Advice needed on old Alde hot water system please...

Page 2 - Passionate about caravans & motorhome? Join our community to share that passion with a global audience!
Jun 16, 2020
1,268
405
935
John, if you can get the Alde working satisfactorily but still don’t like the capacity of hot water you can enlarge it. You need a good quality tank. Stainless steel or copper. (But be carful as some metals might cause a detrimental affect On Alde parts through electrolysis). Plumb this tank in with a small circulation pump and non return valves. This way the capacity can be increased by say 10 litres.

I pinched this text from another forum. There is also a great drawing but I can’t find that now.


obtain a suitable tank 2, 5, 10 litre whatever you want to use. Instal a pipe fitting at the base of one side and the top of the opposite side.
on the water outgoing side of your heater feed it to the bottom port of the new tank. The pipe that was connected there connect to the top fitting on the new tank with a T piece in the line.
fit another T piece in the incoming cold supply with a non return valve in the line if there isn’t one already.
Obtain a 12v pump from eBay that can stand 80 deg C.
insulate the tank (I used a wooden box and expanding foam).
when you want extra water run the pump, water circulates through the tank and heater and you end up with more hot water.
ive just realised I’ve told you slightly wrong above, the new tank is on the ongoing side to the heater so you don’t have to have hot water in there if you don’t want it. Total cost including a stainless tank was about £80. I did and extra 10 litres on mine, worked like a dream.


Bear in mind. The more water you use, the more waste you will have. Are you able to run this into your foul water drain?

John
 
  • Like
Reactions: johnfrosty
Jul 27, 2020
68
9
85
Thanks everyone. Some excellent progress here. A few replies:

Yes, I can see we must have the 2921. It turns out we have the swedish manual printed off. I must have done it years ago (vaguely remember now!). It was hidden in a cupboard, my son found it yesterday. Unfortunately you can't select the text in the PDF version online (images instead of text) so I may be able to use OCR to convert it to text to translate, but more likely I can just manually type in the bits I need to understand, which will begin with the control panel. A few things it has taught me even in Swedish is that the unit which looked to me like a small immersion heater is actually a "circulation pump". That makes much more sense. 25W is ridiculous for a heater but it DID drastically improve the water temperature. I now see that the reason it does that is because it circulates the glycol heating fluid (water in my case for now) around the copper coil inside the unit on the back of the burner, this unit pictured below:



That unit has NO power cables going into it, so I couldn't see how that is the electric heater, and it's not. Apparently it has a copper coil inside in which flows the glycol heating fluid. Then hot water on demand passed over/around that coil which heats it up. It looks like the circulation pump helps keep hot fluid circulating around that coil which would understandably make the water hotter at the tap.

What I dont understand is where the circulation pump for the central heating system is, assuming there is another. If there isn't another, then this pump must do the same, which again stumps me a little as it means hot radiators just to get decent hot water, not nice in summer. Reading the 2920 manual it does talk about a switch somewhere (on the back of the burner I think) which allows the user to select "summer" or "winter" use, and it makes sense that that would prevent the heating fluid going around the radiators when the circulation pump is on, for summer use where heating is not needed but hot water is. Trouble is, I can't find the damn thing! Going to go and have another look now.

One thing I can conclude is that the gas system DOES indeed produce a (just about) adequate shower, and seemingly endless. Another conclusion is that there is no "tank" whatsoever, no storage of hot water at all. But that's fine, perhaps even better, if the burner can heat enough on demand.

I measured how much water comes through the taps, to check the flow from the pump. It took 30 ish seconds to fill a 1.14 litre milk container, so not even 2.5 litres per minute, and that was with both hot and cold running. With only cold running it took around 45 seconds to fill that same container, showing something like 1.5- 1.9 litres per minute. The Shurflow pump states 6.4 litres per min flow rate on it, obviously when new. It's very old, and this flow rate suggests I do need a new pump, or I may just try dismantling it and refurbing it as I know pumps can benefit from a clean up of the impeller etc. Worth a shot anyway. Even just 4litres per minute flow rate would be a huge improvement and plenty good enough to be usable. I had a shower in it last night, and after 8 minutes (twice as long as i would ever need) it was still a constant very warm, mildly hot temperature. Plenty good enough for visitors! It would appear I don't need storage. but if I want a better flow rate I suspect the Propex electric jobbie is still the ideal solution and it would mean I can go without the central heating system (would like to get rid of that) and more importantly, I could permanently isolate gas from going to the burner. It does seem to be working well, and the gas burns a very strong blue clean flame. But with the overall age (as ProfJohn said earlier), my honest preference would never be to use a 30 year old gas appliance in a caravan which was extremely wet inside for several years and quite a bit of rust. But it could tie us over until replacing it with the leccy tank :).

