Boiler, buffer, thermal store or UVC? UFH with PV

[Nickfromwales]

5 hours ago, HerbJ said:

Interestingly, i have just skimmed through the Installation, Commissioning and Service Instructions for the Greenstar i System  and I can find no mention of the lowest modulating level for the boiler....

   

So, as far as I can understand  I am operating this WB boiler exactly in accordance with the MI and I am happy with its performance and efficiency.  These boilers are getting more sophisticated and can be controlled to operate efficiently for most systems. 

Interesting  After I read your comment re the 4kw output, I rang WB and spoke to technical ( as I have another 2 clients considering gas ) at some length. Their response was that they do not produce an 18kw boiler in any guise that can modulate lower than 6kw, with the 4kw only available with a 12Ri boiler. They further concurred that the design of driving the boiler directly into the matched low load wasn't recommended for maximising boiler efficiency, due to the lower temp of the flow and return and lack of promotion of condensing. 

As I said, it will work, but in a smaller house with a lower ventilation and heat loss figure it wouldn't be the way id design it. With no hydronic break between the boiler pump and the manifold pump, which have differing potentials, you either have to have a bypass, a Low Loss Header, or a buffer tank, so I assume yours relies on a bypass ?

 

All interesting and thought-provoking stuff

 

5 hours ago, HerbJ said:

Also, pleased that we avoided the complexity of a TS and other unnecessary kit.

The plug and play WB greenstar stuff is simple to install and maintain, but is only one of many ways to skin one of many differing cats. If I had, for eg, put a 400L UVC in a previous customers home, instead of the 400L TS I fitted, they'd have been on the phone the following week to say the hot water had been running out

@oranjeboom does sound like they are ok with a more conservative DHW solution, but different horses for different courses. 

[dimpsy]

Probably for Nick, what are your thoughts on these

http://www.harlequin-heatstream.com/product-range/

[dpmiller]

^that's interesting, never seen it before. I wonder if one of the extra coils could be used to draw off heat like a TS?

[ProDave]

10 hours ago, dimpsy said:

Probably for Nick, what are your thoughts on these

http://www.harlequin-heatstream.com/product-range/

But what IS it? There is not enough detail. Looks to me like a plastic thermal store tank.

[ProDave]

10 hours ago, Nickfromwales said:

Agreed, but where will 60oC water go? To mixer taps or thermostatic devices to be blended down. The TS comes with a factory fitted TMV, so only deliver ~50-55oC by design, thus offering reasonably similar sustain by means of blending at 'source'. 

I maintain that each solution should suit its owner, so yours suits you, but may not suit others.  A TS heated ( fortified ) by PV or E10 on a cycle would be set to heat to over 75oC so they're not worlds apart by any means. Throw in the two birds one stone appeal of the TS, plus its better DHW production "on demand", and you've got a strong case to go with it imo. 

 

 

As you say, horse's for courses.

 

I don't want to routinely be storing water at 75 degrees. The heat pump won't get it that hot, so it's the immersion heater to get it the final bit.  So I want to store it at a lower temperature.  I will bu using a TMV on the output to deliver HW at the lowest temperature that the thermal mixer showers will cope with, so on the days when the sun shines and the HW in the tank is a lot higher, you will still get the same temperature water, but on the days when there is no significant PV generation and you have to buy the electricity for the final heat up, it will only heat it to the bare minimum temperature. 

[Nickfromwales]

1 hour ago, dpmiller said:

^that's interesting, never seen it before. I wonder if one of the extra coils could be used to draw off heat like a TS?

It is a TS, just a plastic weird looking one. Not sure how they get around no certification? I assume that means no G3, so maybe its a manual fill gravity vessel with one or more coil for heat input and another, if required, for DHW output.

 

24 minutes ago, ProDave said:

But what IS it? There is not enough detail. Looks to me like a plastic thermal store tank.

Agreed, lots of patter on that website, but few facts. 

