Vaillant Boiler not warming enough

[Agile]

Our GP now rings us back after trying to make an appointment to see him/her via the receptionist; before we can actually go and see them... the world has gone feckin mad!!!

Mine just emails me.

But I like that, at least he is on the job!

 

[Steelmasons]

I have spoken to Vaillant technical department. They have said that they can't figure out the problem, although they are suspecting it's a flow & return issue.

Were you not asked for your gas safe registration number?

 

[ripperuk]

Were you not asked for your gas safe registration number?

No because there is an option for homeowners.

 

[Steelmasons]

No because there is an option for homeowners.

You obviously didn't speak with technical then..

 

[ripperuk]

Don't be too concerned guys as I'm not ignoring your advice... I have called an engineer and they'll be coming out on the weekend.

I'm thinking whilst they are at my place to ask them to replace the crappy salus wireless thermostat with a wired version.

This is what I used to have before the salus:

Now the wiring for the old thermostat is still there, so is it possible to replace it with a different thermostat? If so, what can you recommend?

 

[ripperuk]

You obviously didn't speak with technical then..

I rang technical, but I'm not a gas safe engineer, so I could only choose the home owner option.

 

[Steelmasons]

I have spoken to Vaillant technical department. They have said that they can't figure out the problem, although they are suspecting it's a flow & return issue.

...so you were fibbing then...

 

[Rystar00]

I'm not a gas engineer (or a tradesman of any sort!) but I had a similar problem to you. My installer and vaillant technical were all useless (they came out 3 times) so I had to try and figure it out on my own.

Have you got a weather compensating stat? I do and found that the flow temps weren't getting hot enough despite me switching it off and sticking the thing in the fridge! It also sounds like your boiler is short cycling as it's heating the water too quickly.

This is what I did to fix the problem (sure some of the experts here will say I've done the wrong thing but at the end of the day I'm a complete novice DIY-er and I just wanted a CH system that kept me warm!) - forgive me if you've already said some:

1. Change flow temp to as high as possible (75 degrees on mine) (press the little rad button on the boiler main screen)

2. Calculate the heating load of your rads and adjust D.0 setting to match this (range rate it down to suit i.e. total rad kw load is 17kw - range rate D.000 to 17kw);

3. Change D.002 to as long as possible (60 mins on mine).

4. Bleed rads (or tap sludge at bottom of rads VERY gently with rubber mallet to get sludge back into suspension).

5. "Force" water to slow/cold rads by turning off hot ones before balancing system.

Fire up the boiler and away you go (1, 2 and 3 will take about 5 mins to do and will get it 80% working).

Not sure why this seems to do the trick but it seems to smooth out the "heating curve" or something like that to stop the boiler anti-cycling. Search for "vallaint anti-cycling" in google and you will see umpteen posts about the issue!

 

[DP]

I think a visit to the dentist will be more fun than reading the replies from the OP here

 

[DP]

I'm not a gas engineer (or a tradesman of any sort!) but I had a similar problem to you. My installer and vaillant technical were all useless (they came out 3 times) so I had to try and figure it out on my own.

Have you got a weather compensating stat? I do and found that the flow temps weren't getting hot enough despite me switching it off and sticking the thing in the fridge! It also sounds like your boiler is short cycling as it's heating the water too quickly.

This is what I did to fix the problem (sure some of the experts here will say I've done the wrong thing but at the end of the day I'm a complete novice DIY-er and I just wanted a CH system that kept me warm!) - forgive me if you've already said some:

1. Change flow temp to as high as possible (75 degrees on mine) (press the little rad button on the boiler main screen)

2. Calculate the heating load of your rads and adjust D.0 setting to match this (range rate it down to suit i.e. total rad kw load is 17kw - range rate D.000 to 17kw);

3. Change D.002 to as long as possible (60 mins on mine).

4. Bleed rads (or tap sludge at bottom of rads VERY gently with rubber mallet to get sludge back into suspension).

5. "Force" water to slow/cold rads by turning off hot ones before balancing system.

Fire up the boiler and away you go (1, 2 and 3 will take about 5 mins to do and will get it 80% working).

