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In the Telford MI’s, cylinders over a certain size have instructions to bridge the cylinder flow and return tappings together with a simple inline gate valve (iirc) to allow a permanent, adjustable bypass to take this bump out of the road. I wonder if the engineer upped the pump speed, in an attempted to combat the frequency of the low flow issue, eg giving the ASHP access to a bit more throttle; this would account for why you had no cylinder noise issue before. I strongly dislike these filters as they have such low capacity for functioning when these even a slight build up of crud. @canalsiderenovation Get a larger mag filter installed, like a Fernox TF1 or an Adey Magnaclean for easy life going forward. This one will keep blocking prematurely afaic. I'd also ask specifically if the pump speed had been increased and that’s what has caused the cylinder rattle.

Usually the cylinder stat, which I'm assuming is what you're referring to as dual stat?, is not carrying anything like the current for an immersion as the immersion has it's own over-temp safety cut out. Usually the cylinder stat just has a safety cut out to cut the supply to the heat source, or to a zone valve to cut flow as @ProDave has done. So safety cut out is only on a 3A or 5A fused spur. I have to say, I'm thoroughly confused as it doesn't need to be this complicated.

Maybe all cylinders - we've got a Newark that is pretty noisy..... I've always put it down to the coil being corrugated and trapping air - and we haven't got round to putting in anything to get rid of the air yet - next summers job.

Update.. Ordered from these guys, after a week I got a call saying they don't have it and they would refund. Ordered instead from 'plumbing supplies delivered' and after 2 weeks it's arrived and they've sent the T12 instead of T12F so the threads are the wrong way round and it's useless. (I paid for a delivery upgrade to get it fast too) I've come to the conclusion that all plumbing suppliers are utterly useless and it looks like I'm throwing away the 40mm pipework and AAV already fitted under the sink and doing it in 32mm. After a month of messing around 🤣🤣😭😭

Those inline filters get blocked quite easily. In slow time it would be better to bin it and get a Magnaclean or Adey HP filter fitted indoors, they have a much bigger element like an enormous kettle fur collector and a magnet for collecting magnetite particles shed by the radiators - which you should not be gettting if there is adequate inhibitor in the system. Gledhill cylinders have a bit of a reputation for noisy internals, I have seen it reported as a specific quality control issue in the factory.

None of the heat pump functions are controlled by the 24V system only the immersion and the heat pump does not want to control that as far as I can see. I chose to put the dual stat into to the 24V side because the switches in the dual stat look flimsy, you cannot get a piece of flex capable of carrying the full current of the immersion into the gland provided in the dual stat box and I didn't really want high current switching on the tank. If it will help I can wire the dual stat into the immersion direct I just need to be creative with the gland problem.

How deep can these radon membranes go. Is there any reason they can't go flat below the insulation layer and just end up with membrane spanning the whole envelope of building. No corners etc. Any spine walls laid on top.

I haven't had the bill yet. I am annoyed they had to come out again. I think really he should have stayed long enough to see the filter was not blocked. He said he did check and left the heating and hot water on when he left but it was clear from the water temp and cold house that the error code must have appeared pretty much right after he left, preventing the heating and hot water coming on. Yes the engineer mentioned he has seen this on Telford cylinders before but less so on Gledhill.

Lets hope it continues to work. Keep us posted. I hope they reduced the bill somewhat as they didn't need to replace the expansion vessels. Re the rattling sound. I had this with my Telford cylinder. There seems to be a conflict that a heat pump demands a very fast water flow rate, that makes the coil inside the tank vibrate and rattle. If you reduce the flow rate so the tank is happy, the rattling stops but the heat pump has a hissy fit because the flow rate is too low. In my case I had an automatic bypass valve which is really there to cover the time the motorised valves take to open. It took a lot of fiddling with the settings on the bypass valve to essentially make it bypass all the time just to keep the heat pump flow rate happy and reduce the flow going through the cylinder.

Can you just swap the heads on the manifold or are the wires too short? Perhaps that messes up labeling?

I moved away from using SSRs just under 2 years ago to an ESP32 module using 24 VDC to drive contactors. See p3 and 4 on this topic. My issue with the SSRs was that they had about a ½-1% heat loss in the SSR when on -- that's 15-30 W per relay. This caused real overheating issues with the DIN mounted SSRs. The contactor coil losses are a few W, so absolutely no overheating issues. I prefer using 24 VDC for relay control as this minimised safety issues in the microcontrolled modules. You just need to include flyback diodes to prevent the 24V relay contact arcing / wear. You really need to add snubbers for the 240VAC switching relays for the same reason.