 

Apparently square ( rectangular ) TS's are a good option where space is at a premium or where internal doors have been swung and the openings are restricted. IIRC @djvasey went with a Jaspi Ultrastore 500L. Not a bad price either but only suitable ( or necessary ) if you have multiple heat sources as David did. 

 

[PeterW]

10 minutes ago, Nickfromwales said:

 

2 hours ago, dpmiller said:

^that's interesting, never seen it before. I wonder if one of the extra coils could be used to draw off heat like a TS?

It is a TS, just a plastic weird looking one. Not sure how they get around no certification? I assume that means no G3, so maybe its a manual fill gravity vessel with one or more coil for heat input and another, if required, for DHW output.

 

 

Its exactly what it is ... it’s a roto moulded polypropylene inner tank with steel reinforcing around the immersion and pipe entries. Looks like they then insert it into a similar roto moulded outer and then inject foam for insulation. It’s open vented with a DHW coil for mains pressure hot water. 

 

Harlequin have been around for years - they do oil tanks and that sort of stuff but have got into things such as rainwater tanks and now looks like they are doing hot water too. 

[HerbJ]

2 hours ago, ProDave said:

As you say, horse's for courses.

 

I don't want to routinely be storing water at 75 degrees. The heat pump won't get it that hot, so it's the immersion heater to get it the final bit.  So I want to store it at a lower temperature.  I will bu using a TMV on the output to deliver HW at the lowest temperature that the thermal mixer showers will cope with, so on the days when the sun shines and the HW in the tank is a lot higher, you will still get the same temperature water, but on the days when there is no significant PV generation and you have to buy the electricity for the final heat up, it will only heat it to the bare minimum temperature.

 

I agree with @ProDave

 

The main reason I went with a UVC was  that  the prevailing opinion in  ebuild/BH when I was finalising specifications for plumbing was that heat losses from TS and UVC were to be avoided if at all possible and certainly minimised.   This was in mid/late 2015  - the SUNAMP was just coming onto the scene and @JSHarris was sharing his issues with heat losses from his system.

 

I originally had a TS in my design and was persuaded that  maintaining this at 75C,  was the path to huge losses and problems with temperature in my plant room. I was very happy to pay for additional  tank insulation but none of the manufacturers really seem to care about this and only offer relatively modest insulation levels. On reflection,, the heating is not required for most of the year and the PV supplied immersion heaters deal with the majority of our HW  for most of the year , with a two immersion heaters -one top mounted and one bottom mounted.  The thought of keeping a TS at 75C throughout the year to maintain decent HW  seems illogocal, at least for us. ... If the UVC temeperature drops we can recharge it in 40 min or so with the gas boiler, when and if necessary.

 

[PeterW]

1 hour ago, HerbJ said:

I originally had a TS in my design and was persuaded that  maintaining this at 75C,  was the path to huge losses and problems with temperature in my plant room. I was very happy to pay for additional  tank insulation but none of the manufacturers really seem to care about this and only offer relatively modest insulation levels

 

I would have agreed with you after seeing a couple of TS installs however after last weekend and seeing @newhome TS installation, once me and @Nickfromwales had lagged the pipework the losses were really a lot less - tank was covered with spiral galvanised steel and at 75c tank temp we had barely warm tank sides. 

[newhome]

2 hours ago, PeterW said:

 

I would have agreed with you after seeing a couple of TS installs however after last weekend and seeing @newhome TS installation, once me and @Nickfromwales had lagged the pipework the losses were really a lot less - tank was covered with spiral galvanised steel and at 75c tank temp we had barely warm tank sides. 

 

At least there was a tiny little bit of positive amongst all the crap bits then . 

[PeterW]

4 minutes ago, newhome said:

 

At least there was a tiny little bit of positive amongst all the crap bits then . 

 

Yeh it’s probably a 200 litre tank in a 400 litre shell.. 

[newhome]

1 minute ago, PeterW said:

 

Yeh it’s probably a 200 litre tank in a 400 litre shell.. 

