Replacement for a hot water cylinder

[Globalti]

We had an ancient boiler with a cast iron heat exchanger that was weeping at the joints and fizzing and steaming as it heated up. It carried on though and did the job effectively, we had lashings of hot water. My neighbour, a retired plumber, told me that in the good old days plumbers would dismantle the heat exchanger and fit new gaskets. Eventually though it had to go and it wasn't until I tried to move the cast iron core that I realised why the industry has gone over to pressed stainless steel heat exchangers; the damned thing was back-breakingly heavy to lift and certainly couldn't have been wall mounted. Stupidly I took it to the dump and threw it in a skip rather than the local scrapyard.....

The new boiler is a condenser; it is fiendishly complicated and very sensitive; it even conks out when there's a bit of air in the pipes. We have never been convinced that it fully meets our hot water requirements. We trust it so little that for the first time ever we have actually paid for an extended warranty, which we have already used once. When it does throw a wobbler they usually come very promptly but they make no attempt to diagnose the fault, they just throw new parts at it in the hope of fixing the problem, just like your car dealer. It has a fan to blast out the exhaust gases and the condensate drain runs inside into the drains so no freezing problems last winter. We think it has reduced our gas bills by abut 40% though; not certain about that because at the same time it was fitted I doubled up the insulation in the attic, which also makes a big difference.

If nothing else the new boiler is smaller, is hidden at face level inside a cupboard and is certainly using less gas. It does warm the rads up faster than the old one did so I suppose it is better.

 

[asterix]

You were talking to a friend who was talking to several heating engineers! You'll have to do better than that to sell me your story!

 

[lifeson]

[QUOTE 1540205"]
Remember as well that gas boilers now must have an independent gas feed. So if you're replacing an old boiler the man will have to fit more pipe.
[/quote]

Not true.
The boiler can be connected to an existing gas supply providing the supply is adequately sized.

If the OP is only interested in hot water I would not recommend a combi boiler. Modern boilers have a pump cycle programme which will require the heating circuit installed (even if its only a loop of pipework with no rads connected) - most combis do not condense in hot water mode so are no more efficient than a non condensing boiler.
A multipoint would be a better gas boiler option although if you are on the fourth floor, installation may be expensive.
As for reliabiltiy a multipoint would be more reliable than a combi (less parts)

I would recommend a new cylinder with immersion heaters as you initially suggested. You can look at different cylinders though to improve performance:
Unvented -
Pros: The hot water is supplied at mains pressure giving better performance
Con: more expensive to buy and install - requires a vent pipe and qualified installer

Vented
Pro: Cheaper to buy/install
Con: Cold water tank required to fill the cylinder, hot water is lower pressure

Both types can be high recovery (take less time to reheat) and have multiple immersion heatrs installed

 

[Yellow Fang]

Not true.
The boiler can be connected to an existing gas supply providing the supply is adequately sized.

If the OP is only interested in hot water I would not recommend a combi boiler. Modern boilers have a pump cycle programme which will require the heating circuit installed (even if its only a loop of pipework with no rads connected) - most combis do not condense in hot water mode so are no more efficient than a non condensing boiler.
A multipoint would be a better gas boiler option although if you are on the fourth floor, installation may be expensive.
As for reliabiltiy a multipoint would be more reliable than a combi (less parts)

I would recommend a new cylinder with immersion heaters as you initially suggested. You can look at different cylinders though to improve performance:
Unvented -
Pros: The hot water is supplied at mains pressure giving better performance
Con: more expensive to buy and install - requires a vent pipe and qualified installer

Vented
Pro: Cheaper to buy/install
Con: Cold water tank required to fill the cylinder, hot water is lower pressure

Both types can be high recovery (take less time to reheat) and have multiple immersion heatrs installed

Cheers, you sound like you know what you're talking about.

 

[Yellow Fang]

Hmm

these Ecocent air to water heat pumps look pretty good. Most air source heat pumps stand outside in the garden, but these look like they fit against an internal wall. They still cost rather more than an economy 7 immersion heater though.

 

[Globalti]

One reason why I'm happy with our traditional vented system with storage tanks is that it was easy for me to install a 20-tube solar collector.

 

[Zoiders]

It's well known that combis are known to eat through the condensing chamber and I think in the long term a lot of combis are going to turn out to be a loser.

On a cost basis for a flat with only a shower I can't recommend the dual chamber immersion tank enough.

It surpassed all of my expectations in my home, using a mains pressure mixer shower that derives pressure from a main pumping tank with a huge head of water it really is excellent.

A header tank may be something you have to look at installing at the same time if your building does not have a large communal one.

 

[Yellow Fang]

It's well known that combis are known to eat through the condensing chamber and I think in the long term a lot of combis are going to turn out to be a loser.

On a cost basis for a flat with only a shower I can't recommend the dual chamber immersion tank enough.

It surpassed all of my expectations in my home, using a mains pressure mixer shower that derives pressure from a main pumping tank with a huge head of water it really is excellent.

A header tank may be something you have to look at installing at the same time if your building does not have a large communal one.

Interesting, am I correct in thinking that if you don't have loft space for a cistern then you need either an unvented tank or a combination tank (i.e. dual chamber) ?

 

[lifeson]

Correct
A combination cylinder has the cold water storage tank built on top
Con: poor flow rate possibly non existent in a flat


An unvented cylinder connects directly to the mains water
Con: expensive to buy and install (need to be qualified to install unveted)


You could consider a thermal store which has the advantage of unvented hot water but without the complicated installation
Checkout the Albion Mainsflow Electric (pg 9)

http://www.albionwaterheaters.com/pdfs/sales/mainsflow.pdf

 

[Yellow Fang]

I checked my electric bills and smart meter readings last night. My entire annual electricity bill is less than £300, of which about half is for hot water. It works out about 2.5 units (kWh) for hot water per day. When I did the arithmetic, that worked out at about 70 litres of water heated 30 degrees. I'm sure I don't use that much most days. My maths may be wrong of course. When I had another look at my tank, I saw that in several places the insulation had been cut away to provide access to the hot water outlet, drain tap and to allow room to put the big spanner around the immersion heater element. Surely this is like a short circuit to allow heat to escape. I used to have a timer switch to put the heater on for an hour at 6am, an hour at 6pm and 30 mins at 10pm. If I'd left it on all the time, it would have cost me a fortune I reckon. It was only a cheap tank, but if I get another better tank, I hope it's a bit better designed and that it's not going to have lots of insulation cut away for ease of maintenance.

Another slight issue is that although I have economy 7, the specific economy 7 cable only seems to reach as far as where the storage heaters used to be. Am I right in thinking this circuit only comes alive at night time and switches off at day break, while the main circuit switches between day time and economy 7 tariffs? Would a competent heating engineer be able to extend the economy 7 circuit to the immersion heater?