Underfloor Heating - SunAmp, ASHP, Solar

[mikeseaman3000]

Hello Everyone,

I am new to BuildHub after reading a number of articles here.

 

Approximately a year ago we moved into a new build property. Actually it was a self-build that ran out of money and we finished off a couple of things. A significant shame for the previous owner however it was complex hill-side build that was always going to eat up money in the early stages.

The house had many plans one of which was its energy efficiency (Planning for Solar/Wind, ASHP). But these were never finished.

We have underfloor heating & radiators in bathrooms as our source of heating and 300L Ariston Tank for Water. This underfloor is currently running via a Condensing Boiler straight into a mixing control valve to modulate the temperature underfloor, whilst I have radiators and hot water off different zones

Our problem is the efficiency of said system. We have no buffer tank and thus the boiler is called in to retain the underfloor temperature at a setpoint + Error. (45 Degrees +/- 5 degrees).

My view is we are using a sledge hammer to crack a nut. The house had actually been completed in 2011 and between then and now the place has had 2 boilers by the previous owner.. My view is its running to often (on and off).

 

Our house is 260m2 for which is fairly open plan living. We get fairly good Solar Gains when the sun is shining. All rooms are fully insulated, the outer walls very thick. Windows are Nordan (U-Value 0.8 Wm2/k)

The EPC Certificate said our heating requirements per year 20,000kwhr and water 2,000kwhr. I think this was not correct, and done by the agency at a later date.

My background is control & electrical engineering, I have spent a fair amount of time sorting out the Controls for Underfloor (we have 11 ind. Zones) however just cannot get this energy balance right. I use a loxone controller (German Home Automation System) and individual rooms stat’s.

 

Its driving me bonkers now and I am keen to get our bills down. The house is not balanced that well and i am at the end of the line with this boiler.

What do I do?

 

I have spoken with a local agents and they suggest the following:

• Solar ( We have a huge room space that is south-west facing and no shading) : Estimate capacity 8-10kw.
• Air Source heat pump : removed our use of gas
• Buffer Tank or Thermal Battery (Sunamp)

 

Reviewing the Sunamp stuff, seems quite impressive but done see how I can get it to work with a Monobloc ASHP. I do think the suggestion by the local company was to jump on a variable elec-tarrif and charge over night or on Solar.

 

Any suggestion are very much appreciated!

Cheers

Mike

[Barney12]

2 hours ago, mikeseaman3000 said:

Reviewing the Sunamp stuff, seems quite impressive but done see how I can get it to work with a Monobloc ASHP. I do think the suggestion by the local company was to jump on a variable elec-tarrif and charge over night or on Solar.

In short; you can’t currently charge a Sunamp via ASHP as the phase change temp is too high to be efficient with the PCM58 units. They have got a lower temperature unit in the wings (PCM43) which is destined to be chargeable via ASHP but it’s not even reached the live testing phase yet. They were saying a month ago that it’s six months away. Based on Sunamps track record that’s much more likely to be 12-18 months away! 
 

You could of course use solar and off peak electric to charge a standard Sunamp and make it your source for DHW but I would urge HUGE caution about using the current Sunamp units for UFH without very careful planning and that would start with knowing accurately what your heat demand is.

Edited December 24, 2019 by Barney12

[mikeseaman3000]

1 hour ago, Barney12 said:

In short; you can’t currently charge a Sunamp via ASHP as the phase change temp is too high to be efficient with the PCM58 units. They have got a lower temperature unit in the wings (PCM43) which is destined to be chargeable via ASHP but it’s not even reached the live testing phase yet. They were saying a month ago that it’s six months away. Based on Sunamps track record that’s much more likely to be 12-18 months away! 

 

You could of course use solar and off peak electric to charge a standard Sunamp and make it your source for DHW but I would urge HUGE caution about using the current Sunamp units for UFH without very careful planning and that would start with knowing accurately what your heat demand is.

 

 

Thanks for that info. I did read online the Sunamp doesnt work well with Underfloor. The guy who quoted us to do the work suggested the following:

Panasonic Aquarea 12kW ASHP

Sunamp UniQ 12kWh

350lt Hot Water Cylinder

Jinko 305W Solar Panels.

This suggests to me that he was thinking the SunAmp for UFH which could be problematic.

 

[MikeSharp01]

If you are having an ASHP connect it direct to the UFH -  if you get a reversible one you can cool the floors in the summer! You dont' need a battery or a buffer tank, although some have them but you do need to modulate the ASHP output so you need an inverter controlled one or you wont be able to tune for optimum COP.

[SteamyTea]

2 hours ago, mikeseaman3000 said:

Sunamp UniQ 12kWh

350lt Hot Water Cylinder

Why both?

2 hours ago, mikeseaman3000 said:

Jinko 305W Solar Panels.

How many?

[joth]

Sounds like your EPC is figured at current building regs quality of build, around 100kWh/m2 per year. If you've been in for a year you can presumably get a more accurate estimate of annual heating demand from your gas bills.

Also have you had a room by room peak heat load calculation done, and know what the peak heat load is for the house? Has the house has an airtightness test and how is ventilation managed?

It sounds like peak heat load could be on the high side and converting to ASHP on its own to reduce bills risks tackling the symptoms not the cause of high heating requirement. I wonder if it maybe worth investigating fabric-first options to reduce heat load prior to making changes to the heating system design.

[Barney12]

9 hours ago, mikeseaman3000 said:

 

Thanks for that info. I did read online the Sunamp doesnt work well with Underfloor. The guy who quoted us to do the work suggested the following:

Panasonic Aquarea 12kW ASHP

Sunamp UniQ 12kWh

350lt Hot Water Cylinder

Jinko 305W Solar Panels.