 

If I can fill the bath up that still works for me . Half full not half empty .

 

 

[dpmiller]

7 hours ago, PeterW said:

 

Its exactly what it is ... it’s a roto moulded polypropylene inner tank with steel reinforcing around the immersion and pipe entries. Looks like they then insert it into a similar roto moulded outer and then inject foam for insulation. It’s open vented with a DHW coil for mains pressure hot water. 

 

Harlequin have been around for years - they do oil tanks and that sort of stuff but have got into things such as rainwater tanks and now looks like they are doing hot water too. 

Yup Harlequin are well known round these parts. I downloaded the MIs and have put a query in to Moira re using the extra coils for export.

 

It's open vented and filled by a manual filling loop to satisfy a little float level indicator. Excess would just leave by the overflow.

[dpmiller]

On 11/04/2018 at 17:31, dpmiller said:

Yup Harlequin are well known round these parts. I downloaded the MIs and have put a query in to Moira re using the extra coils for export.

 

It's open vented and filled by a manual filling loop to satisfy a little float level indicator. Excess would just leave by the overflow.

Had a call back from the local rep a few mins ago and they're having a butty morning at the local BMs tomorrow so I'll call over for a nosey.

 

But in the interim, it's an appealing product for sure. All the connections are at the top. Coils are 22mm 316SS, he'll confirm length/area/kW ASAP. Insulation is 60mm at the sides, 120mm at the top. Outer vessel PP, inner PE.

 

Current range is "core", 520mm square for normalish applications but will be expanded to a 780mm sq body of 400- 600l, with triple coil options.

 

Ballpark for a 250l twin coil is £850.

MIs attached for anyone that wants a look

f7990181-ffe2-4951-8d0d-d9c51a197d7a.pdf

[Nickfromwales]

31 minutes ago, dpmiller said:

Had a call back from the local rep a few mins ago and they're having a butty morning at the local BMs tomorrow so I'll call over for a nosey.

 

But in the interim, it's an appealing product for sure. All the connections are at the top. Coils are 22mm 316SS, he'll confirm length/area/kW ASAP. Insulation is 60mm at the sides, 120mm at the top. Outer vessel PP, inner PE.

 

Current range is "core", 520mm square for normalish applications but will be expanded to a 780mm sq body of 400- 600l, with triple coil options.

 

Ballpark for a 250l twin coil is £850.

MIs attached for anyone that wants a look

f7990181-ffe2-4951-8d0d-d9c51a197d7a.pdf

Price is V good. Can you find out how much forca fully loaded 600L please. ?  

Ta. 

[dpmiller]

Not yet available. I'll ask him for a timeframe tomorrow as a 400l triple would seem well-suited to us assuming you could pull about 6kW out for UFH. Looking at the recovery times (which are conservative apparently) the coils must be in the 25kw range?

[dpmiller]

A nice bacon and sausage bap courtesy of the chaps at HF and a bit of time looking at the HeatStream. It's a very neat unit. Rep had a 150l with him as it sits nicely in the car...

 

Images on the website aren't completely accurate, all the coils are convoluted SS, similar to TracPipe or the like, so great surface area. Full height coil for DHW, main indirect coil in the bottom third of the tank, and then the second and third coils are above it. Top immersion is long (23") so well into the body of water, and a doddle to replace if ever necessary.

 

No calcs yet on the characteristics of the coils, he'll revert with those. Expect the larger and triple coil units to arrive in Q4.

[vfrdave]

@dpmiller this had me interested but I would probably be looking for a larger unit so timescales wont suit me.  Optimistically I hope to be in the house Q4 

[oranjeboom]

Right, after some more reading I have come back with some more thoughts (and more questions...sorry @Nickfromwales!!).

 

Preference is for a simple setup, only because I am no plumber and have very little faith in the local talent pool to actually fit a system that will work as it should at its best efficiency!

