Replacing a hot water tank - is this reasonable?

[Laurieo]

Its like who wants to be a Millionaire 50/50 and your right answer has gone .
I would take the hot mixer tap off ( after shutting water off) and see if valve/cartridge is working correctly .
If all other hot taps are working it should be the tap ,as your supply dosent know where it is going .

 

[ianmcd]

I would be considering an unvented cylinder which would be about £950 fitted at my prices. But that would need a good mains water dynamic flow and pressure.

and what are you going to heat the radiators with ?

 

[Harry Bloomfield]

I've never had a combi, only HW tanks, so although I know they are commonplace, it's still unfamiliar to me.

You may regret it if you do swap to a combi, think very carefully before you commit to one. They have major disadvantages when compared to the alternative, which you already have a major investment in.

 

[shorn]

and what are you going to heat the radiators with ?

Am I missing something here? The cylinder would, would it not?

 

[ianmcd]

I would be considering an unvented cylinder which would be about £950 fitted at my prices. But that would need a good mains water dynamic flow and pressure.

and what are you going to heat the radiators with ?

 

[shorn]

They have major disadvantages when compared to the alternative

Can I ask what? Everything I'm usually told points to them being more efficient etc etc.

 

[ianmcd]

Am I missing something here? The cylinder would, would it not?

Nope an unvented cylinder simply heats the HW it wont heat your radiators

 

[shorn]

Nope an unvented cylinder simply heats the HW it wont heat your radiators

So the boiler is providing the heat to the rads right? Doesn't it also pass through the cylinder in a coil?

 

[Harry Bloomfield]

Can I ask what? Everything I'm usually told points to them being more efficient etc etc.

They can become more efficient, if you are out all day, or work / live in the place irregularly. They are obviously a cheaper simpler system to install, than what you have.

Filling a bath can take much longer with a combi, because they heat the water from cold. They have to have a much higher Kw capacity, than is needed for the central heating, just to be able to heat up the water on the fly - so less efficient than a correctly sized normal boiler for the heating system, plus stored hot water. Probably a larger gas pipe will be needed to cope with the higher capacity boiler. Much more gas and water is wasted, with a combi, because you have to wait for the heat to get to the water.

A combi boiler, whilst being simpler to fit, is internally much more complex and compact. Almost everything which goes wrong will need a gas qualified engineer to fix it.

 

[ianmcd]

Nope you have a thermal store, the HW that comes out of your taps passes through a coil inside the cylinder and picks up its heat from the hot water inside the store, which is the same water that is circulated through the rads and your gas boiler heats this water , you could fit an unvented DHW cylinder but will need alterations to have the rads heated directly by the boiler, will need additional controls, plumbing etc

 

[shorn]

They can become more efficient, if you are out all day, or work / live in the place irregularly. They are obviously a cheaper simpler system to install, than what you have.

Filling a bath can take much longer with a combi, because they heat the water from cold. They have to have a much higher Kw capacity, than is needed for the central heating, just to be able to heat up the water on the fly - so less efficient than a correctly sized normal boiler for the heating system, plus stored hot water. Probably a larger gas pipe will be needed to cope with the higher capacity boiler. Much more gas and water is wasted, with a combi, because you have to wait for the heat to get to the water.

A combi boiler, whilst being simpler to fit, is internally much more complex and compact. Almost everything which goes wrong will need a gas qualified engineer to fix it.

Thanks, that's a good run down. I work from home, two kids so we use a decent amount of water. Tanks have always worked well for us, so reluctant to change.

Nope you have a thermal store, the HW that comes out of your taps passes through a coil inside the cylinder and picks up its heat from the hot water inside the store, which is the same water that is circulated through the rads and your gas boiler heats this water , you could fit an unvented DHW cylinder but will need alterations to have the rads heated directly by the boiler, will need additional controls, plumbing etc

AH ok. That's what I meant, with changing to an unvented cylinder, the rads would be heated from the boiler. I was aware that there would be some alterations required, but I believe that as everything is there in the airing cupboard (boiler in/out, CH in/out and HW in/out), then it's all possible to do.

 

[ianmcd]

Thanks, that's a good run down. I work from home, two kids so we use a decent amount of water. Tanks have always worked well for us, so reluctant to change.



AH ok. That's what I meant, with changing to an unvented cylinder, the rads would be heated from the boiler. I was aware that there would be some alterations required, but I believe that as everything is there in the airing cupboard (boiler in/out, CH in/out and HW in/out), then it's all possible to do.

yes possible to do but not as simple as that

 

[shorn]

OK. Well to be honest, from everything I've learned from this thread, I'm feeling happy to stick with what we currently have.

It's taken a bit to get my head around how it works, but if I'm understanding a thermal store correctly. The water in the tank is the what is pumped around the central heating system. The boiler feed comes in, coils through the tank and heats the water inside returning directly (pumped) to the boiler. The cold water mains water comes in, is heated in a coil within the tank and then is fed back direct to taps/outlets, via the blending valve to regulate the temp.

Obviously some things to still be sorted, but if it's just a case of a component needing changing (mixer/blending valve) we can do that now and then replace the cylinder with a new thermal store one when required, and replace the boiler with a new one when required. (I'm a bit against changing things until they need to be changed!) On that, when looking at possibility of changing to a combi, we were told the gas feed would need to be upgraded (I believe it is current 15mm) This was a pain as the supply is the other side of the house and upgrading wasn't easy. Would that still be the case when replacing the current boiler with a modern like for like equivalent? is 22mm now expected/standard?

 

[Harry Bloomfield]

Would that still be the case when replacing the current boiler with a modern like for like equivalent? is 22mm now expected/standard?

If it was correctly sized for your original boiler and nothing else has changed - then it should still be adequate.

 

[shorn]

Just checking out the bath mixer now. No isolation valves (of course!) but the HW feed that comes into the bath tap is directly tee'd off just before that for the shower feed. Showers keep HW coming through, bath does not. I'm wondering if the mixer is somehow drawing cold in?