Ormston's renovation project

[ChetT]

Nice work.

How thick are the aluminum spreader plates? Who is the manufacturer?

[Ormston]

Originally Posted by ChetT

Nice work.

How thick are the aluminum spreader plates? Who is the manufacturer?

Plates, pipe and manifolds are made by Myson.
The plates are around 0.5mm thick, to bend or cut them we score with a knife.

Hydronic underfloor heating by MYSON

Steve

[Ormston]

The heating and hot water all run through our dual storage tank.
At the top is a 180L buffer tank for the heating, the bottom tank is 285L hot water storage with as yet unused solar coil.
This has pockets for 2 temperature sensors in the hot water cylinder and another in the buffer tank.

Both have their own 3KW immersion heater for backup/boost if required.

[Ormston]

Heat is currently provided by this cheap and nasty ASHP.

I purchased this very cheaply on ebay, if it provided anything like the stated output it would be a decent machine.

As far as i can tell it originates from China branded as Sirac.
The stated 4.7KW output is very optimistic, best i have seen is 2.8KW when it's 20C ambient outside.









Steve

[Ormston]

The ASHP was only designed as a water heater so has no valves/modes etc. to deal with heating and hot water use.

I initially came up with a simple control strategy which kinda worked.
The output of the heatpump was plumbed to both tanks, the return from each tank had a motorised valve in the return line to the heatpump.

These motorised valves were powered from a changeover relay so that one valve is always energised.
An Arduino Mega measures the outside temp and the buffer temp and through a weather compensation algorithm decides if the buffer needs heat. When the buffer is at temperature the changeover relay switches and energises the hot water valve.

This way i could leave the heatpump's built in controlls set to 50C and it would stop when the water cylinder reached temp.

To monitor what was going on with the system the Arduino Mega writes all measured values to an SD card at 1min intervals. Every few days i could pull the SD card and copy the data to my pc.

Using this data i found the methods i was using for control were very inefficient. The buffer tank would reach temp, switch the valves to hot water and the heat pump would run for maybe 20 mins, shutdown, then restart heating the buffer 10 mins later.

I no longer have the very early data below is an example of some of the data collected and graphed.
It shows outside temp, buffer temp(flow temp to underfloor heating), and the hot water tank high and low sensors.

[Ormston]

I quickly spotted another issue with the ASHP, the lower 2" of the evaporator had iced up and wasn't defrosting during a defrost cycle.
When i opened the heatpump lid i could see the whole base of the heatpump was frozen solid in 2" of ice, the condensate drain was under this ice and not letting anything out.

A few kettles of boiling water later and i restarted the heatpump and adjusted the defrost settings to prevent it happening again.

Got up the following morning to find exactly the same issue

It appears to be a rubbish design, air is drawn in through the evaporator into the heatpump housing and exhausted out the other side of the housing.
This means all the cold wet air from the evaporator has to pass through the entire heatpump dropping it's moisture on the way through.
Also as the inside of the housing is at negative pressure (the only fan blows out the back of the heatpump), water is not very keen an falling through the small drain pipe at the bottom.

The solution has been a trace heater curled up in the bottom of the heatpump across the bottom of the evaporator and poking out through the drain pipe.
I,ve also had to pack the feet of the heatpump to encourage water towards the drain pipe.

Whilst these fixes work, it does add a constant 60w load during the winter to run the trace heater.

Steve

[AC_Hacker]

Originally Posted by Ormston

Heat is currently provided by this cheap and nasty ASHP.

I had a very similar heat pump that was also designed for heating water.

I don't know about yours, but the one I had was designed for indoor use only, and it had no crank case heater or anything.

The evaporator HX was about 4 rows thick, and the height and width dimensions were small, compared to an modern mini-split.

The refrigerant-to-water HX was not so big coiled tube-in-tube.

I looked at the published COP figures and decided that I could make it descent if I got a much larger (Height x Width) evaporator HX with less rows, and created a crank case heater, and replaced the HX with brazed plate, and changed the refrigerant, and on, and on...

Just too much work.

I gave it away.

-AC

[Ormston]

Back to my previous issue, the heatpump running most of the time.

For a few nights i turned the setpoint down on the heatpump (this controls the hot water temp not the heating), the idea was to see if it used less power to heat the water twice a day instead on topping up every time the buffer reached temp.
This highlighted another issue, i would go to bed with the tank at 48C and wake up the following morning with it at 38C.

Again my data logging showed what was going on, even when the heatpump is not running it starts the circulation pump for a couple of mins every 15 to check the water temp. This had the effect of cooling the tank overnight, i could see a drop in temp every time the buffer reached temp and then another every 15mins as the heatpump checked the water temp.

This graph has a bit more data:
Buffer tank (flow temp to heating)
DhwH & DhwL are hot water tank upper and lower sensors
Outside temp
HpLPM is the flow sensor on the return to the heatpump
WeatherComp is the calculated temp required for the heating(setpoint for the buffer)

[Ormston]

Originally Posted by AC_Hacker

I had a very similar heat pump that was also designed for heating water.

I don't know about yours, but the one I had was designed for indoor use only, and it had no crank case heater or anything.

The evaporator HX was about 4 rows thick, and the height and width dimensions were small, compared to an modern mini-split.

The refrigerant-to-water HX was not so big coiled tube-in-tube.

I looked at the published COP figures and decided that I could make it descent if I got a much larger (Height x Width) evaporator HX with less rows, and created a crank case heater, and replaced the HX with brazed plate, and changed the refrigerant, and on, and on...

Just too much work.

I gave it away.

-AC

Sounds very similar, my evaporator is 2 rows thick and it also has a small tube in tube HX coiled in the bottom(and in 2" of ice a few times ).

It's IPx4 rated so should be rain proof although i do have it under a small shelter to keep the worst off it.
Hadn't even thought of a sump heater although it runs often enough and has the trace heater so i'm not too concerned.

I only bought it to get us by for a few months until i could get our GSHP up and running, we're now rapidly approaching our second winter with the ASHP and i haven't even started on the GSHP install.

Steve

[Mikesolar]

Oh boy, I hope it wasn't very expensive. Any heat pump that only goes down to -5 isn't much of a heat pump in todays terms. Get to work on the GSHP asap, lol.

Have you checked that the unit has the proper amount of refrigerant in it?