Design Help - Plumber not helping

[DeeJunFan]

2 minutes ago, joe90 said:

I am following this thread (as best I can) because some of my situation is the same, I.e. ASHP but no PV. From previous threads I came to the decision to use an UVC DHW cylinder ( very well insulated) at a modest temperature because ( and correct me if I am wrong) this type of cylinder can give almost the whole tank of hot water till it runs out but a thermal store will give cooler water as it is depleated therefore not consistent "hot" temp.

 

Yes, i'm with you.  From my limited knowledge that was my thinking.  I have also heard of people plumbing the ASHP directly into the UFH but i'm not 100% as to if thats a good idea or not.

[joe90]

I think you and I are in the same position, waiting for those that know to advise us !!!. I too am having a woodstove but not a back boiler as the house WILL overheat before any real heat is put into the water. Short, burst of feel good cave man flames followed by basking in the glow of embers. I wait with bated breath on the question of tanks, ?

[Nickfromwales]

Plumbing the ashp direct to the UFH is not the issue here. You can, and without issue, BUT you then have to consider the peripherals. 

If using the HP for DHW you'll possibly be into defrost cycles for a part of the year if not more, dependant upon your consumption / usage patterns etc. With a buffer you have a stored body of water that the HP can suck back for defrost 'assist' therefore leaving the UFH loop volume unaffected. 

Also, as @TerryE and @JSHarris have recently discussed in cross talk, the ashp may not be comfortable modulating that low plus it will then be very likely to short cycle. 

@DeeJunFan if you want a design then refer to my first which is ashp to both cylinders accordingly ( 38oC to buffer TS and 55oC to UVC respectively ). 

Pv divert to DHW only and 2 x 3 kw immersions in each cylinder so you can run both space heating and DHW in the event of ashp failure in some reasonable capacity. 

Sizing of cylinders is down to space and intended consumption, which is largely to do with DHW, so perhaps elaborate on that a bit more first . 

[DeeJunFan]

Thanks @Nickfromwales

 

I'll have a look through the ASHP docs and see what the options are for DHW.  I will attach the Manual because i have no idea what i'm looking at.  

 

Hopefully the controller supports the 2 different temp outputs.  @PeterW you have the same unit?  Can it be switched?  I know they were selling some different options?  Did you get a manual you could share with me?

 

The vast majority if not all of our DHW usage will be after 7pm in the evening.  Potentially earlier in the evening once kids are doing sports etc.  The very rare occasion would we have showers in the morning.   Only showers for 2 adults at the moment and bath for 2 kids maybe 3 times per week.  And its only half full but they will grow so 4 showers per day.  Will have a manual boost for the immersion if we are going to have visitors.

eBay_Ecolane_Manual_(1).pdf

Edited March 22, 2017 by DeeJunFan
add manual

[Nickfromwales]

With a cyl stat mounted low on the UVC and the ashp heating it on demand you really should never struggle for DHW. Both tanks will have to be depleted before immersions are considered, so if you went for 300L a piece on the cylinders you should be fine. 

@joe90, the sizing would be different for you as you don't have / intend to ever have pv? 

[Declan52]

I did have a lot of heat loss from my spaghetti junction pipe work at the start as my plumbers where happy with the fact my hotpress would be the warmest room in the house. If i had made it 1m wider growing some medicinal plants would have been a very real option.

Took me a lot of time and effort wrapping the pipe work up in various different materials to try and get the heat loss down. I also tried various different temps to store the water and the sweet spot for me was 65 degrees. 

If i had to do it again i think i would definitely go for a split system as sometimes if i have 2/3 rooms calling for heat it doesn't be long emptying the tank leaving you having a lukewarm at best shower.

[le-cerveau]

This is a re-badged Mitsubishi Ecodan, and it looks like you have the bare ASHP with no controls.  To provide the full heating/DHW control you will need a controller, probably the option that was on the website but not available.  just get the Mitsubishi one FTC5, install manual here Ecodan_FTC5_-_PAC-IF062B-E__PAC-SIF051B-E_Installation__Operation_Manual.pdf, to get full control and do what you want.  I suspect it will be a few hundred quid!

[PeterW]

39 minutes ago, DeeJunFan said:

Thanks @Nickfromwales

 

I'll have a look through the ASHP docs and see what the options are for DHW.  I will attach the Manual because i have no idea what i'm looking at.  

 

Hopefully the controller supports the 2 different temp outputs.  @PeterW you have the same unit?  Can it be switched?  I know they were selling some different options?  Did you get a manual you could share with me?

