New Heat Pump problems Hitachi

zorch

Hi,

Hope I can get some advice.

Our Boiler packed it in around Oct and we decided to get a heat pump on advice from our plumber. We have Approx 3,00 sq ft. Underfloor heating down stairs, Rads upstairs and DHW. Heat pump managing all three as did the boiler.

Aside from the fact that the unit is mostly frozen and is unable to heat the house over the last 3 days ( its a 14KW Monobloc) we are having a mare, this thing is drinking electricity in a serious way. Its not even cold yet

For the whole of last year we used about 6000 KW of Electricity. Gas was never a huge bill. Since we got a day night meter in December we have eaten through 4320 Units - on a roughly 50:50 split. If we didn't get a night meter this thing would be in the river now

House is a BER B rating. The Heat Pump is delivering water on a single circuit at 55 Degrees. Plumber didn't install a Reservoir tank - so the unit is pumping straight into our main control manifold/mixer set.

Guy from Unitherm came out to do an install check and were not overly happy with how it was installed - but they are pushing me back to the Plumber, who thinks its all grand, and that I should be running the unit at 35 degrees and using the immersion for hot water

Anybody have any recommendations on where I can start - this was well over 12K wasted currently

Help please

Wearb

zorch wrote: »

Hi,

Hope I can get some advice.

Our Boiler packed it in around Oct and we decided to get a heat pump on advice from our plumber. We have Approx 3,00 sq ft. Underfloor heating down stairs, Rads upstairs and DHW. Heat pump managing all three as did the boiler.

Aside from the fact that the unit is mostly frozen and is unable to heat the house over the last 3 days ( its a 14KW Monobloc) we are having a mare, this thing is drinking electricity in a serious way. Its not even cold yet

For the whole of last year we used about 6000 KW of Electricity. Gas was never a huge bill. Since we got a day night meter in December we have eaten through 4320 Units - on a roughly 50:50 split. If we didn't get a night meter this thing would be in the river now

House is a BER B rating. The Heat Pump is delivering water on a single circuit at 55 Degrees. Plumber didn't install a Reservoir tank - so the unit is pumping straight into our main control manifold/mixer set.

Guy from Unitherm came out to do an install check and were not overly happy with how it was installed - but they are pushing me back to the Plumber, who thinks its all grand, and that I should be running the unit at 35 degrees and using the immersion for hot water

Anybody have any recommendations on where I can start - this was well over 12K wasted currently

Help please

There might be a better place for this question, but I'll leave it here for a while to give the lads here a chance to comment. btw what number ber B is it? It goes 1 to 3

antoinolachtnai

Do I have this correct?

The plumber is advising you to run it at 35c, and you are running it at 55c?

zorch

Yes,

I can't heat the upstairs Rads and DHW at with a 35Degree output. I have tried, and with that there was no noticeable difference in Electrical consumption by lowering the output temp by 10 degrees. We normally run it at 45 or 50 Degrees (50 works better for hot water - gets the hot water tank to 44. running the system at 45 gets the tank only to 39) , but we changed it to 55 last week as we were getting poorer performance in the colder weather.

I get with new builds you can run the system at a lower temps, but this is a 2005 Build. Underfloor system gets fed with approx 40Degrees.

antoinolachtnai

The higher you put the temperature, the worse the performance is going to be, that's for sure.

When you were using gas, how many hours per day was the boiler switched on?

You have the heat pump turned on all the time or called by the thermostat?

Did you try isolating the hot water cylinder coil from the rest to see if that helped?

It is just a suggestion but I would be inclined to do that and follow the plumber's suggestion for now, maybe running it at 40 C. I can't see how you are ever going to get your hot water to heat with that setup (i.e., no separate zone for the hot water). You need to be able to heat the radiators and UFH at low temperature and the hot water at high temperature to get this to work.

At the end of the day, the plumber has to take responsibility for the installation. Was Unitherm the distributor of the heat pump unit?

zorch

Gas was on for about 6 hours at night between for UFH. DHW & Rads for 90 Mins Morning and night .

We have three separate zones, the UFH has Thermostats in each room - each room downstairs has its own circuit.

We don't have the system turned all all the time - as the cost was getting out of control. its called by Thermostats and globally with timers.

