ASHP low pressure help pls

[canalsiderenovation]

 

 

[ProDave]

Yes that is the tundish.  It should remain bone dry.  IF any water passes through it would pass on the inside, it is just there so you can see if anything is passing through.  You could try rolling up a bit of tissue or toilet paper and sliding it into the space inside.  That will show you if there is any discharge even when you are not watching it.

 

It that remains dry over a few days as you use hot water and it gets re heated, then there is nothing wrong with the white expansion vessels.

[canalsiderenovation]

9 minutes ago, ProDave said:

Yes that is the tundish.  It should remain bone dry.  IF any water passes through it would pass on the inside, it is just there so you can see if anything is passing through.  You could try rolling up a bit of tissue or toilet paper and sliding it into the space inside.  That will show you if there is any discharge even when you are not watching it.

 

It that remains dry over a few days as you use hot water and it gets re heated, then there is nothing wrong with the white expansion vessels.

Thank you

 

I will turn it on later and watch it for a bit. I will then the tissue method too.... will update soon.

[Beelbeebub]

One possibility is that - for whatever reason - the system was drained down during the servicing and air entered the pipes.

 

The plumber will repressurise but as some of that trapped air gets circulated around it will eventually find it's way to an automatic air vent, either in your pipework or in the heatpump. 

 

As that bleeds out you can get a drop in system pressure. 

 

Some systems can take quite a while to purge themselves and require a couple of top up cycles.  My own system takes ages to get rid of all the air, but that's because it's crap. 

[ProDave]

1 hour ago, Beelbeebub said:

One possibility is that - for whatever reason - the system was drained down during the servicing and air entered the pipes.

He says he topped up the glycol levels so that makes sense.

[Nickfromwales]

17 minutes ago, ProDave said:

He says he topped up the glycol levels so that makes sense.

He may have used a pump-up pressure bottle to inject, vs drain down and fill via a towel rad / other. Service guys don't like getting wet.......

[canalsiderenovation]

14 hours ago, ProDave said:

He says he topped up the glycol levels so that makes sense.

I don't think he did, that was one of the things the quote included... service did not include topping up glycol.

[canalsiderenovation]

Hot water had not been on since yesterday as I turned it off on the ASHP as I wanted to manually switch it on today and watch to see if there were any leaks from that tundish. 

 

Haven't turned it on yet and just noticed the black pressure needle has dropped - photo taken 1.10pm(ASHP heating came on at 1pm). Is this normal? 

 

 

Edit to say, it creeped back up again (photo taken below 35 mins later at 1.45 so maybe just dropped as heating came on/is on now..)

 

[canalsiderenovation]

19 hours ago, ProDave said:

Yes that is the tundish.  It should remain bone dry.  IF any water passes through it would pass on the inside, it is just there so you can see if anything is passing through.  You could try rolling up a bit of tissue or toilet paper and sliding it into the space inside.  That will show you if there is any discharge even when you are not watching it.

 

It that remains dry over a few days as you use hot water and it gets re heated, then there is nothing wrong with the white expansion vessels.

 

Turned water on. Watched it for 10 mins with torch looking for any signs of a drip and nothing so far. Let some tissue in and will monitor over next day or so and see if there is any sign of any water.

[-rick-]

22 hours ago, canalsiderenovation said:

One thing I did notice when having a good nosy around is on the bottom of the Gledhill tank. It is not dripping or but there was a copper wet mark on the floor and when I touched the pipe I got a rusty damp finger.

 

 

Don't think I've seen anyone else mention this yet so I will. A small leak like this is all thats needed to drop the pressure in the system. I'm guessing this pipe is part of the DHW heating loop though wider photos would confirm.

 

Unless I'm mistaken, until that dampness is solved I'm not sure it's worth looking for other issues.

Edited 6 hours ago by -rick-

[canalsiderenovation]

19 minutes ago, canalsiderenovation said:

 

Turned water on. Watched it for 10 mins with torch looking for any signs of a drip and nothing so far. Let some tissue in and will monitor over next day or so and see if there is any sign of any water.

 

Spoke to soon! Definately leaking. Turned water off on ASHP.. presume we shoulsld try and avoid using the ASHP to heat our hot water and probably try and get this sorted asap. Maybe I was too quick to doubt the first company then.

 

 

Edited 6 hours ago by canalsiderenovation

[canalsiderenovation]

Just now, canalsiderenovation said:

 

Spoke to soon! Definately leaking. Turned water off on ASHP..

 

 

 

 

I take it it is likely those two white cylinders do need replacing then?

[canalsiderenovation]

17 minutes ago, -rick- said:

Unless I'm mistaken, until that dampness is solved I'm not sure it's worth looking for other issues.

 

Tundish is definately leaking, a lot! 

 

Are we ok to have our ASHP heating on still and just avoid using the ASHP for heating out hot water?

[-rick-]

2 minutes ago, canalsiderenovation said:

Tundish is definately leaking, a lot! 

 

Indeed and that's the bigger problem, though not directly (I think) linked to the pressure loss in the hot water system. Overpressure issues triggering safety systems much more urgent than loss of pressure.

 

2 minutes ago, canalsiderenovation said:

Are we ok to have our ASHP heating on still and just avoid using the ASHP for heating out hot water?

 

I would guess so but listen to the experts here not me.

[canalsiderenovation]

I think we may be wise then getting the company back who serviced it/quoted on the basis we could really do with hot water this week! I only just managed to heat the water to 42 degrees when I noticed the leak so until it is resolved we are kind of stuck and solar isn't doing much!

 

Gym it is this week to use their shower...

[-rick-]

1 minute ago, canalsiderenovation said:

solar isn't doing much!