I am still a bit confused about whether I need to turn on the thermostat (switch on top, and./or dial on front) to get hot water. Logically I don't think I should have to use that as it's measuring room temperature which has nothing to do with hot water supply, but assumptions are risky and unwise, so I assume nothing in that regard.

I also still have no idea where the alleged "1kw" and "2kw" water heater elements are hidden! They can't be in that unit pictured above, because that has no electric going into it, only fat pipes (central heating fluid) and a cold in at bottom and hot outlet (red pipe) at the top which goes to the hot taps.

I will keep digging, but it's looking like it will be usable for now. I will of course be careful, and fit CO sensors, and ensure people only light the boiler when they want a shower. I am hoping (and testing yesterday seemed to suggest it is the case) that the 1kw/2kw switch very slowly heats a tiny amount of hot water somewhere in the system. I woke up this morning with the system all cold, powered off overnight. I turned the 1kw switch on, and I am about to go and check it as it's had a good few hours now. If we are lucky, I think that may provide enough hot water for very occasional hand washing or maybe a small bowl of water to wash up with, or have a shave. If that's the case then we can actually provide hot water to visitors for those small purposes without lighting up (and using up) gas from the bottle. This would mean that most of our visitors who may only shower every few days, have a ready supply of hot water for light duties like washing hands and face etc, and when a shower is needed, the gas burner can be fired up just for the 10-20 minutes it's needed, and then gas goes off again. That would be nice, feel nicer for me than running a pilot light on the burner for a whole week of someone's visit, and would serve their needs for now.

Again, long term the Propex looks an absolutely cracking piece of kit, especially being made in the UK, and would mean I could pull out all this burner etc and make a nice clean spacious cupboard with a tank in the bottom and room for clothes etc above!

Thanks again to everyone for helping, off to see how this 1kw thing works, and maybe some Swedish lessons later too :)
 
Nov 11, 2009
10,916
1,812
40,935
Thanks everyone. Some excellent progress here. A few replies:

Yes, I can see we must have the 2921. It turns out we have the swedish manual printed off. I must have done it years ago (vaguely remember now!). It was hidden in a cupboard, my son found it yesterday. Unfortunately you can't select the text in the PDF version online (images instead of text) so I may be able to use OCR to convert it to text to translate, but more likely I can just manually type in the bits I need to understand, which will begin with the control panel. A few things it has taught me even in Swedish is that the unit which looked to me like a small immersion heater is actually a "circulation pump". That makes much more sense. 25W is ridiculous for a heater but it DID drastically improve the water temperature. I now see that the reason it does that is because it circulates the glycol heating fluid (water in my case for now) around the copper coil inside the unit on the back of the burner, this unit pictured below:



That unit has NO power cables going into it, so I couldn't see how that is the electric heater, and it's not. Apparently it has a copper coil inside in which flows the glycol heating fluid. Then hot water on demand passed over/around that coil which heats it up. It looks like the circulation pump helps keep hot fluid circulating around that coil which would understandably make the water hotter at the tap.

What I dont understand is where the circulation pump for the central heating system is, assuming there is another. If there isn't another, then this pump must do the same, which again stumps me a little as it means hot radiators just to get decent hot water, not nice in summer. Reading the 2920 manual it does talk about a switch somewhere (on the back of the burner I think) which allows the user to select "summer" or "winter" use, and it makes sense that that would prevent the heating fluid going around the radiators when the circulation pump is on, for summer use where heating is not needed but hot water is. Trouble is, I can't find the damn thing! Going to go and have another look now.

