MikeSharp01

I get that but it assumes a static envelope if, using your analogy, the rugby ball is shape shifting as you measure the curve would work only when the ball hits the shape it was when you measured it. In my terms if I leave the windows open when it's cold outside the heat will be removed faster than you are making it up so the temperature will drop and once you close the windows the temperature difference will linger for a period which, in a well insulated building, could last a reasonable time. Obviously the reverse also applies so if you have a big party the house will overheat and stay overheated! Have I got that wrong? We do have a number of internal temperature sensors and via the BMS connection to the heat pump we should be able to adjust things if the Weather Compensation (WC) is not effective. On the whole I suspect when I get it all going that the edge cases I set out above, windows open and parties, will not be an issue but I do think it is important to stress test all the assumptions built into the accepted truth.

The heat pump is running, it has some teething problems but it works very effectively at warming the slab. The heat Meter (EMON Pi) is also up and running. So now I want to move on to setting up the Weather Compensation and see what happens. Looks like you choose a curve setting as best guess and then observe what goes on to fine tune. One thing I cannot see anywhere in the system we have is an internal temperature monitor the typical systems seem too open loop to me. I get the system does not use a thermostat but I don't get how it can get away without having some sort of measure of the internal temperature of the house because it doesn't know how the house is being used, what is coming in via the sun or indeed if the house is cooling or heating more than the output is providing for. Still the heating period has a few weeks to run yet and I want to make every day a school day learning how to heat the place so I guess I should just give it a go, any definitive advice as to the process I should follow.

Yes, sorry, tomorrow I will make a short video of what's going on, I wonder if the thump is happening out at the machine so I will check that as well.

Its a diverter not a mid position, this is what is on the invoice: "CE-ZVD28PW - 28mm 3 Port Diverter Valve" sorry for the misdirection.

I did have them almost wide open, little red floaty things as close the bottom of the dial as possible but I backed off the outer two in an attempt to balance the flows a bit as the middle loop is twice as long as the other two happy to leave it all wide open. Will experiment tomorrow.

No fault codes. I think so it is all 28mm, one clip at least every 500mm, more often usually inside, although not on the risers to the tank entry points albeit they are fixed at the top of course - can look at that and see if there is any flexing. Outside runs are clipped outside the insulation to cable trays with a flexi at the end to the heat pump. As to air I cannot be sure but there is a trap at the highest points of both the tank and UFH loops (see pic for UFH) and I bled the stubs that will be running to the fan coil units upstairs. (Although I could check those again now its been running for a bit.) Here is a pic of the valve and the UFH pipe work

Interesting thought and entirely plausible. Here is the basic circuit I used from the install manual - except that the Underfloor Heating (UFH) is where the buffer tank is as we have no buffer tank. This circuit makes sense this way round although I guess you could put the valve in the return junction. The valve is normally open to the UFH and the Heat Pump sends a signal to the valve to change over when Hot Water heating is called for. So the flow comes up the middle of the valve and goes out either to the UFH circuit or the Tank circuit. Hence as the valve closes, on the spring, to the tank circuit it will have the flow helping it close. If that is the cause of the thump then it's a control problem. Perhaps the Heat Pumps circulating pump should be shut down while the valve changes over although that would be a firmware issue in the controller?

Its controlled by the heat pump and its the valve that came with the heat pump - this one I think: The ZVM28

Been running the new heat pump today testing and commissioning the EMON heat meter. The heat meter is working well and telling me I get about 4.2 COP on heating the slab - with a cold slab at about 12oC. When I switch to heating the hot water the changeover happens smoothly and the heat meter starts reporting HW correctly BUT when I switch back at the end of the valve close we get an awful thump, I guess water hammer? Is this common and what might the / a cure be?

No we decided to get a new one, well two new ones, which I fitted yesterday. Yuk job.

Yes sorry name mix up. To much happening in my world. After 20 years of trouble free service a cistern in one of our bathrooms just cracked without provocation, not been used since Christmas, drowned the router in the stairwell below, left us with no Internet and water everywhere. Sadly its a Fired Earth unit so no guarantee possible- still as I say it has done 20 years.

It is, at least that's what I asked for, it doesn't have a fuse anyway.

We don't need the immersion to clear the legionnaires risk the heat pump does that. So for now I have wired it straight to the CU breaker via a switch fused unit. So as of now we don't have automation of the immersion but there appears to be nothing preventing me using my contactor approach. The rules are clear that you can put stuff in between those fixed points provided it meets the wiring regs etc which is how the diverters do it. So I won't have any high current stuff on / around the tank other than the connection from Switch Fused Isolator to the immersion heater. Final job is to commission the heat meter & EmonPi. Hopefully Sunday, then I will have some real data to play around with and get an impression for how good or bad the system is.