 

The vast majority if not all of our DHW usage will be after 7pm in the evening.  Potentially earlier in the evening once kids are doing sports etc.  The very rare occasion would we have showers in the morning.   Only showers for 2 adults at the moment and bath for 2 kids maybe 3 times per week.  And its only half full but they will grow so 4 showers per day.  Will have a manual boost for the immersion if we are going to have visitors.

eBay_Ecolane_Manual_(1).pdf

 

 

OK thats the puppy I have...

 

If you look at appendix D.2 its a W-Plan they are using BUT there are a number of issues with it how they have it configured

1. The Hot water and UFH feed have to be the same temperature (ie 45c) which does nothing for your COP and is too high for direct UFH Connection
2. If you go direct UFH then there is no circulation pump so you are reliant on the ASHP pump circulating the floor and that will get cut off the moment the cylinder stat drops below the set temperature.
3. The W plan wiring doesn't allow for heating when the DHW is off at the controller so you need to modify the wiring slightly to put power to the off terminal and enable the diverter when the DHW controller is off.
4. Without a buffer tank, the ASHP will short cycle so will be innefficient and potentially cause other issues.

To do all of this isn't complicated but it needs the use of a couple of pipe stats, a changeover valve and a relay.

 

So you need 2 of these - one set to the DHW temp (47c) and one to the UFH temp (32c) Immersion Thermostat

 

And one of these - must be the CR5-02 Version - 3 Way Valve

 

And a standard 220v change over relay DPDT Relay

 

Those valves have the benefit they don't burn out synchro motors, and they can drive the changeover relay. Wire the stats to the output pins (pairs) on the relay, with the input pins to the control box terminals marked as "thermostat". Wire the coil to the WH/YE circuit on the valve head so that when the valve opens to connect the ASHP to the buffer tank/UFH then it connects the relay and switches the pipe stats from the "DHW" temp to the "UFH" temp.

 

The DHW "Off" position on the time clock needs linking to the Heating "On" in the W-Plan so that in the event you don't want a permanent hot water cycle then the valve will drive the ASHP to heat the buffer. Both of the tank control stats are used to drive the pump on/off terminals on the ASHP control box.

 

Finally..... the room stat drives a zone valve between the buffer return and the manifold so it only has access to heat when the stat allows the valve to open. 

 

I've got this drawn up somewhere but need to find it !

 

 

[DeeJunFan]

Great stuff, thanks for that.

 

Yes if you could find drawing that would be great.

 

Thanks

[Nickfromwales]

1 hour ago, PeterW said:

So you need 2 of these - one set to the DHW temp (47c) and one to the UFH temp (32c) Immersion Thermostat

Bugger. 

I needed one of those a while back for a TS with no stat pocket, but it had a spare return tapping that I could have bushed and inserted that into. 

I'll bookmark that site, cheers ? 

[DeeJunFan]

Just now, Nickfromwales said:

Bugger. 

I needed one of those a while back for a TS with no stat pocket, but it had a spare return tapping that I could have bushed and inserted that into. 

I'll bookmark that site, cheers ? 

 

I put this through google translate but it had less of a clue than i do.

 

 

[PeterW]

2 minutes ago, Nickfromwales said:

Bugger. 

I needed one of those a while back for a TS with no stat pocket, but it had a spare return tapping that I could have bushed and inserted that into. 

I'll bookmark that site, cheers ? 

 

They used to do a stem version too with the pocket included but seem to be out of stock. 

[Nickfromwales]

Lol. 

A TS can come with dry pockets cut into the side, basically a metal tube capped at the water side, and the torpedo of the stat just slides into that for referencing the cylinder temp. 

I ordered a TS assuming the manufacturer would have provisioned for the cyl stat. They didn't. My fault. 

One of the spare flow and return trappings would have accommodated that unit and saved me a mountain of grief. 

Type that in ?

[DeeJunFan]

Hoorah, i understood that bit.

 

So i'll outline by Primary school understanding of what i need to do.

 

2 tank system piped using W plan.

UFH tank will be a 300L buffer tank.  calling for heat based on room stats with tank sitting at 32-38 degrees (No need for TS as no need for pre-heat coil) This will have dual 3Kw immersions as backup for ASHP outage.

DHW tank 300L UVC pre-heat with ASHP to 45-55 degrees (CoP dependant??) with Immersion fed from PV and direct electricity.

 

I'm only going to have 2 stats in the house.  1 downstairs and 1 upstairs.  1 stat per manifold.

 

Does that sound about right?

 

D

[PeterW]

Not sure you need such a big buffer tank ..?! 400m of pipe is something like 52 litres so 3 times that at 35c would be fine I expect as you will have a fair bit of time when the DHW is up to temperature and not calling for heat.  

