Grant/ Aerona ASHP expensive...

[JeffGiraf]

Hi all

 

I live in a rented old stone farmhouse in mid Scotland.  House is probably 240m2 or so. There is a fairly new ( fitted last March) ashp retrofitted to old UFH downstairs and undersized radiators upstairs ( though a new towel rail was fitted in the bathroom). Landlord (I know her!) did minimum cost install!

 

But the attic has extra insulation now ( but also coombs, which loose heat) and the out of use chimneys are capped and insulated with wool plugs.

We have also taped all the doors and have thick curtains and lovely old wood shutters.

 

The heating seems rather expensive. It used an average of 1.6kw per hour over the last 28.25 hours (we have a separate meter for the heat pump). For that the rooms stay around 16degC. Thank goodness for the woodburner.

 

Tank and everything, including the "remote" controller are in a dark shed sandwiched between our house and landlords so I have to sit on a wee fishing stool to monitor! It also means it thinks the temp in the shed is room temperature! Pipes in shed are insulated but not amazingly (normal grey foam insulation - not taped or glued, cable tied at some points). Tank is uninsulated beyond the way it comes, (I plan to get a jacket) but at the moment we are mostly using kettles on the fire for hot water and the immersion for an occasional bath rather than keeping water hot as the heating alone is expensive!

 

I have looked at the WC settings:

 

2100  0

2102  50 degC 

2103  35 degC

2104  -4 degC

2105  20degC

 

Outside temp around 2- -2degC daytime at present and colder at night. 

 

Monitor Display Readings a few days were as follows:

 

00  circulating h2o return temp 44degC

( went up from 38 degC as I watched)

01  Compressor op freq. 0hz

02  Discharge temp 88deg C

( I watched this climb from 30 deg C to 88 over about 3 or 4 mins)

03  power consumption value 100w

04  fan control of rotations 0

05  Defrost temp 2degC

06. Outdoor air temp 2degC

07. H2O pump contol no of rotations 3300rpm

08. Suction temp 4degC 

( what is this?)

09. Circulating h2o flow temp went from 39degC to 46degC

 

These were taken as I had previously turned the 50degC high temp down to 45degC but we were all freezing so I put it back up! 

 

I looked through all the installer level setting ( installer hadnt noted them in the handbook but I have!) and apart from 2102 and 2103 they are all at default.

 

For some reason the temperature gauge on the manifold flow pipe reads consistently at around 30-33degC. There is a mixer valve but it is set up at 55degC above the temp of the water from the heat pump. 

 

Any suggestions on how to make it cost less/more efficient would be much appreciated! Thanks

[JohnMo]

First complain to landlord or their agent, they are responsible to fix it and provide you heating that works.

 

Start looking for a better rental property?

[ProDave]

17 minutes ago, JeffGiraf said:

The heating seems rather expensive. It used an average of 1.6kw per hour over the last 28.25 hours (

So the ASHP is consuming 1.6kW to heat the house, assuming a COP of 3, that will translate to 4.8kW of heat delivered to the house.

 

It is very cold at the moment.  Our very well insulated 150 square metre house needs about 1.5kW of heat at the present sub zero average outside temperature.  So your house is larger, older and no doubt less well insulated, so 4.8kW of heat does not seem at all unreasonable.  Don't expect to reduce that significantly other than as above move to a smaller much better insulated house.

 

21 minutes ago, JeffGiraf said:

02  Discharge temp 88deg C

What exactly does that mean?  surely not the heat pump is set to heat water to 88 degrees?

 

22 minutes ago, JeffGiraf said:

Tank is uninsulated beyond the way it comes

Sounds very like it does not have the right sort of hot water tank for a heat pump.  Not much you cn do there as the system is not your to make alterations to.

 

It sounds like your expectations of the property are not matching reality, and as above again, all you can do is move to a better property.

[Nickfromwales]

Exactly the type of property that should never have had an ASHP installed on to.

 

So many useless tossers happy to take the money and say nothing.

 

Whats the EPC? 

[Nickfromwales]

25 minutes ago, JeffGiraf said:

We have also taped all the doors

Not how to live, but I’ve had to do similar in cheap rentals when me and the missus moved in together 30 odd years ago.

 

Laws / regs / acceptable minimum standards have changed now, so this just shouldn’t be happening.

 

16°C is terrible, they keep prisons warmer than that. 

[JeffGiraf]

First off important typo:

 

House is about 140m2 or so not 240m2! 

 

So that makes it more rubbish! Unfortunately any affordable rental housing is like hens teeth in rural scotland so we make do! I have been talking to thw landlord, but the installers are crap so I was trying to go in a little forearmed with kmowledge!

 

@Nickfromwales House EPC is C at 75 so not the worst but not the best.

 

By taping the doors I meant adding insulation tape not taping them up!

 

And yes ashp was done on a grant no surprise!

 

 

@ProDavewhat data do I need to calcate the COP? I don't really understand how its done?

 

I didnt know what discharge temp was either but found this: https://www.sciencedirect.com/topics/engineering/discharge-temperature guess 88 is ok then.

