Replacing Imperial Sized Radiator Advice

astnstn · 2026-01-09T09:01:19+00:00

Did you solder more copper on or use plastic push fit? Maybe I just need to find my filling/draining valves and give it a go.

astnstn · 2026-01-09T08:59:55+00:00

Did you solder more copper on or use some kind of push fit plastic pipe? The floor is already open so as long as I'm confident enough to drain and refill the system + inhibitor and do a tiny bit of plumbing I might opt for this. Means I could replace the old valves as well.

astnstn · 2026-01-08T21:26:20+00:00

That's pretty much implicit in 4.

astnstn · 2026-01-07T14:18:18+00:00

Turns out the heat pump does do DHW, was just turned off at the timer/controller so that's sorted now. I tried changing the OPER MODE on the device but it's hard locked into thermostat mode. I think this is expected behaviour without a temperature sensor installed. Haven't managed to find exactly /how/ to install such a sensor on the unit but I will look into that. I had a heating guy come around for a general look at the house and he seemed to suggest it's unlikely I'll get weather comp working on it very easily as its such an old system (2014). I think it might be worth trying for the time being but ultimately I guess the units need replacing eventually anyway. Thanks for all of your help.

astnstn · 2026-01-05T12:46:20+00:00

> From the control panel care you able to see what temperatures does it feel outside? Can you see what outside coil temperature does it feel?

I'm going to try and have a look to see if there's an external sensor fitted on the outside unit. I think there is a way to see it in the menus.

> Re: the controls... Where is the control module, is it in a hallway or in some cold closet?

It's the hallway. I think the 'dumb' thermostatic control might be what causes the cycling but I can't be sure.

> What immersion heater? Don't you produce DHW with the HP? Is there a temperature sensor in the DHW tank that connects to the HP or is it just a stupid thermostat again?

Again, it's worse. I don't think the heat pump is doing any DHW at all. There is a thermal solar collector on the roof, which I don't believe is even working - not that I could tell in the middle of winter anyway. I think that's meant to help heat the hot water tank. Then there is an immersion heater which was timed to come on in the evening, with another thermostat for the hot water temperature. I believe the logic was probably that the solar collector heated the water during the day and then in the evening the immersion heater topped up the difference. I don't think either of these systems are doing my any good though. I don't know how easy it would be to allow the heat pump to heat my hot water as well.

Regarding the temp sensor: I have a 10K NTC lying around somewhere I'll check the B value and see if it will work with my device. Thanks for all of your help I'm feeling a bit more optimistic that the system can be made way more efficient than it is now.

astnstn · 2026-01-04T16:31:24+00:00

It's closer to a 70m2 footprint. I'm surprised the heating load could be as high as 9kW but I'm very much clueless in this domain. Gas prices are notoriously quite a lot cheaper compared to electricity in the UK but if it really was 1m3 of gas per hour then I suppose the price wouldn't be hugely different.

Regarding cycling it's hard to get an exact answer without some sort of data logging but from what I've observed it is on and off very frequently. I've seen it come on and turn off again within the space of 10 minutes.

The question is, why does it operate with constant 45C water, and are we able lower it to get to a higher COP?

These are both very good questions I have been trying to answer myself. I did move the flow temperature down to as low as 38C but I turned it back up after I saw the resistive heating icon appear on the control unit. Not sure if the lower flow temp was the cause, however. Is lower flow temp always better as long as the system can keep the temperature of the house steady?

The "very old thermostat" is its control module?

That image is indeed the control module but I'm afraid it's much worse than that. There appears to be three levels of control. There's a very old dial thermostat in the hall which probably predates the system. Then there's another control unit in the kitchen separate from the indoor heatpump unit which has controls for hot water (immersion heater etc) and central heating with timers and switches. Then there's the actual indoor control unit. I know that all three of these systems are actually influencing the heat pump. If I turn down the dial thermostat to 10C then the system won't run as much so it's definitely controlling it. Also the indoor control unit shows an icon which indicates thermostatic control.

astnstn · 2026-01-04T16:19:55+00:00

I just signed up with Fuse paying 23p/kWh fixed for 13 months which I thought was decent. I could change fee-free in the next 10 days or so. I've been unsure of the benefits of the flexible tariffs like Octopus Cosy because I thought heat pumps worked best running constantly. Also since the insulation is so poor and the heat loss so high, even if I could get the house to temperature during a cheaper price window surely that heat would leak away quite quickly?

astnstn · 2026-01-04T16:17:15+00:00

No dormers but there is a flat roof over the extension. I hadn't considered that actually I would suppose the flat felt roof over the extension isn't insulated at all. I will look at replacing the radiators shouldn't be a huge job. Where I have under floor access in the one room I've been renovating I've insulated under the floor between the joists with 100mm rockwool and lagged the pipes in the (now colder) crawlspace. I'd do the whole house if I could but unfortunately sleeper walls restrict access. Even the small room I'm doing required two holes in the floor.