 

With my water/house setup, I forgot to mention that the wife wants to be cooking with gas so we'll have gas with any set up then.

I'm not bothered about running 2 baths simultaneously (and not much hindrance IMHO to say they'll have to wait) and I also think that the running of 2 showers simultaneously is unlikely tbh. As long as any recharge requirement does not take 4hrs, but then if whatever cylinder is big enough that should not be an issue I guess? Mains pressure is good and if my tank is circa 300L I shouldn't have any issues with simultaneous shower/bath...I think.

As long as the boss can have her morning or evening bath plus showers running before/after. I'm also keen to install a more econmical bath (130l?) rather than a 250l+ swimming pool.

On the short cycling front, I'd have to play it careful and include a buffer in the setup. Found this thread from last year about boiler efficiencies - may be of use to others who stumble across my pondering over UVC vs TS.

 

Higher standing losses for a TS (over a UVC), but if the TS is in airing cupboard rather than the loft, that will help the situation in the heating months, but could be a problem in the summer months. So I do still have a question mark around that as I know Jeremy tried to do his best to improve on the crap heat TS loss figures he was achieving (and ultimately jumped onto the sunamp option.  Is there a real-life proven TS that actually performs as the published figures state?

 

So as I understand if I go with a TS, I would have to go for a larger size than a UVC or is it vice versa? But with a TS, that would also act as my buffer for my UFH and a UVC would need a buffer also.

So again, as I read it, I can either go for a:
- smaller TS and get a decent gas boiler to support it to match what is being demanded from it in terms of UFH and a simultaneous DHW demand
                  or

- larger TS to dump excess PV into it during the day (especially if I don't go for a Sunamp)

And I do like the sound of low losses, so am considering the Sunamp PV (waiting to hear back from them on costs etc). and have some questions here for the plumber:

On 10/04/2018 at 15:10, Nickfromwales said:

To add, if the combi / SA option was chosen, you could go for a 12kw SA or a pair of 9kw ( so 18kw total ) and offset some of the space heating too. 6 hours of sunshine would charge that lot up and provide a LOT of storage. The gas boiler would then become a standby device for a good 60% of the year. 

 

How much would that setup cost? So a SA PV (5Kw) unit is circa £1700 IIRC so is it fair to say 18Kw worth of Sunamp magic is going to cost circa £7k plus the ' good high flow storage combi' cost [insert bargain figure here] will probably leave me with little left over to actually pay for shower and baths units! Very little demand for gas however (only need would be for cooking in the summer).

 

BTW what is the cost of an annual service for a UVC? As low as £50? http://www.cardiffplumbingservices.co.uk/cylinder-servicing/ Presume that's not you Nick?

 

Not sure if I am at all any clearer on my options. Too many darn options these days! I should have been living back in the stone ages("BIG FIRE or smal fire darling"?)

[Nickfromwales]

5 hours ago, oranjeboom said:

How much would that setup cost? So a SA PV (5Kw) unit is circa £1700 IIRC so is it fair to say 18Kw worth of Sunamp magic is going to cost circa £7k plus the ' good high flow storage combi' cost [insert bargain figure here] will probably leave me with little left over to actually pay for shower and baths units! Very little demand for gas however (only need would be for cooking in the summer).

Not approx, but circa £4k + ( reclaimable ) VAT iirc. 

Ill add more tomorrow.

[oranjeboom]

7 hours ago, Nickfromwales said:

Not approx, but circa £4k + ( reclaimable ) VAT iirc. 

Ill add more tomorrow.

£4k for 18Kw? Reclaimable as in new-build or some other way? thanks in advance for the feedback. 

[Nickfromwales]

14 hours ago, oranjeboom said:

Presume that's not you Nick?

No, Swansea me!

14 hours ago, oranjeboom said:

On the short cycling front, I'd have to play it careful and include a buffer in the setup. 

Yes, in whatever guise that takes. 

