Removing old boiler (1989) and HW cylinder, putting new one in kitchen and all pipe works - how much?

[Matt]

Bet you are regretting using that hacksaw.

[Doctor Drivel]

[Lobster]

When you say a thermostat, aree you sayiny it is compulsory to have to have roomstat in the one room which is not covered by a TRV? I'm about to have a system installed and was intending to go for a towel rail in the bathroom with manual valves, and no roomstats (all other rads with TRVs) - does this design not cut the Part L mustard? Had a look at the approved doc but can't find this.

Thanks David

[Dave Plowman (News)]

But Drivel with his habit of spending other's money unwisely will have a pumped circulation system from the twin 'combi's' fitted on the next planet.

'Cause he hasn't a clue.

[Dave Plowman (News)]

Dead on cue. What a wanker.

Give some figures about the likely extra cost of installing a combi other than in the kitchen, the cost of the circulating pump to give near instant hot water to that kitchen tap, and the likely degradation of the water quality in that long loop which will effect the taste of tea, etc, made from it, against the cost of heating *fresh* water in an electric kettle. And then compare to the cost of using an ordinary kettle on a hob.

And just f**k off back to the planet Zog.

[Dave Plowman (News)]

What a fool. A 'tank.cylinder' system can have any performance you want - assuming the tank provides the required pressure and flow into a cylinder sized accordingly, up to the point where they run out. Which is down to design - not principle.

A combi is restricted by the available gas and water supply.

Only a fool doesn't understand this.

Only on planet Zog.

[andrewpreece]

I'm not sure of the source, but when I installed my own boiler I was surprised to find out that for new installations ( post 2001 I think ) all CH systems had to be controlled by a thermostat in a room. The reason is that the thermostat actually turns the boiler off instead of letting it mess around occasionally heating up the loop water and circulating it through the bypass valve, when all the TRV's are off because the house is up to temperature.

I can't imagine this would happen very much except in special circumstances, e.g. you had the CH on and the weather became warm enough that the house was so warm that the TRV's shut off. Then the boiler would still try and keep the CH loop hot, wasting energy.

You'll have to search around for a reference, or go back through the Google Archive of uk.d-i-y, which is searchable by keyword, if you didn't already know.

A word of warning, the room you choose to have the thermostat to go in must not have an alternative form of heating in it e.g. open fire, else the thermostat will shut off the CH. Also, the room should really have a radiator in it that is slightly less powerful than those in the other TRV'd rooms, as you want all the trv'd rooms to get up to temperature before the thermostatted room is, otherwise, by shutting the boiler down it will prevent the trv's from achieving their set temperatures.

I cannot see that your design meets the regs, as the boiler cannot be completely turned off when the house is up to temperature. Don't take my word for it though, DYOR.

Andy.

[Doctor Drivel]

If you want 1.5" pipes all over the house, then yes.

[Doctor Drivel]

Yes, a fabulous way of having hot water instantly at the taps.

[John Rumm]

"Salesman" is the word you are searching for ;-)

1989 does not sound that old really... is it actually broken now? If not then don't fix it. When you must replace it, then do so with a reliable high efficiency boiler, but until you need to there is not much to be gained.

Might be true. But can be changed.

Not aware of it being illegal however.

If the rads do not have TRVs then they will need replacing to come into line with Part L of the building regs. You may also need to replace the lockshield valves if when you convert to a sealed system since the higher pressure can cause older ones to seep a little.

Make sure this is a viable option first. Check you mains cold water flow rate (stop watch and a bucket!). If you are getting less than 20 l/min it will be marginal for a decent combi. Also allow some overhead in case the water pressure is reduced in your area. Note also the time of day you do the flow rate test. If you routinely take a shower at the same time as half the neighbourhood you may find the flow rate available when you need it is not good enough.

Assuming the above is ok, then look for a *very* powerful combi (minimum of 35kW - but more is better) to get anything like decent performance on bath filling. Alternatively retain the stored water components of your system and use the heating circuit of a combi to drive those much like the current boiler does, but use the hot water circuit of the combi to drive a shower (where the mains pressure is handy), or the kitchen / basin taps etc.

