Which boiler system is best?

housebuyer143

I live in a largish 4 bed detached house and the hot water tank is leaking and the boiler is faulting, so it's time to change it. 

Which system would you recommend best for our house? 

We have fantastic (and maybe a little too strong) mains pressure but want to ensure our showers remain as powerful as they are now. 

We do not use a lot of water and only heat the tank 20 mins a day. 2 adults and a child live here. We want to ensure we have enough hot water to run the radiators (of which we have 15) and the showers at the same time if needed.

What are the pros and cons of a combi system or a hot water tank and boiler system? 

grumbler

housebuyer143 said:

... hot water tank is leaking and the boiler is faulting...

....

We ...want to ensure our showers remain as powerful as they are now.
What are the pros and cons of a combi system or a hot water tank and boiler system? 

Is it not worth saying what boiler, HW system and what showers you have?

housebuyer143

grumbler said:

housebuyer143 said:

... hot water tank is leaking and the boiler is faulting...

....

We ...want to ensure our showers remain as powerful as they are now.
What are the pros and cons of a combi system or a hot water tank and boiler system? 

Is it not worth saying what boiler, HW system and what showers you have?

The boiler is an old glow worm one, so its coming out regardless and the tank is leaking, so its coming out as well. Its a megaflo pressurized cylinder. I suppose I wondered what set up tends to be better. Can you get good pressure and performance from the correct sized combi over the tank and boiler set up? 
I think thats my preference, but will regret putting something in, that is not as good.

Bendy_House

There are pros and cons for each system. And I suspect the pros of the combi - and there certainly are some - will be becoming outweighed now by the rising cost of energy, and the almost-certain future benefit of having a stored hot water system which can be heated by alterative methods.

Assuming your mains flow is a solid way-above-20lpm, backed by an equally solid pressure - say 3bar or so - then a large combi should give you a shower that's fully satisfying. Only the largest combis will provide two showers like this at the same time.

Anyhoo - must dash. Dawgs need walking...

housebuyer143

Bendy_House said:

There are pros and cons for each system. And I suspect the pros of the combi - and there certainly are some - will be becoming outweighed now by the rising cost of energy, and the almost-certain future benefit of having a stored hot water system which can be heated by alterative methods.

Assuming your mains flow is a solid way-above-20lpm, backed by an equally solid pressure - say 3bar or so - then a large combi should give you a shower that's fully satisfying. Only the largest combis will provide two showers like this at the same time.

Anyhoo - must dash. Dawgs need walking...

Thank you. That's an interesting thought. Currently we can heat the water with gas or electric through the tank which is useful if the boiler goes down...
If I go for a combi I will look to the largest then 👍

Section62

housebuyer143 said:

grumbler said:

housebuyer143 said:

... hot water tank is leaking and the boiler is faulting...

....

We ...want to ensure our showers remain as powerful as they are now.
What are the pros and cons of a combi system or a hot water tank and boiler system? 

Is it not worth saying what boiler, HW system and what showers you have?

The boiler is an old glow worm one, so its coming out regardless and the tank is leaking, so its coming out as well. Its a megaflo pressurized cylinder. I suppose I wondered what set up tends to be better. Can you get good pressure and performance from the correct sized combi over the tank and boiler set up? 
I think thats my preference, but will regret putting something in, that is not as good.

Personally I wouldn't replace a boiler/cylinder with a combi, for no other reason than whatever the future of domestic water heating is, those with the ability to store hot water will have the cheaper options available to them.

Ripping out a system boiler/cylinder now will increase costs when the time comes that a replacement gas combi boiler is not an option.

I would also only replace an older gas boiler if it was clearly about to fail.  I'd prefer to keep it running for as long as viable so I could step over to a reasonably priced heat pump, which is likely to become the default for most homes sooner rather than later.

housebuyer143

Section62 said:

housebuyer143 said:

grumbler said:

housebuyer143 said:

... hot water tank is leaking and the boiler is faulting...

....

We ...want to ensure our showers remain as powerful as they are now.
What are the pros and cons of a combi system or a hot water tank and boiler system? 

Is it not worth saying what boiler, HW system and what showers you have?

