ASHP setup temperatures

[chris wills]

Ive done a quick study of KW used since Sunday night at the new settings, thats:

I've set the return to ASHP temp to 35 now and made the pump to circulate the water come on at minimum 34 degrees. Both UFH and first floor rads all on 24/7

It comes out as 82KW used in 2 days, thats more than I had before......somethings wrong with the setup, house is still warm and family happy, but im not paying a forecast of £160 per month, based on my current supplier.

Please see picture of my setup here, any suggestions.

Also believe there should be check valves in there somewhere?

[rogeriko]

The 2 port valves are check valves. I would not put a timer on the underfloor heating just leave it on 24/7, because if the slab cools down overnight in the morning the pump will run all day to heat it up again. But of course you were at work after waking up to a cold house in the morning. Once the slab gets hot the return will be the same as the flow, or very close.
I suggest you connect the flow from the heat pump directly to the pipe going out to your system with only one pipe going to the buffer top. This way you get the full temperature of the heat pump flow going to your radiators instead of going into the buffer and getting cooled down by all the cold water in the buffer. The temperature going out to your system right now will not be the same as coming out of the heat pump.

[TT]

Do you have a set back function?
Worth dropping a degree or 2 at night.
Do the underfloor heating manifold have lights to indicate zones drawing heat?
Who designed the heating system?

[chris wills]

The 2 port valves are check valves. I would not put a timer on the underfloor heating just leave it on 24/7, because if the slab cools down overnight in the morning the pump will run all day to heat it up again. But of course you were at work after waking up to a cold house in the morning. Once the slab gets hot the return will be the same as the flow, or very close.
I suggest you connect the flow from the heat pump directly to the pipe going out to your system with only one pipe going to the buffer top. This way you get the full temperature of the heat pump flow going to your radiators instead of going into the buffer and getting cooled down by all the cold water in the buffer. The temperature going out to your system right now will not be the same as coming out of the heat pump.

Could you sketch the idea up please so I have a better understanding.
Many thanks for your feedback

[chris wills]

Do you have a set back function?
Worth dropping a degree or 2 at night.
Do the underfloor heating manifold have lights to indicate zones drawing heat?
Who designed the heating system?

No setback function
The manifold does not have lights but I can tell easily by the position of the valves
Heating system was designed not so good and the a-hole went bankrupt too. It's a long story and I'm trying to get the effiency improved. It actually works quite well otherwise

[rogeriko]

Like this

[chris wills]

Ok, so does that not just bypass the buffer tank and cause the ASHP to cycle more frequently?

[Fionn]

The buffer would appear a bit superfluous given the amount of underfloor pipe you have?

[rogeriko]

Ok, so does that not just bypass the buffer tank and cause the ASHP to cycle more frequently?

No the heat out from the HP still goes to the buffer when there is no demand. Your radiators will be hotter this way. Put the Radfan blowers on your radiators, they work and are not very expensive.

Does your heat pump outside keep going into defrost mode? Can you see this on the control screen? Maybe thats where your money is going.

[chris wills]

Ok, so does that not just bypass the buffer tank and cause the ASHP to cycle more frequently?

No the heat out from the HP still goes to the buffer when there is no demand. Your radiators will be hotter this way. Put the Radfan blowers on your radiators, they work and are not very expensive.

Does your heat pump outside keep going into defrost mode? Can you see this on the control screen? Maybe thats where your money is going.

i can understand that logic, will take some pics at the weekend to show you.
Family are good with the heat now as it's on constantly, I'm trying to reduce the cycling periods.
As for defrost, I recall having issues with Italy years ago and a delonghi engineer coming out to disable it. He said it was not required on that model pump as it kept going to constant defrost.

What I don't get is how the stored heat in the buffer is then released to the rads and ufh?

[rogeriko]

Lets say all the zones are off and heat pump is off and buffer is hot. When 1 zone calls for heat, pump comes on and takes heat from buffer and when buffer cools heat pump comes on to replenish buffer and continue heating house. When zone goes off heat pump still runs to top up buffer and then shuts down.

[chris wills]

That sounds like a good control method, however if you look at my current setup diagram, there is a temperature switch on the return pipe to the ASHP which is the only thing that activates the grundfos pump. I think this is incorrect tbh?
What I need is for the circulation pump to be controlled by te call for hot water to the ufh and rads. This is where I'm a bit stumped.

[Tigger]

Fionn,

My under radiator convector is made by Radfan, I didn't find the Speedcomfort one when I was looking for them.  I like the idea of the remotely mounted thermostat and the fact that you can link multiple units so you can fill the bottom of the radiator.  If I buy any more for any other rooms I think this might be the one to go for.

I did look at making my own from some PC cooling fans that I'd got but decided for the price of buying a ready made one, it wasn't worth the hassle, I was clearly feeling unwell as that's not quite the spirit of Navitron Bodgeneering is it 

Ian.

[brackwell]

How big is this house it appears you have 3 floors?
Where are you?
What is the rating of HP?
Do you have a EPC for the house as without this how do you know what might be a reasonable heat requirement?
What are you doing for Hot water ? How many people?

I am more concerned with the big picture at the moment. Just because some salesman said X does not cut it with me.

Ken

[brackwell]

Why measure the return temp? Is the COP not determined by the Out temp?  The diference between IN temp and OUT temp is a function of heat loss. If the heat loss is too great the temp difference across the HP is to great and the COP poor. To rectify this can only be to reduce the heat loss by reducing the circulation temp OR by increasing the flow rate and that could be a fundamental problem if this system is just a HP bolted on to a old boiler system especially if small bore pipe!  Who says the HP is man enough for the job? and not just too small a HP slogging its guts out and achieving a very low COP.

Measure the HP OUT temp and report

Ken