This suggests to me that he was thinking the SunAmp for UFH which could be problematic.

 

Large amount of guess work going on but I would imagine (hope).....

 

ASHP heating the water cylinder (thermal store?)  in the low 40’s for max COP. 
Cylinder possibly acting as buffer for UFH.

Cylinder passing pre-heated water to Sunamp for DHW delivery. (Sunamp being charged by solar where available).

 

[pulhamdown]

That's exactly what I plan to do when our oil boiler expires.  We built a well insulated low energy house six years ago, but retained the one year old oil boiler from our old house.  We have a thermal store, supplied by the oil boiler, solar thermal, a log burner burning our own wood, and three immersion rods.  We also have a 3.7kw PV system.  Apart from the expense, I can't see too many problems, except perhaps finding someone enlightened enough to fit the new kit!

 

[mikeseaman3000]

On 24/12/2019 at 15:08, SteamyTea said:

Why both?

How many?

Good Question. Why Both. My view is you need is 350Lt Cylinder for Hot Water and another storage for your buffer. Larger the better? 

We are intending on 24 Solar Panels.

 

On 24/12/2019 at 22:14, Barney12 said:

Large amount of guess work going on but I would imagine (hope).....

 

ASHP heating the water cylinder (thermal store?)  in the low 40’s for max COP. 
Cylinder possibly acting as buffer for UFH.

Cylinder passing pre-heated water to Sunamp for DHW delivery. (Sunamp being charged by solar where available).

 

Possibly. I am trying to figure out what the best thing is here. The Heating Company have offered up a number of solutions.

Reading a fair bit of info on the SunAMP its probably not worth it?

 

On 24/12/2019 at 15:51, joth said:

Sounds like your EPC is figured at current building regs quality of build, around 100kWh/m2 per year. If you've been in for a year you can presumably get a more accurate estimate of annual heating demand from your gas bills.

Also have you had a room by room peak heat load calculation done, and know what the peak heat load is for the house? Has the house has an airtightness test and how is ventilation managed?

It sounds like peak heat load could be on the high side and converting to ASHP on its own to reduce bills risks tackling the symptoms not the cause of high heating requirement. I wonder if it maybe worth investigating fabric-first options to reduce heat load prior to making changes to the heating system design.

 

Rooms on average lose around 1 Degree C every 6 hours with the heating off. Hard to equate what the heat losses are? I have temperature logging in every room passed through my smart controller.

 

Guess my biggest question is do rip out my boiler now and go with the ASHP & Buffer Tank.

I am making a major mistake? I reckon the boiler will not cope with cycling. Tried reducing this but without a buffer tank i cannot get away from it.

 

The Energy Saving Trust are basically going to give us a loan to replace the boiler with ASHP and then give us a grant over 7 years that covers the cost of the ASHP.  Certainly within that timeframe we will have to replace the boiler

[SteamyTea]

9 minutes ago, mikeseaman3000 said:

Why Both. My view is you need is 350Lt Cylinder for Hot Water and another storage for your buffer. Larger the better? 

Too large may be a problem if you are trying to maximise on your solar (the 7.3 kW_p PV), but I can see your thinking.

 

14 minutes ago, mikeseaman3000 said:

Rooms on average lose around 1 Degree C every 6 hours with the heating off. Hard to equate what the heat losses are? I have temperature logging in every room passed through my smart controller.

Should be fairly easy to work that out knowing the fabric areas and the temperature differences.

[Eileen]

We have  a Sunamp Uniq 12 heated electrically for our DHW - it ran (via an Eddi controller) entirely from our 10kw solar from early March to mid Nov and at other times of the year we give it an overnight (potentially economy 7) burst. This is with the 10kwh electrical battery taking priority, but even then the Sunamp has been getting solar power the odd day recently. There is no hot water tank installed. UFH is powered from a low temp Daikin ASHP. 

 

Re your OP: Our EPC certificate (101 rating) says 11,000 for space heating and 2,400 for DHW while actuals were 1,800 (input to ASHP so output around 6,000) and 1,000 (only 2 of us though). We're 380 sq m.

Edited February 14, 2020 by Eileen
Added a bit re EPC

[Nick Laslett]

On 14/02/2020 at 13:16, Eileen said:

We have  a Sunamp Uniq 12 heated electrically for our DHW - it ran (via an Eddi controller) entirely from our 10kw solar from early March to mid Nov and at other times of the year we give it an overnight (potentially economy 7) burst. This is with the 10kwh electrical battery taking priority, but even then the Sunamp has been getting solar power the odd day recently. There is no hot water tank installed. UFH is powered from a low temp Daikin ASHP. 

 

Re your OP: Our EPC certificate (101 rating) says 11,000 for space heating and 2,400 for DHW while actuals were 1,800 (input to ASHP so output around 6,000) and 1,000 (only 2 of us though). We're 380 sq m.

 

Hello Eileen (or Nigel), how did you get your Sunamp and ASHP installed? Was it a package with UFH and PV? What size is your ASHP?

 

Very torn between the simplicity of the Sunamp vs the comfort of traditional UVC domestic heating installation.

[Eileen]

Hi Nick - our ASHP is 6kwDaikin Altherma and was installed by the plumbers, and the UFH separately bya specialist sub-contractor working with our plumbers. This is entirely separate from the electrically heated Sunamp, which we just use for DHW and which was also installed by the plumbers. At the time Sunamp really weren't geared up to supporting people like that with no previous Sunmp experience (as opposed to highly-motivated diy self-builders) but I think that's improved now.

 

We recently had to replace our Sunamp under warranty as it leaked PCM material. Apparently that was a known problem with V1 of the new range (a missing O ring , now fixed. A specialist installer came and did that.