Sunamp not leaking - yet

[Russdl]

A bit of a long story:

 

It transpires a joint in our DHW manifold has been dripping unnoticed for what would seem to be yonks. It drips onto a pipe directly below, that drip then tracks along the pipe to a water circulation pump and then drips off the back of that pump on to a pipe below it before finally hitting the wall leaving very obvious evidence, unfortunately that evidence is nicely hidden behind the Sunamp, hence it's gone unnoticed.

 

After reading @Jeremy Harris recent woes I took a good look around mine and discovered the evidence of this leak. The trouble is, this leak only materialises when the Sunamp is charging, all other times the pipes are bone dry, initially it seemed to be the rear plastic moulding of the pump that was leaking as that was the only place where water was evident, it had long evaporated from the copper pipe work. I blagged a replacement pump off a friend and felt certain my problems were over, except that replacement pump seemingly started leaking in exactly the same place so I widened the search and eventually found the source.

 

Throughout the days usage the joint remains bone dry, it's overnight when the Sunamp is charging that it starts to drip which lead to an unpleasant discovery. There is a pressure gauge on the cold supply to the Sunamp and early one morning I saw it indicating 13bar! Maximum operating pressure for the Sunamp is 10 bar. The pressure instantly reduces to around 5 bar when a hot tap is opened. If I isolate the cold supply and open a hot tap it reduces further to around 3 bar, but no lower.

 

So every night (for years potentially) when the Sunamp charges the pressure builds to 13 bar and forces water to leak from an otherwise water tight joint in the DHW manifold (maybe this small leak has prevented anything worse happening?) 

 

What can I do about this? There are two 500ml expansion vessels fitted. Do I need another, larger expansion vessel? 

 

Is there something much bigger going on here?

 

Any help gratefully received. 

[ToughButterCup]

Ugh.

SWMBO has hidden the SunAmp behind a (moveable) linen cupboard. Thanks @Russdl

[Dillsue]

I don't think the mains supply gets anywhere near 13 bar so it's unlikely the 13 bar is coming from the mains, if that's where your "cold supply to the sunamp" comes from. If there's a non return valve on the supply then it's possible that as the sunamp charges and warms up the expanding water causes the pressure to increase?? The expansion vessels you mention should absorb this if they are working and connected. There should be pressure on the expansion vessels so probably worth checking that the vessels are connected to the pipework and that they are pre pressurised to allow the internal diaphragm to flex and absorb the expanding water. 

 

There should be a pressure relief valve on the vessel/feed to protect the sunamp being over pressured. Is that fitted and working?

Edited May 6 by Dillsue

[Russdl]

@Dillsue I probably didn't make it clear but that is my view as well that the expanding water as the Sunamp heats up is causing the pressure rise.

 

There is a non return valve on the cold mains supply, and on closer inspection it seems like only one of the expansion vessels is working properly. I can get air in/out of one of them, but not the other the other one.

I guess those things break down? Would going from two 500ml expansion vessels to just one be enough to cause this big water pressure rise?

 

1 hour ago, Dillsue said:

There should be a pressure relief valve on the vessel/feed to protect the sunamp being over pressured. Is that fitted and working?

 

I don't know. I don't think so. Can you throw any light on what that would look like and where I'd find it?

 

[Russdl]

I seem to have got the dodgy expansion vessel working again, they're both now charged to 3.5 bar and the Sunamp is on and charging in the daylight so I can keep an eye on the pressure.  

[Dillsue]

If you Google 15mm pressure relief valve you'll see what they look like. If you've not got on the pipework or Sunamp then you probably want to get one fitted to protect the sunamp.

 

Have a look at the manufacturer's instructions for the expansion vessels as they'll tell you what the should be recharged to. The diaphragm inside can fail over time but youll know if they've failed if you cant pre charge them when removed from the install.

[Russdl]

No, there's no pressure relief valve in or around the Sunamp, and no mention in the MI's. I think I recall Jeremy's replacement Sunamp having some pressure relief facility that his previous set up didn't. I'll have to re-read that thread.

 

It looks like getting the second expansion vessel working again has fixed my problem. There has been negligible change in the pressure after charging the Sunamp for a little over two hours. I guess my lesson learnt is that those little expansion vessels that are pretty much out of sight, shouldn't be out of mind. I'll add them to my list of things to check every 6 months to make sure they're holding they're charge. I don't think I've checked them once since we moved in.

[Dillsue]

If or when the expansion vessels fail the pressure relief valve takes over to stop overpressure so fit one if there isn't one. 

[Russdl]

@Dillsue good advice. At least one of my expansion vessels had effectively failed as there was no air in it. And I’m guessing there was nothing in the working expansion vessels as well hence the over pressure I saw. Now they are both charged up again everything looks fine - too my eyes at least. 

[Russdl]

I’ve had another read through @Jeremy Harris’s thread and he noted that the latest Sunamp models are limited to 5 bar instead of the 10 bar of the previous variants, mine being one of those. 
 

After getting the expansion vessels to play ball I’ve got around 5.7 bar, which is around 2 bar above my known water pressure from when we started the build and, knowing what has happened to previous Sunamps, higher than what I wanted to see. I was curious so turned off the cold feed to the Sunamp.
 

Pressure remained the same (trapped in the hot circuit).

Ran a hot tap until it stopped which was only a few seconds - pressure dropped to 2.5 bar (I was expecting zero??)

Deflated the expansion vessels - pressure dropped to 2 bar (was definitely expecting zero now!)

I ran every hot outlet in the house, non of them ran apart from one shower (it was running cold so I guess that’s just cold water getting past the thermostatic mixer when full hot is selected?)

Still 2 bar of pressure. 
 

I’m assuming my pressure gauge is knackered and miss reading by +2bar. Is that likely?

 

If not, where is the 2 bar hiding and why can’t I get it out of my hot circuit?

 

So, to recap I’m sat here with cold supply off, hot taps open, expansion vessels without air and showing 2 bar on the pressure gauge. Any clues??

[Dillsue]

Slowly unscrew the pressure gauge. As soon as you can turn it by hand wiggle it and any pressure should vent via the loose threads. Slowly undo it while keeping wiggling, assuming at all times there's 2 bar trapped in the pipework. Keep towel handy!!

[Russdl]

I was thinking of trying that 

 

Let’s see what happens…

[Russdl]

Well that was uneventful, tiny dribble of water, gauge is off and still firmly stuck at a little over 2 bar, which makes that previous high pressure I saw a little less terrifying.
 

I an’t see any way to adjust/calibrate it so I’ll guess I’ll get a new one and fit a pressure relief valve at the same time. 

Edited May 8 by Russdl