jamesdiyer

I've sent them the vaillant report and await their response. I want the installer to increase pipe size first (and remove as many connections as possible) and see if we hit flow. If not then we can add buffer and pumps. I think the installer will just want to install the volumizer as a buffer and be done. Which imo is just masking a bad install. I don't know why the vaillant guy loved a buffer and expanded mode so much.

I did try running without filter mesh and made no difference to flow rate.

Apparently running a secondary pump inline is not allowed, said something about cavitate. His recommendation is change tubing to 32mm internal, from the 26mm internal now (22m total). And then buffer if needed.

Thanks both, that sounds a good suggestion and saves changing the primary which I feel would be difficult to achieve without baring the cost. It's a shame it's not wider. I'll see if the installer will just do this, the vaillant man loves a buffer than (and running on expanded mode) but doesn't seem to mind how I run it, as long as it hits the flow needed.

How would I know if the heatpump is complaining? At the moment I don't believe it will matter, we have a heatloss around 9.5kW at -7C. So the machine is big and doesn't need more than what we have flow rate to happily provide that at delta t 5. The machine is big as I'll add a other 100m2 to the system in a year or two - at which point it will need more flow but I'll have to put a pump on that system as it'll be UFH so will change all He was talking about minimum flow at 50% of pump and the machine not starting or something, but it made sense. It's a situation that seems if flow rate is not raised guarantee isn't approved or so.

Need to speak to installer. I don't see how I won't end up with a buffer really. As he wil say that's how he wanted to install it and it's going to change the pipe to 32 internal (from 28 now)

Well. Vaillant have been, they said the flow rate is a bit low at 1750 not 2095. But more that not hitting 995l/h at 50% pump effort, it's doing 960l/h. Their suggestion was to run a buffer tank like planned, and questioned why I'd be running a volumizer at all. And said I need to arrive at 2095l/h the norminal to get guarantee active.. Seems very much like, computer says X. Stuck between a bit of a rock now. Don't really want buffer tank, but need to hit 2095 and also high flow at 50% - apparently.

Thanks. A basics mental exercise makes it quite easy to understand why a joint with a smaller internal diameter would be bad. Vaillant here Thursday so let's see what they say.

To add to this as it's interesting. I live somewhere when a storm rolls in we won't see the sun for a week, temperatures will be well below zero and the ground will be snow. I previously heated via a huge wood boiler and radiators. I opted for pressure valves and no glycol. In 4 years here we have not had a power cut for more than 20 minutes in winter. Also I forgot to drain the boiler when going away last Christmas, obviously it wasn't running, nothing froze and it was well under 0. I think it takes a lot for a system to freeze as a result. I do keep a big log fire in the house for emergencies. I'll leave my ashp running to setback when we go away, as the house drops to 12C without it if not less. I also have a big machine so we can reheat - plus use log fire, if it gets cold. And anti freeze valves should it ever fail and freeze.

Yes agreed.

It was -2C here yesterday morning. But yes it's modulating a lot and I'm not doing delta 5 much. It's trying to run aroun 25-30C temps and then cycling.

And I confirm those two valves connecting to heating inside after 3way are dn20 so 16mm internal. They shouldn't have been there. So we will take those out and see then see about upgrading the 25mm plastic. Then the elbows. Then see if the full pipe need be re run in 35 copper/40pñ

Fyi taking the strainer out made no difference to flow, so it's not the issue.

Vaillant Spain technical head called me. Confirmed 1750l/h isn't enough or acceptable. Said the tube is too small. They have to come out and do an inspection/commissioning for guarantee, so when he comes they will look and then speak with installer.

Unless the primary can run a lot higher flow than 2000? Which I would expect to see (unless limited to max of 2050, so see DHW on theoretical >2050 and heating on 2050. The heating circuit is always going to be lower flow than DHW due to the increased pressure drop, so the system need be designed so it can flow in that and hit a required flow rate, and the DHW flow is just secondary and whatever it is... No? But in your scenario we can come back to the 25mm pipe that was installed between the 3 way and heating and heating and volumizer on return leg. Which will be changed when they're back.

Thanks, I'll email them. That's better as Dutch and available here. The brands mentioned earlier and British and don't distribute in Europe.

Yes of course sorry. Can't edit it now.

Okay thanks. What filter did you install? I see your point on the index, but the system is quite simple, as sketched previously. Immediately splits into two 22mm coppers after the 3way diverter, so flow halves, then it runs 22mm with 15mm tees to 6 radiators on each of the 22. So I cant see how having what I felt was the index circuit I drew earlier being the issue; that index circuit can't really change, but the new installed pipe could have (should have) been different - to try get max flow. So I'm pointing at the primary as it seems the issue to me. Plus the guidelines say it's an issue as pressure per m is too high and to achieve 15kw at DT 5 isn't possible. I'm happy to be wrong. But to me everything screams that the install of the new pipe was not done to best practice - and thus is wrong. If flow is king a 15kw machine demands bigger bore pipe.

So, looking at the pump chart a flow of 1750l/hr gives a pressure of ~65kPa. My pressure looks calculations say the 26mm internal gives a pressure of 11kPa, but 32mm gives kPa of 4.5. Thus change to 32mm would reduce presse by ~6.5kPa and bring system pressure to 59kPa give or take. Giving a flow of... 2000l/h. Also the pressure per m of the 26 is ~550Pa/m well over the guidelines of 350Pa/m. A 32mm id would be 219Pa/m

Do people think that DN25 strainer is a flow block? The mesh seems very wide to be honest. I really can't see that being my issue, but the piping. I'm determined to hit over 2000l/h as I know it's possible. 1750 will be ok. I'm not happy with the installer being a cowboy and the money that was paid. It would have cost not much more to do it in the 40mm it should have been done in to start with, but he doesn't do calculations and that's how he always does it. Vaillant have to come out for a guarantee inspection/comission so we will see if they know more than nothing.

Do be cautious using AI for calculations, I've used it for some and it's often missing things and making wrong assumptions. I think your calc is simplistic but when it get a bit more complicated the simple ones fall down. It can be used to check calculations you've done a bit better if you know what to prompt / assume.

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Thanks but yes the internal plastic pipe fittings are a lot less than 28 cooper. 26 id plastic and maybe 20 id fitting. I'm not going to push for chabing those elbows. What I want is the whole thing done in 35 copper or 40 plastic with compression fittings - don't alter bore. I cleaned the strainer and went from 1650 to 1750. I'm sure that going to 32mm id pipe will push is well over 2000l/h. I'm going to work out how to prove it later. I'm really unhappy with the installers lack of care and though and more so with Vaillant Spain who are useless.

That's an idea thanks! I'll look for some here and in bigger bore. You think that the beauty of using plastic is not just that it's faster but that it's bendable... It's a shame I paid someone a lot of money and am now having to waste your and my time, plus difficult discussions with said installer.

Can I calculate how much? So I can say to the installer, if we improve this I think flow will improv by X?