Combi v System for 4 bedroom house

[oldbutnotdead]

Look at the Intergas offering.
Fit a 24kw combi as open vented and hook it up fo the cylinder.
Boiler can deliver water to kitchen and utility area, cylinder to washing drawoffs

That's near enough what I've got. There's one small snag (in these low flow temperature days)- the option to run flow at a high temperature when the cylinder calls for heat is an installation either/or with the combi section on the Rapid 24 and 32.
You can run with a cylinder but the max cylinder temp is then determined by the heating flow temp- not ideal for piping hot water if you run at 55 or 60° to the rads.
It may be possible via Opentherm but I don't know how yet.

 

[fixitflav]

One not mentioned yet is that if the gas boiler or supply fails you can still heat it with the immersion heater!

The OP mentioned this in #18.

If you must get a combi you need an adequate dynamic flow rate from the mains water!

He's not thinking of getting a combi, rightly IMO!

But I would always go for a pressurised one. Very few systems give many leaks when pressurised.

For a new installation, depending on the house layout, likely to be a toss-up between open vented and pressurised, but he already has open vented, so not likely to be worth changing.

 

[Harry Bloomfield]

Very few systems give many leaks when pressurised.

That is at odds with my own experience and there are frequent problems reported on this forum.

 

[DP]

That is at odds with my own experience and there are frequent problems reported on this forum.

My thoughts too. And witnessed.
Was about to respond but then refrained

 

[fixitflav]

That is at odds with my own experience and there are frequent problems reported on this forum.

And how many leaks is "many"? One is more than enough

 

[Harry Bloomfield]

There is

And how many leaks is "many"? One is more than enough

There is almost never a time on this forum, when one or more are not struggling to deal with pressure loss on a sealed heating system.

 

[RobGra]

Thanks to everyone,I really appreciate your advice.
I'm going to get quotes for both retaining the CW storage tank in the attic, and converting to a pressurised HW storage cylinder in my airing cupboard. I'm leaning towards the pressurised cylinder. I have a Hive already fitted, and would like to keep, I'm not sure an open therm system would be advantageous?
Suggestions welcome, as long as it's a long warranty!

 

[fixitflav]

I'm going to get quotes for both retaining the CW storage tank in the attic

And retaining the F/E tank presumably (not to be confused with the CW storage tank).
If it were me I think I'd replace the boiler with another heat-only, and let that settle down for a while before going ahead with a pressurised HW storage cylinder.

 

[RobGra]

And retaining the F/E tank presumably (not to be confused with the CW storage tank).
If it were me I think I'd replace the boiler with another heat-only, and let that settle down for a while before going ahead with a pressurised HW storage cylinder.

Yes, keeping the small FE tank in the attic.

I kinda think I'd like to get it all done at the same time.

 

[old duffer]

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[fixitflav]

Yes, keeping the small FE tank in the attic.

I kinda think I'd like to get it all done at the same time.

No problem, your choice!

 

[RobGra]

Apologies for revisiting this again, but it would be good to get a bit more advice:
I've started to get quotes, on both a system and heat only boiler.
The guy advocating the system boiler said that a pressurised radiator system is much more efficient (which I can understand) and
he would do a pressure test on my radiator circuit to make sure there were no leaks. I quite like this idea, along with a new closed vent cylinder. It would get rid of all the tanks in my attic.
However, the comments above about possible/probable leaks when the radiator circuit gets pressurised is giving me the fear, especially if a pipework leak occurs under a floor etc.

Am I worrying needlessly, or am I better sticking with an open vented system?

Help!

 

[bernardgreen]

or am I better sticking with an open vented system?

If the tanks in the attic are not a problem them I would keep the vented system for both cylinder and radiators.

A leakage test may show no leaks on the day of the test but newly pressurised pipework may started to leak after a few cycles of hot--cold.

Two friends regret their decision to "up-grade" to un-vented radiators.

One was able to find the leak ( stain on ceiling ) and then with floor boards lifted easy to repair ( re-solder a joint )
The other has yet to find the very slow leak which requires the pressure being manually restored about once a week

 

[fixitflav]

The guy advocating the system boiler said that a pressurised radiator system is much more efficient (which I can understand)

I don't know where he gets that from, I can't see any reason why it would be.

am I better sticking with an open vented system?

IMO, yes you are. Apart from the leak risk, the various parts, boiler, pump, F/E tank are separate so easier to work on, all inside with a system boiler.

 

[Mister Banks]

I went from a vented 20 year old system to a pressurised system 8 years ago. There have been no issues with leaks so far. Touch wood!