[PeterW]

And a 300 UVC taken to 45c on the ASHP and topped for the last hour with the immersions at low rate should last you a good chunk of the day

[Alexphd1]

We are planning a similar system to mentioned above. Ashp + pv (kw unkown)> 500l thermal store> UFH +  DHW. We also plan a 18kw log gasification boiler with another 750l thermal store with 4 solar thermal panels feeding this. The biomass/solar thermal store will have a DHW coil acting as a pre head for ashp cylinder also if biomass cylinder temp rises above ashp cylinder then a pump will automatically come on to transfer heat between the two tanks. I was thinking legionnaires risk could be minimised with DHW heated as needed via a coil rather than stagnant water in a hot water cylinder. I was looking at the stainless steel joule thermal store for the ashp, cheapest I found was in Poland ( kotly.pl.com) . If anybody has better prices, let me know.

Edited March 22, 2017 by Alexphd1

[Nickfromwales]

Iirc Telford manufacture for Joule so I'd try direct to Telford first via Trevor at Cylinders2go ( +44 7939 996940 ) and mention the forum and my username. 

 

19 hours ago, PeterW said:

Not sure you need such a big buffer tank ..?! 400m of pipe is something like 52 litres so 3 times that at 35c would be fine I expect as you will have a fair bit of time when the DHW is up to temperature and not calling for heat.  

 

I've gone for the larger TS as it'll negate drawing excess electric from the grid to supplement / top up the UVC temp, with the PV offsetting losses and hopefully giving that essential daily nudge towards 60+oC. That's best perpetuated by not removing too much heat from the UVC in any 24hr period by using low grade heat from the ashp to reinforce the DHW delivery with max CoP. I have not accounted for the UFH loops, but TBH I'd rather see the UVC dropped to 250ltrs before I saw the TS size reduced as heat transfer 'en-mass' from the HP is best derived from not using a cylinder coil to transmit the heat but by heating a larger body of water directly ( so via flow and return tappings on the TS body ).

I guess that a 200L TS may suffice, but my worry is about the low grade heat being sapped quicker than the ashp can replenish it. The whole basis of my 'design' is around producing lots of DHW via the ashp at low CoP, rather than supporting it with electricity, with the pv powering the HP and excess going to the UVC. 

[DeeJunFan]

1 hour ago, Nickfromwales said:

Iirc Telford manufacture for Joule so I'd try direct to Telford first via Trevor at Cylinders2go ( +44 7939 996940 ) and mention the forum and my username. 

 

 

I've gone for the larger TS as it'll negate drawing excess electric from the grid to supplement / top up the UVC temp, with the PV offsetting losses and hopefully giving that essential daily nudge towards 60+oC. That's best perpetuated by not removing too much heat from the UVC in any 24hr period by using low grade heat from the ashp to reinforce the DHW delivery with max CoP. I have not accounted for the UFH loops, but TBH I'd rather see the UVC dropped to 250ltrs before I saw the TS size reduced as heat transfer 'en-mass' from the HP is best derived from not using a cylinder coil to transmit the heat but by heating a larger body of water directly ( so via flow and return tappings on the TS body ).

I guess that a 200L TS may suffice, but my worry is about the low grade heat being sapped quicker than the ashp can replenish it. The whole basis of my 'design' is around producing lots of DHW via the ashp at low CoP, rather than supporting it with electricity, with the pv powering the HP and excess going to the UVC. 

 

OK, so the terms buffer tank and TS are interchangeable in this situation?

 

I'm all for keeping it simple so these plans are sounding good.  

 

Thanks for all the help @Nickfromwales and @PeterW

 

Still waiting for the plumber number 2 proposal so i'll stick it up here when i get it.

 

Thanks

D

[Nickfromwales]

A buffer is just a dumb vessel with a coil / tappings, but when you upsize it, add things like a DHW coil and start 'multitasking' with it you'd then refer to it as a TS.  

( imo  ). 

 

[DeeJunFan]

are you calling me a buffer tank?

[Nickfromwales]

4 hours ago, DeeJunFan said:

are you calling me a buffer tank?

You've been called worse, c'mon

[DeeJunFan]

Just now, Nickfromwales said:

You've been called worse, c'mon

I've been called worse this evening.

 

I'll give you a clue.

First word is something you play football with, second word is something your wife carries around with her.  And they are also dumb vessels!

 

[Declan52]

33 minutes ago, DeeJunFan said:

I've been called worse this evening.

 

I'll give you a clue.

First word is something you play football with, second word is something your wife carries around with her.  And they are also dumb vessels!

 

Head purse???

Hand rampant rabbit???

Foot perfume???

 

[DeeJunFan]

43 minutes ago, Declan52 said:

Head purse???

Hand rampant rabbit???

Foot perfume???

 

Were you there?

 

Edited March 23, 2017 by DeeJunFan