Old baxi boiler question

[liamj6]

hi I currently have a baxi solo 40 rs boiler that was in when I bought the house so is the original about 20 years old. Reading the manual it says it has a max heat output of 11kw- I am looking to have the boiler replaced for a baxi duo tec 40 kw combi, Will the increase from 11 kw to 40kw be noticeable on my heating or is it nothing to do with heating. Cheers

 

[Darren Jackson]

The solo was a heat only boiler so did not need a high KW rating. Where as a combi boiler has to instantly heat the incoming cold mains water by at least 40 degrees at an average of 12 to 16 litres per min. So the extra KW's are required for the hot water only. You will not notice it on the heating side.

 

[Harvest Fields]

The solo was a heat only boiler so did not need a high KW rating. Where as a combi boiler has to instantly heat the incoming cold mains water by at least 40 degrees at an average of 12 to 16 litres per min. So the extra KW's are required for the hot water only. You will not notice it on the heating side.

Unless you the engineer fitting it flushes your radiators properly. Then you will notice the difference.

 

[liamj6]

Thanks darren for your reply- we’ve been in the property for just over a year now and up to now boiler has been ok, we have a vented cylinder with header tanks in attic and hot water for washing up is always in good supply just conscious of age of boiler and our future plans for property in that seeking to replace.

Another question I have is the plan is to relocate the existing boiler from the kitchen to the attic with the flue installed through the roof. This will make it easier when we come to extend the property as it won’t need to be moved and the removal of the old hot water cylinder and header tanks to make the bathroom bigger.

It had been recommended to us to go for the 40 kw as it has a flow rate of 16 litres per min, as when the bathroom is refurbed we want a rain shower with plenty of power and the hotter the better. The plumber for the bathroom had suggested a unvented system instead of acombi as he says the pressure on hot taps is superb. Could I still achieve a good pressure on the shower by having a 40 kw combi boiler?

 

[Harvest Fields]

Thanks darren for your reply- we’ve been in the property for just over a year now and up to now boiler has been ok, we have a vented cylinder with header tanks in attic and hot water for washing up is always in good supply just conscious of age of boiler and our future plans for property in that seeking to replace.

Another question I have is the plan is to relocate the existing boiler from the kitchen to the attic with the flue installed through the roof. This will make it easier when we come to extend the property as it won’t need to be moved and the removal of the old hot water cylinder and header tanks to make the bathroom bigger.

It had been recommended to us to go for the 40 kw as it has a flow rate of 16 litres per min, as when the bathroom is refurbed we want a rain shower with plenty of power and the hotter the better. The plumber for the bathroom had suggested a unvented system instead of acombi as he says the pressure on hot taps is superb. Could I still achieve a good pressure on the shower by having a 40 kw combi boiler?

In my opinion. Yes you could as long as you don’t intend on putting an ensuite in when you have the extension done. If you do I would convert the system to a sealed system with an unvented cylinder as you have already been advised. This can all still go into the loft if space allows and you have enough mains cold pressure.

 

[Darren Jackson]

40 KW should give you plenty of hot water. But Combi boilers are not that good when the washing machine is on or another tap is on a loo been flushed elsewhere in the property etc etc...it robs the other outlets of flow and can be a nuisance. I would fit a system boiler and an unvented cylinder with appropriate sized pipework to larger properties but it all boils down to the incoming supply rate and pressure. Combi's are great for smaller properties. But not as good the more outlets and bathroom / showers you have.

 

[liamj6]

When you talk about other outlets being robbed of flow I am right in thinking with a Combi boiler if I was having a shower with the shower needing say 15 litres a minute, if the washer was on I would notice a difference in pressure on the shower?

My concern or might be a misunderstanding is if I went for a unvented cylinder powered by a system boiler, say a 210 litre cylinder how long would I have hot water for a shower with a flow rate of 15 litres a min, i don’t want it always running out. if I use all the water in the cylinder how long would it take to heat up to temperature the cylinder full? Also is there any noise with a unvented cylinder in that now with my vented system it’s noisy when header tank is filling.

 

[liamj6]

Also how do I go about refilling my existing baxi solo 40 rs after draining, had to replace a damaged joint, kids and there toys...

 

[Darren Jackson]

The new cylinder would have a rapid heat recovery coil and would not take long replenishing the hot water supply at all you would not even notice mate. Yes you would notice the second another tap, washing machine etc etc comes on there will be a big loss in pressure. One home I went to recently had a 40Kw worcester combi installed and there drench head shower actually stopped all together when anything else was turned on or flushed. There well happy now with a 28mm mm fed unvented system installed. There were three bathrooms and two en suites a cloakroom and utility room to cope with.

 

[ShaunCorbs]

Also how do I go about refilling my existing baxi solo 40 rs after draining, had to replace a damaged joint, kids and there toys...

Do you have an little tank in the loft ?

 

[liamj6]

I do yes, I’ve got the cold water header tank which I cleaned recently out as was filthy and then a smaller one next to it here’s a pic this tank could do with a clean too

 

[ShaunCorbs]

That's your heating system water

So to drain you need to turn the water off to that either by an valve or a piece of timber and a zip tie

Turn the elec off to the boiler / system and manually open your port valves (small leaver on the side push to manual) and open all the trvs (eg on setting 5)

And then open a drain point once it slows down (the flow of water) start at the highest point airing the rads to drain the water out the system


To refill close the drain port and any rad air bleeders you left open

Get some inhb and turn the ISO valve back on / remove you zip tie pour your inhb in and wait for the tank to slow / stop filling

Start are the most lowest and furthest away rad and bleed it until water comes out (you may need to take a break for 5-10 mins if air stops coming out)

Repeat with the others and once your done leave it an hour then move all the port valve leavers back to auto and turn the power back on

run your system on like normal

In a few days time when the system is off go around finally and air all the rads