14 hours ago, oranjeboom said:

Higher standing losses for a TS (over a UVC), but if the TS is in airing cupboard rather than the loft, that will help the situation in the heating months, but could be a problem in the summer months. So I do still have a question mark around that as I know Jeremy tried to do his best to improve on the crap heat TS loss figures he was achieving (and ultimately jumped onto the sunamp option.

As you have PV you must remember that either cylinder may routinely max out at the immersion set temp, eg 60-65oC for an UVC or 75-80oC for a TS, so would be a heat loss issue either way.

"Higher standing losses over an UVC"? Not necessarily, if you consider you have a bunch of additional connective pipework between the heat source and the boiler buffer tank, plus the additional surface area of the buffer. That lot on top of the UVC would equal that of a TS imo, but you'd only suffer THOSE particular losses during the months that the heating is required, and when not required that peripheral tank and pipework fall dormant. Then your just back to the losses of the UVC, so remember that the heating losses of the peripherals with that setup would be advantageous, eg go towards your heating needs, and the tanks could be placed strategically to make the best use of that, eg UVC in the airing cupboard and the buffer in the cupboard under the stairs with the UFH manifold  

 

@JSHarris's TS was a different beast. That TS was an open-pipe aka gravity 'combination store' which has a feed and expansion tank ( cistern ) at the top of it which is open to atmosphere ( bar a plastic lid to stop excessive dust ingress etc ). When fully heated you can literally remove the lid and swish your hand around in warm water. Jeremy primarily chose that as it made 100% sure he dodged any certification schemes or annual 3rd party maintenance plus no D1 / D2 discharge, but it still required an overflow from the cistern. The combination tanks have much more latent losses than a sealed and pressurised equivalent tank as they ( the equivalent ) are not open to atmosphere and don't suffer steam evaporation / associated convected losses at all.

NOTE : ANY SYSTEM WILL STILL NEED TO BE INSPECTED REGULARLY, FOR SAFE RELIABLE OPERATION.

 

With, for eg, a gas install but no G3, you could simply ask your annual gas service agent to encompass the basic additional system checks within a slightly elevated gas service / inspection fee perhaps, or you can inspect it yourself. They should be on board with that as they will likely be the ones who carried out the install . If DIY is favoured, eg no gas, get your system installer to put a couple of additional pressure / temp gauges in key locations so you can just monitor the important ones, PRedV still correctly operating being one, at a glance. All you need then is a clipboard to remind you what to check and to record your findings. Simples. 

 

14 hours ago, oranjeboom said:

Mains pressure is good

 

14 hours ago, oranjeboom said:

I also think that the running of 2 showers simultaneously is unlikely

 

14 hours ago, oranjeboom said:

I'm also keen to install a more econmical bath (130l?) rather than a 250l+ swimming pool.

All pointers that you could happily cope with an UVC and gas can recharge it quickly enough TBH. Id only recommend the TS if your DHW remit was more 'aggressive'. Size is important, so with you having PV to fortify DHW / offset losses id go for a 300-350L UVC. When thats satisfied id set a PV diverter to dump excess into the buffer via a second immersion so any excess gains in the heating seasons goes into space heating. A buffer volume of 120L would be my recommendation, and remember you can have that as a horizontal vessel on a cradle if it helps to tuck it in somewhere.

 

I'd only revert to a TS here if you simply don't have the space for two cylinders, but you should also be aware that a TS will ultimately have around the same, or possibly less, losses as the UVC + buffer option so don't get hung up over that. Bear in mind that those losses are only problematic if they exceed the fabric / ventilation heat loss of the space that they reside in  Other than that, they'll go towards your heating requirements / clothes airing needs. Just consider the satisfaction of sliding on your favourite pair of brown and cream Y-fronts when they're toasty warm........

 

14 hours ago, oranjeboom said:

Very little demand for gas however (only need would be for cooking in the summer).

Dont you eat in the winter? People from Kent are very strange.......  

 

Go LPG for cooking and fit an ASHP? PV will boost DHW and offset the juice the HP uses. Bet you wish I hadn't just said that eh ? 

