@adamk when i had my ASHP fitted by Octopus, removing old boiler and flue into roof was included in the quote, maybe it was me being fastidious about dotting is etc, wonder if anyone else had same level of service
I would have thought that including removal of the boiler was essential to be sure of qualifying for BUS, and so no installer would risk not doing it. The flue and the DHW tank not so.
Mine removed boiler and loft tank but left the flue which penetrates a flat roof. I think that's fairly reasonable, the best time to remove the flue is when the flat roof is next resurfaced. I would have done the same.
@agentgeorge My retrofit quote was for the complete installation and commissioning; the work included removing the old vented DHW tank, draining and removing the cold water storage tank from the loft and terminating / tidying up the pipework. I did have to remind them that they had agreed to remove the old plastic cold water storage tank as though they had terminated the pipework and drained the tank, they thought that they were to leave it in situ in the loft. I pointed this out and they dutifully cut up and removed the tank and re-arranged the lagging that had covered it to add to the layer of loft insulation where the tank had been. They also removed all the old piping for the gas boiler and filled the void where the flue had been. All work was within the contract price and I imagine the scrap value helps to defray costs 😉. Regards, Toodles
Toodles, heats his home with cold draughts and cooks food with magnets.
I kept all the scrap, got £20 for the gas boiler, have a ton of old copper from 2 previous boiler installs, most 22mm to so nice and heavy.
They did fill the hole in the ceiling, but there was no cold tank to remove, that went with boiler 1 to boiler 2 repositioning.
Also got a good bucket of brass fittings from the old boiler strip down, and lead from the roof replaced by the new extension for the utility/machine room
@toodles nope my installer only capped the flow return and dhw pipe work. had to get my plumber to remove the boiler, hw tank, loft tank, tidy pipe work in the cupboard (as we had the new tank in a different location), remove the 28mm gas feed and cap the meter.
this is essentially what i got for my £11300 (7500 BUS in that):
heat pump and short soak away all sat on old path.
a short run of about 2m of 28mm pipes up the wall to meet the 28mm that my plumber had run (primary pro and felixis on this pipework they ran)
electrics via a long external run of about 10m of cable from my meter henlys as seemed the easiest route to me. they had to come back to add another box as they initially used the wrong rcd/mcbs.
new HP Vaillant hw tank and valves filter and connect up all the pipe ends from the 28mm and 15mm rad circuits my plumber ran for them.
re route flow and return old tank cupboard and cap hot and cold.
Octopus also would only cap off the old pipework and joined the ASHP into the existing Flow Return and DHW feed.
I watched their plumber and pointed to a better place to cap off each of the pipes, especially the old 10mm that went to the radiators Ive replaced with UFH; I won most of the suggestions, and ended up with a boot full of 10mm and 22mm copper.
@jamespa this is my flow temp graph. doesnt look as smooth as yours, ignore the spike at the beginning that was me messing with settings:
I have only just spotted this post, sorry I missed it earlier. Unfortunately you dont give the OAT at the time so its difficult to compare, but it looks like its on for about 30mins at a time, whereas mine is on for about an hour at a time. There is more we could work out from the gradient and on/off ratio if we chose to, but for now we dont need to. The physics is fortunately simple, the next steps less so!
In assuming that you are operating with the system fully open. If that's the case then this suggests that the system volume relative to the difference between the min output power and the demand at whatever OAT this is lower than mine (roughly half). I do experience a profile like this but only when its much warmer outside than at present.
You will likely benefit from
Increasing system volume with a volumiser. If you consider going down this route look to double system volume not just a small increase.
Increasing permitted flow temperature hysteresis (installer settings)
(possibly - untested idea but logic says it should work) operating in expanded mode and setting a minimum flow temp of 30-33, or whatever is the min flow temp that gives stable operation. Dont change the curve, the minimum FT setting is a separate parameter. The system will then 'bounce off' the 'target room temp' on the sensocomfort which might result in longer run times albeit somewhat larger room temp excursions.
All of the above will increase run times, the first without increasing room temp excursion, the last two at the expense of increased room temp excursion. That said upward excursions, which is what principally you will get, arent particularly noticeable by most people compared to downward excursions.
Personally I would probably let it run for a couple more days to collect data at a range of OATs (its mild all week I think) and then perhaps do some experimentation. I might go for the last of the above initially
I have a sneaking suspicion that your house may be better suited to the next size down heat pump, but its difficult to be certain without a bit more data. Its equally difficult to be certain that this is the explanation for relatively disappointing COP, but it does seem likely. Its totally uncertain whether it will materially affect SCOP, only time will tell that one, its quite possible that it wont.
This post was modified 3 weeks ago 10 times by JamesPa
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
@jamespa I contacted the installer and asked them to balance the rads. They’ve replied, surprisingly, and will be over this Friday. I assume they are doing this as part of the commissioning process and don’t send me an invoice.
When I asked the installer if it could be run open loop he reconned I had plenty of volume. I’ve got probably 10m+ total of 28mm just on the primaries, maybe the same for the flow and return 28mm. Then the old U of 22mm that runs in the 1st floor and ground floor must be 10m. After that it’s several m of 15mm to various rads.
on the rads I probably need to replace 3 single panel ones, one double that’s only got fins on one panel and I’ve got a 1800x400mm towel rad to go in the other bathroom when we renovate it. The utility/shower room already has 1800x500mm towel rad which is 22mm tubes.
@adamk I run the downstairs UFH as an open loop, the kitchen/lounge pipework is 250m of 16mm, add to that the 4th bedroom 100m, which is restricted to 1L/m flow rate. The upstairs bedrooms are on TRVs and the bathroom Towel Rail is always open and on full flow. I used to have a 450mm wide TR, but increased it to 500mm and changed from chrome (awful heat transfer rate) to white to double the heat output. I wouldn't stick with a 400mm wide TR as it’s a ball ache to get a towel to fit nicely on it. The downstairs en-suite is getting an electric heated TR, easier and more flexible positioning of it than trying to connect it to the ASHP
When I asked the installer if it could be run open loop he reconned I had plenty of volume. I’ve got probably 10m+ total of 28mm just on the primaries, maybe the same for the flow and return 28mm. Then the old U of 22mm that runs in the 1st floor and ground floor must be 10m. After that it’s several m of 15mm to various rads.
There are two definitions of sufficient volume. The first is sufficient for defrost which is the min system volume manufacturers quite, typically around 30l. The second is sufficient to give a long run time at moderate oats when load is less than min output of heat pump. That figure is considerably higher. My system volume is 200l for a 7kW pump. The more the better. If you are not running fully open I advise you to do so, as I do.
@jamespa hopefully after the rad balancing it will perform better, as I think at the moment the water is short circuiting back to the hp through the fully open lockshields, though I’ve done some very basic balancing recently to see if it helps. Essentially I don’t think the hp is seeing the whole system due to the unbalanced rads.
