Aga supplying water - too hot?

[yellowtriumph]

Well its interesting that you have posted to the thread since I was going to do so myself, with the latest update, in only a few weeks time. But I'll post now and update later too.

On reflection the problems did start when I replaced the Stuart Turner pump - but it was absolutely 'like for like'. With regard to your thoughts - my wife (who is not technical) said you're pumping through too much water and swamping the thermostat. My reply was that the thermostatic 'bits' are totally enclosed in a chamber and cant be aware of how much water is flowing through it - just how hot the water is and will try and mix hot/cold to get the output temperature within range. Is this incorrect on my part? That said, before I tackled any other solution I did try turning down the gate valve on the hot water feed in case it was being overwhelmed even though I was sceptical. However, I found the temperature out of the shower fluctuated quite a fair bit with no consistancy - otherwise I would have stuck with that if it was a solution.

Pipework. The pipes in the shower installtion are all 15mm.

Stat: The current one is not so old (£120 - eek) , Do remember the spec is a max of 75deg input temp and I am feeding it with nearer 80deg - I think I am over cooking it.

As per my earlier postings, a few weeks a go I finally got round to fitting the trc thermostatic valve in series with the hot water feed. The result was a 100% instant success - but this can't really be a surprise. I now await the time in a few weeks time when I switch on the radiator in our small en-suite bathroom and the temperature of the hot water in the supply tank to the Aga drops.

However, I am interested in your thoughts. or indeed anyone's thoughts, about the flow rate of the (too) hot water being too great. Regards.

[yellowtriumph]

Hi YT

Most showers would be around the 40 mark so a flow from the Mixer at 50 should need to be mixed down further by the shower . If it is a long way from kitchen to the bathroom it may be advisable to fit one in each room to avoidproblems due to heat loss in the pipes

Thank you john, distance is not a problem with my installation. Approx 40deg does seem to be the consensus. Regards.

[yellowtriumph]

I thought readers might be interested to know how 'things' went during the winter months - since fitting the rwc thermostatic mixer valve last October.

I know this is a long thread, so a few posts up I summarised our problem and situation if anyone would like to catch up quickly.

Due to the mild weather, and the fact that we were away during late Jan/Feb, we did not feel the need to switch on the small radiator in our small bathroom which acts as a heat sink to our second hot water cyclinder. This is a pity really as it would have given much more valuable information to the forum if I had done so - if only for a week - I'm a bit annoyed with myself over that one.

What I can say is that the themostatic mixer valve continues to work well and unsurprisingly the temperature of the showers we have is consistantly acceptable and controllable.

As 'Aagaman' very correctly pointed out to me when I was embarking on this, all I am really doing is treating the symptoms rather than sorting out the root cause of our problem. But, I do not think I have been able to determine exactly why this problem (of excessively hot water) flared up after many years of otherwise perfect performance. So, the proposed 'get around' of plumbing in an inline thermostatic mixer valve continues to work well. I would recommend the rwc range of products on the basis of our experience - the mixer valve is clearly made to a very high mechanical standard, and was very reasonably priced. I hope this has been of some help to the forum.

[jonsox]

Hello All,
Been reading the Aga hot water saga with interest as I have a two oven Aga which heats the hot water and has done so for the last 30 years. Recently however one of the two heat sink radiators ( one in airing cupboard ajacent to the hot water cylinder and the other in the shower room next door) started to weep from a pinhole.
I obtained two new rads shut down the Aga ( Oil fired) and comenced draining the boiler jacket & primary coil in the indirect cylinder plus the two rads after tying up the ballcock in the heating coil header tank in the loft.
Lots of dirty water later, the water was still flowing! would not stop even though header tank was empty!..Shut off the main cold water feed to the cylinder and eventually the flow from the primary circuit stopped! Ego an internal leak in the cylinder ( how long the leak had been present I have no idea)
Went to order a new cylinder and discovered by accident that there are two types of indirect cylinders one for gravity feed primary coils and one for pumped feed coils. The Aga is of course gravity feed. After almost ordering a pumped feed cylinder I looked for a gravity feed one only to find that there is very little info concerning them and the fact that a pumped primary coil cylinder will not work with an Aga.
I eventually found a gravity feed one ( called a dual feed? does this mean it has 2 primary coils) and am currently awaiting delivery of same ( I am assured it will work with a Aga!).....needless to say the pipe work will need altering, as although the connections are the same (1"-28mm for the coil and 1" - 22mm for the cold feed and hot water take off) the spacings are different.
Just wondered if anyone else has come across this problem and / or knows how to tell a gravity from a pumped feed cylinder? Been without hot water for several days now and things are getting smelly!

[yellowtriumph]

Its interesting that you posted this. As part of our 5 year electrical inspection we have to have fitted to new thermostatic safety cut outs fitted to each immersion heater in both our two indirect cylinders. However, the second cylinder (the one producing very hot water) has virtually no headroom above it and so it will have to come out to have it fitted.

The chap that came to look at it asked about how well it worked - I said "too b******y' well, the water is far too hot". He said, 'perhaps you have leak from the indirect coil direcly into the cylinder. I had never thought of that.

So it's coming out in a few weeks time, to have the new safety cut out fitted and he will inspect the existing 25year old cylinder and replace if necessary. I will report back my findings.

