Viessmann boiler set at max just to get enough heat

[fronty]

Just had a new Viessmann Vitoden 100w heat only boiler installed, I have to turn the dial all the way to max just to get some decent heat, if I turn it all the way (so it's pointing at reset) it'll settle at around 76 degrees. Is this normal? It's modulating fine, I was maybe expecting to set the dial at the dot at 4, but that's not hot enough to heat the hot water cylinder. Pump is on medium speed setting, any slower and some of the rads don't heat up.

 

[gmartine]

Heating set point is too low.

 

[fronty]

Sorry I dunno what that means, manual seems to indicate position 6 should be giving me 80+

 

[gmartine]

Do you have weather compensation, call the installer back if not sure.

 

[king of pipes]

Town will be along shortly he fits these how many radiators do you have ? and what KW output is the boiler that you have had fitted . Cheers kop

 

[chris watkins]

As above, why have you not called the installer back to sort it ?
How long are you leaving it on for.

 

[chris watkins]

Just turned my one up to max & got high 60's so I would guess you have Weather comp on, If you boost the hot water does the rad disappear to be replaced with a tap?

 

[townfanjon]

Sorry I dunno what that means, manual seems to indicate position 6 should be giving me 80+

80 + , no chance its a condensing boiler , as others have said is it on WC ? Is there a bypass ?

 

[ShaunCorbs]

I would say it's modulating down due to the temp rise

 

[fronty]

As above, why have you not called the installer back to sort it ?
How long are you leaving it on for.

It was only installed on Friday - will be giving them a call tomorrow.

 

[fronty]

Town will be along shortly he fits these how many radiators do you have ? and what KW output is the boiler that you have had fitted . Cheers kop

26kw, 13 radiators.

 

[fronty]

Just turned my one up to max & got high 60's so I would guess you have Weather comp on, If you boost the hot water does the rad disappear to be replaced with a tap?

I don't think I have weather comp, no mention of it by the installer. I don't have a hot water boost, it's a traditional heat only boiler. Cylinder stat is set to 65.

 

[Gasmk1]

does the temp go up to about 65 degrees then drops down then back up then down if so its a flow problem the return temp is out of alignment with the flow (too great a difference)

 

[fronty]

does the temp go up to about 65 degrees then drops down then back up then down if so its a flow problem the return temp is out of alignment with the flow (too great a difference)

No once it's got up to temp and modulated the flame height down, the temp stays constant, have it running at 72 at the moment and seems fine although still not sure the rads are as hot as they were on my old Baxi.

Something else I noticed, I've had a F2 fault code (temp limit) and noticed after the boiler shut down that the latent temp kept going up and up and up, seems I don't have pump overrun any more which I had on my old boiler. Something else to call the installer about tomorrow!

 

[fronty]

Here's the heating curves, doesn't say what they are without WC though. But position 6 should generate temps between 60-90, hence wondering why I can't get more heat when dial is on max...

 

[Gasmk1]

thats the curve for wather compensation what controls do you have. is there a small white box on the outside of your house on a north or north west wall may be high up

 

[townfanjon]

I doubt if this has WC , its not required for boiler plus , its just combis unless somebody knows different .
IMO the boiler is working fine , if the rads aren’t as warm as your old Baxi , it will be because it probably wasn't a condensing boiler and had a much highter flow temp .

 

[king of pipes]

The best advice is to get your installer back , post a picture of the install is the benchmark section completed in the installation manual it would be interesting to see the figures? how long did the install take . Kop

 

[fronty]

Install took about 4 hours in total, no idea if that's quick, it felt quick to me. I've kept the same controls. There's deffo no WC on this and thinking about it more I don't think it would work as in summer there wouldn't be enough heat for the DHW.

Anyway here's some more pics...

Before:

During:

After:

Benchmark (interesting return temp there, but I am going to go round all the rads anyway and rebalance them for a 20 degree drop if I can):

 

[fronty]

Hah, did you spot the temp? 93.7!!! That's after the boiler shut down without pump overrun. Something else to ask them about.

 

[king of pipes]

Oh dear thats not right I am afraid to say that you have a poor install there bud have you paid this chap? please say no Is he a approved installer for viessman I very much doubt it looking at that, get gas safe out to inspect the job 4 hours for a install has alarm bells ringing it takes longer than that to do a chemical clean the gas supply will most probably be undersized do you have other gas appliances this could be a serious problem . All the best Kop

 

[fronty]

22mm gas pipe runs to behind the kitchen unit (where there used to be a floor standing boiler) then reduces down to 15mm for the last 1.5m, so I believe the gas supply is okay although don't know if the gas rate in the benchmark indicates an issue. There are no other gas appliances in the house.

Not sure how thoroughly the system was cleaned, he said the water in my system was already clear, no discolouration, probably because I flushed it and added inhibitor in the summer. The paperwork says he used MC1, no idea what that is.

This was all done through Hassle Free Boilers, they are accredited by Viessmann, I checked before buying as wanted the 10 year warranty. I'll be calling tomorrow to make sure they register it.

