New boiler installation


1 Apr 2016
Reaction score
West London
United Kingdom
Hello all.

After a bit of advice/guidance. Sorry for the long post!

My trusty old Vaillant combi boiler has been playing up - it was 18 years old so chucking more money at it seemed pointless. I've had a replacement fitted this week, another Vaillant combi installed by a Vaillant Advanced installer thus qualifying me for their extended 10yr warranty. The existing installation was looked at by the engineer prior to the quote, which was later agreed on prior to him starting the work.

I paid upfront for the boiler and sundries, the labour payment is upon completion of commissioning and my being satisfied that the system is working.

I have a few questions which I'm hoping some kind soul(s) might help me with.

i. Takes a deep breath.....
I had a Hive fitted which was using just the Heating channel for obvious reasons. It's worked flawlessly for 3 years on the old combi. The engineer had some "issues" with the existing Hive and insisted on replacing it with the heating only unit stating the existing dual channel one wouldn't work. He said just the receiver would need replacing, but ended charging me for a whole kit - this wasn't mentioned at quote time. Looking at the Vaillant manual wiring diagram it states that there are two Room Thermostat (RT) terminals, one of 24v and another of 230v. The dual-channel Hive works on 230v. Could he not have just connected the Hive into the 230V RT terminal rather than me have to spend another £180, seems to me he either doesn't understand his electrics or I'm misunderstanding completely - not for the first time.

ii. To qualify for the 10yr warranty with Vaillant conditions have to be met, some of which are;

Install a "Vaillant Advance Boiler Protection Kit"
Follow the commission process completing the Benchmark commissioning form with all values entered.
Clean/flush the entire system pipe/rads dose with inhibitor.

He installed the Vaillant Advance Boiler Protection Kit as agreed - so no issue there.

However, he's barely filled out half of the Benchmark form - I'd assume this wouldn't meet with Vaillant T&C's, therefore, rendering my warranty worthless?

He used a Magnacleanse to flush the system but didn't use an agitator on the rads and the way he piped it up I can't see how it would have circulated around the whole system. He had one leg on the flow just below the boiler and one on the return again just below the boiler and was using the internal boiler pump to circulate - seems to me that the water would have just flowed through the Magnacleanse around to the return just before the boiler as that would have been the path of least resistance - shouldn't he have added the Magnacleanse in/out onto the return pipe so the water flows out of the flow, through all pipework, through any open rads and back to the return and through the Magnacleanse? The water looked so clean, yet I know there is sludge in parts of the system. Again, maybe I'm not getting it.

He didn't balance rads, left several completely shut off and there two in the loft are stone cold even though TRV's and lock-shields are open. I saw no evidence of him following the Magnaclense practice of shutting off all but the furthest rad, agitate rad, flush for 5/10 mins, shut off, open next furthest rad, repeat until you get to the nearest one. There are definitely cold spots on some of the rads - shouldn't the Magnaclense have helped with those?

He had to install a filling loop as he claims the built-in one isn't working, I asked him to contact Vaillant about this as far as I'm concerned it's faulty and should be fixed under warranty.

I don't like to argue with people but this is a decent chunk of money, I don't think it's unreasonable to expect a professional installation to Vaillant specs - the last thing I want is a load of sludge entering the boiler due to someone cutting corners and me having to pick up the tab due to a poor install.

I think that's it. If you got this far - thanks for reading!

Any comments would be really welcome.

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The 24v is for opentherm or the vaillant equivalent of anyway.

All hive controllers run on the 230v.

It's of the old box was working and then as soon as it's swapped it wasn't. I can't comment any furthy on that, coincidence maybe?

The filling loop, the built in ones are rarely good any way so fitting an external one is better. It's also easier to swap if by any chance the taps do leak.

When commissioning the boiler the paperwork rarely gets every box filled in, I assume a lot of them aren't required on every boiler, my benchmark has literally got 2 boxes filled in, and I've got my warranty cert and building control.

I would have expected the guy to have gone round and made sure all the rads were getting heat during commissioning.

Balancing the rads it's nice if they do this, but rarely do installers do this.

As for the system cleanliness, maybe it wasn't that dirty to start with, I don't know.
Clean/flush the entire system pipe/rads dose with inhibitor.
Clean and flush the entire system properly is nothing to do with using the combi pump or Magnaclean..Done absolutely to the book is a days job with specialist equipment and chemicals.Some fitters on here say they rigidly stick to that...most do not at an install.The norm...right or wrong...Is what your fitter did...If you speak to Vaillant they will cover their backside and say whatever covers them ..It is a minefield..Good luck.
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I am very disappointed that you installer did not check and balance the rads. That is such a basic thing to do for any customer.

You do not say if you already have TRVs but any new boiler should have them.

Some may not like me saying it, but I often get the impression that boiler maker's "Advanced Installers" are mostly rated on how many of the firms boilers they fit rather than how well and comprehensively they fit them!

I doubt that I have ever fitted more than 10 boilers in a year and that is probably because I like to take the time to do the job properly ( which is very time consuming! )
Some may not like me saying it, but I often get the impression that boiler maker's "Advanced Installers" are mostly rated on how many of the firms boilers they fit rather than how well and comprehensively they fit them!

Sadly for the customers that is true of several manufacturers.
Possibly nothing to do with yours but I had a Vaillant boiler fitted a couple of years ago and it was constantly running all night after it had been fitted - even when the controller was switched off and the thermostats were turned down to zero. I had to turn the power supply off to stop it. Next day I phoned the installer up to come back and sort it out but while I was waiting, I phoned Vaillant up too. They told me what it was straight away. Like someone has already said, they are set up to run on Vaillant controls which are 24v. Anything else and you have to remove the 24v link on the boiler PCB. I mentioned that it was a Vaillant installer that fitted it and he said "They all forget to do it". I removed the link myself instead of waiting for the installer to come and told him not to bother. Any chance you could have the same problem?
All hive controllers run on the 230v.


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