Ecodan 6kW - is it "cycling", or normal operation?
I'm struggling to understand the "logic" used by the FTC6 to run the compressor and pumps.
Graphs from today, 8 degrees OAT, WC curve target is 40 degrees
Graph shows flow temp and power consumption for the complete setup over a couple of 20 minute cycles.
The first part of each cycle makes sense - compressor starts up, flow temp increases. Compressor runs harder, flow temp increases further. Reaches target temp, compressor backs off a bit.
Flow temp stabilises for a bit, then everything shuts off - including both pumps. Flow temp is steady, because the water isn't moving.
After 2 minutes, the pumps start up, flow temp drops rapidly.
3 minutes later, the compressor starts up again.
I don't understand why everything switches off when the flow temp is stable?
I don't understand why both pumps switch off the instant that the compressor stops?
The reason why the pumps were stopping is because the heating was switching off.
The Evohome controller starts "modulating" the BDR91 boiler relay as all the TRVs get to within 1 degree of target temperature. Since it can only modulate by switching off, it starts cycling every 20 minutes (the minimum number of cycles, set in the system configuration).
After a few minutes, the Evohome boiler relay switches on again, the pumps start running, flow & return temps start to drop, and the compressor switches on.
This wasn't happening before, because it was cold outside, and a couple of rooms weren't getting close to target temperature. Evohome was continuously calling for heat.
Main culprit was the bathroom, losing a lot of heat through the extractor fan ducting. The electrician had removed the baffle flaps, because they fouled the flexible ducting. I've refitted the flaps, modified the ducting, and they now work. Much less heat loss, bathroom gets up to temperature, so now the Evohome is cycling.
Not sure what to do about this?
I guess I could disconnect the boiler relay, and just use the Mitsubishi wireless remote as a the controlling thermostat, and the Evohome as adjustable TRVs (without any "call for heat" function)?
I'd have to find a suitable location for the Mitsubushi wireless remote though - somewhere that it actually has some control over the heatpump, but doesn't switch it off too soon.
@clockworks That all makes perfect sense and highlights that heat pumps don't need external control from on/off boiler thermostats they just hamper performance.
Sounds like moving the wireless thermostat is the correct option for you. Hope it works out for you.
Rather than disconnecting the Evohome boiler relay, I've added a switch across the relay contacts. This way, I can either have it on continuously, or flip it back and give Evohome control.
The boiler relay was just wired up as a "zero volt" thermostat to the FTC6 - closed circuit for heat, open circuit for no heat.
With the switch closed, Evohome will just be controlling a few TRVs as limiters, while the Mitsubishi remote is doing the "call for heat" and controlling the heat pump. Basically the same as if I was just using a few wax TRVs, but programmable.
Now that I'm back in pure WC mode, I don't think the wireless remote will be having any influence, apart from "on or off"?
- 26 Forums
- 2,238 Topics
- 49.8 K Posts
- 405 Online
- 5,900 Members
Join Us!
Podcast Picks
Latest Posts
-
RE: Testing new controls/monitoring for Midea Clone ASHP
@cathoderay thanks- yes will keep an eye out for the de...
By benson , 24 minutes ago
-
RE: Solar inverters - where does the energy go when clipping?
Absolutely right! 🙂 And not all will quote o...
By Batpred , 33 minutes ago
-
RE: Renewables & Heat Pumps in the News
Hoping so as well! I am no specialist. The language use...
By Batpred , 46 minutes ago
-
RE: My experience with 3 heat pump surveys: Heat Geek, British Gas & Octopus
You are right but ... Adias aren't trvs. They vary the ...
By JamesPa , 49 minutes ago
-
RE: Octopus Cosy Heat Pump Owners & Discussion Thread
This will differ from house to house depending on how i...
By JamesPa , 1 hour ago
-
RE: Replacing knackered oil boiler with Samsung ASHP - Perthshire
The Water Outlet temp on the controller screen will dis...
By Mike H , 2 hours ago
-
Do you need the DHW tank as high as 50°C @egp01 ? Ha...
By Transparent , 3 hours ago
-
RE: The Hidden Secret to a Successful Heat Pump: Pipe Size Matters
@old_scientist Just to say that during our retrofit, we...
By Toodles , 3 hours ago
-
RE: Daikin Altherma 3M ASHP and British Gas Hive Home
We have a Daikin EDLA08 8kW monobloc (DHW is handled se...
By Toodles , 3 hours ago
-
@old_scientist @jamespa So this was last nights DHW r...
By bontwoody , 4 hours ago
-
-
@springswood we install these nationwide and I have the...
By dgclimatecontrol , 5 hours ago
-
RE: RDSAP10 effect on existing heat pump EPC rating?
Just returning to this issue after a few days working i...
By Mike Patrick , 6 hours ago
-
RE: DESNZ doing a survey which asks the right questions!
Fair comment. I have a feeling that ratings more gen...
By JamesPa , 11 hours ago
-
RE: Daikin Octopus installation update - I saw my first defrost. 😍😂
@jancold Not a plumber but I believe that i...
By RadWhisperer , 11 hours ago
-
Thanks! My consumer unit collection is ready with the W...
By Batpred , 14 hours ago
-
RE: Designing my house system with a mix of air to air and air to water
@jamespa Cheers James, it's great reading. In quite a f...
By pipebaron , 22 hours ago
-
RE: PV Panels on roof in Conservation Area
If there is any way you can determine daily oil consump...
By JamesPa , 22 hours ago
-
RE: Grant 13kW Aerona3 - issues getting zones to temp
attached is prelagged in case indicates anything. &nb...
By Crimson , 1 day ago
-
RE: Solis S6-EH1P8K-L-PLUS – Why I Chose It and What I’ve Learned So Far
Via the cloud and via the online, similar data is shown...
By Batpred , 1 day ago