 

[ShaunCorbs]

22mm gas pipe runs to behind the kitchen unit (where there used to be a floor standing boiler) then reduces down to 15mm for the last 1.5m, so I believe the gas supply is okay although don't know if the gas rate in the benchmark indicates an issue. There are no other gas appliances in the house.

Not sure how thoroughly the system was cleaned, he said the water in my system was already clear, no discolouration, probably because I flushed it and added inhibitor in the summer. The paperwork says he used MC1, no idea what that is.

This was all done through Hassle Free Boilers, they are accredited by Viessmann, I checked before buying as wanted the 10 year warranty. I'll be calling tomorrow to make sure they register it.

They might be but the company that installed it isn't

So no 10 year warranty

 

[king of pipes]

Mc3 is a cleaner which needs to be circulated through your system for a minimum of 2 hours , mc1 is the inhibitor added when fully commissioned and tested , again your choice but I would have the install inspected by gas safe it costs you nothing and you will have peace of mind your safe and your boiler warranty will be intact . Kop

 

[ShaunCorbs]

First of all I would contact Viessmann and check what warranty you have serial no is ontop of the boiler right hand side of the flue

Also you would on a system have a flow temp of 65-70 dc and a return temp of 50-55dc

 

[ShaunCorbs]

where did you see the 10 years warranty offered by them just had a quick look cant find anything on there site?

 

[fronty]

It's in their quote:

Hassle Free Boilers
1 Viessmann Vitodens 100W 26kW Heat Only Boiler
Including:
- Boiler supply and installation
- 5 year Viessmann manufacturer warranty
- 2 year workmanship warranty
- Magnaclean magnetic filter
- Supply and installation of boiler flue and controls
- Full system clean, flush and protection*
1 Viessmann Warranty Extension (Additional 5 Years)
1 Condensate Soakaway
1 Viessmann Horizontal Flue Kit
1 Heat Only/System Boiler Installation Pack (22mm)

 

[ShaunCorbs]

love the *

"Full system clean, flush and protection*"

in short 5 years as standard

then the warranty extension eg you paid to have it upgraded

Condensate Soakaway ?????? should be a white pipe below the boiler where does that go (breakfasts in the way to see)

also looks like the flue is running downwards to the outside should be the other way so theres a fall to the boiler

 

[fronty]

Yep they drilled a hole through the wall and installed a soakway (in a flowerbed) for the condensate. Flue angle looks like an optical illusion, here's another pic:

Why do Viessmann say no pump overrun is required?

Open Vent Boilers - Viessmann UK

 

[fronty]

Here's the asterisk:

* The system clean and flush involves the system being flushed with mains pressure water and appropriate cleaning chemicals. We will not complete a 'powerflush'. A 'Magnacleanse' clean is an alternative to a 'powerflush' and is available as a chargeable option where advised or requested.

 

[ShaunCorbs]

Yep they drilled a hole through the wall and installed a soakway (in a flowerbed) for the condensate. Flue angle looks like an optical illusion, here's another pic:

View attachment 35971

Why do Viessmann say no pump overrun is required?

Open Vent Boilers - Viessmann UK

that doesnt look good @townfanjon

looks like its ready to pop off

doesnt require p over as its a stainless steel hex

 

[townfanjon]

Looks like a typical “thrown - in” boiler rather that a fitted one . 4 hours , Lol .

 

[fronty]

Reason I'm querying the pump overrun is I had an F2 fault code (temperature limit) think it was due to the latent temp rising in the hex after shutdown and triggering a fault - it's been okay since I turned the flow temp down a bit but wondering if this happens a lot when there's no pump overrun.

 

[townfanjon]

Reason I'm querying the pump overrun is I had an F2 fault code (temperature limit) think it was due to the latent temp rising in the hex after shutdown and triggering a fault - it's been okay since I turned the flow temp down a bit but wondering if this happens a lot when there's no pump overrun.

Nope dont need pump overun , could have been air , they do airlock on installation, once its gone they arent a problem.

 

[fronty]

Looks like a typical “thrown - in” boiler rather that a fitted one . 4 hours , Lol .

Well, I kinda feel like I agree with you, I was surprised when they said they had finished, it all just felt a bit rushed.

I did try and find a local installer but half the time the phone just rang and rang, or I left a message and no-one called back, or they didn't do Viessmann, or they couldn't offer any interest free credit... in the end I was kinda exasperated and just went with HFB because they were cheap, could do Viessmann and did 3 years interest free credit. I already had a nagging feeling after talking to them that they would just sub it out (despite asking if they used their own people). I couldn't see how they could offer national coverage without using subbies. And the two guys that turned up had come all the way from Rotherham (I am in Hampshire).

Anyway, my main priority is to ensure I get the 10 year warranty so will be asking them for proof of this tomorrow (and I'll double check with Viessmann too). If no proof is forthcoming then they'll be in breach of contract as that's what I paid for,