Vaillant Combination Boilers

[sooty]

Hi,
Does anyone know about combi boilers?

Currently I have a very old Vaillant boiler that is about the same age as me! It has never been changed as it has NEVER broken down or given any faults. I have seen the goverments "Energy Saving Trust" grant of £400 off so thought I might as well upgrade it now.

I have applied for the grant and have been given a £400 off voucher as my current boiler is a X-Rated (under G-rated!) for energy efficancy. The current combi has a flow rate of only 6.5L.

I have been adivsed to go for either a Vaillant ectTEC plus combi 837 which has a flow rate of 15.2L or for an extra £170+VAT I can get a ecoTEC 937 plus storage combi which has 15L of pre-heated water plus the flow rate of 15.2L (same as the 837 but with a tank attached). Does anyone have any experiance of either of these boilers? Will they be ok for a 4 bed-room house? I have 2 bathrooms with non en-suite.

I know they say "Don't fix it unless its broken" however my current boiler is so old I am worried it will break down one day in the middle of winter plus this £400 off is coming to an end soon.


I know this is a car forum but I thought I'd give it a shot!



Thanks

[elvismiggell]

Have asked swmbo as I'm pretty sure this is part of what she does at work.

Will let you know what she says.

[elvismiggell]

From Elise:

Hum…

If it has a hot water cylinder it is not a combi.
I wouldn’t have thought a combi is the best idea for a 4 bed place with 2 bathrooms.
They will have problems like we do, you can’t have 2 places supplied with hot water at once, which if fine in a smaller place but not so good in a bigger property.
An installer should do something called a heat loss calculation, based on the size of the room they know the size of rad needed, based on the rads they know the output the boiler needs to have, in watts. This will tell you if the boiler is adequate for the property.
Vaillant are good, but I don’t know anymore about the specific boilers. Or if there are new magical combi boilers with tanks? Not sure what the point would be though.
Defiantly worth doing something, gas bill will go down.

Not much help im afraid

Sounds like it's worth getting someone to tell you whether it's adequate for your needs.

[NickPicks]

I had a Vaillant combi (non-condesing) at my last house. It was fantastic except for for diverter valve sticking twice (first time replaced under warranty, second time was about £200). My installer said they've redisigned the diverter so it shouldn't stick as much.

I think the new type of combi with storage only has a small storage to start feeding hot water before the boiler can switch over (I think the OP said 15 litres). This helps with the usual combi complaint of having to run water down the plug for 2 minutes before it's hot enough to run the bath.

We've just replaced the 20 odd year old (balanced flue, storage system) boiler in our house with a Veissmann condensing combi boiler. It's fantastic. It does take about a minute to give hot water in the morning, but that's not too bad.

The amazing thing with ours was the gas savings: We use Eon's online account, where we have to supply our own meter readings. When we typed them in, they wouldn't proces it as it had "failed validation", which means the reading was too far away from the expected value. Our new boiler had used about 10% of the gas that our old one would have!
(The old one did also have a stuck open zone valve, so the radiators were getting hot during the summer when the hot water was on)

We did ours before the scrappage scheme, but it was still well worth it.

I would get your installer to check whether a combi will be suitable for a house as large as yours. Ours is 4 bedrooms, but only 1 bathroom. We only ever have low flow problems if the shower is running at the same time as the bath, and the kitchen taps are running, then the shower loses a bit of flow. This is very unlikely to happen though.

[SammoVWT]

Heatload calcs are pretty easy. Work out the losses from the rooms, tbh the radiators should already be sized to compensate for heat loss, so it should just slot in.

To find the right size, as a rough guide (you need to look up bsria heat loss estimates etc) for your home, unless youre going to work out your U values for every part of insulation you have.

Basically, in lamens terms, Width x Depth x (Heatloss (in kW)) - if its a over 2.5m high say for example 4-5m double it if not dont worry.

then factor in window size, they will have a loss factor dependant on area & direction.

Total together for each room, total for house size boiler accordingly.

