Posted by: @derek-m

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For some homeowners it may therefore be possible to take advantage of these temperature differences. Run the heat pump to recover or even boost the IAT during the warmer day time period, and setback or at least reduce the IAT during the nighttime period.

This of course is easier said than done, since after an overnight setback the IAT will probably not have recovered by breakfast time. If the home is unoccupied for much of the day, an alternative could be to initiate a setback at say 8am, when the OAT is still quite cool, then start the recovery and boost after lunch when the OAT will likely be higher. Simulations show a 7% to over 10% reduction in energy consumption could probably be achieved.

I think that there are broadly two main use cases of interest namely 'in all day' and 'out all day'.  Obviously this ignores more complex shift patterns but if we understood the behaviours for these two use cases it would be a good start and we could probably extrapolate to others.

In the 'out all day' scenario there must be an argument for a rapid breakfast time reheat of the air only (to the extent possible), with no attempt to restore the fabric temperature.  Probably this would mean  a higher IAT to achieve the same perceived comfort level.  Fancoils or even COP 1 fan heaters might be the optimum in this scenario.

Even in the in all day scenario it may be that some way of rapidly heating the air confers a comfort benefit that buys time to reheat the fabric.

It sounds like you have taken the model you shared a few days ago and added thermal mass and carry forward of deficit.  If so then well done and hopefully you might post a copy at some point so others can play.

@jamespa

I have some further improvements that I wish to make, but once completed I will post a copy for dissemination.

@jamespa

Hi James,

I have now completed some further improvements to the modelling tool.

It is now possible to adjust the desired IAT setpoint and also the OAT value to one decimal place. This therefore provides the capability to ramp up and down the setpoint and more closely match variations in OAT.

Have fun in the 'Playroom'.

@derek-m Thanks, I look forward to 'playing'.

Slight tangent, found out my plumber didnt go by designers loop plan, 26 loops meant to be in house, he only put in 17, he said it would have been waste of pipe, not happy but it is what it is.

This means i will need higher flow temp as loops longer?

Always on would be more beneficial in this case i take it. 

Posted by: @newhouse87

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Slight tangent, found out my plumber didnt go by designers loop plan, 26 loops meant to be in house, he only put in 17, he said it would have been waste of pipe, not happy but it is what it is.

This means i will need higher flow temp as loops longer?

Always on would be more beneficial in this case i take it. 

I suspect it is more to do with the heating capacity rather than the number of loops. If you have the specified length of pipework installed, it should not matter if it is 17 loops or 26 loops.

Obviously if your installer has fitted less pipework than was originally specified it may be necessary to operate the system with a higher LWT.

Did your installer reduce the price charged if he installed less pipework?

@derek-m same amount of pipework, i saw it when it was down, all rooms covered at 150mm spacing. I jut thought if i have a few loops over 100m rather than specified 80 for example it would take higher flow temp to get rooms to temp and end up costing me more money forever.

He probably thought id never find out so didnt give any discount, price was agreed to plumb whole house before he even got design plans for ufh.

So having few less and longer loops wont have much impact?

Posted by: @newhouse87

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@derek-m same amount of pipework, i saw it when it was down, all rooms covered at 150mm spacing. I jut thought if i have a few loops over 100m rather than specified 80 for example it would take higher flow temp to get rooms to temp and end up costing me more money forever.

He probably thought id never find out so didnt give any discount, price was agreed to plumb whole house before he even got design plans for ufh.

So having few less and longer loops wont have much impact?

I would say in theory, no, it should not have much impact.

Applying the laws of physics, the pipework at the flow end, where the water enters the pipework, will be slightly warmer (probably 5C) than the pipework at the return end. The quantity of thermal energy transferred from the water into your home is dependent upon this temperature difference and the flow rate. If you have the same flow rate coming from the heat pump, the flow rate down individual loops will be greater if there are only 17 loops instead of 26. The same quantity of thermal energy should be transferred.

Just as the physical size of a radiator will limit its heating capacity, the same will apply to UFH.

The main limitation would be if the required higher flow rate, down individual loops, cannot be achieved. I would suggest that you discuss this aspect with the person who designed the UFH system layout.

@newhouse87

One question that I forgot to ask, 'did your installer balance the flow through each of the loops to match the heat loss of that particular area'?

@derek-m he did no such thing, the day he came he was there for an hour or more fiddling with settings i think. All the flow rates were essentially the same even the bathroom next door to heat pump had 2.5l/min same as sun room at other end of the house. Thanks to ye guys on here i know about ufh now and when weather gets cold i will be altering the flow rates accordingly. 

Even the ext rt setting was enabled on unit when it left factory and it took technical lead from unitherm to figure out what it was, causing massive electricity consumption in the middle of the night when no call for heat from stats. This winter i should be set up much better thanks to this forum.

So first day of heating season today. Temps in house were down to 19 in living areas and 16/17 in bedrooms. started my wc at 38-5 and 28-20 as per derek m suggestions. Currently flow rate at 34l/min and flow temp 28.4deg. Have it on since 7am.  Going to run until 9pm and then setback until 5:30am. House noticeably warmer already and living areas up 3 degrees to desired 22degrees, solar gain playing large enough part id imagine.

Would 2kwh per hour be normal for 242 sqm house.

Consumption is entirely dependent on house construction. 

My house, a 1930s solid wall build with about 70% retrofitted IWI, 30cm loft insulation, double glazing throughout with no trickle vents, no additional floor insulation but only 205 sq m, generally sits around 2kW gas consumed (morning and evening heating only) either end of the season (eg now), 4-5kW in the shoulder season (heated 24x7 or 6am-11pm, depending on which end of shoulder), and 7.5kW (heated 24*7) when its below zero several days in a row (the house takes about a day or more to warm/cool fully). 

If I do the heat loss calculations for my house they typically come out at about 10.5kW if I assume that the natural ventilation is the typical one recommended for estimating older houses.  If I assume only 0.5 air changes per hour I get to almost exactly 7.5kW, matching the measured consumption (assuming the gas boiler is ~100% efficient, which is perhaps just believable as its a condensing boiler and I operate at a flow temperature of 55C).

Hope that helps.