Posted by: @benseb

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Agreed I definitely don’t think ASHP are “set and forget”, there’s a whole spectrum of issues that don’t get flagged by errors. 

I’m no engineer but between work and home we’ve had 7 ASHPs so I do know my way around them and can spot when things don’t look right. 

are you in the U.K.! At a design life of 20 yrs each (correctly installed) that would make you 140yrs old!

probably the better controls are those from boiler manufacturers such as vaillant. I know they are almost “fit and forget” because I ve been installing them for 15yrs!

Posted by: @alec-morrow

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Posted by: @benseb

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Agreed I definitely don’t think ASHP are “set and forget”, there’s a whole spectrum of issues that don’t get flagged by errors. 

I’m no engineer but between work and home we’ve had 7 ASHPs so I do know my way around them and can spot when things don’t look right. 

 

are you in the U.K.! At a design life of 20 yrs each (correctly installed) that would make you 140yrs old!

 

probably the better controls are those from boiler manufacturers such as vaillant. I know they are almost “fit and forget” because I ve been installing them for 15yrs!

 

Unfortunately at work we had Husky heat pumps installed (x3) which were awful. We’d often come in on a Monday morning and it would have thrown a fault and the big stone office would be 10c. so we ditched them and now have Panasonic units. 

Then I have an Ecodan at home. 

@benseb

Partially closed radiator valves both lockshield and TRV's will restrict the flow around the system, and hence the water pump will need to work a little harder to achieve the required flow rate.

Because it is not possible to match the standard heat output from the radiator to the heat loss of a particular room, with all the valves fully open, there will be different air temperatures achieved from room to room.

If you know the individual heat loss of each room, and the standard heating capacity of any radiators within each room, it should be possible to calculate the approximate water temperature required to meet the heat loss.

By using the spreadsheet that I posted recently, the required water temperature for each room can be obtained. Just as the speed of a convoy is set by the slowest ship, the LWT of the heat pump is determined by the room requiring the highest water temperature.

Therefore starting at the room requiring the lowest water temperature, gradually reduce the flow rate through any radiators using the lockshield valves. This will therefore divert some of the flow from this room to the other one's.

It can be a slow process but should be worth it in the end, since your system should be operating in a more balanced and efficient manner.

Posted by: @heacol

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@benseb the Delta T should be between 5 and 10 Deg C. Try reduce the speed on one of the circulating pumps. This will increase the Delta T and further reduce your running cost. Do you have a buffer tank? If so see if you can pipe it out, this will further increase your performance.

@heacol I have a 12kW Samsung ASHP with a 50 litre buffer tank and two fixed speed water pumps - primary pump = 19-20L/min and secondary pump = unknown flow rate.  I use weather compensation and turn thermostat up well above room temperature to optimise efficiency. However, the COP is nothing like what Samsung claim it could be. How much benefit would I get from removing the buffer tank and secondary pump and replacing the primary pump with a PWM primary pump? I have been told the buffer tank is essential as during a defrost cycle, the heat pump has no access to the radiators if the thermostat is not calling for heat at the time (ie CH valve is closed). If true, this sounds like a design fault, but it is difficult to get accurate info from Samsung.

@mike-h I am doing a presentation on exactly this at PowerXlive in London on wedensday. You will see a significant increase in performance if you remove the buffer tank, remove all control in the common areas, keep the control in the bedrooms and either, if your house hase a large thermal mass and or under floor, run it on weather compensation, if not then use the temperature sensor inside the Samsung controller to control the temperature in the house. The less interferance there is, the better the performance will be.

@heacol Thanks for that info. That is very helpful. Do you think the defrost cycle could be a problem if the heating is off at the time of the defrost cycle and the CH valve is closed?

@mike-h The heating circuit should never be closes, you need to install a 3 port diverter full ball valve, either a Belimo, Esbe or Sintesi (from V Flow solutions) You must NEVER install a Honeywell type 2 or 3 port valve with a ball inside. THEY DO NOT WORK WITH HEAT PUMPS as they significantly reduce the flow rate, increase the pumping costs and reduce the performance. It really is common sense, let the water flow, anything that will stop the flow will affect the performance.

Defrost, in reality, requires less than 1 Kw from the heating system, so as long as water is flowing, there will be no problem.

Posted by: @heacol

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@mike-h The heating circuit should never be closes, you need to install a 3 port diverter full ball valve, either a Belimo, Esbe or Sintesi (from V Flow solutions) You must NEVER install a Honeywell type 2 or 3 port valve with a ball inside. THEY DO NOT WORK WITH HEAT PUMPS as they significantly reduce the flow rate, increase the pumping costs and reduce the performance. It really is common sense, let the water flow, anything that will stop the flow will affect the performance.

Defrost, in reality, requires less than 1 Kw from the heating system, so as long as water is flowing, there will be no problem.

Thats interesting about the Honeywell valves. Our flow rate is below what it should be due to them using 28mm plastic instead of 35mm copper so we’re trying to eek out any extra flow we can. 

I guess the V Flow valves will need a plumber to replace (or are they the exact same size so can be easily swapped?)

@benseb You may need a plumber to install it, once you have done it, you may find the pipe is OK, if not, you can install another pump in series and run it on speed 1 or 2.

Posted by: @heacol

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@mike-h The heating circuit should never be closes, you need to install a 3 port diverter full ball valve, either a Belimo, Esbe or Sintesi (from V Flow solutions) You must NEVER install a Honeywell type 2 or 3 port valve with a ball inside. THEY DO NOT WORK WITH HEAT PUMPS as they significantly reduce the flow rate, increase the pumping costs and reduce the performance. It really is common sense, let the water flow, anything that will stop the flow will affect the performance.

Defrost, in reality, requires less than 1 Kw from the heating system, so as long as water is flowing, there will be no problem.

@heacol Many thanks again. Sadly the UK's No 1 heat pump installer has installed the Honeywell valves you have warned me about.

@mike-h I hope you are putting that in inverted commas 🤣

@heacol I am trying to fix my flow rate.  I can get 30 litres per second but with the [single] pump running @95% of capacity and using 106w and making a bit of noise doing so.  I have put in two zone valves, 1 normally open for the UFH, and one normally closed for the hot water.  The latter closes the former during the hot water cycle.

I want to replace these with a diverter valve as you suggested.  I don't seem to be able to find the VRG330 series, though the VRG130 series looks quite similar.  screenshot from specs below, specs look very similar to me.

Is the VRG130 series ok for heat pumps?  Is it possible to buy the VRG330?

[edited]

I think I worked this  [difference in specs] out from the charts below.  Still can't find anyone stocking the VRG330.

My current zone valves are

normally open for the heating circuit

normally closed for the hot water

Still trying to work out the impact the above two valves have during heating and hot water, respectively.

Thanks

William