What's the issue? Help Please ?

[canalsiderenovation]

So, I'm all ready to sort this solar PV and get it ordered but the plumber seems to have his knickers in a twist about solar diverting any excess to the tank. He is saying Alto energy (the company who have designed the system for the ASHP and allow the RHI to be claimed) are saying the mitsubishi system for the ASHP is not compatible for us to have a solar system to divert any excess to the tank as all the controls are built in, something about legionnaires and the tanks having built in controls which isn't compatible and Alto not taking responsibility for maintaining it if we don't have tanks with controls all built in.

 

He had quoted for a Mitusubishi 11kw 1P air source heat pump with 210 Litre Preplumbed Pressurised cylinder (I noted we want to change this to either 300/400 litre now we are having solar as per the recommendation on here).

 

Now I know lots of people on here have an ASHP and a tank that they use with a solar PV controller (iboost, solic200 etc) for the solar to divert to the immersion. I can't understand what the problem is, is it just that a Mitsubishi system won't allow this? 

 

Can you advise if there is a particular spec that I can go back as saying works with the ASHP, or what I can say so I can go back and pretend I know what I'm talking about! I'm sure someone in the chain of plumber/Alto is being deliberately difficult.....

 

Any help would be really great. 

 

Thanks

[arg]

I think the issue is:

• For efficiency (or just the plain ability of the unit to do it) ASHPs for DHW are normally run with a relatively low tank temperature.
• The low tank temperature theoretically risks legionella growth.
• One way to combat this is to, at regular intervals controlled by a timer, raise the tank temperature to 60C in order to kill any legionella.
• Some systems just run the ASHP harder (less efficiently) to do this, but many ASHPs can't deliver the 60C+ output temperature required.
• Some systems have an extra resistance heater as part of the ASHP or its plumbing (effectively a willis heater with a fancy label on it!) to boost the output temperature of the ASHP, so the ASHP "system" can handle the legionella cycle.
• Some systems put a conventional immersion in the tank and control that to run the legionella cycle.

So you need either a control system that can do both the legionella cycle and the solar divert all in one system, or else you need a dedicated immersion heater (not part of the rest of the system) to accept the solar divert.

 

If your giant tank has room for two conventional immersion heaters, that's probably the easiest way forward from where you are.

Edited September 9, 2020 by arg

[JamesP]

Not sure if this helps, we have a MITSUBISHI ECODAN PUHZ-W85VAA with a 300 Litres PRE PLUMBED EHPT30X  cylinder, 3.74 PV array with an Eddi PV diverter.

All works fine.

[PeterW]

He’s talking rubbish

 

http://www.greengenuk.com/mitsubishi-ecodan-installation-11-2kw-heat-pump-polperro/

 

Perfectly acceptable and what he hasn’t done is RTFM.... 

 

Basically this is a straight wiring job, the FTC5 controller has a boost setting.  They wire the Eddi/iBoost NV switch to the correct terminals as per the installation guide. 

[Roundtuit]

As @arg says.  There should be no issue, as long as the tank has an immersion heater.  My ASHP (Hitachi Yutaki, but not really relevant) has a legionella control function that switches on the immersion for a set period on a regular basis to raise the water temperature.  To do that, the immersion needs to be wired to the heat pump, whereas to use a solar diverter, the immersion needs to be wired into the diverter. We've used an Apollo Gem diverter, as is was the only one I could find at the time with a decent programmable legionella control function.  There's been debate on here before about whether legionella control is actually necessary, but that's another story.  Best play it safe and keep the plumbers happy methinks!

[canalsiderenovation]

23 minutes ago, arg said:

So you need either a control system that can do both the legionella cycle and the solar divert all in one system, or else you need a dedicated immersion heater (not part of the rest of the system) to accept the solar divert.

 

Hmmm, what sort of system would do all this in one system? What would be the most cost effective solution? 

[arg]

5 minutes ago, canalsiderenovation said:

Hmmm, what sort of system would do all this in one system?

 

You've got replies upthread suggesting two possibilities:

• Take the boost output of the Mitsubishi controller and instead of just wiring it to an immersion, wire it instead to an override input on a solar diversion controller.  @PeterW suggests Eddi or iBoost controllers can accept this.
• Ignore the Mitsubishi's legionella feature and do it all in a separate controller.  @Roundtuit suggests that Apollo Gem can do both solar divert and legionella cycle in one controller.

