Hitachi Yutaki M efficient operation - Air Source Heat Pumps (ASHPs)

RE: Hitachi Yutaki M efficient operation

renewyfiend — Wed, 15 Jan 2025 02:47:55 +0000

A reason i believe is causing a low delta-t is the waterflow that is too high

I also tried lowering the internal waterpump speed but have not found yet how to do that. The setting in the installer section of the controller did have a deltaT setting and a HP ON deltaT setting I changed both to the same increase but the waterpump speed still is 100%

How did you try changing the deltaT?

I have a modbus gateway from which I can extract most relevant information. No real cycle information to be found though. Once can monitor and deduce it sure.

RE: Hitachi Yutaki M efficient operation

Toodles — Fri, 10 Jan 2025 16:14:08 +0000

@iraknic Please note, I don’t have any experience at all (diddly squat) of UFH plumbing but if a circuit has both send and return valves, it is probably only necessary and better to just constrict the flow to the circuit and leave the return without any restriction. I may be talking through the wrong orifice of course! Regards, Toodles.

RE: Hitachi Yutaki M efficient operation

iraknic — Fri, 10 Jan 2025 15:50:19 +0000

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i attach the setup of the buffer, highlighting the return lines and the specs of the water pump that is placed after the buffer. I thought of closing a bit of the outlet and return valves of the left side of the buffer (to and from) the manifolds and increase the flow of the primary pump (from hp to the buffer) to see what happens

RE: Hitachi Yutaki M efficient operation

JamesPa — Fri, 10 Jan 2025 09:49:56 +0000

Can the secondary flow be reduced by manually decreasing ufh flow at the manifolds?

Yes. Its the same as turning down the lockshield on a radiator

RE: Hitachi Yutaki M efficient operation

iraknic — Fri, 10 Jan 2025 09:14:42 +0000

@jamespa the buffer was fitted to increase water in the system due to the existence of zones. @editor
I am measuring the temps at the manifold using an IR thermometer. In my case it seems that the primary water pump is slower than the secondary (after the buffer) one? Can the secondary flow be reduced by manually decreasing ufh flow at the manifolds?

RE: Hitachi Yutaki M efficient operation

Mars — Fri, 10 Jan 2025 08:42:55 +0000

@iraknic how are you monitoring your UFH delta T?

RE: Hitachi Yutaki M efficient operation

JamesPa — Fri, 10 Jan 2025 08:35:16 +0000

Does this means that there is unbalanced flow between the primary circuit (hp and buffer) and secondary circuit (buffer and manifolds)? The circulating pump in the first circuit is adjustable but the second is not

Yes, almost certainly.

I dont know if the HP can control the buffer, some can. If the buffer has two temperature sensors at different heights then its possible in principle to use this information modulate the speed of one or other pump so that on average the rates are the same (which is ideally what you want). It would be worth looking at the HP manual and the buffer in case it can do this.

Otherwise you are down to adjusting the pump rates. The HP might adjust the primary pump to suit its needs. If it does so and unless the HP does feature buffer management, Id be loathe to touch this. That said there is generally no harm in turning the primary up, HPs complain about low flow (because its not enough to take the heat away) more than about high flow.

Im surprised that there is no adjustment on the secondary pump, many have three settings.

Having the primary a bit faster than the secondary will tend to force the thermocline (barrier between 'hot' and cold' water, assuming its stratified) down the tank, which means that the feed to the emitters should be at the same temperature as the feed from the heat pump, thus minimising the sacrifice in efficiency which would occur if the feet to emitters is lower temp than the feed from the heat pump. Obviously this will cause a little bit of recycling through the heat pump, but its better so far as I understand these matters than pushing the thermocline to the top which is what happens if the primary is slower than the secondary.

Do you know why the buffer is fitted? Generally they are a bad idea in heat pump systems, albeit that many installers put them in because its pretty much guaranteed to reduce callouts (by masking problems).

RE: Hitachi Yutaki M efficient operation

iraknic — Fri, 10 Jan 2025 07:28:03 +0000

So i think i have narrowed it down without however knowing the solution. Buffer creates a loop. Hp provides the required water temp to the buffer but somehow the energy is not diverted to the ufh but returns to the hp, hence the low dt and the reduced temp at the manifolds compared to the outlet reading of the hp. Does this means that there is unbalanced flow between the primary circuit (hp and buffer) and secondary circuit (buffer and manifolds)? The circulating pump in the first circuit is adjustable but the second is not

RE: Hitachi Yutaki M efficient operation

iraknic — Wed, 08 Jan 2025 21:09:11 +0000

@jamespa there is indeed a large noisy water pump placed after the buffer tank that circulates the water through the ufh and the fan coils. However flow rate is regulated at the manifolds and i wouldn't expect that there is a significantly faster water flow through the ufh. Nevertheless i will measure the temp at the hp exit and see

RE: Hitachi Yutaki M efficient operation

JamesPa — Wed, 08 Jan 2025 20:19:56 +0000

@jamespa i will try to have a reading as near to the hp as possible. I understand the whole mixing issue and pipe losses you ve mentioned, however why the return temp is still higher than the manifold temp?

I dont know, unless water is circulating in the UFH much faster than its coming out of the heat pump so basically its going round and round the UFH being topped up a bit by water from the heat pump and rather than top to bottom stratification you have two loops inside the buffer with a turbulant interface. This is however pure speculation!

It could also be measurement error which would be an easier explanation!