So the Heat Pump system struggles to do DHW, UFH and Rads all at the same time. (that's not a big issue)

Program currently is:

Night time is solely for UFH (6 hours), early morning is DHW and Rads (2 hours) and evening (90 Mins). Rads come on 60mins after DHW

Plumber told us we were crazy to get a day/night meter! - so taking full responsibility (if you can call it that) when someone else is paying the bills is easy.

Our DHW tank probably needs to be replaced as its not holding temps very well, and I'm not sure the coil setup in it is best for Heat Pumps lower temps. But that's only going to help the DHW. and will probably cost me another 2K

antoinolachtnai

Firstly, you have to decide whether you are going to hold the plumber accountable or not. He designed this system. He is the one who has been paid to make it work.

I wouldn't touch the cylinder for now. The cost of heating a year's water for the typical household is a couple of hundred euros a year. It is really not that material. Any possible saving doesn't merit replacing a moderately insulated cylinder with one costing two grand unless it is actually leaking. (Though one thing you can do is insulate the pipes around the cylinder.)

The design of the coil is not material to the problem you are having. It doesn't matter what sort of coil you have, warm water in the coil will never lead to hot water in the cylinder. The efficiency is always the same. If you had a bigger ('quick recovery') coil, then sure, the water would heat faster. But unless your use is pretty big, that is probably not that big a deal.

Check the meter once or twice a day and take a reading. Do you have a separate electricity meter on the heat pump or will the heat pump measure it? It would be a lot better if you had a separate meter. Also, note down the daily outdoor temperatures. Outdoor temperature will make a big difference.

I would try heating the UFH and rads only at 35C for 24H a day and see how much that costs and see if it can give you comfort. I would give this two days to see how it 'develops'.

This will probably work for the UFH but might not be enough to heat the rads. If this is the case, you might have to add a couple more rads.

If you can get the house to heat at a reasonable cost, you can solve the hot water problem later. (I would think that the time to use the heat pump to heat the hot water would be in the afternoon, when the air temperature is highest, but that's just me. And of course, most of the year, the air is warm and heating the water will be much less energy-intensive.)

zorch

Thanks for the help,

We previously set the system at 40 Degrees for four days straight, and the rads didn't feel hot to the touch (Luke warm) and were failing to heat the rooms up stairs. Im not sure if the Rads/pipes we have are just not effective at those temps. Down stairs was ok at that stage, not hot.

Normally system uses about 38 Units each night (so that includes uses the 6 hours UFH, 2 hours of DHW in the am and Rads in AM). it's the only thing in use at that time. but to be safe you could say 35. I think last few days it's trying to defrost during the day and unable to do anything else.

when you look at the literature from the vendors (Mitsubishi / Hitachi) they say that they can run comfortably run at upto 65 degrees output.

Am I compounding my problem by upping the output temp when the outdoor temp is colder? Again the vendors tell you that the system automatically compensates for external temps.

antoinolachtnai

You are almost certainly compounding your problem by upping the output temp when the outdoor temp is cooler. It is making the elements frost up faster because you are drawing more heat out of them.

I don't know if they say they're going to run 'comfortably'. I agree that it is within spec. But it just won't be efficient. The COP will be lower and as a result it will end up being more expensive than gas or oil.

The rads aren't going to feel warm to the touch. The problem is probably that you don't have enough emitters (rads).

Have you any idea how much electricity the system used when you had it at 40 heating the upstairs and downstairs only? Did you run it 24/7?

You really need to get some more expertise here, from people who can stand over the setup. The plumber and the distributor need to get involved. The plumber is the one who advised this setup.

Latro

You are doing it wrong.
First of all let it pump 24/7.
Set the same flow temperature upstairs and downstairs for few days and see how it goes.

Don't worry about radiators upstairs being only lightly warm. It doesn't matter as long as the comfort is sufficient. Most of your heat will be produced downstairs and will eventually find its way upstairs. The rads are there for only a small top up. If they have TRV's leave them fully open as they may restrict water flow unless any given room becomes too warm.

Set flow temperature as low as you possibly can. Every degree counts. It will require a little bit of experimenting from you. Your plumber is guessing when he is setting flow temperature. Every house and its inhabitants are different.

With large underfloor radiator I really doubt that you would ever need water flow higher than 35 degrees providing it's on all the time. The flow temps you are running now are very high. You are not taking advantage of having UFH. Heat pump is relatively cheap source of energy as long as it is set to produce low temperature water. Heat produced by HP should cost about 55% of the same from oil.