Not sure why this seems to do the trick but it seems to smooth out the "heating curve" or something like that to stop the boiler anti-cycling. Search for "vallaint anti-cycling" in google and you will see umpteen posts about the issue!

All I can say is exercise caution when attempting some of the advice posted here.
Tap the radiator base gently........where do you think the sediment might end up? What will you suggest when hot water starts running hot and cold repeatedly?

 

[Agile]

I would go anywhere else instead of to a dentist!

Even to repair a Ferroli !

 

[jdp80]

I've ended up here on a search after seeing the same issue as the OP

I have a Vaillant 637 which I suspect is oversized for the house. (Modern, reasonably insulated detatched, 15 rads)

I'm noticing in the mornings that it takes 30-40 minutes for flow temps to go up to the max, despite this being a time when most rads are calling for heat.

Here's the boiler's flow temp over the past two days

You can see that at 0630, with all the TRVs and DHW switched on (Evohome) it took until 0710 before flow temp hit the max.

I'm assuming that the flow temp should go high, then the return temp to gradually rise until everything had heated up, and then should modulate down until the thermostats switched off, but instead flow+return seem quite similar values:

The rads should be balanced, there's a Magnaclean which is clean and it had additive recently.
I will set a manual partial load and see if there's a difference tomorrow.

The other thing I'm not sure on is whether Evohome TPI somehow conflicts with the anti-cycling time. It seems to be continuously calling for heat during that period.

 

[Micahel Hall]

Maybe you could have the decency to post an update since changing the parameters.
You might also have the decency to thank all involved.

I have a Gloworm HXI 18 that is second hand & I firmly believe no one who was called to look at the fault it had could resolve and cure it! I believe this Heat only Gloworm is the same as one or two Vailant boilers which is prevalent these days as the secret service of company buying is rife these days = money money money! Any how this boiler from day one did not reach target temp and never did for 6 months ! I said to my wife I think the bastard PCB's faulty so I changed the flow sensor but knew I was basically onto a looser due to the resistance of the new one same as the old one ! There is a bloke who always on this forum goes for the pump but no pal the 15/60 pump is adequate for the resistance of this new system in a static caravan & if I thought the pump was at fault as in thousands of systems I've looked at I would have stuck a 25/55 in & would have had apat on the back from those houseowners........ Vailant and Gloworm will never admit that the circuit boards have an inherent fault which is as sdame as most doctors......... Starange fault this is though becuse although the ow temp fault existed for the first 6 months it rectified itself the second season & reached target temp without a blink now the third season is upon us the bloody thing is at it again with low flow temp although the target is set at anything from 60 to 80 C the best temp is 52 & the burner is off....... Would all you engineers recommend a new PCB to save the hassle.

 

[dilalio]

I have a Gloworm HXI 18 that is second hand & I firmly believe no one who was called to look at the fault it had could resolve and cure it! I believe this Heat only Gloworm is the same as one or two Vailant boilers which is prevalent these days as the secret service of company buying is rife these days = money money money! Any how this boiler from day one did not reach target temp and never did for 6 months ! I said to my wife I think the bastard PCB's faulty so I changed the flow sensor but knew I was basically onto a looser due to the resistance of the new one same as the old one ! There is a bloke who always on this forum goes for the pump but no pal the 15/60 pump is adequate for the resistance of this new system in a static caravan & if I thought the pump was at fault as in thousands of systems I've looked at I would have stuck a 25/55 in & would have had apat on the back from those houseowners........ Vailant and Gloworm will never admit that the circuit boards have an inherent fault which is as sdame as most doctors......... Starange fault this is though becuse although the ow temp fault existed for the first 6 months it rectified itself the second season & reached target temp without a blink now the third season is upon us the bloody thing is at it again with low flow temp although the target is set at anything from 60 to 80 C the best temp is 52 & the burner is off....... Would all you engineers recommend a new PCB to save the hassle.

Ignore mode set due to post hijack

 

[Micahel Hall]

Ignore mode set due to post hijack

dilalio don't you like the fact that I've said I've got a Gloworm heat only boiler which is produced by the same company i.e. Vailant?
There is no need for a high handed attitude such as yours so stuff it.