ACV Cylinders - back to front??

[Worcester]

Just visited a site today where they are having big problems with insufficient volume and insufficient flow of hot water.

Happens to be heated by ASHP (a cascaded bank of 5 x 9kW) so posted it here (maybe I should have put it in the commercial forum )

Attached a schematic, looking from the front of the cylinders, the cold / mains in is top right and then they are plumbed in SERIES, so out of top left into top right of the next one, and again, and then out of top left to showers / (demand) etc

Are these plumbed in back to front?

Anyone else seen them plumbed in SERIES before ?.....

The fourth one appears to have been configured as a buffer tank for the Heating circuits..

Thoughts / comments please - and yes I have sent loads of details up to ACV technical.

It's not one of ours, however the original installer isn't interested in fixing the problems.

 

[Ermintrude]

Err yes looks wrong. Floors should be off bottom and pumps off the top with a shunt into the headder (base of tank) . Reverse flow? Why the hell not put it on to headders like any sane person? Fine with dense heat but from a gshp? Is it tidy or dogs dinner?

 

[Ermintrude]

No blending valve? On DHW? What size heat pumps? 3 x 70kw @ 80c? Dream on!!!

 

[Ermintrude]

No blending valve? On DHW? What size heat pumps? 3 x 70kw @ 80c? Dream on!!!

Do they need all that water? Not be better with a few buffers and one dhw? I'm sure u can put in series, problem is that the heating load stealing all the heat from top and your not getting stratification and thus a hot water getting cooler across the bank not hotter??

 

[Worcester]

Its 5 x 9kW hight temp (CO2) heat pumps, it's a golf club so regularly suddenly need loads of hot water (tournaments)

Looks neat and tidy - photos here:https://plus.google.com/photos/1048...ms/6076141310691016593?authkey=CKqjwZHLgcu4fA

The first three are for DHW, the fourth looks like it's being used as a buffer tank

 

[Worcester]

It's using the existing rads - no changes to the heating circuit - hence the high temp heat pumps running at > 50° - the CO2 ones can do that, and some get a reasonable CoP

 

[Worcester]

It's a pair of custom made manifolds to go from 5 heat pumps to 4 cylinders... and no, they don't have a reverse flow balanced set up for them, so cylinder 4 has further to travel than cylinder 1

All flow from the HP's to the cylinders relies on the HP circlulation pumps (on the return side, HP side of the manifold)

 

[Ermintrude]

Shouldn't cylinder 1 be the longest and thus coldest. And 3 the shortest and thus hottest as at this point DHW leaves system? The recovery will be horrific on a system set up like that? I would have 2 300l on DHW and two as a buffer if not 5! The cylinders can recover very quickly due to s/a but 50kw for all 3 , take 9 years to recover each cylinder will gobble 65kw easy for fast recovery so why not superheat buffers ? Because as soon as top end of cascade cools it's game over and red hot ashp

 

[Nostrum]

As ermi has said those cylinder aren't going to stratify with the way they've been connected, multiple returns and the heating return dumped in the bottom as well I would imagine. Therefore, surely you'll need to have 1200 litres of water at a suitable temperature (50 +) to achieve a steady supply of DHW? That's a big ask from 5 9kw units.

 

[Gray0689]

What a waste awww

 

[Worcester]

Yep, was installed by an allegedly leading award winning company. Mind you, they are a very big fan of Mitsubishi Ecodans guess that says quite a bit!

I wouldn't be surprised to see some litigation over fit for purpose around this one.

I reckon that it could salvaged with a complete redesign of the hydraulics, though with natural gas available on site, whether it's worthwhile trying to salvage any of the heat pump usage with a bivalent control system, vs two gas boilers will be an interesting exercise.

Why they have plumbed it like they have has me completely confused, and I'm also pretty sure that the DHW flow is back to front through the cylinders as well. I can't see how this works hydraulically at all. Seems like a complete dogs dinner.

Incompetence, a mistake or bad design? Not sure, does it matter?

Still waiting for a definitive analysis from ACV, all they did was send me the installation pdf, not what I was expecting..

Anyone get any other ideas as to the best way to connect them ? -

 

[Ermintrude]

Spent rest of day trying to figure it out too. ACV may have designed the system , buts it's Defo wrong installed wrong. . Possibly thought process was for 900l of 45c and a buffer for the heating? Bi valiant as discussed defo way forward. The load probably was what cooked the HP.