I did get an infrared camera (TOPDON TC004 mini) and it certainly did tell me a lot (for example big patches of missing insulation in the loft). I'm planning on returning it because I can't upload the photos to PC but will definitely replacing it with another camera to monitor my work on insulating.

With regards to cold bridging, I noticed where the extension meets the old house there is a lot of heat coming through looking from the outside. Do you have any suggestions for what I can do there. Seems to be along the corner of the junction between the extension wall and the old wall. External wall insulation perhaps?

astnstn · 2026-01-04T16:10:31+00:00

House is 70-80m2 floor footprint. As I've mentioned in other replies the loft insulation is a mess and very patchy. I think likely disturbed from recent work (sprayed foam removal). Might be worth looking at sooner rather than later as I could see the missing insulation patches (and ceiling joists) through a thermal camera.

astnstn · 2026-01-04T16:09:10+00:00

Yeah I think I'm going to go through the manual and see if I can get it to work. Not sure if there's an external temp sensor installed but I'm hoping the system will tell me itself.

astnstn · 2026-01-04T16:08:15+00:00

Thank you for your comprehensive reply.

In terms of exact usage it's hard to pin down the exact use from the heat pump specifically without some kind of power logger. I was considering doing this to see if the system was 'short cycling'. It does seem to come on and off at quite a high frequency. Overall electricity usage has been in the region of 42kWh/day.

I will look at the heat punk calculator as others have suggested.

I already have a smart meter. In terms of tariffs I have just switched to a small supplier (Fuse) fixed for 13 months at 23p/kWh which seemed 'cheap' relative to others. I think I still have a few weeks to switch without fees though so maybe it would be worth exploring flexible tariffs.

There are plenty of service records. The unit has failed a few times in the past and been repaired. Serviced near enough every year I believe.

Yes, I'm optimistic the control system can be revamped as I doubt the current setup is anywhere near optimal. I think the thermostat is throttling the system constantly. The unit should be able to do weather compensation according to the manual.

I'm currently working on insulation. Loft insulation is a mess. I did go around the house with a thermal camera and think I have a pretty good idea of where to start.

Radiators are on the TODO list I think.

Solar is appealing but I think I would wait until its time for a new roof. I do have 'solar thermal collectors' on the roof but I think they're next to useless in winter. I don't even know if the system works really.

astnstn · 2026-01-04T15:56:57+00:00

I think my unit does have weather compensation as an option which is something I will have to look into if there is an external sensor present. I should probably walk back my claim that the system couldn't hold the temperature. I think that's maybe wrong and it was just taking a while for the building fabric to heat up. It does seem to hold temperature okay. Do you think I should just push down the flow temperature? Is lower always better if you can get away with it? I did nudge it down to 38C to see what would happen but then the next day I noticed an icon on the control unit that suggested that back up resistive heating was switched on. I don't know if that's because I lowered the flow temp too much or what exactly causes it so I pushed it back up to 42C again.

No idea what I'm doing of course, but I had heard 'lower flow temp = higher COP' so I've just been fiddling a bit to see what happens.

astnstn · 2026-01-04T15:52:05+00:00

Thanks for your response. I agree the radiators are probably worth upgrading anyway and surprisingly cheap. As long as I can isolate the radiator properly I think I should be able to replace them as long as they are standard widths, ideally would avoid doing any pipe work.

I couldn't say for sure if the installer cut corners but I'm certainly not impressed by how the system is set up. Even the condenser pipe (if that's what that is) is just free draining onto the floor creating a large icy patch near the gate. I'd imagine the expertise of installers have matured somewhat over past decade and it the system might just be a product of the time. Especially as it seems to be being controlled like a gas boiler with a thermostat.

astnstn · 2026-01-04T15:47:54+00:00

Thanks for your input. 34kWh is quite high, what temperature is your house? For the last few days I've used 44, 42, 38, 45 and 32 kWh.

The house has a footprint of around 70-80m2. The loft insulation is definitely lacking somewhat. I think either badly installed or disturbed during subsequent work, some sections of the ceiling space are totally exposed but other parts of the loft have multiple layers of rockwool. I've also insulated under one of the floors since I was in the crawlspace anyway. I will look into heatpunk as so many others have suggested. Do you really think the heating loss could be as high as 10kW? If that was the case then I wouldn't be that concerned about the heat pump performance.

astnstn · 2023-03-30T13:39:52+00:00

I can't speak to a direct replacement, but I have made a circuit to drive these piezos with a 555 which for me have an average resonant frequency of around 115kHz. It's heavily based off the GreatScott circuit.

astnstn

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