One thing I can conclude is that the gas system DOES indeed produce a (just about) adequate shower, and seemingly endless. Another conclusion is that there is no "tank" whatsoever, no storage of hot water at all. But that's fine, perhaps even better, if the burner can heat enough on demand.

I measured how much water comes through the taps, to check the flow from the pump. It took 30 ish seconds to fill a 1.14 litre milk container, so not even 2.5 litres per minute, and that was with both hot and cold running. With only cold running it took around 45 seconds to fill that same container, showing something like 1.5- 1.9 litres per minute. The Shurflow pump states 6.4 litres per min flow rate on it, obviously when new. It's very old, and this flow rate suggests I do need a new pump, or I may just try dismantling it and refurbing it as I know pumps can benefit from a clean up of the impeller etc. Worth a shot anyway. Even just 4litres per minute flow rate would be a huge improvement and plenty good enough to be usable. I had a shower in it last night, and after 8 minutes (twice as long as i would ever need) it was still a constant very warm, mildly hot temperature. Plenty good enough for visitors! It would appear I don't need storage. but if I want a better flow rate I suspect the Propex electric jobbie is still the ideal solution and it would mean I can go without the central heating system (would like to get rid of that) and more importantly, I could permanently isolate gas from going to the burner. It does seem to be working well, and the gas burns a very strong blue clean flame. But with the overall age (as ProfJohn said earlier), my honest preference would never be to use a 30 year old gas appliance in a caravan which was extremely wet inside for several years and quite a bit of rust. But it could tie us over until replacing it with the leccy tank :).

I am still a bit confused about whether I need to turn on the thermostat (switch on top, and./or dial on front) to get hot water. Logically I don't think I should have to use that as it's measuring room temperature which has nothing to do with hot water supply, but assumptions are risky and unwise, so I assume nothing in that regard.

I also still have no idea where the alleged "1kw" and "2kw" water heater elements are hidden! They can't be in that unit pictured above, because that has no electric going into it, only fat pipes (central heating fluid) and a cold in at bottom and hot outlet (red pipe) at the top which goes to the hot taps.

I will keep digging, but it's looking like it will be usable for now. I will of course be careful, and fit CO sensors, and ensure people only light the boiler when they want a shower. I am hoping (and testing yesterday seemed to suggest it is the case) that the 1kw/2kw switch very slowly heats a tiny amount of hot water somewhere in the system. I woke up this morning with the system all cold, powered off overnight. I turned the 1kw switch on, and I am about to go and check it as it's had a good few hours now. If we are lucky, I think that may provide enough hot water for very occasional hand washing or maybe a small bowl of water to wash up with, or have a shave. If that's the case then we can actually provide hot water to visitors for those small purposes without lighting up (and using up) gas from the bottle. This would mean that most of our visitors who may only shower every few days, have a ready supply of hot water for light duties like washing hands and face etc, and when a shower is needed, the gas burner can be fired up just for the 10-20 minutes it's needed, and then gas goes off again. That would be nice, feel nicer for me than running a pilot light on the burner for a whole week of someone's visit, and would serve their needs for now.

Again, long term the Propex looks an absolutely cracking piece of kit, especially being made in the UK, and would mean I could pull out all this burner etc and make a nice clean spacious cupboard with a tank in the bottom and room for clothes etc above!

Thanks again to everyone for helping, off to see how this 1kw thing works, and maybe some Swedish lessons later too :)
I had a Propex cabin heater in a Trigano pop top and they are well made and customer service when required was very good. So I’d expect similar for their water heating systems.
 
  • Like
Reactions: johnfrosty
Jul 27, 2020
68
9
85
I am trying to work out how to drain the heating fluid. It should be 40% glycol, it's currently 100% water. I got to page 4 of the Comfort 2920 manual, but page 5 is missing, which is where it explains how to drain the system, dammit! If anyone knows where I might find a drain valve I would be grateful for a hint! thanks
 
Last edited by a moderator:
Jul 27, 2020
68
9
85
This appears about the best help I can find, different model but no doubt comparable info, link below in case someone else in same situation happens across this little thread in the future!: https://www.manualslib.com/manual/559295/Alde-Comfort-2923-2928.html?page=3#manual

PS - Is there a specific type of fluid i should buy? The manual just says anti-freeze like in a car, but "not a diesel". We only have a diesel car, but i am pretty sure the anti freeze is the same between petrols and diesels, except for colour. Can I just use any anti freeze concentrate or should I buy something specifically sold for caravans? (A question which helps consumers get fleeced quite often, I know!)
 
