. 17-18ft seemed such a long way for the heat to travel.

Yes, the lounge rad faces the diner, but the diner's rad is at a right angle to the lounge.

So I suppose tha under-sized rads (at least the one in the lounge) is part of the reason why the boiler will sometimes trip out if we turn the boiler's stat up from 3-4 to 5-6. The boiler does not trip-out while running, but is most likely to trip out once the heating system stops - when the pump stops circulating (either when its timer goes off or when the rooms have reached temperature and the room thermostat kicks-in to turn the heating off).
I guess return water is too hot because the rads can't offload all the heat, so the very hot water entering the boiler's heat exchanger at low speed as the flow rate slows once the pump is off would be the cause of the trip-out?


If it matters, I have attached a more accurate plan of dimensions, radiator locations and radiator sizes, along with the typical room temperatures if we have the lounge at comfortable 21'C:

[Potstubsdustbins]

FB the boiler should not trip out, there is a problem but with being able to examine same I can only make suggestions.

1, the main boiler stat is out of calibration allowing the whole thing to get to hot.

2, the overheat stat is out of calibration and operating at to low a temperature.

3, the system should have a bypass fitted and either has not or the adjusting valve is closed.

4, The boiler should have a pump over run and the auto timer has failed.

5, the system is clogged with dirt and needs a flush.

Colin

[FB.]

FB the boiler should not trip out, there is a problem but with being able to examine same I can only make suggestions.

1, the main boiler stat is out of calibration allowing the whole thing to get to hot.

2, the overheat stat is out of calibration and operating at to low a temperature.

3, the system should have a bypass fitted and either has not or the adjusting valve is closed.

4, The boiler should have a pump over run and the auto timer has failed.

5, the system is clogged with dirt and needs a flush.

Colin

Yes, the boiler has an "over-run" where the pump will keep cycling for several minutes after the boiler has turned off.
But it seems that when the on/off timer in the airing cupboard goes past its off notch, then the power supply to the heating system is literally cut off and everything stops instantly. So if the heating system is running when the airing cupboard timer goes off, then it's as if someone had just pulled the plug in it.

The overheat-trip-outs tend to happen, therefore, when the timer/controller in the airing cupboard literally pulls the plug when the run time is over even if the system is still running; in those instances the power to the system is cut and the boiler is unable to circulate the hot water and the heat in the exchanger ends up not being carried away by the now-stationary water - therefore the heat builds up in the boiler's case and trips it out.