Heat Pump Sizing?

matt_drummer

Were you planning on the heat pump being less than 1 metre from the boundary of your property?

That isn't allowed under the current rules.

I just read again, that is what you want to do.

Why don't you just move it over by one metre?

If your house is like I suspect then you don't even need it on the roof, you could just fit brackets to the front wall of the house.

michaels

matt_drummer said:

Were you planning on the heat pump being less than 1 metre from the boundary of your property?

That isn't allowed under the current rules.

I just read again, that is what you want to do.

Why don't you just move it over by one metre?

If your house is like I suspect then you don't even need it on the roof, you could just fit brackets to the front wall of the house.

Thanks, could go on the front wall but is then back to being a long pipe run to the heating/hot water circuits.  Also because of the size and layout of the windows and garage door there is not actually a good space except for again within 1m of the boundary.

When we had the house extended we built the garage right up to the boundary at ground floor level back about 5m from the front behind which is a rear door from the garage to a 1m side passage.  Then the whole house (about 13m front to back) is extended at first floor level 1m in from the boundary, leaving a 1m wide, 5m long flat roof, anything on this roof is therefore within 1m of the boundary.  The neighbouring property then has a 3m drive and the only windows on the side are for kitchen/hall/bathroom hence we have no problem satisfying the MCS noise rules.  As you say though, it does not come under permitted development as it is within 1m of the boundary and in theory falls foul of the no development above ground floor level within 1m of the boundary 'rule'.  Not sure if the planners could also decide it 'looks a bit industrial' for a residential area?!  I am biased but think it is a reasonable argument that it would not lead to a 'terracing effect' which is what the 1m rule is about.

michaels

So we are now up and running - second hand 12kw LG heat pump off eBay for £400 - the price was low because it involved getting the 140kg unit off a first floor flat roof but 3 hours in a thunderstorm/torrential rain and my son and I managed to get it down - not without him suggesting couple of times we just push it off and hope for the best....

It is currently installed on the back wall, not where we would chose but it means we were able to just go straight through the wall and onto the radiator tails of a rad on that wall and the position means it is permitted development. Valved off the not working gas boiler so the water has to go round the rad circuit not through the boiler (does mean that two small rad in the downstairs bathroom and utility are not in the circuit).  Added a second pump to boost the flow as the 1.25 inch heat pump out goes straight into a short section of 15mm (getting a flow rate of about 15l/min) and also various strainers, bleeders, non-return valves, a flow/heat meter, PRV, expansion vessel etc - mostly using eBay parts or old plumbing bits we had lying around.

Currently running 100% on the quiet setting with a weather curve of 50 at -10 and 25 at plus 15.  Have set the flow temp hysteresis to max to prevent cycling as currently we only need about 2kw of heat (max) and the unit only modulates down to a draw of about 1.3kw (so I suspect at least 6kw output at current air temps)and the unit is running short cycles with long gaps, unfortunately the control does not seem to turn the unit off at above 15C air temp.

Our peak heating demand is about 7-8kw and I am hoping our rads can output this at 50 flow (max is 57 if needed) but we will see - my design for fully efficient HP operation says we need to change about 9 rads out of 16 to achieve a 43C flow with a 5C deltaT.

Hot water is provided by immersion, 12kwh max heated overnight into a 180l tank at 70C and then topped up by up to 9kwh in the evening for up to 10 showers a day.

Electricity comes from out 62kwh leaf and a v2H unit (max output 4.5kw), night rate is currently 7 hours at 7.5p per unit.  Thinking about the Tomato tariff with 6 hours at 5p per unit.

Thinking in the winter if we need say 8kw at a cop of as low as 2 that would be 4kw per hour - 17 hour of peak would be 17 x 4 = 68kwh plus the hot water, 9kwh and normal house usage 4kwh and we are talking 80kwh of storage needed.  We do have a second leaf 40 so in theory can swap the 2 over to increase storage up to about 80 useable but then with charging up to 3 cars (13kw), heating the hot water (3kw), heat pump (4kw) and running the dishwasher and washing machine all overnight that is getting close to the 100A main fuse limit!

Finances
Say the gas boiler was working with gas at 6p per unit and 90% efficient
Annual hot water - 20kw per day using electric at 8p per unit = £584, using gas at 6.25p per unit and 90% efficiency £500
Annual heating 18,000kwh using electric at 8p per unit and an SCOP of 3 = £480, using gas at 6.25p per unit and 90% efficiency £1240

Saving from using electric: £760 - £85 = £675 which means I recover more than the cost of the install (pricing my time at zero) in a year.

However in reality we only have the second 40kwh leaf to use with the heat pump so should probably price in the depreciation - might be more cost effective to accept that on the coldest days we will need to use some more expensive electricity and sell this 'spare' leaf?  Also need to consider that the 62 leaf will be out some days when we are travelling further than our 24 leaf can manage so will also need to use expensive electricity on those days.

Reed_Richards

I also have an LG Therma V 12 kW heat pump.  I might be able to answer questions but it sounds as if you got everything sorted very rapidly.  You might find that the heating function switches off if the outside temperature exceeds 15 C but that may depend on which series you have.

michaels

Thanks

Think you have seen my comments on buildhub. 

