Correctly replacing a boiler?

Tinders

Tinders

Tinders

Soldato
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There's a voice that keeps on calling me.
Hi Guys, I know theres a few Pro's here so I just wanted to garner some advice.

My folks are having a new boiler fitted, out goes a WB Greenstar 28CDI Combi and in comes some Vailant 30kw Combi, via some govt scheme. So hopefully like for like.

Im not convinced that the last boiler was fitted correctly, so this time im planning to be home so i can keep a bit of a friendly eye on them.

Whats the actual correct procedure for having a boiler replaced by the pro's?

Ta muchly!
 
I don’t think they did a system flush, is that mandatory on a new boiler with old rads? The condensate trap was badly done Aswell.

Like I say I’m not sure what they should be doing as best practise or what is mandatory. Or it just a case of remove the old one, fit new, flush, refill and walk away, I would assume they should fully test the whole system and Balance the rads and what not?
 
Its not mandatory to powerflush the system but really all new boilers should be fitted with a magnetic filter and a chemical flush at least, and then drained and re filled with inhibitor.

They should have course test the heating to make sure all rads are working but the system may not require balancing if they all worked previously.
 
While i can understand your concern be careful not to P*** off the plumbers.Having someone asking questions about their competence might be taken the wrong way
 
Thanks guys, I certainly wasnt going to be a busy body around the engineer but i just wanted to make sure the right things were done.

TBF the boiler replacement scheme is pretty much a scam, they just replace the boiler and sod off, they really should be looking at the system as a whole and ensuring the whole system is efficient, in many cases its a poorly maintained system that once remedied would give greater gain with the existing boiler.

This guy came and replaced the boiler, its 30kw output but really thats not correctly sized for a large house imo, but at least he put a decent filer on and altered the condensate pipe and lagged it. But they really are boiler fitters nowadays rather than true heating/combustion engineers, as when we discussed sizeing up boilers and radiator delta T, he wasnt all that well clued up, but thats the same in most trades now.
 
Tinders said:
Thanks guys, I certainly wasnt going to be a busy body around the engineer but i just wanted to make sure the right things were done.

TBF the boiler replacement scheme is pretty much a scam, they just replace the boiler and sod off, they really should be looking at the system as a whole and ensuring the whole system is efficient, in many cases its a poorly maintained system that once remedied would give greater gain with the existing boiler.

This guy came and replaced the boiler, its 30kw output but really thats not correctly sized for a large house imo, but at least he put a decent filer on and altered the condensate pipe and lagged it. But they really are boiler fitters nowadays rather than true heating/combustion engineers, as when we discussed sizeing up boilers and radiator delta T, he wasnt all that well clued up, but thats the same in most trades now.
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If we're being pedants no tradesmen are engineers :p
 
30kw is giant even for a massive house heating wise. You size a combi based on hot water demand.

When I had my boiler fitted after doing the rest of the central heating system myself we had a good chat and they did know there thing. Even when it came to running at lower temps and recalculating the delta of the radiators to suit. I had already done mine to a delta of 30c, so the rads are pretty substantial.
 
Well it’s 24kw for the heating, which for a 4 bed 3 story Victorian with an extension isn’t enough imo due to the heat losses due to it being holy as hell :p
 
It’s a good idea to go by the manufacturer specifications, also make sure the flue is the current distance from openings and down pipes, if lower than 2m from the ground it should be protected (assuming this is moving). Flue pipe should be sealed, if it’s a timber frame house it should have a fire sock around it (if they’re installing a new one)
Condensate pipe should go in to foul waste (I think, might want to check that).
Also check for clearance in front of the boiler some manufacturers specify a certain distance in front, underneath and each side for maintenance (Ideal for example (a make I see frequently) ask for 450mm clear in front 15mm either side and 150mm underneath).
Nothing wrong with a friendly question to the installer, just have a chat with them and see what they say, if they um and aar it might be a bit of a worry. Just see what they say.
 
99% of gas boilers that people fir are oversized. You'll be fine.

For instance, im in 115sqm 1960s house. I'm running on 8.5kw air source heat pump at 350ish% efficiency.

Your new boiler will be 90% efficient so even if they didn't do the sums you should be absolutely fine.
 
Kimi said:
99% of gas boilers that people fir are oversized. You'll be fine.

For instance, im in 115sqm 1960s house. I'm running on 8.5kw air source heat pump at 350ish% efficiency.

Your new boiler will be 90% efficient so even if they didn't do the sums you should be absolutely fine.
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Except if you get the calculations wrong your boiler could rarely be condensing and you will lose quite a bit of that efficiency as the boiler won't condense.
 
You set the flow temperature yourself - so knock it down into condensing territory, and it'll just fire up less often.
Your rads do need to be sized for the lower temps though - so here's hoping they were well oversized in the first place!
 
Transam said:
You set the flow temperature yourself - so knock it down into condensing territory, and it'll just fire up less often.
Your rads do need to be sized for the lower temps though - so here's hoping they were well oversized in the first place!
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You want it to stay on not cycle to be efficient.
The perk of opentherm is that it manages the glue temp for you. Big delta in temperature required and it goes to full power, only a few degrees and it will flow at 25c.
 
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