[oranjeboom]

On 21/04/2018 at 09:23, Nickfromwales said:

On 20/04/2018 at 18:32, oranjeboom said:

Presume that's not you Nick?

No, Swansea me!

Next time I;m there visiting the MIL in Clydach I'll drop you round a case of delicious Fosters*

 

* or Afghan/Crafy Devil/Cwtch!

 

On 21/04/2018 at 09:23, Nickfromwales said:

Higher standing losses over an UVC"? Not necessarily, if you consider you have a bunch of additional connective pipework between the heat source and the boiler buffer tank, plus the additional surface area of the buffer. That lot on top of the UVC would equal that of a TS imo, but you'd only suffer THOSE particular losses during the months that the heating is required, and when not required that peripheral tank and pipework fall dormant. Then your just back to the losses of the UVC

Okay, ready for the stupid questions:

1) So in the 'summer' months (fingers crossed) I rely pretty much on the PV panels to heat up the UVC, any further goes back to the grid (or a Sunamp if I can afford it)?

2) On those days when summer fails, the boiler kicks in to boost the UVC (rather than the immersion and drawing leccy from the grid)?

On 21/04/2018 at 09:23, Nickfromwales said:

and the tanks could be placed strategically to make the best use of that

Yes, I had planned to have the UVC in the cold loft, but it makes sense to place somewhere in the heated envelope. heat loss vs loss of heated space! Will only have an open staircase so can't place anything under there, no matter how impressive I make it look (already had difficulty persuading the wife on an exposed internal brick wall, so I don't think a copper spaghetti display is going to go ahead).  Just need to find some dimensions then on the cylinder and buffer tanks and see what cupboards I am going to hide them in.

 

On 21/04/2018 at 09:23, Nickfromwales said:

All you need then is a clipboard

Probably the cheapest item in this plumbing set up, one that I won't be  needing your advice on you'll be glad to hear. 

 

On 21/04/2018 at 09:23, Nickfromwales said:

Just consider the satisfaction of sliding on your favourite pair of brown and cream Y-fronts when they're toasty warm........

And then to prance around in them in a nice warm house. Neighbours are going to love that!

 

On 21/04/2018 at 09:23, Nickfromwales said:

On 20/04/2018 at 18:32, oranjeboom said:

Very little demand for gas however (only need would be for cooking in the summer).

Dont you eat in the winter? People from Kent are very strange.......  

Just living off the fat from Xmas and Easter....

 

On 21/04/2018 at 09:23, Nickfromwales said:

Go LPG for cooking and fit an ASHP? PV will boost DHW and offset the juice the HP uses. Bet you wish I hadn't just said that eh ? 

Ahhhh shuddup!

 

I was pondering this very thing last night, even asked the boss again "are you sure you want to cook with gas"? as I was hoping that electric cooker she used on holiday was a persuader, alas not. At the moment we probably go through only 6-7 47kg LPG bottles living in the static caravan per year (4 humans, 1 stray cat doesn't tend to shower) so was already wondering how much demand there would be on the boiler in summer for hot water. With a 350L UVC that should do me for a bath in the morning and some showers and then it's heated in the day again for evening demands. If that's accurate (and the sun serves us well over the summer period) I'd only need one LPG bottle in the summer for cooking. I'd love to tell the gas company where to go with their standing charges! Just need to try and work out how much the boiler would be used in the winter if there's minimal output from the PV.

Edited April 24, 2018 by oranjeboom
spellink mistayke

[newhome]

3 hours ago, Nickfromwales said:

 

Dont you eat in the winter? People from Kent are very strange.......  

 

 

Oy! That's a few of us on here you've just insulted! Nothing strange about @Onoff and I ! 

[Nickfromwales]

1 hour ago, newhome said:

 

Oy! That's a few of us on here you've just insulted! Nothing strange about @Onoff and I ! 

Internet bullying at its finest.