Marvin

No clear response over the phone from DNO. Email sent requesting clarity on the following: Under the Energy Network association (ENA) EREC G98 regulations, I understand there is a limit of 3.68kW which can be fed into the network. There are inverters that can be limited to 3.68kW feed into the network whilst handling a home generated PV array above this. Obviously these are G98 compliant inverters. Please confirm these inverters set at less than 3.68kW comply with your requirements under a G98 connection. Kind regards I'm sure I will go blue if I hold my breath... As I have just received the automated response! M

(The thing I like about Buildhub is the wealth of knowledge shared and differing opinions which usually results in a solution! And the people who have the patience to explain - thank you.) I am now contacting DNO....

Yes, you and conor probably will. Have been reading your info. Very interesting. I came across the pump searching for one small enough for our bungalow. We had already renovated and upgraded the insulation, airtightness and installed MVHR. Because we heated the bungalow and hot water only using bottled gas we also knew our energy usage results, which were worse than theory but better than hoped and this helped us choose the unit.

Good question. Yes the only place below the flat roof that does have a wall across the span. I am also not sure about the insulation being crushed, the EPDM being worn by vibration or the vibration entering the building but will react to these if they arise.

Other view...

So, ASHP on flat roof. Boiler going. Now, where the hell do I put the heat pump supply rotary isolator?

Thank you ProDave and TonyT I prefer the inverter with the limiting 3.68kW as, when available, I can use more to charge the car. Also it sounds a bit geeky to start messing around with relays etc and no matter how brilliant it will not impress the boss! Yes we have to avoid the big power items using batteries. We are going to wait for technology to catch up on the battery front...

Our MVHR covers up to 250m2 but we are only 106m2. This was bought larger on purpose to try and reduce wear and noise. We used rigid pipes and insulated all of the pipes, in and out with rigid insulation. We have summer/winter option and humidity sensors for the wet rooms. MVHR very quiet. It uses about 20 watts on normal We have 3 niggles: Cooking smell lingered until I read here that it's a good idea to put the system on boost when cooking. Sound travels a bit between rooms down the pipes and I am yet to put baffles in. (lazy and so it cant be that bad) If we leave the en-suite room door shut the extracted air is only replaced with the colder air entering under the door so we have to open the door some time after use. We have realised that if the temperature outside is above the inside temperature we are better leaving the system on "winter" as the cooler air being expelled cools the fresh air coming in. Also we have had no humidity issues. I clean filters about once a year and inspected the condensation trap once so far with no problems. Installed in 2018 and it has worked for us: https://www.polypipe.com/sites/default/files/HRX2_MVHR_Technical_Data_Sheet.pdf Ours system includes the summer bypass. Hope this helps Marvin

Thanks Pro Dave. Didn't know I could put 5160w system into grid? Yes. I expected a bank of relays and the brief interruption to the power, so am avoiding the internet/wifi . Ah! so does this mean you can have inverters that limit the supply to the grid? We have an Electric Vehicle with a slow charger so would use that dump first and or the batteries ( as the batteries will be used during the night will probably be the priority).

On the MVHR whole house system here we used Domus Thermal Duct Insulation on rigid duct. probably more work fixing but less cost buying I think... https://www.domusventilation.co.uk/ventilation-solutions/ducting-range I used cable ties to keep the insulation on.

Hi Can you buy equipment that will monitor the 240v ac output amperage/wattage from a PV system, and depending on the power, turn relays on/off to swap the power supply to and from a PV or mains supply to different circuits. This assumes the PV is not connected to the mains My brother always says its not if, but how much, so I suppose my real question is would this be expensive to do. I am working on a 5120W PV home system. There is still lots to decide including splitting the system to connect to the mains in part as I can use the rest for several low wattage continual use items in the house with battery storage including the MVHR. Thanks Marvin

I sent information to the manufacturer of my small whole house system and they sent me a specification and layout.

Hi Edders You can go for single unit or a whole house unit, you can go for individual humidity levels, one single humidity sensor, you can just stick fans in or open a window. All these choices work. It would be knowing the building design, use ( and sometimes location if exceptional), materials, thermal resistance and air tightness that will give a holistic evaluation to choice. No point sticking draft excluder on a barn door if there's no roof. More details would help. Marvin

Oh!

Up stairs bathroom ceiling?

I assume you realise that the surface area of the ground and the depth of the pipe/slinky in that ground determine the efficiency effectiveness of a GSHP?

I assume you will be spacing the trenches for a slinky wider apart....?

Did some yesterday where the footings were low. There goes my calcs again!

Well that's a question with many answers. Are you talking about Mechanical Ventilation Heat Recovery? MVHR

Surely the shortest Q&A ever!

First as LSB says the market is very hot and secondly there's the problem with obtaining materials, and then there is the increasing cost of the materials. I am already storing the materials for the next 3 (all be it small works) jobs and paid £78 for copper pipe which cost me £57 last year. I'm not surprised your not happy. I have even advised my brother in law to hold off (not sure his misses is speaking to me). Brother in law's shed order: delivery second week of September! Its not a rant it's frustration! I have the same problem myself. Delivery today: half missing and on back order I wouldn't mind but they delivered the walls but not the floor! Marvin

So thank you everybody for that thrilling journey of thought. I guess the answer is no, the energy used varies with demand.

I still wonder how you are going to heat all this water...

Ok. So now the question is about storage capacity and recovery rate. If you need to fill 250 litres for the bath in say 15 minutes, not only do you need the correct, tap, water pressure and pipework, but also the right amount of water storage of both cold and hot water. In simple terms you turn the hot tap on and hot water comes from the hot tank, but at the same time cold water enters you hot tank to replace the hot water filling your bath. Therefore 250 litres of hot water in 15 minutes equalls 250 litres of cold water in 15 minutes. If the mains cannot supply it at this rate then you need to store it in a tank in the building. Whilst the cold water is draining from the cold storage tank the mains will be trying to fill it back up again, and the time taken to fill it is called the recovery rate. More maths, but don't forget you have to take into account any other use of water in the building whilst this is going on otherwise the recovery rate will be longer. M

No matter what size the mains pipe is or how much pressure in it, if it gives you 18 litres a minute, that's what you got. I only know two ways that might increase this: more pressure or a bigger pipe. I say might because you do not know if the street main can supply more quicker. It was already indicated that the pressure fluctuates therefore so will the flow rate. My bet is this system will not reliably work without being gravity fed from tanks in the building. Anyway, a whole new subject is how you propose to supply the hot water quickly enough. Good luck Marvin