[canalsiderenovation]

Literally just had a call from the plumber. The penny has finally dropped! I've sent all the information summarised in this thread hopefully he realises what a plank he has been!

[canalsiderenovation]

55 minutes ago, PeterW said:

Perfectly acceptable and what he hasn’t done is RTFM....

 

I had to google RTFM ? I'm glad I checked before I told the plumber to do this ?

[ProDave]

Also, we debated this a while back, and the conclusion was if you are on treated mains water, into an unvented tank, then the risk of legionairs is almost zero, so many of us don't use the timed legionairs heating cycle anyway.

[joe90]

5 minutes ago, ProDave said:

Also, we debated this a while back, and the conclusion was if you are on treated mains water, into an unvented tank, then the risk of legionairs is almost zero, so many of us don't use the timed legionairs heating cycle anyway.

nor me!

[canalsiderenovation]

13 minutes ago, joe90 said:

nor me!

 

Well sounds like that is a definitive answer on that point then 

[Pete]

8 hours ago, PeterW said:

He’s talking rubbish

 

http://www.greengenuk.com/mitsubishi-ecodan-installation-11-2kw-heat-pump-polperro/

 

Perfectly acceptable and what he hasn’t done is RTFM.... 

 

Basically this is a straight wiring job, the FTC5 controller has a boost setting.  They wire the Eddi/iBoost NV switch to the correct terminals as per the installation guide. 

I am reading this with interest as my ASHP is the last job on my house and if a plumber does not know how to wire/set the system up what hope do I/we have as fairly competent DIYers? (Sorry if this is hijacking this thread)

[canalsiderenovation]

20 minutes ago, Pete said:

I am reading this with interest as my ASHP is the last job on my house and if a plumber does not know how to wire/set the system up what hope do I/we have as fairly competent DIYers? (Sorry if this is hijacking this thread)

 

From what I can gather it is Alto energy who seem to have caused a lot of the confusion but I would have expected the plumber to have known what I was told in this thread.

 

In fairness to our electrician who just happened to be on site as we're meeting on another matter, he picked up on part of the conversation and seemed to know exactly what I was on about and spoke to the plumber.

Edited September 9, 2020 by canalsiderenovation

[Benjseb]

If you have solar and a diverter (we have an Eddi), then link the ASHP immersion connection to the boost input on the diverter

 

Something to consider, none of these systems are intelligent enough to work out that during the week the cylinder temp has been sat at 60c+ due to lots of sunshine. It’s just a basic timer

 

So then in a dull day it runs legionnaires cycle when it’s not needed, just because it’s been 7 days. 
 

there really should be some logic to say only run if the tank hasn’t hit 60c for an hour recently

 

We’ve  just turned the legionnaires off ?

[SteamyTea]

2 hours ago, Benjseb said:

We’ve  just turned the legionnaires off

Sometimes people forget the really obvious.

 

KISS

[shirebuild]

On 09/09/2020 at 10:57, canalsiderenovation said:

..

He had quoted for a Mitusubishi 11kw 1P air source heat pump with 210 Litre Preplumbed Pressurised cylinder (I noted we want to change this to either 300/400 litre now we are having solar as per the recommendation on here).

 

 

 

I have searched but I can't seem to find any reference to having a larger cylinder if you have solar, is there a discussion somewhere else about this someone could point me to please? We are planning a 170L cylinder with a 6KW ASHP (Ecodan) for a 3 bed / 2 bathroom house so would be curious to read! We'll also have solar/Eddi diverter and want to make sure we spec it right!

[ProDave]

33 minutes ago, shirebuild said:

 

I have searched but I can't seem to find any reference to having a larger cylinder if you have solar, is there a discussion somewhere else about this someone could point me to please? We are planning a 170L cylinder with a 6KW ASHP (Ecodan) for a 3 bed / 2 bathroom house so would be curious to read! We'll also have solar/Eddi diverter and want to make sure we spec it right!

170L would be far too small.

 

Bear in mind an ASHP will generally heat the water less hot than a gas or oil boiler.  We run our hot water at 48 degrees.  So when you draw hot water it will mix less cold with it that you may be used to so will use more out of the hot tank.

