System or combi boiler?

[newgal85]

You should look to have the lead pipes replaced

Yep definitely need to do that asap

 

[firemant]

Hi Stigster - Thanks! I forgot to mention water pressure is low downstairs and decent upstairs and water is coming through led pipes

That does not make a great deal of sense. What do you have downstairs, and are you refferring to hot or cold, or both. Whatever scenario I can think of will result in a greter pressure down than up - if iot is noticeable at all.
For it to be opposite suggests that there is/are valve(s) in play

 

[Burger]

Not sure I’d have another combi, in my last house (2 up 2 down) we had a Worcester 28si 2, which was great, but I work on a lot and majority of them aren’t that great. Just my opinion though.

 

[MC78]

Hi guys

We want to do a whole revision of our boiler system- we currently have a system boiler at the moment with a water tank upstairs. One bathroom currently with electric shower and a 2nd bathroom still being constructed. What do you guys advise? Please let me know if this is in the wrong forum and I can move accordingly - thanks

If you want a powerful shower, the key is to make sure that the combi boiler is powerful enough to supply a hot water flow rate of at least 12-15 litres a minute.

 

[fixitflav]

Yep you are right- I have a cold water tank in the loft and hot water tank next to upstairs bathroom (which is very old so definitely needs cleaning out)

Consensus seems to be that unvented cylinder is the way to go for improved shower, provided your mains water pressure and flow are adequate. Needs checking before finally deciding. Specially if your current cylinder is on its last legs.
Is there anything wrong with the existing boiler? If you decide to replace it, you could go for heat-only, if there's room to install separate and expansion vessel, if not another system boiler.

 

[JohnnyM]

I went on a Baxi product training day last week (Baxi 600 series) and not one of the of the installers there had a Combi in their own house. A bit of food for thought?

 

[JohnnyM]

Looks like I went on it twice

 

[fixitflav]

I went on a Baxi product training day last week (Baxi 600 series) and not one of the of the installers there had a Combi in their own house. A bit of food for thought?

Friend of mine runs a gas company, made redundant by BG early 90s, struggled for a couple of years, then combis took off and he's never looked back, gets most of his work from combi callouts. He wouldn't have a combi in his own place.

 

[kasser]

Doesn't a system or heat-only boiler use less gas than the equivalent combi one?

With the combi, water needs to be heated instantaneously, you need a big power output for that. With system boilers, you heat up a tank of water then keep it warm.
So cheaper to run a system boiler.

 

[Scott_D]

Doesn't a system or heat-only boiler use less gas than the equivalent combi one?

With the combi, water needs to be heated instantaneously, you need a big power output for that. With system boilers, you heat up a tank of water then keep it warm.
So cheaper to run a system boiler.

Would be good to know the actual figures for this

 

[kasser]

You

Would be good to know the actual figures for this

You don't replace a 24kW combi with a 24kW system?
If you look at the heat input of system boilers, the range is much lower than combis.

 

[Scott_D]

You

You don't replace a 24kW combi with a 24kW system?
If you look at the heat input of system boilers, the range is much lower than combis.

I mean the gas useage of a combi vs a boiler and cylinder

 

[fixitflav]

I mean the gas useage of a combi vs a boiler and cylinder

For a given property, combis usually rated 2-3 times higher output than system or heat-only, due to the need to get a decent hot water flow. So instantaneous gas usage is higher (can mean increasing gas pipe size). Overall consumption for CH probably doesn't vary much, just depends on the efficiency of each. For HW, depends on type of use. If it's all in one lot each day, combi could be better. If (more likely) it's many small draw-offs combi likely to be worse.

 

[newgal85]

Thank you to everyone for your advice - I've gained a lot if knowledge from this forum!

Decided to go with system