Posted by: @heymikey

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I have raised this with the installer but just wanted opinions. I thought originally the left side was back to front but surely the flow setter would read zero

If those temperatures are correct the buffer is plumbed wrongly, with the input from the heat pump at the bottom and the output to the rads at the top.  Flow from heat pump and flow to radiators should be at top, returns at bottom, like the diagram.  This is a rookie error if the figures are correct.  I can't see why this would cause the flow setter to read zero because flow will still occur, it will just be more turbulent within the buffer tank.

The bigger question is why install a buffer at all.  It WAS working satisfactorily but something changed.  So the fix is to work out what changed and change it back, not add a pointless additional component which can only degrade performance.

Are all your trvs fully open?  Could anyone have changed the lsvs?  Has the mag filter been cleaned, has the water pump in the heat pump been checked, is there a filter that isn't obvious.  These are some of the questions that need to be asked and should have been asked and answered.

The stuff about 2 zones was Bow Locks btw so you were right to resist.

I assume the Wilo pump in the photo is on the load side, not the heat pump side.

In this case changing the settings on the Wilo will not influence the flow through the heat pump, that's normal, it's the buffer tank doing its job of hydraulic separation. Which you probably don't need as James said, since it worked fine without the tank before something clogged that pipe.

>  I thought originally the left side was back to front but surely the flow setter would read 0? 

Good catch!

I see the circulator is upside down. It's the beginning of a trend! Have you double checked if the flow setter is upside down too? There's probably an arrow on the side to indicate direction of flow. Since it's on the top pipe, flow through this device should go towards the tank.

If the tank connections on the left are on the heat pump side, and the bottom is hotter than the top... they're probably inverted.

Hot (flow from heat pump) is supposed to be on top, as shown on the schematic you posted...

Regarding the circulator, as long as it is flowing in the right direction then it's okay, but it is possible to remove the motor (4 screws), and flip it around, so the display and controls are in the user-friendly orientation and the cable doesn't bend like it currently does. Takes about 5 minutes, but apparently someone was in a hurry. With that level of workmanship, I'd recommend double checking absolutely everything else.

Since you have temperature probes, good idea to also check if the flow and return are not inverted on the heat pump side, who knows, if they took out the circulator inside to check it maybe they put it back in the wrong way!

@jamespa 
Thanks James, I agree with you on most of this. it's just that I'm not a plumber or heating engineer so my knowledge is literally based on what I've read or watched. It's hard to argue something that's not your field and I was trying to step back a bit and let experts do their job. Maybe a mistake but again when you don't have someone in your corner it's hard to fight it. Thing is that this is all remedial work which costs me nothing. But maybe it will in the future on efficiency. I will compare it this winter and if I have to I'll ask them to put it back or just pay someone I feel who is better qualified. 

If it is plumbed wrongly and the bottom left is from the Heat Pump, top right is to the heating circuit and the bottom right is back from the heating circuit, that only leaves the top left being the return to the heat pump. If that is the case wouldn't the flow setter read 0? The arrow is pointing up which makes me think that it does flow in from the top left. This whole set up has confused me. I know its hard to say without being here and seeing the pipework but something seems wrong. 

TRV's are fully open, nothing in the mag filters, lockshield valves were all messed with as closest rads were getting all the flow and the furthest getting nothing. I've been adjusting them to balance them using temp probs as above. 

They are coming back out Next Friday so any advice on how to proceed would be great. Temped to do a pipe trace before hand to fully understand how it all flows.

@bobflux 
yes the wilo pump is on the heating circuit side.
The flow setter is not upside down as the arrow is pointing up. towards the tank. plus I get a 28l/min.

I don't mind the wilo pump display being upside down. if anything I prefer it so I know nobody has messed it up 😀

Good shout on the heat pump flows not being inverterted. I'd be surprised since Grant did come out and check everything. Nothing is impossible I guess.

I do not have a low loss header or volumizer so i'm guessing in the future if I was to get this sorted I could get plumbed in a way so this can become a make shift one? is that a good idea?

duplicate ignore

Posted by: @heymikey

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If it is plumbed wrongly and the bottom left is from the Heat Pump, top right is to the heating circuit and the bottom right is back from the heating circuit, that only leaves the top left being the return to the heat pump. If that is the case wouldn't the flow setter read 0? The arrow is pointing up which makes me think that it does flow in from the top left. This whole set up has confused me. I know its hard to say without being here and seeing the pipework but something seems wrong. 

@bobflux may have solved this with his observation that the secondary pump is the wrong way round.  Alternatively it depends what the 'flow setter' actually is.  I suggest to trace the pipes back to the heat pump but for sure the one with the highest temperature is the feed from the heat pump because that's the only source of energy.

Posted by: @heymikey

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TRV's are fully open, nothing in the mag filters, lockshield valves were all messed with as closest rads were getting all the flow and the furthest getting nothing. I've been adjusting them to balance them using temp probs as above. 

All understood but the fact remains that, based on what you say,  something changed to reduce flow and that MUST be fixed, adding additional components is not the solution.  The corollary is that what changed needs to be found.  

Posted by: @heymikey

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. Temped to do a pipe trace before hand to fully understand how it all flows.

Definitely do this.  While you are at it measure temperatures and post the results.

Posted by: @jamespa

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@bobflux may have solved this with his observation that the secondary pump is the wrong way round.  Alternatively it depends what the 'flow setter' actually is.  I suggest to trace the pipes back to the heat pump but for sure the one with the highest temperature is the feed from the heat pump because that's the only source of energy.

I don't think this solves it as being upside down would mean the pump is pulling the other way and it would be the coldest flow as it would have been thru the rads and cooled down? 