It does not seem to switch off for example in the mild days we have just had and moves to very short cycles instead so probably need to sort this.  I can only sort of monitor energy usage as I see whole house usage on my V2G but don't know the specific usage by the ASHP, presumably I can get some sort of wifi monitor like the smart plugs have.  In theory I have an output monitor but I suspect it may need some calibrating, also one of the temp probes is in a pocket but the other is simply taped to the copper tube so they may not be reading equivalently.

The heat pump is a U32 which I think means series 2?

I am wondering it I can add a wifi switch to the 'thermostat' terminals on the heat pump unit, I think two are an L and N feed and then the third should be the switched L but don't want to blow up the boards by getting this wrong!  With this I should be able to then control unit on/off using anything I want, for example time, wifi temp sensor probably using smartthings. I am hoping that this will control on/off but when it is then on the weather comp curve will still apply.  This would then let me do things like turn the unit off when it is warm outside via an outside temp sensor and also using the inside temp sensor have a lower target temp at night.

I then have all the questions re how best to balance the rads, whether to use the TRVs etc etc

It is certainly a learning exercise!

Oh one Q - do people add gycol/antifreeze and if so to what mix?  I have disabled the immersion support heater element via the dip switches so will only be using the heat pump.

Reed_Richards

My Therma V can either be controlled by "Water" or "Air + Water".  "Water" means pure Weather Compensation where the Leaving Water Temperature is determined entirely by the outside temperature.  "Air + Water", to the best of my understanding, throws in Load Compensation where the LWT is also influenced by the difference between the actual room temperature and the desired room temperature set on the controller.

I have a third party controller with a wireless room thermostat and I can use that to turn the heating function of the heat pump on and off, including remotely via my house WiFi.  But this means I can't use the Air + Water control algorithm.  (Actually I probably could if I wanted the same room temperature whenever the heat pump is on but I don't).  Anyway, the simplest way to add a WiFi switch is to use the facility for a third party controller and use a WiFi-capable controller.  I use a Drayton Wiser.  I recommend you use one with the ability to set or limit the number of cycles per hour, which I believe rules out Hive.  

Reed_Richards

Oh, and my heat pump was installed with a lot of expensive glycol initially.  Bit since then a number of small modification have been made, some of the original mix was lost and topped up with water so it may be fairly dilute by now.  My system never had an immersion support heater, or rather it was never connected.

michaels

Reed_Richards said:

Oh, and my heat pump was installed with a lot of expensive glycol initially.  Bit since then a number of small modification have been made, some of the original mix was lost and topped up with water so it may be fairly dilute by now.  My system never had an immersion support heater, or rather it was never connected.

Thanks

I aim to be more DIY on the controller simply using a wifi smart switch, a smart temp sensor and samsung smartthings automations as it is all kit I already have.

I think the unit has an inbuilt immersion that at least on my model you can chose to have 'full power', 'half power' or none and which is supposed to have a separate mains supply - I have selected none using the dip switches (I think you can also configure on the controller but only if it is on via the dip switches) which has the plus of there not being any additonal big load on the unit supply wiring.  With 12kw being too big for me especially with no hot water usage and my rads ability to emit that much energy also being doubtful I am never going to need the full power that that option adds.

FreeBear

michaels said: I can only sort of monitor energy usage as I see whole house usage on my V2G but don't know the specific usage by the ASHP, presumably I can get some sort of wifi monitor like the smart plugs have.  In theory I have an output monitor but I suspect it may need some calibrating, also one of the temp probes is in a pocket but the other is simply taped to the copper tube so they may not be reading equivalently.

For monitoring electrical consumption, I use the Peacefair PZEM-016 - Accurate enough for my needs.

As for temperature sensors, you can get a clip on style - https://atcsemitec.co.uk/product/pipe-clip-surface-temp-sensors/ - Quite often used inside gas boilers. Can be a little expensive depending on where you buy them. I've got a couple that I wired to a pair of cheap LCD temperature modules to balance radiators.

Sensors sitting in a thermowell are best if you are aiming for ultimate accuracy, but for heat pump monitoring, you don't really need to go that far.

greenbee

FreeBear said:

michaels said: I can only sort of monitor energy usage as I see whole house usage on my V2G but don't know the specific usage by the ASHP, presumably I can get some sort of wifi monitor like the smart plugs have.  In theory I have an output monitor but I suspect it may need some calibrating, also one of the temp probes is in a pocket but the other is simply taped to the copper tube so they may not be reading equivalently.

For monitoring electrical consumption, I use the Peacefair PZEM-016 - Accurate enough for my needs.

As for temperature sensors, you can get a clip on style - https://atcsemitec.co.uk/product/pipe-clip-surface-temp-sensors/ - Quite often used inside gas boilers. Can be a little expensive depending on where you buy them. I've got a couple that I wired to a pair of cheap LCD temperature modules to balance radiators.

Sensors sitting in a thermowell are best if you are aiming for ultimate accuracy, but for heat pump monitoring, you don't really need to go that far.

Every time I read about your temperature sensors and monitors I feel I should got and buy some... but realistically I know that I'll find that the set up here needs work and I really can't face what that would involve! I do, however, have a thermal imaging camera for my phone and just a quick try of it has revealed where some of the potential issues are. More time needs to be spent with it though. 

I'm currently trying to decide whether to ask the heating engineer to come and get the air out of the UFH or try to do it myself. The sloshing noises are getting to me, and I'm not sure that it will all work it's way out and into the radiators.