Jobs done today The feet I bought to go underground the heat pump were 1m long, so trim them down to a more manageable length of 800mm. Moved the heat pump from patio to closer to the final location. Used a simple garage trolley located under the manufacturers pallet. Next job is to cut off the pallet away at the light end (condenser end) and affix a foot. This will give something to lever against so when in final position the remaining pallet can be removed and the other two feet added. Completed all wiring as far as possible. So 3 core cable for power, 2x0.75 screened cable to outside unit and further 2 core to the smart grid connection (can't complete this as cable from house is currently connected to other heat pump. I heat the summer house as part of the same zone as the house, it runs at 18 to 19.5 normally, but sometimes we need it warmer, so I normally use a thermostat to trigger a second setpoint for the heat pump, which works fine and floor just buffers the heat. The Hiaer unit, I will utilise the smart grid connection, and set a 2 Deg uplift in flow temp when the connections across terminals for SG2 (EVU signal) are closed. The same connection can reduce the cooling flow temp should I need it. Also made some covers out of excess OSB from the house build, to cover some gravel I need to travel over. Looks like next weekend to do the heat pump change over.

dMVHR can be useful in an apartment or retrofit, but in a new-build house a central MVHR unit normally has the advantage. Only 2 holes to cut through the outside wall, only 2 visible external grilles, no visible boxes on the internal walls, constant-flow-rate fans to counteract the build-up of filter debris, only 1 set of filters to change, no worries about noise from fans or the outside world, many more units - PassiHaus-approved or otherwise - to choose from, the availability of a summer bypass (on good units), a single point of control, pre-heater and/or post-heater* options if needed, often lower installation costs (except in retrofit). *could be added to ducted dMVHR too.

You can cover this in another thread rather than clogging this one up. Just need to start it.

The planning consultant could be a good call. I have, in the past, instructed architects to design a scheme that did not gain planning consent, so quite a waste of time and money. I would favour shortlisting a couple of architects and asking each to produce a sketch scheme for an agreed fee based on your brief and input from a planning consultant.

No planning yet. Planning shouldn't be an issue, seems strange someone external getting involved at the point of him quoting us before we have accepted. We are only just consulting various architects at the moment.

Yes. We only had an initial call as we are just beginning the journey, we have further architects to meet with. An external planning consultant at extra cost was mentioned in the pricing structure that was emailed after the call and she was cc into the email, of which she has replied and would look at any constraints and make a detailed analysis... We hadn't agreed to this not accepted the architects quote!

Does your plot currently have planning? If not, I could imagine the architect having concerns about whether planning is feasible for the plot and asking a specialist about it before taking you on.

Your red flags could be justified or you could have a very helpful architect trying to 'get you ahead'. In the latter case the fault would be not to have explained that to you. Not sure what 'analysis', but do you mean the arch has given your personal details to someone without your permission?

My guess is that it would flex too much on a ceiling as you tried to apply the plaster, but maybe not. On a wall it's possible, but there you have a rigid support behind it. BTW, not mentioned above is the need for a airtightness membrane; I'd choose Intello or similar. There are other threads on the topic if you need more info.

Best solution is an insulated concrete slab IMHO

More thinking of biological gunk blocking it than corrosion.

Trouble I have answering this thread is the heat pump control is being somewhat taken over by another 24v system, so it's a can of worms. Simple made difficult.

When I did my new build I priced up Fresh-R, but got push back from building control on flow rate not matching building regs. But the concept is good and can be made to work with ordinary MVHR units, using cascade ventilation. So extract from all wet rooms, add air in a central location, so it passes through other areas before being extracted. Between room fans if layout demands it.

The same guy from yesterday came out. The filter was blocked (this bit). He said he did test it before leaving but obviously more crap got in it. He has shown me exactly what to do to check the filter now for future. The rattling sound is actually the coil at the bottom of the Gledhill tank. He has adjusted the flow etc and its 18.2lpm. There is a little rattle and he showed me if you apply a bit of pressure to the top and bottom pipes it stops. I'm still not sure why we have this now and didnt before. He has used zip ties to apply this pressure. Not ideal but for now we have heating and hot water. I think perhaps in the long term we need to get someone else out as I don't know why we have had no rattle for years and now do. He did say you can fit a valve/additional pipework. 20260117_104834.mp4 Going back to yesterday. The issue with the tundish was all to do with the pressure issues and there was quite a leak from here which needed tightening. He said that was likely the cause of the pressure drop and subsequent issues. The expansion tanks did not need replacing, just pumping back up.