Think the AC lads seen it in a pool or something and thought we can do that easy. So copied but not paid attention to the requirement for 210kw of 90c heat

 

[Gray0689]

What's there electric bill ?

 

[Worcester]

What's there electric bill ?

Horrendous! That along with the problems of insufficient Hot Water have been the trigger to finally do something about it.

It has been wrong from day 1 - client wasn't aware as they didn't know what to expect from the system.

As I understand it the control system can trigger the immersion heaters, and I reckon that have been boosting the whole of the heating system, when it's not achieving temperature. The controls are VERY basic, and lacks sensors where I would have expected to find them.

The challenge is who's going to pay..

 

[Ermintrude]

Horrendous! That along with the problems of insufficient Hot Water have been the trigger to finally do something about it.

It has been wrong from day 1 - client wasn't aware as they didn't know what to expect from the system.

As I understand it the control system can trigger the immersion heaters, and I reckon that have been boosting the whole of the heating system, when it's not achieving temperature. The controls are VERY basic, and lacks sensors where I would have expected to find them.

The challenge is who's going to pay..

We shall all chip in and help towards the £16k to put it right. Us tradesmen don't like to see the industry dragged down by halfwhit

 

[jonny5isalive]

We shall all chip in and help towards the £16k to put it right. Us tradesmen don't like to see the industry dragged down by halfwhit

Got a laugh from me. Very good

 

[oz-plumber]

"The challenge is who's going to pay.."

You ?

From the pics the installation was done @ 5 - 6 years ago ( dates on equipment from photos )

If you go to court defending the customer, you are going to end up with carp like:
- system maintenance, life of system, why has it taken so long for the system to be proven inadequate, has the use of hot water changed over that period..and so on.

If it was me looking at this job in respect to fixing it up, I would be getting an engineers report done on the system.
That way you can keep an arms length away from that side of proceedings.

As for repairs / rectifications, it could depend on what you feel and the customer feels is the best way to go.
Once again, it may be better to have an engineer have some involvement in this.

I'm not saying that you can't design a new or repair the existing system.
It may be beneficial to you to have a company design a new system, so that your backside won't be on the line in the future with this already upset and skeptical customer.

 

[Worcester]

"The challenge is who's going to pay.."

You ?

It's not OUR install!!!

We were ORIGINALLY called in because one of the heat pumps wasn't working and the original installer says it's out of warranty > 3 years and wanted £750 just to turn up to look at what was wrong with the heat pump.

Then the can of worms opened, as when I started looking at it I started asking about the running costs and why it was configured they way it was.

Hence my earlier post about possible litigation against the original installer "not fit for purpose"
Reading through the original installers website they are much bigger on air-con (A2A) than they are on A2W heating.



Or - were you meaning that if we fix it and it still doesn't work, it will just come back to bite me!

 

[Gray0689]

Worcester
Rip them silly heat pumps out and either if natural gas a few boilers in Sequence or a wood pellet boiler with buffer
1 of them acv cylinders could cope with the hot water demand if done properly

 

[Nostrum]

Without looking at it in depth, could you not re configure?

2x buffers into which heat pumps heat and heating circuit flow and returns are connected, 2x DHW cylinders in parallel.

DHW prioritised, heating zoned off when DHW temp drops, 600 litres of DHW on tap with 600 litre buffers in reserve, heating should be able to pick up fairly instantly once DHW satisfied.

Could sequence buffers if you felt the need.

Are they claiming RHI ? Seems a shame to rip it all out.

Gonna spill the beans on who did it?

 

[Ermintrude]

But those buffers need to be hot hot hot to recover. Dhw should be at 85c in ACV not 45, hence the current MASSIVE volume of Luke warm water - heat pumps only dishing out the love at 50c ! Cylinders feel bit like old boiler in massage parlour....... Never quite hitting the boil!!

 

[Nostrum]

Flow is king for the heat pumps, quick turn over needed hence 2 buffers on standby. Once you start losing the pumps won't be adequate to keep up with demand.

those ACV's are tank in tank aren't they? They have a big surface area to match the big flow rates required.

 

[Ermintrude]

Huge s/a deliver fantastic flow rates but need very dense heat very quickly to work well. 70kw at 80c ish!!!

 

[Nostrum]

Do they defy the laws of physics then?

 

[Ermintrude]

Do they defy the laws of physics then? í*½í¸„

Always do! Put in 80c and deliver at 85c