If you do this then don't forget to budget for new shower valves if your current ones are unable to cope with the high pressure. If you go for the whole house fed from the combi, then having a thermostatic mixer also becomes more important, because the temperature of the hot water is more prone to vary in response to demand.

Not having it in a bedroom may be a good point when selling (or for someone sleeping in the room). There is no safety hazard with it in the bedroom, but they can be noisy enough to irritate some people.

This may or may not be a good idea - depends on how you use your hot water.

That sounds about right (assuming two men) or three to four for one man. (took me about four days to do all of what you describe).

2000 - 2500 (including the boiler) sounds fair. Perhaps a bit more if there are lots of rad vales to replace.

[Lobster]

Or even the rads themselves, if they are as old and crabby as two of ours were when we had a sealed system fitted a few years ago: both of them 'blew' without warning a couple of days later; ie a hole appeared - in the middle of a panel - and just about flooded out the house.

Actually it was particularly galling as after the first rad went, and we replaced it, we decided that it would be sensible to replace the second one urgently as well: however, before we had a chance, that one blew too (on the very next day), with identical results (fortunately in the room below the original, which was already totally trashed...)

David

[Set Square]

I thought that one of the features of sealed systems was that - in the event of a leak - they should only spill a couple of litres of water before running out of pressure. Is this not so?

[Matt]

Drivel by name, dribble by nature. Time for you to go home but you must do better tomorrow Drivel, sales here are lagging behind probably down to too much leaflet reading among plumbing counter assistants, yet sales of copper tanks in Japan are soaring, so much so we now have an office and warehouse over there to handle all the demand.

[Tony Bryer]

A finite amount of water: initially the volume which the expansion vessel has taken up when pressurising the system and then the rest of the water in the system above the hole - either a steady drip, or at a greater rate if an AAV in the boiler or elsewhere is letting air in. But at some point it will stop whilst with a gravity system and header tank supply not turned off the water will flow indefinitely.

[Doctor Drivel]

This one should be back at the clinic by now.

[Lobster]

Did I write that?! OK, I was exaggerating a bit, but it was certainly a goodly amount of liquid, enough to soak the carpet and sofa in the room below the bedroom with the trashed rad.

David

[Dave Plowman (News)]

Long time since you did any plumbing? Apart from flooding a house recently? Wouldn't it be a good idea to get some re-training if you wish to give advice here? Or simply leave it those with some recent real world experience?

[Dave Plowman (News)]

True it will, but a well designed 'open' system will in fact 'consume' very very little water, so doesn't need a full flow feed. If you really are worried about the possibility of a flood, fit a flow restrictor. You could probably set this at something like a maximum of a litre a month, or even less. The standard header tank for an open system will last probably about two years before running out on a well designed system. Basically, pressurised systems are a con for most houses. Fine if space is at a premium, or in a flat, etc.

[Doctor Drivel]

The point was in case of a leak. If away fro 4 weeks and the sealed system springs one, only the water in that part of the system will leak, with an open vent system is will be a continuous water fall.

Boy some people are dumb.

[Nick Atty]

My inlaws have just had a boiler replaced. Glancing at it last time I was there it looks as though they've converted the system to pressurised at the same time (not to a combi - it's still got an external pump and tank). There's a new bright red accumulator connected to the boiler output pipe, with a filling loop, a gauge and a pressure release valve. I *think* it's a condensing boiler (there seems to be a new outlet through the wall) - I'll have a better look next time I'm there.

Any ideas why anyone would want to do this? They haven't made any other obvious changes to the system (I'd have zoned it myself - it's a large house).

There are still problems with it that the fitters keep coming back to: apparently it works fine for hot water, but soon if the heating comes on, the pressure drops and it stops working (which sounds to my inexpert ears like an old system not liking being pressurised and developing a small leak somewhere) .