Posted by: @jamespa

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All understood but the fact remains that, based on what you say,  something changed to reduce flow and that MUST be fixed, adding additional components is not the solution.  The corollary is that what changed needs to be found.  

This part was fixed as they piped new primaries to the airing cupboard. Flow was restored. 

Posted by: @heymikey

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I don't think this solves it as being upside down would mean the pump is pulling the other way and it would be the coldest flow as it would have been thru the rads and cooled down? 

It looks from your temperatures as if flow to rads is from top, return from rads at bottom.  Flow from heat pump at bottom, return to heat pump at top.  This would be correct for a phe but is a rookie mistake for a buffer.

That said temperature measurements on pipes can be wrong and we don't know at what point in the cycles you captured this.  I would definitely trace the pipework for absolute certainty.

Posted by: @heymikey

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This part was fixed as they piped new primaries to the airing cupboard. Flow was restored. 

So why did they add an unnecessary buffer, probably incorrectly plumbed?  And if new primaries fixed it what was wrong with the old ones that somehow had changed from when it was first installed?  Doesn't make sense.

Posted by: @heymikey

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TRV's are fully open, nothing in the mag filters, lockshield valves were all messed with as closest rads were getting all the flow and the furthest getting nothing. I've been adjusting them to balance them using temp probs as above. 

Well something caused the flow to reduce from 40l/min to nothing, this didnt happen by magic,  Have you maybe turned lsvs down too much, at least one should be fully open, often several.  If you have balanced for a specific deltat then you could possibly have done this , depending on the demand at the time.

Posted by: @heymikey

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it's just that I'm not a plumber or heating engineer

Neither am I.  But I do have a background in physics and engineering and can think logically.  Sadly quite a few heating 'engineers' can't do the latter!

Posted by: @heymikey

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It's hard to argue something that's not your field

True, and what the BS merchants rely on.  I take the view that, if a tradesman can't or wont explain their reasoning,  it's because they don't understand it, not because I would be unable to understand it if someone were to explain it!

Posted by: @jamespa

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It looks from your temperatures as if flow to rads is from top, return from rads at bottom.  Flow from heat pump at bottom, return to heat pump at top.  This would be correct for a phe but is a rookie mistake for a buffer.

That said temperature measurements on pipes can be wrong and we don't know at what point in the cycles you captured this.  I would definitely trace the pipework for absolute certainty.

If the return was at the top the flow setter would read 0? I'm guessing they only work one way. As u said I think a pipe trace needs doing and I'll do it Friday when I have time.

Posted by: @jamespa

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So why did they add an unnecessary buffer, probably incorrectly plumbed?  And if new primaries fixed it what was wrong with the old ones that somehow had changed from when it was first installed?  Doesn't make sense.

I think he said my house is fairly large (19 rads) and very long pipe runs in the loft. It's a L shape. It made sense at the time. I guess I didn't want to think I knew best.

Posted by: @jamespa

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Well something caused the flow to reduce from 40l/min to nothing, this didnt happen by magic,  Have you maybe turned lsvs down too much, at least one should be fully open, often several.  If you have balanced for a specific deltat then you could possibly have done this , depending on the demand at the time.

Deffo something did and I think it was either fibre glass or the Inta strainer came out and got lodged, or a push fitting possibly. I did balance the radiators down but I didn't go nuts. Most say a delta T of 5 to 8 but mine was closer to 2-4. And had many with the lockshield fully open at the further ends. Definately didn't choke it as the return flow rate was good. 24ish.

I don't mind a buffer if it works and get a good temperature difference. I don't want mixing causing wasted energy. I don't have a volumiser so sort of helps with volume. Can a buffer be repiped as a volumiser? 

Thanks for all your input, I appreciate it. 

I had issues with similar temperature probes, the error can reach a few degrees, which matter in your case since the temps are pretty close.

Best accuracy is with the probes taped to a copper pipe (brass fittings have too much thermal mass and take too long to settle), then the whole thing wrapped with an insulating sleeve, taped shut. Without the sleeve the measurement depends on the ratio of heat transfer from the pipe to the probe versus heat loss from the probe to ambient. Also check the probes display the same temp when mounted on the same pipe!

If the heat pump is defrosting by going into reverse gear, then flow temperature will be lower than return, then return to normal once it resumes heating...

The circulator control panel can be rotated relative to the body, so to know which way it flows, you have to look at the body not the panel. Here's mine:

The arrow is on both sides. Anyway it's a centrifugal pump, so the suction is whatever side connects to the center of the impeller through the bulge in the back.

> Can a buffer be repiped as a volumiser? 

Yes

Posted by: @bobflux

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I had issues with similar temperature probes, the error can reach a few degrees, which matter in your case since the temps are pretty close.

Best accuracy is with the probes taped to a copper pipe (brass fittings have too much thermal mass and take too long to settle), then the whole thing wrapped with an insulating sleeve, taped shut. Without the sleeve the measurement depends on the ratio of heat transfer from the pipe to the probe versus heat loss from the probe to ambient. Also check the probes display the same temp when mounted on the same pipe!

Yes all those probes in the photo are tucked and wrapped around the copper pipes and insulated with no air to interfere with the readings. I will put all 4 on the same pipe to see how much they differ on Friday. I'll put on a fixed temperature and watch them and see what they do.

Posted by: @bobflux

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The arrow is on both sides. Anyway it's a centrifugal pump, so the suction is whatever side connects to the center of the impeller through the bulge in the back.

That's really helpful, I'll look soon to see what the direction is.

Thank u for your thoughts and help also.