Well, it's gone very well. On Wednesday the system was commissioned with no issues so the MCS cert and the G cert will be issued. When I get a bit of time I will write up the whole thing for a blog as its been a very interesting mission but we got there. It was great to see the heat coursing through the slab pipes. I have not calibrated the Camera for emissivity.

Self building is a mission (pardon the pun) but an absorbing and rewarding one, we are looking on in awe! You blog is wonderful - keep it up and keep on keeping on.

Makes sense, not sure we will ever need it here in the deep south!

Nothing in the manual about that, manual is sparse to say the least, but it does have an output called 'additional heating'. As I mentioned above the heat pump can make water at 75oC, so it shouldn't need additional heating.

I am sorry, I was not trying to complicate things, I think maybe I was confused by the dual stat being part of the kit, so I thought we'll as I don't have all the other gubbins in the Telford schematic, on the assumption the dual stat was some sort of safety device for the immersion and knowing that the heatpump cannot make water above 75 degrees that I should just provide a fail safe for the immersion using the dual stat via a contactor and because 24V controls are in my blood I took that approach as it both protects the tank and allows me to turn the immersion on or off remotely. Nick is also right everyday needs to be a school day for me and nothing about this stuff is difficult - just new to me, so having you chaps around to point out the straight and narrow is a real help. Anyway the good news is I have just powered up the heat pump for the first time and it is now working on heating the slab also tried domestic hot water and that works but the changeover seems to cause a differential pressure error (174 on the cool energy app) Anyway here is the current status 20 minutes into heating the slab.

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.

Which schematic are you referring to. The only one I have is in the manual and looks to refer, as you say to a boiler based system. (Link: https://www.telford-group.com/download.php?file=VG9ybiBUZW1wIEluc3RhbGwgR3VpZGUgMjAyMy0yNDUucGRm) It does say controls provided must be used but I obviously cannot use the above circuits as I don't have; the programmer - that's in the heat pump, the three way valve operation - that's controlled by the heat pump, the pump - that's in the heat pump so I just used the dual stat to limit the immersion. The max output temperature of the heat pump is 75oC so it should not need any boosting as legionella should be gone with 30 minutes at 60oC. I cannot see anything in the manual for the heat pump about an inbuilt booster heater but it does have provision for what is called additional heating (5A@240V) as an external connection. (See image below) So I am using the dual stat to control the immersion (despite it being an intelligent one - which can do all kinds of things on its own. I could take the additional heating signal from the heat pump (terminal 1) and use that to drive, via an appropriate interface, the call for immersion signal discussed in the thread above but as far as I can see the heat pump manual makes no reference to the use of that signal other than as part of the commissioning check list and nothing to say this additional heat source should be controlled by the additional heating signal.

Yes I have, via the contactor route I discussed. I am not sure if the Heat Pump has a boost heater I will check that but whatever happens I don't want that heat getting round the UFH so control of three way valve won't happen but I could just kill the power to HP I suppose using the same signal.

Yes the safety stat but as it's a heat pump it cannot reach dangerous temperatures so I have assumed that I don't need it for that, is that not OK, and have put it into the immersion circuit as described here: and you commented on at the time. It's a Telford Tempest Heat Pump cylinder and the two pockets are shown in the image below, which was taken as we worked out the pipe runs, hope it is enough but I can get a full picture tomorrow - not quite sure why I don't have one already. There is nothing low down only the two showing.

Almost complete on the HP install all flushed through, pressure tested everywhere and filled for testing (still need the inhibitor) Powerup tomorrow, would have been yesterday but weather stopped us because you have to take the lid off the HP to make the final electrical connections if you want a BMS connection. Anyway the final challenge is to fit the temperature probes into one or both of the pockets in the UVC. There are two pockets one at about 50% height and one at 75% height and there are two probes. One (A) looks after the immersion heater and the other (B) looks after the Heat Pump - sends Domestic Hot Water (DHW) data direct to the HP presumably for the HP to know it has got the water to the required set point. The tank is quite dumpy and 200l so I assume it makes no difference as the tank probably does not stratify so well that it matters. Have I go that right? To help me out I have used the top pocket for both so if it does stratify I am working on the hottest water and I can read the temperature from the BMS and its reading the same temp as the immersion limits.

An old Architect of my acquaintance once told me that if you cannot get your hand into the crack then you do not need to worry about it, hopefully one of our friendly Structural Engineers will be along shortly with a view.

Just another thought, we kept the service void in the utility room and had we not done so we would have had problems with mounting things like threaded inserts through the VCL used for things like munsen clips and the like.