 

It is a Grant Aerona tank. I meant no extra jacket or anything.

 

The living room with the burner in it stays at around 17-18degC even overnight with the door to the rest of the house open. 

 

Why would the temp gauge at the manifold read around 15degC lower than the flow temp?

Edited Sunday at 23:31 by JeffGiraf

[JeffGiraf]

Thanks for your replies so far!

[jamesdiyer]

I live in a big stone house in equally cold environment. We are doing around 2kw electric input currently at 2C. However we are warm at 20C inside. Contrary to what some people think, it can work very well with the right emittors. 

 

If you're flow temps are high but you're not warm, I'd say you have an emitter issue - emitters too small.  You need to get a grip on the UFH and why it's not working well - I'd say the landlord should be paying for someone to look at it. It sounds like the whole thing is a mess and needs to be dealt with properly. 

Edited yesterday at 04:38 by jamesdiyer

[JohnMo]

9 hours ago, JeffGiraf said:

Grant Aerona tank.

It will not need an additional jacket, keep your money in your pocket. The what steel is just a shell protector with insulation side.

 

9 hours ago, JeffGiraf said:

Why would the temp gauge at the manifold read around 15degC lower than the flow temp?

Mixer on the UFH, it's mixing the flow temp down to limit floor output and protect the floor. It will have a temp control knob,if you increase that the flow temp through the floor increases. The basic mixer just work on a ratio control, it's assuming 70 Deg hot water from a boiler, if you can turn it up do so. Adding even a couple degrees to flow temp will have a big effect on room temp (after 24 hrs)

 

Other thing are you running the heating on all the time or an on off time cycle?

[Dillsue]

17 hours ago, JeffGiraf said:

There is a fairly new ( fitted last March) ashp retrofitted to old UFH downstairs and undersized radiators upstairs ( though a new towel rail was fitted in the bathroom). Landlord (I know her!) did minimum cost install!

 

These were taken as I had previously turned the 50degC high temp down to 45degC but we were all freezing so I put it back up! 

Questionable UFH and known undersize radiators are never going to give you a working system. Running at 50 degrees flow temp is always going to mean bigger bills than running at lower temps.

 

One thing to be conscious of is that ASHPs guzzle electricity when it's cold so best not to get too hung up on what it's using in a cold snap. Look at the average for a few weeks or month at a time.

 

If your landlord cut corners to save ££ at what seems to be at your expense then her being an acquaintance is where your biggest problem lies. If a tactful conversation doesn't get her to sort out the heating then you're a bit stuck.

 

If you want to sort out the heating then starting point is a heat loss assessment so you can resize the radiators and get someone knowledgeable to see if they can make an educated guess at the output of the UFH. If it's not adequate for a low temp heat pump flow then it can either be replaced or add radiators to the rooms with UFH. If the landlord isn't going to sort it out then there's alot of effort and expense for you to do it!!

[Beelbeebub]

The first thing to note is that this sub zero weather will cost alot to heat especially with a HP. 

 

For example, my gas consumption is about £8 a day in these conditions. 

 

You say parameter 21-00 is set to 0. This is fixed flow temp. 

 

Look at parameter 20-01, that should be the temp your HP is outputting. The default is 45C, and maybe that is too low?

 

It will also have been too high for the milder weather. 

 

The default for 21-02 is 45C, so the fact it's been set to 50C implies someone has changed it - possibly because your heating system needs more than 45C in these conditions.

 

 

[Beelbeebub]

 

The suction temp is the temp the refrigerant gas is when it leaves the outside coil and enters the compressor, it is then compressed and leaves as a hot gas (discharge temp) 

 

So a suction temp of 4C means the air moving over the coil outside was probably at about 4C 

 

Then 88C gas was leaving the compressor. Which seems a bit high for heating mode, I would expect it to be more like 50-55C for a 45C (water) flow temp.  That suggests something might not be quite right. 

[JeffGiraf]

8 hours ago, JohnMo said:

Mixer on the UFH, it's mixing the flow temp down to limit floor output and protect the floor. It will have a temp control knob,if you increase that the flow temp through the floor increases. The basic mixer just work on a ratio control, it's assuming 70 Deg hot water from a boiler, if you can turn it up do so. Adding even a couple degrees to flow temp will have a big effect on room temp (after 24 hrs)

I think this may be one of the main issues. The mixer only goes up to 55 degC and is now on max ( installers left it on 25 degC took me a while to work this out!). Is it possible to remove the mixer, or the pump and mixer from the system as there is the system pump anyway?

 

 

12 hours ago, jamesdiyer said:

I'd say you have an emitter issue

Yes I think this is also part of it. I dont know if the installers included the conservatory floor space ( approx 9m2) in the calcs but it is practically outside so I have turned the manifold flow adjuster to 0 for this section. We also have a hallway of about 4m2 which is not working which reduces the effciency too.

 

12 minutes ago, Beelbeebub said:

 

You say parameter 21-00 is set to 0.

Sorry is 01. It is on WC. My daughter was after my attention while I typed so I made some mistakes!