If you need a hand and you have some plans for your house I can help

Also flow problems will be down to pump, the boiler is only for efficiency/heat exchange, they will have a recommended flow rate for efficiency/operation purposes. The hard bit is getting the right pump rather than the boiler imo (does also depend on the length of pipework in the house, obviously, more copper at a small diameter will need a large pump just to overcome the resistance)

also remember kW is a rate of energy, so you will need maybe 10% extra to cope with heating

(just for info, my eco 485 (i think) vaillant boiler has difficulty managing the valves and needs resetting every week or two, other than that works nice)

[NickPicks]

Heatload calcs are pretty easy. Work out the losses from the rooms, tbh the radiators should already be sized to compensate for heat loss, so it should just slot in.

If this is the case, how come the radiator in my downstairs toilet (about 1m x 1.5m) is larger than the one in my upstairs bathroom (about 3m x 2.5m)? (They're both double panels)

Personally I think it's because my system was designed by an imbecile.

I've started installing underfloor heating, which is fantastic in the room I've done so far.

[sooty]

From Elise:

Hum…

If it has a hot water cylinder it is not a combi.
I wouldn’t have thought a combi is the best idea for a 4 bed place with 2 bathrooms.
They will have problems like we do, you can’t have 2 places supplied with hot water at once, which if fine in a smaller place but not so good in a bigger property.
An installer should do something called a heat loss calculation, based on the size of the room they know the size of rad needed, based on the rads they know the output the boiler needs to have, in watts. This will tell you if the boiler is adequate for the property.
Vaillant are good, but I don’t know anymore about the specific boilers. Or if there are new magical combi boilers with tanks? Not sure what the point would be though.
Defiantly worth doing something, gas bill will go down.

Not much help im afraid

Sounds like it's worth getting someone to tell you whether it's adequate for your needs.

Thanks... I've had it checked and this boiler is the best for my house I was told. It is the best domestic Vaillant.
The "actoSTOR" 15L tank is attached behind the boiler... Basicly it fills this up and is insulated, when you release water then this tank is filed with hot water causing it to pump out the exsisting hot water in the tank. It means it has a higher preasure and INSTANT hot water in one. The tank is insulated so it is not heated and re-heated.

[sooty]

I would get your installer to check whether a combi will be suitable for a house as large as yours. Ours is 4 bedrooms, but only 1 bathroom. We only ever have low flow problems if the shower is running at the same time as the bath, and the kitchen taps are running, then the shower loses a bit of flow. This is very unlikely to happen though.

Like I say the old boiler is about 25 years old and is very energy un-efficent... it has a flow of 6.5L and we never have any flow issues. The new one has over 15L flow rate so I know we wont have any issues with it.

[SammoVWT]

Personally I think it's because my system was designed by an imbecile.

This sounds about right

[nortona6]

Hi,
Does anyone know about combi boilers?

Currently I have a very old Vaillant boiler that is about the same age as me! It has never been changed as it has NEVER broken down or given any faults. I have seen the goverments "Energy Saving Trust" grant of £400 off so thought I might as well upgrade it now.

I have applied for the grant and have been given a £400 off voucher as my current boiler is a X-Rated (under G-rated!) for energy efficancy. The current combi has a flow rate of only 6.5L.

I have been adivsed to go for either a Vaillant ectTEC plus combi 837 which has a flow rate of 15.2L or for an extra £170+VAT I can get a ecoTEC 937 plus storage combi which has 15L of pre-heated water plus the flow rate of 15.2L (same as the 837 but with a tank attached). Does anyone have any experiance of either of these boilers? Will they be ok for a 4 bed-room house? I have 2 bathrooms with non en-suite.

I know they say "Don't fix it unless its broken" however my current boiler is so old I am worried it will break down one day in the middle of winter plus this £400 off is coming to an end soon.


I know this is a car forum but I thought I'd give it a shot!



Thanks

If your doing it for environmental reasons and not economic go for it. The total cost of a boiler change out can depend on where you live and other variables. I think the average total cost of change out is around £2500 and to recoup the costs will take years. I'm in the mind if it ain't broke don't fix it. The new condensing boiler life expectancy is around 5-10 years. The old style boiler was between 15-20 years.