Ideal Logic Combi 24 no hot water or heat

prowla

That's less than ideal...

FataVerde

I just can't decide whether to go for the Viessmann 050-W 30KW or 25KW. I wonder if the 30KW is not overkill for my 1BR, 1bathroom and 12.5 flow rate. On the other hand, the price difference is just £100 and the 30KW modulates down to 3.2, just like the 25kW. It also comes with higher flow rate at 12.2lpm vs 10lpm on the 25KW in case I ever get to improve my flowrate. 

FreeBear

Don't get too hung up on weather compensation - You would need a sensor mounted outside on a north facing wall at least 2m above ground level and well away from any doors, windows, vents, or flues. Depending on where you are in the UK, it is debatable whether it will save much money, and is something else to go wrong. With only four radiators, I don't think you'll find a boiler that will modulate down low enough to make it worthwhile.

If you are replacing radiators, punch the numbers in to this heat loss calculator - https://www.stelrad.com/basic-heat-loss-calculator/ (and do the same for rooms that are retaining the old radiators). Oversize the new rads by 30-50% (subject to space & cost). This will enable you to run at a lower flow temperature which will push the boiler further in to condensing mode and save on fuel. Add up the heat loss for each room (before applying any 30-50% uplift), and this will give you a rough idea of the minimum your new boiler needs to modulate down to.

If you go for a Viessmann boiler, do shop around. Some places offer a 5-7 year warranty, others, 10 year. one or two will even go to 12 year. But you will find the longer the warranty, the price will generally be higher.

FataVerde

FreeBear said:

Don't get too hung up on weather compensation - You would need a sensor mounted outside on a north facing wall at least 2m above ground level and well away from any doors, windows, vents, or flues. Depending on where you are in the UK, it is debatable whether it will save much money, and is something else to go wrong. With only four radiators, I don't think you'll find a boiler that will modulate down low enough to make it worthwhile.

If you are replacing radiators, punch the numbers in to this heat loss calculator - https://www.stelrad.com/basic-heat-loss-calculator/ (and do the same for rooms that are retaining the old radiators). Oversize the new rads by 30-50% (subject to space & cost). This will enable you to run at a lower flow temperature which will push the boiler further in to condensing mode and save on fuel. Add up the heat loss for each room (before applying any 30-50% uplift), and this will give you a rough idea of the minimum your new boiler needs to modulate down to.

If you go for a Viessmann boiler, do shop around. Some places offer a 5-7 year warranty, others, 10 year. one or two will even go to 12 year. But you will find the longer the warranty, the price will generally be higher.

I found the Viessmann 30KW for £2100 with 10-year warranty. I think it's a good deal and does not tie me to any careplan. The one thing Which? reviews and some former vendors say is that apparently replacement parts are hard to get.

FreeBear

FataVerde said: I found the Viessmann 30KW for £2100 with 10-year warranty. I think it's a good deal and does not tie me to any careplan. The one thing Which? reviews and some former vendors say is that apparently replacement parts are hard to get.

With a 10 or 12 year warranty, the availability of parts shouldn't be a problem (unless it is in the middle of winter and the boiler has gone kaput). Having seen inside the boiler, aside from the electronics, there isn't much to go wrong.

FataVerde

FreeBear said:

FataVerde said: I found the Viessmann 30KW for £2100 with 10-year warranty. I think it's a good deal and does not tie me to any careplan. The one thing Which? reviews and some former vendors say is that apparently replacement parts are hard to get.

With a 10 or 12 year warranty, the availability of parts shouldn't be a problem (unless it is in the middle of winter and the boiler has gone kaput). Having seen inside the boiler, aside from the electronics, there isn't much to go wrong.

I'm getting the Vitodens installed this Sat. I managed to get Heatable to match a much cheaper quote I found online so I'm now getting the installation for a fixed price of £2,095 from a more established firm at least.  I asked them to connect the boiler to my Nest and heatlink over OpenTherm. The alternative would have been the Worcester Bosch Greenstar 4000 30kw from Boxt. Identical price and 10-year warranty actually.

Anything to keep an eye on during the installation? Are they supposed to bleed all radiators for those chemical flushes?

FataVerde

Thank you, all! You helped me navigate this boiler saga in a more informed manner and I managed to get a good deal for a boiler that seems perfect, even though slightly too strong, for my property. I can't wait for warm water.

FreeBear

FataVerde said: Anything to keep an eye on during the installation? Are they supposed to bleed all radiators for those chemical flushes?

Open up the TRVs on every radiator (or even take the heads off), and the chemical flush will do its job. The installer probably won't balance the system afterwards, so you'll have to tweak it come the winter. He may well need to bleed the radiators though.

£2100 is a pretty good price - A bit cheaper than mine, but then it wasn't a straight swap.

ThisIsWeird

Good news, FV, and a cracking price!

Yes, in order to validate the warranty, almost certainly a 'powerflush' or some other form of chemical flush should be carried out. And, again also almost certainly, a magnetic filter will need adding to the return pipe to the boiler to continue catching any remaining sludge.

What I would do is to 'chat' or email Vitodens (never heard of them :-) ) and tell them you are having the X model installed soon, and what should the installer do in order to comply with the T&Cs.

FreeBear

ThisIsWeird said: Yes, in order to validate the warranty, almost certainly a 'powerflush' or some other form of chemical flush should be carried out. And, again also almost certainly, a magnetic filter will need adding to the return pipe to the boiler to continue catching any remaining sludge.

Mandatory requirements for a warranty -

• System flush - Chemical as a minimum, A power flush could be done if you want (still uses chemicals)
  Magnetic filter fitted to the return.
  Scale inhibitor (Calmag, Fernox, or similar) on the cold water feed.
  Completed Gas Installation certificate.
• The installation registered within (I think) 30 days with Viessmann
  

Not sure if Viessmann insists on an "approved" & trained installer like WB does - I hope not, as the guy that did mine failed to configure the boiler, and there are a number of small details that leave much to be desired.