Jun 16, 2020
1,268
405
935
If you are correct then the working of the system is very different than the new models which store some water and is either heated by gas or electric or both. Again, if you are right. Could it be that the electric elements just preheat the water for the gas therefore acting as a boost.

John
 
Jul 27, 2020
68
9
85
Well now you say that, yes I do think it's storing "some" hot water, just not the amount I thought. When I saw those two units on the back (higher one contains copper element, lower one contains circulation pump) I assumed one was a storage tank. And yes I suppose to some degree the top one is, as whatever water is contained around the copper element, will of course get heated whenever the element is warmed. Again, I can't see how it's electrically warmed because no power is going in, but it does get warm with just electric on (no gas) so I am guessing there is a heating element (1 or 2 kw switchable) inside the tall "burner" tube. That would surprise me, but with no electric cables going into the unit behind, and having read the manual which explains that the unit just has copper pipes in (which are heated by drawing hot water from the "boiler" (burner tall unit at front), I think that's about right.

So yes, whatever water is around the element does appear to get heated even without gas, so there must be an element and some degree of storage.

I just tested this today. I ran the 1KW switch for one hour, no gas at all. I then got about 2 inches deep in a washing up bowl of pretty hot water. So that's the storage capacity I suppose. I don't want to use 2KW, so that would suffice for hand washing and occasional stuff like that. Firing up the gas for showers when necessary. My understanding is therefore....

1KW heats that element and the surrounding water slowly.
2KW does the same but heats it faster, and reheats faster after the hot is used, but still slow compared to gas.
Gas heats it on the fly and does a pretty good job considering its age and size, and of course heats that small storage capacity first.

This would tally with the user manual where it says it's best to "preheat" the "boiler" system before a shower to "get the most hot water possible". Actually, having tested it many times, I would reword that to what I think is more accurate....... "Preheat the burner to ensure the entire system is at optimum temperature so that the water has a consistent hot temperature". You don't get any more water by preheating, but you get it hotter to begin with, burning hot actually, but once that small reservoir of preheated water is used up (which is max one minute, as per my early tests, nearly boiling water by all accounts!) it then runs on the 'heat on the fly' system which produces a seemingly endless supply of water which is plenty hot enough for a good shower, weak pressure but nice hot temperature.

Starting to make sense now. I will use the 1KW permanently on when visitors are using it, with instructions to show them how to light the gas for a shower when needed.

Still stumped on two things:

1. How to drain the central heating fluid to replace with glycol mixture.
2. What to use as the glycol, I checked and have a good supply of red antifreeze for use in the transit we have, does anyone know if that will do the job?

Thanks again to everyone's generous time and effort helping make sense of all this. I now think I both understand the system well enough, and can provide a tolerable shower for those who want one, and hot water for hand washing and shaving without the gas. A nice compromise for now. I will keep the swear box running to work towards the Propex unit next year :).
 
Jul 27, 2020
68
9
85
oh and PS, sorry... to anyone who has owned an older caravan with the taps I have (no microswitch, just pressure system) - Where on earth can you find a replacement tap washer?!! We need a few. A couple of taps drip and that causes the pump to kick in occasionally which is quite annoying especially at night when sleeping. I have the old washer which measures 14mm outer diameter and perhaps 4mm thick, with a hole in middle. It should be encapsulated inside a brass ring. I have searched high and low and all I can find is imperial (1/2", 3/4" etc) but this is 9/16ths in imperial measurements, and I have yet to find one. If anyone has a link which might find me one, I'd be grateful!



