More central heating advice sought

[Martin Westerman]

We're currently having a fairly substantial extension built, and will soon need to decide on heating options. I'd be grateful for advice and opinions that would put me in a better position to discuss the options with the builder's "tame" plumber.

First some background on the house and current heating system. We bought the house about 18 months ago. It's 35 years old, with what I believe are original (dimplex?) radiators, and the pipes to the ground floor rads are buried wihin solid floors. The boiler is an Ideal Classic (of unknown age, suspected 60KBTU), with fully pumped CH/DHW using a 3 port valve. Hot water cylinder is about 1m high and located in a large airing cupboard. The loft header tanks are metal and look well past their use-by date.

I suspect some pumping over into the expansion tank occurs (and may have done for unknown years) as there seems to be some "gurgling" as the pump starts and there always seems to be a little air to bleed from near the pump. The pump itself is set on the fastest of 3 speeds, as it fails to cold start on any other speed.

Currently we only have one bathroom, and four sequential (pumped) showers make the last person in the queue shiver as the hot water runs out.

I've basically avoided doing anything with the system as this extension and revamp has been "around the corner" for ages now. The extension will add a kitchen (6.5 x3.5m), small utility room (2 x

1.5m), bedroom (5 x 3.5m) and en-suite bathroom (1.5 x 3.5m). I've done a very unscientific flow test and measured about 15l/min at the kitchen tap.

What we're ideally looking for is a system that is capable of:

1. heating the larger house
2. coping with at least 4 showers (if stored DHW)
3. hopefully delivering 2 decent showers in parallel (and by decent I mean more than at header tank pressure)

The first choice would seem to be whether to keep the existing boiler, or replace it for greater capacity / reliability / efficiency.

The second choice would seem to be whether to start from scratch with the radiators and buried-in-the-floor pipework.

After that, options so far include:

1. Keep system pretty much as-is, but install larger and faster recovery indirect cylinder, CW tanks, etc. Add pump for showers.

1. Pressurised cylinder. I've some concern about running existing radiators and pipes at higher pressures than they're "used to" (especially a leak in a solid floor would not be fun)

2. Largeish combi. Concern about water pressure as above, also I've some doubts about ability to deliver 2 showers in parallel.

1. Thermal store / heat bank. Seems ideal in that it would provide header tank pressure CH, with mains pressure DHW. Not sure what the drawbacks might be other than maybe cost or possible lack of awareness by plumber.

Any comments on the above (or any additional) options welcome, along with any other suggestions. Recommendations on makes / models to consider would also be gratefully appreciated.

Thanks in advance, Martin

[Lurch]

On Sun, 21 Nov 2004 19:07:33 +0000, Martin Westerman strung together this:

That's what I was thinking, although my advice on specifics of the subject may be misinformed so I'll leave that to a couple of others who know more about these than me. What I did think was that this is not a project for a 'tame' plumber. I would consider looking for a local installer with more knowledge of these systems before agreeing to anything with the builder.

[Owain]

"Martin Westerman" wrote | What we're ideally looking for is a system that is capable of: | 1. heating the larger house | 2. coping with at least 4 showers (if stored DHW) | 3. hopefully delivering 2 decent showers in parallel (and by | decent I mean more than at header tank pressure)

An alternative might be to install a new CW tank and HW cylinder in the extension, for the kitchen and en-suite. That would mean the existing cylinder and tank would have about half the workload and should be less inadequate.

The new HW cylinder could be heated off the primary of the existing boiler, possibly boosted with electric immersion in the depths of winter if the boiler is struggling (which it probably will, especially with recovery of hot water temps, but with twice the amount of stored hot water this may be less inconvenient that what you have now). The primary circuit you run into the extension can, if large enough pipes, run both the HW and the radiators in the extension.

Having an independent system in the extension would then mean you could rip out the boiler and old tank/cylinder and replace with better, in the future, with less disruption. Once you have installed the new boiler, tanks and controls, both HW cylinders should then give quick recovery performance.

You probably want to stay with a vented tank system both because of your concerns over pipework leaks, and because 15l/m at the mains won't be at all great shared between two showers.

Owain

[Roger Nevell]

I think you should give the Combi idea a miss. Currently available domestic combi-boilers deliver about 12-14l/m, this would be marginal for two simultaneously operating showers. Also, at 15l/m, I'm not sure your supply pressure would be high enough. Fine for one though, so maybe a hybrid system would suit?

Roger

[Martin Westerman]

Thanks to all who took the trouble to reply - I'm hoping to be meeting up with the plumber later this week and may post his proposals for any reactions.

Roger - the chances of you being a different Roger Nevell to the one I know seem rather slim. Hope life's treating you well and (assuming you're not a complete stranger) do you fancy a beer if we can manage to meet up over Christmas?

BRs, Martin