CE-iVT10 timer settings

[dexter]

Hi everyone.

Complete ashp newbie here. In march this year my oil boiler was replaced with a CE-IVT10 ashp. This is connected to a large gledhill  TS which provides central heating and dhw via an indirect coil which was originally supporting a hybrid system but now only connects to the ashp. 

The ashp is performing well, but there is a minor issue in HW supply. Currently, ashp user settings are configured for HW mode only, with ashp in eco mode which varies HW set point accordingly. However, if HW is drawn say 10pm but not sufficient to deplete the TS to trigger ashp demand, we can find that tank temp has dropped to just above the set point less differential in the morning, giving insufficient stored heat for anything other than a quick shower. After this, the ashp kicks in, and brings the TS back up. 

In the absence of a boost button (another story!), I wanted to know whether I could use the timer settings to force the system to ignore the eco mode set point at say 7am, and use a timezone tank temp setting for an hour. If the timer is enabled and on/off times are set, does this mean that the system ignores the timer settings and reverts to non-timer mode when set to off...or does it literally turn the whole heat pump off?

My brief chat with the team at CE suggested it would act as an override, but they couldn't confirm this because they very honestly admitted they have never used them!

I would only be using this in summer when the ashp is only providing HW. 

Anyone actually used the timer settings at all? Would a sudden increase in tank temp set point cause any issues for the ashp?

Any advice appreciated.

 

[Wil]

I ended up boosting the immersion for an hour with my final 4.30-5.30am cheap rate to make sure there’s always enough for the morning showers. Couldn’t get the time settings to reliably boost the heat.

[JohnMo]

I would say your only option is to use a timer in summer. But you are heating a big chunk of water for the output of DHW.

 

But are you actually getting a decent CoP with this setup? I suspect keeping a TS hot for DHW and CH must cost an arm and leg.  I would look at dumping the TS all together and install an invented cylinder for DHW and the a 3 port divert to switch from DHW to CH. I assume you have a low temp heating system?

[dexter]

The TS seems quite efficient tbh. Hp only runs to top it up, and at present that's about 10 mins once a day. In HW mode it only uses tank set point, so not continually running pump to check supply and return temps. The only issue is wind-up timing..once running, it can maintain water temp as it is drawn through tank.

TS does have an immersion, so that is a possibility...but hp would be so much easier if it simply had a 10 mins boost function to get it up to speed!

[dpmiller]

Do you really need to weather-compensate the DHW temp? I use the timer function on our iVT9 for what you're proposing, basically doing a set-back of DHW temp overnight and then boosting it just before the end of the E7 timeslot, ready for showers

[dexter]

My cold water feed is from an above ground storage tank due to pressure issues, so it's temp is generally higher than direct from mains. The warmer it is, the less is extracted from the TS when drawing HW. So it seems to work quite well. Adopting eco mode has reduced input demand significantly, as the set point drops to match the rise in temp of the stored mains water. Entirely by accident rather than design tbh.

[dexter]

Obviously, reverse is true when it is cold..so probably balances out.

[dexter]

You may be able to clarify...I understood these hps always used fan and compressor compensation, even in day mode. The eco mode only changes the tank set point temp? 

[dpmiller]

there's a bit of blurb in the v6.6 manual- and IIRC something slightly more detailed bit chenglish in the original Sprsun manual. But broadly, Day mode allows use of the full performance envelope, Night caps it for low noise, and low is weather comp. However, even the non WC modes throttle compressor speed based on ambient temp so...

 

what might be useful for you is U02- startup differential and shutdown differential. They control how much below setpoint the unit starts, and how it slows down as it approaches setpoint.

[sharpener]

7 hours ago, JohnMo said:

I suspect keeping a TS hot for DHW and CH must cost an arm and leg. 

 

Once the TS is up to temp it doesn't take much. My 210 l TS has a rated heat loss of 1.9kWh per 24h. Somewhat less in practice (maybe the rated loss is at 60C but in summer I have it at 45). So with a CoP of 3 that is about 10p a day at cheap rate. This wasn't the original plan but at that cost it is not worth trying to change it.

 

 

 

7 hours ago, JohnMo said:

I would look at dumping the TS all together and install an invented cylinder for DHW and the a 3 port divert to switch from DHW to CH

 

Given the above I don't think you could justify the capital cost of doing that.

 

Edited 19 hours ago by sharpener

[dexter]

10 hours ago, dpmiller said:

what might be useful for you is U02- startup differential and shutdown differential. They control how much below setpoint the unit starts, and how it slows down as it approaches setpoint.

Thanks, I haven't played with that but logically to reduce diff to three from default 5 and increase stop to 2 from default zero might help, but it seems to then defeat the point of eco mode. Probably worth a try. 

[dexter]

8 hours ago, sharpener said:

Given the above I don't think you could justify the capital cost of doing that.

That was pretty much my thinking. Effectively, the entire TS behaves like a giant quooker tap for DHW. So very efficient in the summer. Winter not so, because the TS also has to cope with CH. But it does mean the heating reaches temp very quickly. We will see where we are after a full year of use!

[dexter]

However, still cannot get my head around the timer. Does it then need loads of timezones configured, and when it is "off" in C103 and C104 does that mean the hp is off, or does that mean the timed settings are off and it reverts to those set in U01 for day mode or U11-13 for eco mode?

[dpmiller]

timezone can work two ways- full on/off, or programmable setpoints. Enable it only for setpoint, then add whatever timezones you need in C105-108. 

 

I *think* that these setpoints are then fed into the WC, but I'm not sure if they act as a minimum or maximum...