Heat Pumps: anyone have one/thought about it?

PermaChanged said:
We've got a 300l cylinder, we had originally asked for a 210l but I'm super thankful that, by luck rather than judgement, we ended up with the larger one.

I've dropped storage temps to 50c with a 7c drop pre recharge - will see how we get on with that.

The water is allowed to cycle 24/7, with individual room thermostats dictating heating - set back temps of 18c and living temps of 21.5c at the moment, I think current flow temps are around 30c based on the weather compensation.
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I've dropped our water storage start up temp from 46° to 44°. Max is still set to 50. I'll see how it goes.
 
One thing I keep meaning to ask about is that when there is demand for heating in the house, the temp in our hot water tank drops. I don't know if this is normal. I asked the service engineer last time it was serviced and he wasn't sure.
But it very much looks like heat is being pulled from the hot water tank when the UFH is on. Has anyone else noticed this in their system?
 
That's not normal. Sounds like the zone valve for the hot water isn't closing when there is not a demand for heat so both loops are open to the heat pump.

The flow temps for heating will be lower than the hot water in the tank so if both loops are flowing, it will draw heat from the hot water tank. This will probably be causing your heat pump to cycle more.

Usually they are set up as hot water priority, if the tank is calling for heat then its getting all the flow from the heat pump. If it's not then it goes to the rads, it shouldn't be doing both at the same time, particularly when you have UHF as the flow temps will be far lower for heating.
 
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rangor gubbins said:
One thing I keep meaning to ask about is that when there is demand for heating in the house, the temp in our hot water tank drops. I don't know if this is normal. I asked the service engineer last time it was serviced and he wasn't sure.
But it very much looks like heat is being pulled from the hot water tank when the UFH is on. Has anyone else noticed this in their system?
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This shouldn’t happen. The pipe work should have a 3-port valve, splitting the flow to either the cylinder or the central heating system. It shouldn’t be a single loop. Can you see this in your system?

Edit: comment above is a far more likely scenario. I can’t imagine any installer would plumb them in series!
 
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@b0rn2sk8 @Coran thanks. that makes sense. I'll see if i can track down a zone valve in the pipework.
I have a feeling this has been happening since the start. We've had the system for a few years but i only installed lots of extra temp sensors and emonPi and Home Assistant to record in the past 18 months, which has let me see in detail what's going on.
 
Ended up going with an independent.

Same spec heatpump, rads of my choosing and I get given all the pipework design sheets etc.

Same price as Octopus (with BUS) but install in January.
 
Here's our weekly flow and return averages, currently the home is on a 19.5c daytime setback temperature and 21.5c 4pm - 9:30pm

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On Sunday we used a lot of hot water due to spring cleaning the place, which is why there's a water temp and flow/return anomaly.
 
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Not had our quarterly bill yet, but I've put together a little Excel spreadsheet to give ourselves an idea of running costs.

Between the 2nd and 6th of November we used 86 units, charged at 11.13p per unit - £2.39 per day. I've still got efficiency gains to be made with sorting out loft insulation, and wrapping all exposed/non insulated joints with this stuff - https://www.amazon.co.uk/dp/B0BZMTD8RL?psc=1&ref=ppx_yo2ov_dt_b_product_details

Hoping to lower the temperature compensation curve of the heat pump flow rates with these marginal gains, and maintain a lower constant flow rather than cycling which is no doubt costing.

For the 21 days I've been monitoring the heat pump meter, we've used 405 units, £45.08 worth - the first few days were more expensive per day due to higher flow rates/stored water temps. Ideally I want to be spending ~£2.50 per day on the coldest days.
 
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PermaChanged said:
Not had our quarterly bill yet, but I've put together a little Excel spreadsheet to give ourselves an idea of running costs.

Between the 2nd and 6th of November we used 86 units, charged at 11.13p per unit - £2.39 per day. I've still got efficiency gains to be made with sorting out loft insulation, and wrapping all exposed/non insulated joints with this stuff - https://www.amazon.co.uk/dp/B0BZMTD8RL?psc=1&ref=ppx_yo2ov_dt_b_product_details

Hoping to lower the temperature compensation curve of the heat pump flow rates with these marginal gains, and maintain a lower constant flow rather than cycling which is no doubt costing.

For the 21 days I've been monitoring the heat pump meter, we've used 405 units, £45.08 worth - the first few days were more expensive per day due to higher flow rates/stored water temps. Ideally I want to be spending ~£2.50 per day on the coldest days.
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Do you have a smart meter?
 
PermaChanged said:
No, not a smart meter. It's a separate metre for the heat pump and related ancillaries so I've just been taking regular meter readings.
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Presumably you still have a smart meter for your electricity though to get your average rate down to 11p per kWh? Batteries too to allow you to use it during the day?

*Edit:* great work on improving efficiency though. I’m trying to improve mine but in reducing the flow temperature, I’m finding it cycles more often as I can’t emit the heat quickly enough (heat transfer is proportional to difference in temp between room and radiators). Trying to find a good balance between lots of cycles at low temp and fewer cycles but squeezing more heat out of the air.
 
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Coran said:
Presumably you still have a smart meter for your electricity though to get your average rate down to 11p per kWh? Batteries too to allow you to use it during the day?
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I'm not entirely sure what the definition of a smart meter is to be perfectly honest, my assumption was that it's one which has some kind of monitoring available for me to take note of, like peak times of use? We don't have one of those.... if by definition we're talking about one that communicates total usage to our supplier remotely, then yes we have one of those!

We have two separate meters, one solely for heat pump and ancillaries (pumps etc), and one for the rest of the home /electrics. The heat pump meter is on the "Heat Pump" tariff, whilst the home is on either standard or super economy, I can't remember which! https://www.electricity.gg/electricity/tariffs/

Still playing with flow temps, Heatgeek recommend opening up all thermostats to max temps so you've got constant flow/demand for heat and then adjust flow temps until a point that you have continually flow of water at the right temperature which is the most efficient way to run, so heat in to the building is equal to heat loss of the building - https://www.heatgeek.com/3-steps-to-maximise-your-heat-pump-or-boiler-efficiency/
 
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I fit ASHP for a living in new builds and old houses! There are a lot of factors with older houses but it can be done !

New builds are obviously easier as they are specced for ASHP according to the Energy Performance and SAPS, mainly use underfloor heating as that works best with the lower flow temps, allthough we have fitted radiators in new builds on a ASHP and they work well as long as they are correctly sized for the flow rates

Old houses can be retro fitted to existing pipework as long as your flow and return to the rads are not 10mm or smaller.

We mainly fit Daikin althermas and Mitsibishi eco dans, which consist of an outdoor unit and then a hydro box and tank all in one unit.

Any questions feel free to ask away! Been around ASHP for years!
 
rangor gubbins said:
@b0rn2sk8 @Coran thanks. that makes sense. I'll see if i can track down a zone valve in the pipework.
I have a feeling this has been happening since the start. We've had the system for a few years but i only installed lots of extra temp sensors and emonPi and Home Assistant to record in the past 18 months, which has let me see in detail what's going on.
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I spoke to a service engineer (and sent him graphs of the flow temps) and he agreed something is awry, so he's coming to investigate. It's due for a service soon so we'll do both at the same time.
 
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