Boiler temperature

[Merlin5]

I've got a Vaillant Eco TEC Plus 831, installed last year. I'm playing around with temps. It was set by the engineer at 60c target temp for water, and 60c for the rads.
The water always gets nice and hot. I was watching the blue display readout on the boiler as I ran the kitchen tap and it reached 70c. Why would it reach 70c with a target of 60c? I'm happy with the temperature but not sure why it goes 10c over the set temp.


The radiators are all on at the moment, newly installed at the same time as the Vaillant. They're all pretty hot now but I can easily keep my hand on them at 60c. That however doesn't go over the target temp. So I just increased the boiler temp to 70c for the rads. It's maximum goes to 75c. Now the rads feel just right, almost too hot to keep my hands on for too long. Does 70c seem right or too high? I set the thermostat (Salus RT500RF) to 23c and currently the room temp has reached 20c. I presume the higher I set the boiler temp, the faster I can achieve the selected room temp?

 

[Merlin5]

all your assumptions are correct provided your radiators are adequately sized and your home has good thermal efficiency. You can set the boiler to 80c but if the rads are too small and the building has poor thermal properties then your rooms either will not achieve the desired temperature or it will take forever to get there.

around 70c is fine for the rads. The temp for your hot water seems high but that's down to personal preference. i always recommend around 50c.

It's quite a cold and old house tbh. Even with my new double glazed upvc windows in all the rooms and the rads at 70c, the thermostat is still showing 20.5c in my bedroom and the heating indicator still flashing on the thermostat, so yea, the thermal properties of the building are presumably not very good. Yeah, I think it IS going to take forever to reach 23c that I selected 2 hours ago.

 

[Merlin5]

well there's your answer. are they cavity walls or solid? you can get cavity wall insulation and loft insulation done for free in certain places.

are the rads old or new?

It's an edwardian terraced house so solid 9 inch walls I believe.

The 4 rads, heated towel rail and the Vaillant Combi are new, installed a year ago. The rads were only used sparingly for the first time last winter and then last night for the first time since January.

 

[Merlin5]

Hi guys, I've got some questions about servicing the Eco TEC Plus 831.

A gas safe registered central heating engineer installed my central heating (4 rads, towel rail and combi boiler) about November last year and said Vaillant would contact me about a service. Should be about £90 to £100 I think he said. Is that too expensive, is it worth me getting anyone else other than Vaillant to do it? The engineer was going to service it himself for around £80 to £90, but we sort of fell out with each other since so I can't really get him to do it now I don't think, he never answers my calls.

Haven't heard from Vaillant yet, is it absolutely vital I contact them and have it done and would it void my 7 year warranty if a service isn't done? But even regardless of warranty, does a year of usage on a quality brand like Vaillant mean that it might be less important to service it before 2 years?

Haven't used the central heating that much, just a few weeks last winter and that was only the heated towel rail and one or two other rads now and then.

 

[Merlin5]

I have the same boiler, remember it wont condense properly (and be its most efficient) if your return flow temp is above 60 ish, (google will confirm) currently I`m running it for CH at 58 I think, but when it gets really cold will increase that as performance is obviously less.

Thanks, I'll keep that in mind.

Valiant boilers come with 7 year warranty,(can't remember) it only remains valid if you use a Valliant approved engineer for servicing & you have the boiler serviced regularly.

So, if the boiler went wrong (most unlikely), you might up end up with a expensive repair bill, if Valliant don't honour the warranty.

Yeah, mine has a 7 year warranty. So is up to a £100 for a service about right?

 

[Merlin5]

Just found my benchmark checklist. http://i.imgur.com/DaLCOyj.jpg

Seems I'm premature as it's commissioned 11th Jan this year, even though the system was installed around November. So the 7 year warranty began in January. I've just arranged a service for 10th Jan in the morning with a gas safe engineer. £65 inc VAT, which is excellent. Apparently takes 30 to 45 minutes.

 

[Merlin5]

My gas engineer plugs a flue analyser tester in, it then runs through a program of various tests.
He does a few other tests for carbon monoxide, flue,etc, & he gone in 30 minutes.

But, some engineer's do a more in depth service.

See this link.

Cheers, I'll watch that in a bit. The guy coming mentioned he does a CO test, and I'm guessing he'll do most of the other things you mentioned.

interesting to see the temp drop, gives us a ballpark estimate as to how much it drops, how many rads?

I've got 2 single and 2 double rads and a heated towel rail. As I'm a bit clueless, I don't understand what you mean by my temperature drops.

 

[Merlin5]

Apparently these condensing boilers only achieve their claimed efficiency if the flow return temp is below 55 degrees, Google this and you will find loads. Essentially you want the return temps as low as you can get them (I think), this though I think will be difficult as when it gets colder you will need to up the temps to get adequate performance.

Flow = newly heated water coming straight out of boiler to radiators.

Return = water coming back to boiler after going round the radiators.

Ah, ok. I'll look into.


I'm a bit confused now about the servicing. I'm mostly doing this to keep the warranty valid. I posted on another forum that has professional engineers, and one of them said,

"For £65 you won't be getting a service. What you'll have is an inspection to see if it needs a full service. A service would mean a new seal worth £20, draining the appliance to check/recharge the expansion vessel and a clean out of the trap as well as all the safety checks. I don't doubt filling the service record is all you want, and he'll fill it in, but if your burner seal gives way or main heat exchanger leaks as a result of not having the full service, the only thing Vaillant will offer is an expensive repair or monthly subscription.
I advise customers to have a full service initially then short services/inspections for one or two years in between."

When I contested him on this, he was curt and basically replied that is what is needed and that he knows what servicing involves and I don't.
So how come when I booked my service, I wasn't told for £65 I'd be getting a pre-service inspection, not a full service? As far as I'm concerned, I'd booked the boiler to be serviced, and if there's nothing wrong with it, I just pay £65 and the warranty is valid. Now that doesn't seem to be the case. So now I'm wondering if I have to spend more and get this seal done and draining of the expansion vessel, regardless if it needs it or not, or, if the inspection would show these things up anyway and if he determines if they need doing? Anyone know?

 

[Merlin5]

Thanks FlyingFish and justalex. Sounds good to me.

Sorry to be over cautious, but just for arguments sake and further clarification on this point that guy made to me:

"if your burner seal gives way or main heat exchanger leaks as a result of not having the full service, the only thing Vaillant will offer is an expensive repair or monthly subscription."

So, if the engineer comes and does his functional, visual and safety tests and determines from good combustion analysis readings that a full strip down/full service/heat exchanger test and seal replacement isn't necessary, he'll fill in the service record and the warranty remains valid.

What happens though if the burner seal DOES later on decide to break or the heat exchanger leaks a few months later, even though a full service was determined not to be needed. Are Vaillant still obliged to honour the warranty and repair for free, or will they say I didn't have a full strip down service and didn't replace the seal and charge me to fix it?

 

[Merlin5]

I really wouldn't worry about it! Sounds like you spoke to someone having a bad day.
The burner seal was only an issue on the early models, (made from rubber) which would perish very quickly and allow heat to escape causing damage. For the past few years the seal has been made from graphite and is best left alone apart from a visual check.

But even so, if you keep the servicing up to date, your warranty will cover any faults as long as they are not the result of bad installation or cowboy servicing or misuse.

Cool, thanks. That puts my mind at rest.