[john]

A Double feed cylinder is just a conventional one . Two tanks , one to feed the domestic hot water cylinder and one to feed the indirect primary coil. As opposed to single feed such as primatic where the the primary is filled via an airlock in the coil.

A perforated coil would just behave as a primatic .( should not produce excessive hot water)
Excessive heat could accelerate corrosion of the primary coil though.

[jonsox]

Hi Yellowtriumph,
I used to have a green one!!........but only a mere 13/60
Re the Cylinder question. I would not have realised that the cylinder had an internal leak until I came to drain the primary circuit to replace the radiators.
Having said that, a few years ago we did suffer from a similar problem of much too hot water. Our Age service engineer suggested spacing off the water jacket inside the Aga this he did fairly simply ....just removed the top and enough vermiculite to expose the water jacket. undid the clamping bolts and spaced it off with some large washers about 1mm thick.
This cured the too hot water problem but a little later the pressure relief valve on the feed pipe to the cylinder failed and had to be replaced, but the primary circuit was only drained just enough to facilitate this so any internal cylinder leak was probably missed.
Lately the water had been getting very hot again just before the radiator started to leak. I am wondering now if the intial problem of overhot water was indeed being caused by such a leak which had been present for some time and the overheating also caused the pressure relief valve to fail?
Will keep you posted as to what happens when I replace the cylinder. Will maybe have to move the water jacket back again.
Still not sure how to tell a gravity fed cylinder from a pumped one though? apart from taking a salesman's word for it?
As a matter of interest I also intend to fit a backup / booster immersion heater and wonder what is the 'safety cutout' of which you spoke?

[yellowtriumph]

The safety cutout ? - as you will probably know an immersion heater consists of two parts, the heating element itself and the temperature control 'element' (thermostat) which sits close by to the heating element. Generally, the thermostat fits inside a tube which passes into the body of the cylinder - in this way it can be changed if it becomes faulty (and you have the headroom above the cylinder!)

The thermostat is wired in series with the heating element and will have a temperature setting control on it - to allow you to set and control the temperature of the water you're heating. Modern electrical safety regulations now require the use of an integrated safety device to limit the maximum temperature that the water can be heated to. This is to avoid the possibility of the immersion heater heating the water far too much. So, in effect the thermostat has to settings - one that the user can set to control the temperature of the water being heated up, and second one (not usually user adjustable) to be the absolute maximum temperature that the weater can be heated to if the user operator control fails. This is all integrated into the top of the immersion heater - there's nothing seperate etc.

If I have to have my cylinder replaced, I will have one with a horizontal immersion fitted in case it has to be replaced in the future.

If you have the time (and inclination) to read through this topic (which I started a long time ago) you will see that I too went through the 'marlarkey' of splitting the water jacket away from the barrel etc.

[jonsox]

hello yellowtriumph,
Thanks for your reply.....yes I understand the immesion heater has a setable thermostatic controller just wondered if your 'safety cutout' was a seperate device I didn't know about. I guess all good quality immersion heaters will have the additional safety cutout?...one would hope so anyway.
Not recieved the new cylinder yet but will let you know how I get on reconnecting it and how it behaves.
Cheers for now
jonsox

[jonsox]

Hello all ,
Just thought I would update you on fitting a new cylinder to my AGA ....cylinder finally arrived after having to cancel the first one ordered as they did not deliver and would not answer the phone or emails they were Competitive Heating Supplies .com...strange people! Contacted
http://www.gasapplianceguide.co.uk/AGA% ... inders.htm who could not have been more helpful and got a bespoke cylinder to me c/w Imersion heater in 2 days.
Original old cylinder was fitted some 40 years ago so I expected cold water feed & outlet pipes to be 3/4" and not 22mm ..so purchased correct olives for 3/4" pipe to 22mm fitting all fitted OK & leak free.....The 28mm primary coil feeds from the AGA however were not! I'm not sure what 28mm pipe equivalent was 40 years ago...think it was 1" which is measered internally? However I was assurred I could use 28mm fittings with no problem. Whilst the compression nut would go on the pipe the olives would not ..I used 'Flowflex' 28mm fittings!.... much cursing later I tried a 28mm olive from a pack of spare olives and found it fitted perfectly as did those which came with the fittings on the cylinder, albeit a slightly different shape with no grooves in them. Went into B&Q and purchased several more packs of 28mm olives which again fitted fine. So had to replce all the olives which came with the Flowflex fittings.
Got the primary circuit to the AGA connected up and turned on water with new furnox....again no leaks so well chuffed just lit AGA and will report tomorrow on heating performance....just wondered if anyone else had had the problem with Flowflex fittings and older pipe?
more later
John

[jonsox]

Hello all,
Final update!..... AGA now all fired up and up to temperature, Hot water cylinder performing as the old one....no noticable difference...... shower this morning was perfect ...and very welcome after 2 weeks travelling to my sons house to use his!!....luckily he only lives a short distance away!
Just have to adjust the lockshield valves on the heat sink rads for the flow which will 'waste' just enough heat to prevent the water getting too hot....This tends to vary slightly from winter to summer as you might expect and of course with hot water usage.
I imagine with a little thought one could have a cylinder stat open a valve to the rads when the water got too hot and close it when it cools ....will think about that .....rather than keeping the wastful system that has worked for the past 40 years...... especially with current oil prices!
Cheers for now and thanks to all for the very useful info I found on this forum
jonsox