 

We have a 300L UVC and find that is adequate for a 3 person 2 bathroom house.  and with the water heated to 48 degrees by the ASHP there is plenty of capacity for surplus solar PV to heat it hotter.

[Gone West]

3 hours ago, shirebuild said:

I have searched but I can't seem to find any reference to having a larger cylinder if you have solar

Is that solar thermal or PV. We had a 180l UVC heated with an EASHP which was heated to 45C with a backup immersion. We never used the immersion and never ran out of hot water and that was for just two adults.

[shirebuild]

Thank you. It's PV not solar thermal so I suppose we want to go somewhere in between 170 and 300. Am I right in thinking there's a trade off between using the cylinder as a handy thermal store from PV when the sun shines VS using unnecessary mains power to keep excess water heated when its not? We are 2 adults now but will be 3 or 4 within 15 years!

[RomyD]

Sorry to resurrect an old thread but we have a similar plumber issue. Ecodan and preplumbe cylinder and plumber says it wont work with an i-boost. I don't quite understand the solution described here.

 

Have I understood it correctly in that the output from the Mitsubishi FTC powers the immersion heater (for legionnaires control) periodically and that all that is needed is to wire this power to the 240v i/p on the i-boost? 

So now the FTC will (if the option is turned on) do the legionnaires boost thing (if there is no solar) and the iboost will top up the cylinder temperature in any event when conditions allow?  

I've looked for a wiring diagram but I cannot find anything useful.

Hope the questions makes sense.

tks,

Edited February 8, 2022 by RomyD

[ProDave]

41 minutes ago, RomyD said:

Sorry to resurrect an old thread but we have a similar plumber issue. Ecodan and preplumbe cylinder and plumber says it wont work with an i-boost. I don't quite understand the solution described here.

 

Have I understood it correctly in that the output from the Mitsubishi FTC powers the immersion heater (for legionnaires control) periodically and that all that is needed is to wire this power to the 240v i/p on the i-boost? 

So now the FTC will (if the option is turned on) do the legionnaires boost thing (if there is no solar) and the iboost will top up the cylinder temperature in any event when conditions allow?  

I've looked for a wiring diagram but I cannot find anything useful.

Hope the questions makes sense.

tks,

The issue is the Ecodan controller wants to control the immersion heater and turn it on and off as it needs.  BUT so does the iboost.  If you simply connect the two in parallel it is likely to end in smoke somewhere if both should ever try and turn on at the same time.

 

By far the simplest solution is turn off the Ecodan legionairs function and connect the immersion heater only to the immersion heater.

[Marvin]

17 minutes ago, ProDave said:

The issue is the Ecodan controller wants to control the immersion heater and turn it on and off as it needs.  BUT so does the iboost.  If you simply connect the two in parallel it is likely to end in smoke somewhere if both should ever try and turn on at the same time.

 

By far the simplest solution is turn off the Ecodan legionairs function and connect the immersion heater only to the immersion heater.

Is that right? If they only use the positive cable to control the power, and the immersion has a thermostat in-built surely its just the same supply 2 different ways in, one way in or no way in?

 

Perhaps I'm missing something.

 

I can certainly switch my light on with power from 2 sources, so to speak.

Edited February 8, 2022 by Marvin
Clarification, hopefully.

[ProDave]

2 minutes ago, Marvin said:

Is that right? If they only use the positive cable to control the power, and the immersion has a thermostat in-built surely its just the same supply 2 different ways in, one way in or no way in?

 

Perhaps I'm missing something.

 

I can certainly switch my lit on  with power from 2 sources, so to speak.

You would need to know EXACTLY how it is connected in extreme detail before designing a solution that will work with both.  In my case (LG heat pump) it uses a double pole contactor to switch the immersion.  The PV diverter just switches the L with a solid state relay.  So instantly a conflict there.

[Marvin]

8 minutes ago, ProDave said:

You would need to know EXACTLY how it is connected in extreme detail before designing a solution that will work with both.  In my case (LG heat pump) it uses a double pole contactor to switch the immersion.  The PV diverter just switches the L with a solid state relay.  So instantly a conflict there.

See. I thought I was missing something!?