Check if your heat pump model has weather compensation curve control option. If it was made within last few years it most likely has.

If it does ask your plumber to set it on or if you feel confident you can do it yourself. It is nowhere near rocket science. It was designed to be set by average person.

I would recommend to start with these settings:
outside temp points: +15,-5
water flow points: +25,+35
It should be your baseline but if possible experiment going lower on both ends with the water flow gradually by 1-2 degrees.

It is considered superior to internal thermostats.

It will reduce on/off cycling to nearly 0, reduce number of defrost cycles and will extend life span of the compressor.

Latro

Guy from Unitherm came out to do an install check and were not overly happy with how it was installed - but they are pushing me back to the Plumber

What was he not happy about? Monoblock units are very simple instals.
Simpler than oil boiler imo. Half decent models have everything contained within one casing.

zorch

I can't get the detail from them, But he was onto head office for a good while and ended up taking a load of photos of the manifolds etc to have it reviewed back in the office - obviously the Plumber is not going to tell me its not done right - so I'm stuck in the unknown.

zorch

we are current spending the same in value terms, on a monthly basis. So this thing is never going to save me running costs as is never mind paying itself back in 3-5 years.

If I leave it on 24/7 isn't it not just going to eat electricity - all the time. The night meter is my only saving now, if I let it run 24/7 cost is going to increase?

0lddog

zorch wrote: »

......Aside from the fact that the unit is mostly frozen and is unable to heat the house over the last 3 days ( its a 14KW Monobloc)...........

Can you elaborate on this ?

Have you seen it go through defrost cycles ?

If so, does all the ice clear from the unit after a defrost cycle ?

punisher5112

Try use it more on the night rate if possible.

Rackstar

Isn't a heat pump supposed to run 24/7? And aren't they designed for airtight A rated houses with under floor heating, and not meant to be used with rads? That's my understanding, sounds like wrong tool for the job

ShanE90

Firstly as said already your HP is not a boiler and shouldn’t be run like one, there’s more than likely nothing wrong with the unit itself but more the controls and installation.

For proper production of DHW to 50deg the cylinder coil surface area needs to be 2.5m2 or greater. The HP needs to be able to produce hot water independently of space heating as this requires a higher flow temp. It’s impossible to heat the dhw tank and run space heating simultaneously as both require different temps. Normally DHW has priority for 60 min to reheat the tank, unit should then switch back to space heating where it is locked into for a minimum time usually 30min before DHW can take priority again

As said previously run the heat pump all the time at the lowest possible flow temp...with a heat curve somewhere around A0 W35 and A15W25. Every degree the flow temp is reduced by will save 2-3% in energy... if your running a fixed flow temp your wasting energy because once your house heats up you’ll overheat it on milder days...

Best thing to do is have your plumber come out with someone who understands the system and controls better

Latro

zorch wrote: »

If I leave it on 24/7 isn't it not just going to eat electricity - all the time. The night meter is my only saving now, if I let it run 24/7 cost is going to increase?

It will until your floor is fully saturated with heat then it will drop off a lot and will only consume a fraction of it. It might take 2-3 days, it depends.

Imagine you have to travel 3000km trip with a car and you have 2 days to get to the goal. Right now what you do is driving at full speed lets say 240km/h at full throttle and red line rpm just to stop every hour for 2 hours instead of driving at 80km/h in 1 or 2 stints.

Both ways will get you to the destination on time but at 80kph you will burn half the fuel. Also your engine would be far more likely to last longer not only because you don't rev it high but also because you don't stress it with reheating it from cold every time it is started.

zorch

In the defrost Cycle - after about an hour the bottom 100cm inches are defrosted - out of about 1.4M

HappyAsLarE

Latro wrote: »

It will until your floor is fully saturated with heat then it will drop off a lot and will only consume a fraction of it. It might take 2-3 days, it depends.

Imagine you have to travel 3000km trip with a car and you have 2 days to get to the goal. Right now what you do is driving at full speed lets say 240km/h at full throttle and red line rpm just to stop every hour for 2 hours instead of driving at 80km/h in 1 or 2 stints.