Making good headway. I still have to find a way to sort this terrible mess out too! Such a shame :(

 
Jul 27, 2020
68
9
85
Not hopeful but if anyone can make sense of this I would love to know! There is a switch on the boiler which is a choice between "T" and "T" with a cross through it (i.e. no T). I assume T refers to thermostat, but not sure which one. I typed the relevant text from the manual into a translator and got this in relation to T (6) and No T (7) switch positions. My best guess is to go for 6, but I am very unsure. maybe someone else who has had the Alde system with that T switch on it, could explain what it does? I want no central heating at all, and ideally no need to use the room thermostat to get the circulation pump to run. That pump needs to run whenever hot water is needed, as it keeps the coil hot and improves water heating. After hours of playing with it we found we needed to have the thermostat on max, to keep that circulation pump running. But we paid no attention to the T switch (not knowing what it does), and can't remember which way around we had it. If anyone has a clue please shout, otherwise I will just leave it on T (6 below). Thanks again

(This is taken from page 12 of this manual - https://products.alde.se/storage/media/15554089235cb5a81b3d35c/bruks-och-installationsanvisning-2921.pdf)

"6. 12 or 220 volt circulation pump, whichever is selected, breaks simultaneously with the heating coil in the immersion heater via the room thermostat.

7. 12 or 220 volt circulation pump, whichever is selected, switches off via the room thermostat. The heating coil in the immersion heater continues to heat until the built-in thermostat breaks"
 
Jul 18, 2017
2,988
617
6,935
Hi Damian, thank you very very much for posting that.

First things first - the first link i posted - i said i would install that outside the caravan. I am aware of the risks and wouldn't install inside. I would probably build a weatherproof vented box outside on a plinth, a few feet away from the caravan.

Thanks for the info on pressures, I never really understand this. I assumed (stupidly perhaps) that the immersion tank systems would just use whatever pressure was coming in, but I now realise the caravan only pumps on demand so the tank wouldn't have a constant pressure to do its thing. Makes sense so those are out!

Now then... that suggestion you made - WOW! That looks PRECISELY what I need! Thank God I posted (and you did!). It's a lot of money but there is no way to do any kind of proper job cheaper than that really so we will find it and go for that. I only have two questions and since you've fitted a couple maybe you could help with answers....

1. It says "Fitted Socket 16Amp" - That's a concern. The rest of the description sounded like it was designed for a standard 13a socket, until I read that. Is it a misprint do you think? Just thinking it through (Ohm's Law is it?) 800 watts divided by 240v = 3.33 amps. Hmm. confused, maybe you can clarify? I wouldn't want to draw 16 amps down the cable we have available really.

2. 6 litre or 10 litre - I have NO idea whatsoever what is needed for a short shower, or a long one for that matter. I also have no experience of caravanning really. If in doubt obviously 10 litre would have to be chosen. But I wonder if you know if people can have a reasonably quick but effective shower from a 6L tank?

Thanks again, very much indeed!
Why don't you contact ALDE themselves about it as they are very helpful?
 
  • Like
Reactions: johnfrosty
Nov 11, 2009
10,916
1,812
40,935
Why don't you contact ALDE themselves about it as they are very helpful?
When we went out for the first time this year I used our van shower for the first time and we have a 15 litre grey water container. It was about one third full. This is about on a par with what the daily shower allowance was if I was away working and water was scarce. We told the guys “ to wash upwards as far as possible. Wash downwards as far as possible and then wash possible. “ 😂

Course of my wife needed to wash her hair the Elan Dams wouldn’t be enough.
 
Last edited:
Jul 27, 2020
68
9
85
I found the drain for central heating and now that I topped it up with water I am going to drain it down fully and mix proper 40/60 ratio of glycol to water, to fill it from empty. I know this may cause air pockets to deal wih but its the only way I can know the correct mixture is present.
The only info I can find for glycol fluid for central heating system is to use "regular car anti freeze for petrol engines". I have plenty of anti freeze, but I have never heard of antifreeze "for petrol engines", Whats that all about?! A vehicle cooling system doesn't mix or have any relationship to the type of fuel used for combustion, so is this just a phrase someone picked up and it sticks around, or am I wrong and there is a different type of anti freeze for petrol or diesel vehicles?!
 
Nov 6, 2005
4,583
358
20,935
I've never heard of different anti-freeze for petrol and diesel - just use VW spec G13, that's what the modern Alde systems use as it copes with the full range of materials.
 