The boiler is an old glow worm one, so its coming out regardless and the tank is leaking, so its coming out as well. Its a megaflo pressurized cylinder. I suppose I wondered what set up tends to be better. Can you get good pressure and performance from the correct sized combi over the tank and boiler set up? 
I think thats my preference, but will regret putting something in, that is not as good.

Personally I wouldn't replace a boiler/cylinder with a combi, for no other reason than whatever the future of domestic water heating is, those with the ability to store hot water will have the cheaper options available to them.

Ripping out a system boiler/cylinder now will increase costs when the time comes that a replacement gas combi boiler is not an option.

I would also only replace an older gas boiler if it was clearly about to fail.  I'd prefer to keep it running for as long as viable so I could step over to a reasonably priced heat pump, which is likely to become the default for most homes sooner rather than later.

Thank you. I never consider that aspect and it's worth considering because it's a lot harder to put the tank back in once it's gone..

The boiler unfortunately is beyond saving.. We bought the place a few months ago knowing it was old, but I have been told my s few people now that there are no parts for it as it's so old and to take it out and get a new one. 

BUFF

Bendy_House said:

Assuming your mains flow is a solid way-above-20lpm, backed by an equally solid pressure - say 3bar or so - then a large combi should give you a shower that's fully satisfying. Only the largest combis will provide two showers like this at the same time..

Or a storage combi like a Worcester Bosch Highflow or the Viessman equivalent.

As already mentioned, I don't know that I would, personally, go to the cost of replumbing when the next replacement cycle will probably require putting back stored DHW. How long do you expect to be in this house?
Combis also tend to be less efficient at DHW. I think that I would pay close attention to correctly sizing your replacement unvented cylinder.

housebuyer143

BUFF said:

Bendy_House said:

Assuming your mains flow is a solid way-above-20lpm, backed by an equally solid pressure - say 3bar or so - then a large combi should give you a shower that's fully satisfying. Only the largest combis will provide two showers like this at the same time..

Or a storage combi like a Worcester Bosch Highflow or the Viessman equivalent.

As already mentioned, I don't know that I would, personally, go to the cost of replumbing when the next replacement cycle will probably require putting back stored DHW. How long do you expect to be in this house?
Combis also tend to be less efficient at DHW. I think that I would pay close attention to correctly sizing your replacement unvented cylinder.

Thank you. I plan to be in this house 10-20 years so I would begrudge putting a cylinder back if I took it out. 
I currently have 170ltr tank but honestly we use so little hot water we never heat it all. Is it worth going smaller or would you say to stick to the same size tank as a like or like replacement? 

Rodders53

20 minutes on an unvented 170 litre is not far off the full reheat/recovery time for a tank of water (although the boiler may not run for the entire time if less water has been used).

I'd suggest that 170 litres is about right for a 4 bed 2 bath/shower room  house.  Some might suggest more.

Unvented all the days long:  You know it will work for your use.

Immersion in it as:
   emergency backup for gas boiler faults and
   possibly solar panel divert if/when you install panels and
   possibly economy overnight on an agile tariff if/when you go EV (and gas is more expensive)

Planning for heat pump use may be worth an investigate / pricing up.  If the boiler and Megaflo are both past their sell by then so may the radiators and other parts in the system... Making larger radiators for lower flow temperatures a wise upgrade.
  

Section62

housebuyer143 said:

The boiler unfortunately is beyond saving.. We bought the place a few months ago knowing it was old, but I have been told my s few people now that there are no parts for it as it's so old and to take it out and get a new one. 

Has it stopped working though?  Old boilers have relatively few moving parts that are likely to fail - one of them is the thermocouple which typically can be replaced with a generic one costing a few pounds.

People who can make a nice profit from installing a new (combi) boiler will be more than happy to convince you the existing boiler is both highly inefficient and impossible to repair.  What they won't mention is the combi will need more repairs and won't last very long.

The only absolutely sound reasons for getting rid of a working old boiler is if it is in a position where it will be in the way of (say) a kitchen replacement, or that not having a working boiler for a few days would be life endangering.  If you have a HWC and immersion heater then you aren't so critically reliant on the boiler not failing at an inconvenient time.