 

If this is related to using the immersion then don't. Using the immersion is worse than using the ASHP to heat the water at this point.

[canalsiderenovation]

3 minutes ago, -rick- said:

 

If this is related to using the immersion then don't. Using the immersion is worse than using the ASHP to heat the water at this point.

 

Thank god we have no sun forecast! The Solic diverts any excess but we likely are not getting any excess but were yesterday as that is what gave us majority of hot water then 🙄

[SimonD]

24 minutes ago, canalsiderenovation said:

I think we may be wise then getting the company back who serviced it/quoted on the basis we could really do with hot water this week! I only just managed to heat the water to 42 degrees when I noticed the leak so until it is resolved we are kind of stuck and solar isn't doing much!

 

Gym it is this week to use their shower...

 

I'm guessing the drips are warm? It definitely appears to be an expansion vessel issue, but it doesn't mean that the expansion vessels need to be replaced. They may just need recharging. From what we've seen we can't be sure that the service involved a proper check of the expansion vessels. Personally, I find it slightly surprising that both have failed a the same time after just 5 years or so.

 

It's actually easier to check the expansion vessels on an unvented cylinder than heating because you just need to isolated the incoming mains (there's usually an isolation valve just before the multi-bloc and then you open a hot tap to take out the pressure, leave the hot tap open while you check and adjust the expansion vessel pressure). 

 

[ProDave]

Okay progress. We know the hot tank is over pressurising when the water is heated which does indeed usually indicate the expansion vessels(s) have failed.  I am a little surprised as there are two of them so would expect them not to be particularly stressed.

 

This is not something to ignore.  You have to trust your gut feeling and get the person that quoted to replace them or a different plumber that comes trusted or recommended by a friend.  This does not need to be a heat pump plumber as these expansion vessels are the same regardless of whether it is a heat pump, gas or oil boiler, or just plain direct immersion heated.

 

Switch off the solar diverter for now and only heat the hot water occasionally as needed using the heat pump to heat it.

 

A lesson here is be there when the next plumber comes so you can engage with them and when they find a problem like this they can probably show you what they are testing that made them conclude they need replacing.  One would hope they had de pressurised and concluded the air bladders are burst and they would be able to show you.

 

EDIT: to add to the above post, if you have a car pressure gauge and a bicycle pump we could talk you though checking the pressure to be absolutely certain if they have failed or just not enough pressure in them.

[canalsiderenovation]

I think we will just get them sorted for now. We haven't paid for services for a few years so I guess this is payback. I am going to be here and will ask him to show me them and explain everything too. 

 

Would we have caused this by using the solar to heat our how water and not having the ASHP heat our hot water/turning it off for a large amount of time?

Edited 5 hours ago by canalsiderenovation

[ProDave]

Heating the hot water will heat it hotter than the ASHP so there will be more expansion.  But that should not be a problem.  You have two expansion vessels for the hot water, I only have one, and my single expansion vessel is still working fine.

 

If you wanted to keep the 2 old ones you could refurbish them with a new bladder in each, or even ask they guy if he would replace the bladders for less than the cost of replacing the whole thing?

[Dillsue]

Maybe I'm missing something but has the system been seen to be over pressured and lifting the relief valve that likely feeds the tundish?? OPs video shows the tundish dripping with the pressure guages showing around 1 bar?? At that pressure the relief valve shouldn't be passing which suggests a leaking relief valve?? Giving the releif valves manual actuator a full turn or 2 to lift the relief valve may well get it to reseat??

[-rick-]

I think there are two problems.

 

1. The pressure loss from the ASHP water system

2. The leaking tundish from the potable water side of the system

 

I'm not sure if we have seen enough info yet to be sure.

[canalsiderenovation]

1 hour ago, ProDave said:

If you wanted to keep the 2 old ones you could refurbish them with a new bladder in each, or even ask they guy if he would replace the bladders for less than the cost of replacing the whole thing?

 

I will ask to keep the old ones. I am going to ask lots of questions when the company comes round and ask them to show me the burst bladder. I will also raise the other points on here people mention to be sure what they doing will fix the issue. The quote says 50% deposit before they come so I will have sort that. We are kind of stuck really with no hot water..

Edited 4 hours ago by canalsiderenovation

[Beelbeebub]

Which part of the system is that leaking tundish linked to? Is it the domestic hot water or the system loop? 

 

Is there a pressure gauge for the DHW tank?

 

There are 2 reasons water is ending up in a tundish. 

 

1) the valve is faulty, the seal may have hardened ornvt some debris on the seal. 

2) the expansion vessels are faulty allowing the pressure to rise too much and triggering the relief valves (as they should).

 

It would seem to be very unluck to have both loops (system and DHW) faulty at the same time

 

So the first thing is to note the cold pressures of both the system loop and the dhw tank. The system is typically 1-1.5bar cold and maybe 0.5bar higher when hot. The relief valves are often 3bar (but not always - it should say on the valve) 

 

The dhw cold pressure will be your mains pressure, that can be anything up to 5bar, though often 2bar or so. Again, when hot it should be 0. 5 to 1 bar more and the pressure relief will typically be 5bar or more. 

 

If the pressure on either system is rising by more than 0. 5-1bar it might be the expansion vessel. If the pressure isn't rising above the value marked on the valve but water is passing then you prob have an iffy valve - they are designed to fail safe i.e. leak or open early rather than open late. 

 

If valves are faulty (activating before design pressure) they need replacing by a g3 certified plumber.  Very occasionally they can be cleared by activating them *if* the issue is debris on thr valve seat. 

 

If the vessels are faulty (big pressure swings) it could be thry are simply out of gas - tyre pump to refill or they could have ruptured the membrane, in which case new vessel.