Has anyone looked at the differences between VRC720, VRC720/2 and VRC720/3? I’m using the oldest VRC720, but I think newer versions have small amounts of new functionality.
When we first installed our Arotherm, one of the things I wanted to be able to do (but was impossible) was use an external “call for cooling” in order to turn cooling on/off based on slab temperature, rather than room temperature. This was something our installer followed-up on with Vaillant but got nowhere. However the VRC720/3 manual now explicitly describes how to do this! Not sure I’d use it now I have an ebus interface, but this is one of the new features. It looks like there are others too:
pre-heat functionality
a new DHW mode.
potentially a way to limit the influence VF1 buffer sensor has on desired flow temp.
What is interesting, and I don’t quite understand, is that “ext. cooling demand” option appeared in my controller after the external unit firmware was upgraded. I assume this is because the controller is designed to be extensible and picks up these options from elsewhere. Still strange though as internal firmware wasn’t update. I haven’t tried the cooling demand yet though.
Other new features haven’t magically appeared, and would likely need a controller upgrade.
since mid November, i have an 55/6 ashp installed.
I tried to set it up in a way to minimise the on/off’s, and run it as slow/low as possible, and still keep the confort. So far, i have 220 on/offs and 2350 hours of running time.
Now, the question: by chasing the cop/scop, did I overlooked the compressor ? I am aware that 2350hours might be a lot. What is the life expectancy for this part? Should i change anything in the actual way of working?
Reducing on/offs is more important than runtime for the life of the compressor, so you’re doing the right thing. Vaillant say that a well maintained heat pump should last 20-25 years.
1 on/off every 10 hours is good, whereas 10 on/offs per hour would not be good for the compressor.
Does Vaillant state anywhere what an acceptable/rated number of cycles is for a given time? I’ve had 1500 on/off cycles over 3 Months / 1000 hours active running time. I won’t get rid of the cycling since the pump is too large but it would be interesting to get an actual rating for acceptable cycling directly from the manufacturer.
Due to the ongoing problems of improving insulation, I’m edging closer to swapping out a gas combi for an ASHP, via the HeatGeek umbrella.
I’ve been monitoring room-by-room temperatures for a while, initially using emoncms/emonTh, and more recently using Home Assistant - I now have temp/humidity sensors in all rooms. These are showing a range of temperatures across the house, and confirm that the rooms I have always felt were cold, are in fact cold.
Since last December I’ve been building up a spreadsheet full of temperatures, gas use, and gas tariff costs, had heatloss surveys carried out by British Gas and People Powered Retrofit last year, and have just had one carried out by a HeatGeek this year. (NB the HeatGeek was the only one who checked for approximate levels of insulation using a boroscope through airbricks, light fittings and extractor fan, plus one hole in one wall which will need to be carefully repaired, rather than relying on Building Regs at the time).
The ‘proposal’ is moving along, but not yet signed off, and I am now wondering about the proposed monitoring of the heat pump (Vaillant Arotherm 7kW) with Vaillant sensoCOMFORT Wireless Controls. I’d like to be able to contribute to the Heatpump Monitor database, but also want to have access to, and be able to download, my own data. The plan is to run with pure weather compensation (I’m doing something equivalent with my gas combi at the moment).
Is there a resource that explains the different types of monitoring kit, the pros and cons of each, accuracy, reliability and ease of use and the cost of installing each?
Hi, I have a level 3 OEM but my installer unfortunately did not request the remote room thermometer; to add it after is £75 which isnt cheap. Doesn anyone know if I can use a Heatmiser neostat (connected to a neoHub wifi network) would work? Heatmiser say it works with Apple HomeKit, Google Assist, Alexa and IFTTT. Thanks.
We’ve had our 5 kW Arotherm installed for 3 months now and overall it’s working well. One issue that’s arisen is the transition from hot water to house heating is sometimes quite noisy (a few of the rads get clunking noises - sometimes quite loud). We have our hot water to heat up to from 12-3 am (52 C with an offset of 6 degress) and then the heating to kick in at 3.30am. I suspect the noises are caused by hot water in the system hitting the rad when the valve swiched to the heating loop. There doesn’t appear to be a significant amount of air in the system.
Can anyone suggest a way to prevent or attenuate this affect? Thanks.
I’m seeing a similar behaviour here but probably not as pronounced as on your side. The reason is exactly what you described - a hot water bolus hitting the radiators causing sudden thermal expansion. The only mitigation I can think of is increasing the time delay between the end of the hot water and starting the heating to allow the water to cool down a bit more; but this takes quite a bit of time because it’s just sitting in the insulated pipes. Do you have smart thermostats and could switch off flow to the problematic radiators when the bolus hits and only enable them a bit later when the flow has cooled sufficiently?
Thanks for the reply, glad it’s not just me. I was hoping to avoid using TRVs if at all possible. I’m not clear on the system behaviour, i.e. does the valve switch to heating mode when the HW cycle is completed (and is there some pump overun?). Or, does it stay on HW mode until the heating cycle is activated. I’m using the Eco setback mode so in theory the heating should stay off until called for. I suppose what I’m trying to ascertain is, does the hot bolus hit the rads at the end of the HW cycle or beginning of the heating cycle?
I think it’s the beginning of the heating cycle. We recently had some warm weather and I started a hot water run. At the end of the run the pump just shut off because it was above 15° C outside and there was no heating demand and the remaining hot water in the pipes slowly cooled off over a couple of hours.
Edit:
The valve will switch to heating mode after the hot water run but the pumps will be off if there is no heating demand so the hot water does not circulate.
Thanks for that. So, if there was some pump over run after the valve has switched it could occur at the end of the HW cycle. I’ll have to note the time next time it wakes me up.
Note the switchover from DHW to CH and how the flow rate drops from maximum (as used by the DHW run) to the normal heating flow rate. If there is no heating request it looks like this:
Note how the flow rate drops to zero after the DHW run (it was >15°C) and the temperature slowly decays. Note this was a legionella protection run hence the super high temperatures.
There might actually be another way to solve your problem: You can set a maximum allowed flow temperature in your controller, probably meant to protect UFH circuits from too high temperatures. If your typical heating flow temperatures are significantly below the hot water temperatures, you could just set the max allowed temperature to e.g. 45°C or even lower. I recall reading somewhere that this maximum flow temperature constraint led to a heating interruption after hot water runs, which would be exactly what you would like to achieve. I’m not sure though and can’t find the thread where I read it.
Many thanks for the informative reply. From your second graph, (if I’m interpreting the data correctly), it looks like you still get a hot bolus in the heating many hours after the HW cycle has ended. So, it looks like increasing the interval after HW would have minimal effect. I already have the max temp set to 45 C so, at least in my system, this doesn’t seem to prevent the heating from activating.
Good catch, there is a minimal bolus effect even after that time. However, it is much reduced. Have a look at this graph, which shows the flow temperature measured at the pump (HMU Corrected) vs. the temperature at the radiator measured via an IR probe (Object temperature) at the time of switch-on from my last graph. Radiator temperature peaks at approx. 27°C even though temperature at the pump peaks at 45°C.
If the switchover occurrs directly after the DHW run, the peak is more pronounced (35°C). Note that this is the radiator temperature measured in the middle of the radiator over a ~10x10 cm patch by the IR probe. Peak temperature at the radiator inled will be higher.
Sure, a properly insulated heat pump will not lose a lot of energy from the water stored in the pipes but maybe just an hour delay can help with the noise you’re experiencing.