  • Like
Reactions: johnfrosty
Jul 27, 2020
68
9
85
Does anyone know roughly how many litres of fluid the Alde Comfort 2921 system holds (or 2920)?

I don't have a pump so will need to replace it and remove air locks manually, which doesn't look fun especially as I don't have the breather valve (referred to in manual), no idea why it's just not there on the back of the boiler. So I am hoping I can just open the top of the expansion tank, and tilt the caravan up and down back and front, and replace the entire system with decent long life stuff mized with de-ionised water. Knowing the total amount would be good but I can't find details anywhere so far. Has anyone had experience of removing air locks by opening the expansion tank and tilting the van?
 
Jul 18, 2017
2,988
617
6,935
Does anyone know roughly how many litres of fluid the Alde Comfort 2921 system holds (or 2920)?

I don't have a pump so will need to replace it and remove air locks manually, which doesn't look fun especially as I don't have the breather valve (referred to in manual), no idea why it's just not there on the back of the boiler. So I am hoping I can just open the top of the expansion tank, and tilt the caravan up and down back and front, and replace the entire system with decent long life stuff mized with de-ionised water. Knowing the total amount would be good but I can't find details anywhere so far. Has anyone had experience of removing air locks by opening the expansion tank and tilting the van?
With a modern caravan we would lower the front as far as possible as we have the bleed valve at the rear of the caravan. We then run the pump for about an hour so all air collects near the bleed valve which can then be released to remove any air. Are you sure there is not a bleed valve somewhere on the system? Maybe ALDE can advise on Tuesday if you phone them.
 
Jul 27, 2020
68
9
85
Thanks, yes I can't find any bleed valves which is a pain. I will try calling them Tuesday.

When you say "run the pump", do you mean the Alde service pump or (I assume you mean) the built in CH circulation pump?

If the latter, I could perhaps just add concentrate and run that pump to send it around and mix it up a bit. I would rather drain and replace the entire system, but really not sure I am going to manage that and the caravan can't be towed unfortunately.
 
Jul 18, 2017
2,988
617
6,935
Thanks, yes I can't find any bleed valves which is a pain. I will try calling them Tuesday.

When you say "run the pump", do you mean the Alde service pump or (I assume you mean) the built in CH circulation pump?

If the latter, I could perhaps just add concentrate and run that pump to send it around and mix it up a bit. I would rather drain and replace the entire system, but really not sure I am going to manage that and the caravan can't be towed unfortunately.
We run the built in pump so that it moved the fluid around the system. Mix is normally 50/50. I am told that one cannot chuck the old fluid down the drain as apparently it has to be disposed of in the correct manner?
 
Jul 27, 2020
68
9
85
Thanks. Yes so I am hoping I can maybe just drain it via the plug i found underneath (it gushes out), then top up by pouring 50/50 mix into the expansion tank, no pumps and maybe no breathers/air release as i can't find any. Is there any chance that could work?
 

Damian

Moderator
Mar 14, 2005
7,231
666
25,935
The system uses about 10 Ltrs of glycol/water mix at 40% but no higher than 50%
There should be an air valve on the back of the boiler, on the left hand side as you look at the front, at the top is a right angled fitting attached to a pipe, the air valve should be on the topside of the angle fitting.

If you still cannot find it, then the only way of bleeding the air, as you dont have the filling pump, is alternately raising and lowering the front and back of the van, with the heating on and the circulation pump running
 
Jul 27, 2020
68
9
85
Thank you very much Damian. I printed the small section off entitled "Filling the system". It doesn't explain bleeding it and I am still struggling here. I am considering attaching a 12v pump to the drain plug under the bottom of the caravan where the door is. I thought I could take off the cap on the expansion tank, and 'push' the fluid in from the lowest point, and that should (in my logic anyway) push upwards causing air to escape from the expansion tank before screwing it shut again. Just an idea.

You mention an air valve. I am not sure if I have that, but I attach a few pics I just took in case these show the valve you're referring to? thanks again

PS - You're not referring to that "Eurofit" valve are you? I assumed that contains hot water for the taps (red pipe) and I can't see an air release on it anyway.





 

ASK THE COMMUNITY

TRENDING THREADS

Latest posts