 

2 minutes ago, Beelbeebub said:

Then 88C gas was leaving the compressor. Which seems a bit high for heating mode, I would expect it to be more like 50-55C for a 45C (water) flow temp.  That suggests something might not be quite right. 

I will mention it to the installer. Landlord and I emailed today. He was obtuse about upgrading pipe insulation in the freezing shed ( some joints arent even insulated, 28mm pipe has 22mm bore insulation on it and none of it is sealed! ) but we will keep on!

 

Can anyone recommend good pipe insulation? It is pretty much outdoors tempwise but is not exposed as its in a shed.  Especially want to know how to insulated the valves and corners and the bits of pipe that are fixed v close to the floor/ wall.

 

Thanks again Jeff

[JeffGiraf]

I stood in the cold shed today and watched this happen ( as I measured pipes for insulation landlord has agreed to get):

 

The flow temp displayed on the remote control heat pump seems to be on a cycle where comes on for 18 mins, starting fast and gradually slowing, bringing the flow temp to 46degC then shutting off for 24 mins. Flow temp drops to 32degC in this time before pump kicks in again.

 

 

Is this how it should be working?

 

 

[JeffGiraf]

8 hours ago, JohnMo said:

Other thing are you running the heating on all the time or an on off time cycle?

Open system always on

[Michael_S]

23 minutes ago, JeffGiraf said:

I stood in the cold shed today and watched this happen ( as I measured pipes for insulation landlord has agreed to get):

 

The flow temp displayed on the remote control heat pump seems to be on a cycle where comes on for 18 mins, starting fast and gradually slowing, bringing the flow temp to 46degC then shutting off for 24 mins. Flow temp drops to 32degC in this time before pump kicks in again.

 

 

Is this how it should be working?

 

 

Nope, should be a constant burn, sounds like your emitters are too small or there is a circulation issue such as TRVs restricting the flow.

[JeffGiraf]

6 minutes ago, Michael_S said:

Nope, should be a constant burn, sounds like your emitters are too small or there is a circulation issue such as TRVs restricting the flow.

Trvs are all open... spunds like emitters are too small.

[Beelbeebub]

49 minutes ago, JeffGiraf said:

.... The mixer only goes up to 55 degC and is now on max ( installers left it on 25 degC.... 

This may not be a good idea, temps that high may cause issues with the slab and floor coverings - the mixer and pump system is there to run the UFH at a lower temp than the rad system. IIRC thr max floor temp is supposed to be 28C, running at those flow temps will almost certainly result in parts of the floor getting hotter than this. 

 

 

[JeffGiraf]

Ok, but same emitter system used to get house to 20degC when previously supplied by Vito boiler.....why??

[Beelbeebub]

4 minutes ago, JeffGiraf said:

Trvs are all open... spunds like emitters are too small.

What are your radiator sizes? Are the ufh heated rooms warm enough? What is your floor temp in those rooms(cheap laser thermometer will do) 

 

Look at what the return temp (parameter 00) and output temp are (09). Ideally they should be 5-7C apart. If the return is climbing closer to the output then your emitters aren't getting rid of the heat quick enough. It could conceivably be a radiator loop that is too open and the flow is all rushing thorough there, hardly losing any heat. 

[Beelbeebub]

Link to the manual. 

 

https://trade.centralheating.co.nz/assets/resources/Chofu-Operating-Installation-Manual.pdf

[JeffGiraf]

2 minutes ago, Beelbeebub said:

14 minutes ago, JeffGiraf said:

Trvs are all open... spunds like emitters are too small.

What are your radiator sizes? Are the ufh heated rooms warm enough? What is your floor temp in those rooms(cheap laser thermometer will do) 

 

Look at what the return temp (parameter 00) and output temp are (09). Ideally they should be 5-7C apart.

Ah they are about 2deg apart at best

[Beelbeebub]

4 minutes ago, JeffGiraf said:

Ok, but same emitter system used to get house to 20degC when previously supplied by Vito boiler.....why??

Potentially the Vito boiler was supplying higher flow temps and each emitter was outputting more. 

 

This is why radiators and pipes sometimes need to be swapped for bigger ones when a HP is installed. 

 

Get an IR thermometer (better yet an IR camera for your phone - can use it to track down heat leaks in the walls too) 

 

Check your rads, your (heated) floors. 

 

Is there a rad that is especially hot, in particular if it's flow and return are very close - they should be 5-7C different. 

 

It's possible one of the rads is "short circuiting" the flow, which cause the HP to shut down (as the flow and return are too close) and your overall heat output to buikding is lower plus less efficient because of start stopping. 

[Beelbeebub]

3 minutes ago, JeffGiraf said:

Ah they are about 2deg apart at best

Either your emitters are very undersized - thr ufh loops should be OK, the whole. Point of ufh is it being a big emitter. Maybe your rads are too small? What type are they? Single panel, finned? Double panel double fin?. How big are they? Rads for HP should be bigger than what is typical in a boiler heated house. Your plumber should be able to tell just looking - 'they look bigger than I wound expect" or "nah, looks. like I. Would expect for a gas boiler house" (ie too small!) 

[Beelbeebub]

As I said the other option is one rad being "too open" and starving the other ones.