@ngillam No way to control defrost cycle, but that isn't your issue it only increased 5C in 30 mins before the defrost started that isn't normal, its as if you were emptying the tank as it was trying to heat it back up.

@gary That's a good observation on emptying the tank!!  I wasn't at home but will check with the other half if she was up earlier than planned.  Once again, you're a fountain of knowledge.

Does my flow and return seem nominal to you?

Thanks,

Neil

Flow and return are fine, what isn't is the rate at which it is changing.

If I look at my HW run last night to get from 37C to 42C flow mine took 5 mins yours took 30 mins, hence my comment on was the HW being used at that time, if you have never had an issue before with HW heating up in that time period there is some other factor here.  See what happens tomorrow morning I guess 

Is this a pump issue? What jumps out at me on the chart at the the time of the defrost cycle is that the return drops dramatically first, and pulls the flow temp down slightly with it. Two minutes later the flow drops right down and only then looks like a normal defrost cycle, but rather than the flow temperature bouncing straight back up at the bottom of the cycle it takes few minutes and in addition the tank cools slightly as the return temp goes up several degrees before the flow temp goes back up. None of that looks normal, but I can't think of an obvious cause. The latter bit looks like the HW pump might be running while the defrost is taking heat out.

I would expect a HW cycle to stop when a defrost is needed (I don't HW at night though) and then just restart. There is meant to be enough volume in the primary circuit to enable defrosts. 

@harriup @gary I really do need some help with this one.  It seems my HW never gets up to 47 target now due to defrost cycle running every hour.  It gets to 41 or 42 before defrost cycle (the controller shows inverted colour heat pump symbol) which seems to draw down the tank temp to 38ish before defrost cycle ends. 

Gary, your comment on slow warm up, yours seems a lot quicker than mine, I have a 5kw but even allowing for your step up in power it still seems very slow.  Thinking about it a historical comment of yours mentions enough heat throughout the day.  My tank once up to temp seems to dwindle back down quite quickly, it's a pre-plumbed cylinder 210L, I have timers set to 24hrs on pumps and can only think all this is related.

Can I ask what other ECODAN owners have there settings on for defrost and settings for HW duration etc.

My partner went out last night so I had to put the HW on constant to ensure she had hot water for shower, checked in the early hours when she came in and immersion heater had stepped in, disappointing!

Suggestions welcome, it's only 2 degs outside but defrost seems to be really hampering our comfort at present.

Thanks,

Neil.

@gary Weird one, checked with partner, she wasn't using the hot water during this period!

check what the HW pump is set to on the cylinder it should have 3 positions it should be on 3 which is the highest setting

@gary Yep, it's on 3.  Here are the last two hours of info:

Every hour it does this, this is the first winter we've gone through since heat pump installation so first time it's seen these temps.

Thanks,

Neil.

Posted by: @ngillam

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have timers set to 24hrs on pumps

What does this mean do you have hot water being pumped round a circuit?

@ngillam that all looks normal it’s just defrosting

@gary

I have two of these in the control room, one looks to be UFH manifold side and the other DHW.  I have it set 24hr because if it isn't then outside of times it won't send hot water to taps/showers or bath.

My DHW settings:

Max temp - 47

Drop temp - 7

Max op time - 90mins

Mode Restrict - 55mins

Similar to yours?

Thanks,

Neil.

So it will only run for 90 mins before shutting off and that currently isn’t long enough to reach your set temp

In the HW schedule on the FTC when is that set for? .

Is a pump running constantly if you have that Heatmiser thermostat set to on 24hrs a day?

If so I’m wondering if you are circulating HW round a pipe which would explain why your hot water is losing temp quickly and won’t be helping with the hot water heating up