Both ways will get you to the destination on time but at 80kph you will burn half the fuel. Also your engine would be far more likely to last longer not only because you don't rev it high but also because you don't stress it with reheating it from cold every time it is started.

This is an interesting analogy. The reason it is less efficient to drive fast is because drag increases to the square of the velocity. There is no such relationship for heating though.

My big issue with the advice “leave it run all the time” is that driving 3000 km is rarely necessary. As is having a house maintain a comfortable room temperature 24/7.

MOD note: Dont post in this thread again. Your are just pulling it off topic and not helping. Wearb

0lddog

zorch wrote: »

In the defrost Cycle - after about an hour the bottom 100cm inches are defrosted - out of about 1.4M

Not clear what exactly you mean.

Does it go through a defrost cycle by itself ?

or is it that this defrost is happening after you turn it off / the weather to warms up ?

( BTW an iced up outdoor unit is not going to function anyway efficiently )

What is the model number of the Hitachi unit ?

Water John

Is the unit sized too small, pushing it beyond its limit and thus not defrosting fully and thus very inefficient?
The house is 280 sq mt. My hunch is you need a bigger unit, which you may find strange.

zorch

it does go into defrost cycle by itself, but struggles to complete it and can't do anything else while attempting that.
The unit is the Hitachi Yutaki-M 14KW Monobloc ATW Heat Pump

If you read the data on Solflex website you can see that the predicted consumption difference between flow temps is only 500W for 35C versus 45C flow temps. that has been my experience - that the reduction in flow temps does not have a huge difference in electrical consumption.

Latro

zorch wrote: »

...only 500W for 35C versus 45C flow temps...

Isn't it quite a lot if it was ran 24/7?

My 9kW unit operates most of the time between 400 and 800W. It only jumps to 1500-1800W for very short period after the defrost cycle when it is very cold around 2 to -2 degrees. Adding extra 400-500W would nearly double the power consumption.

ShanE90

When the unit reverses for defrost does it complete the cycle? The coil should be cleared fully each time in a couple of munutes (2-4) if the coil isn’t clearing the unit will forgever be chasing itself in a cycle of heating/defrosting.

That 14kw unit needs a minimum of 200litres of water at a flow rate of 40l/m from your heating circuit to collect enough heat to defrost the evaporator. If you have a water volume of 200litres when you defrost the water temp will drop by 10 degrees. If you only have 137 liters of water the temp will drop by 15 degrees and so on. However if you have 400l of water the temp will only drop by 5 degrees.

Have you any idea of water contents and also do you have a buffer tank sounds like defrosting could be an issue...if you have zones closing/trvs shutting down and low water volume then you’ll drop the heating circuit temp by too much and will be unable to defrost fully, the unit is then in a continuous cycle trying to heat and then trying to recover after defrost.

cruiser202006

Sounds like a bit of a mess! Is it a monobloc? Did he change cylinder? Hitachi’s we use normally are set up for 40 flow 35 return. I’m guessing upstairs rads weren’t changed changed and sized for delta 20?? Your at nothing timing it to come on to heat upstairs for 90 mins if rads aren’t sized properly

zorch

It's a Monobloc, they didn't change the cylinder or rads, no buffer tank, the cylinder is upstairs on the far side of the house so pipes go up to attic - across and down so obviously heat losses on the way

I certainly think its a mess but if the Plumber and Hitachi's rep think is all fine and dandy -I need someone else to advise and help me get this to a sustainable solution

spudstyle0978

Hi guys sorry to jump in here I can’t find anywhere else.

i just moved into a new build and my house is only run by the hitachi heat pump. During the last few days been cold it has gathered a considerable amount of ice on the vent side and back. 2-3 inches all over and chunk starting to grow on the front. I have not seemed to find it defrosting and I’m watching it quite a bit. I am running the room temps at 20c but it’s struggling to reach 15. I know it’s still heating but it’s consistently running trying to build heat. To the point I went out and manually defrosted it today myself. I think I seen the neighbors defrost as steam coming from them. And they don’t seem as iced up as mine

can you give me any advice. Was it ok to defrost myself. Is it normal for it to freeze over to this extent.

thanks

Michael

Sleeper12

Edit:

Curse These Metal Hands

Anyone ever have an issue with these after electricity is gone? Power went today for a couple of hours and hadn't worked since the power came back, first it gave a defective pump warning now its saying low water pressure.