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Discuss Plumbing Problems – Hot Water Loop in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

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S

Star Cruiser

Rinnai rep has been and it seems their boilers are mainly for hot water only, not space heating needs. So gyms, hotels etc. He mentioned about speaking with his Technical dept to see if they could incorporate a heat exchanger plate to do my other bits - ufh, towel rails, etc. I think I can discount them.

ACV seemed to be a good outfit. Awaiting to receive further info on system recommendations. One thing that does concern me is only 40mm of insulation on their thermal store. Would much prefer 100mm to minimise heat losses.
 
G

Gray0689

Go for kingspan solar tubes
Varisol would be my recommendation for your set up as you can add on if you feel you want more in future
 
E

Ermintrude

The thicker the insulation isn't the rule of thumb. If you increase insulation by 60mm u increase the external surface area of the outside of the tank a lot. There is a defined relationship for pipe lagging and cylinder insulation, as the cost in increased insulation doesn't offset the heat retained. But ACV are very good. They don't do poor. If your really concerned about heat losses build the thermal store into a compartment insulated well with celotex or.****** Move cylinder into house then any list heat will simply be heating and keep airing cupboard warm. Pipes will loose more heat than cylinder, kingspan kooltherm will stop that tho.
 
G

Gray0689

Agree with above
And acv you really can't go wrong there the best imho
 
Messages
192
Seems that nobody has anything good to say about Hot Water Loops.

I live in a converted schoolhouse in France. The challenge I gave the plumber is that I do not like running cold water to waste while waiting for hot water to arrive at any of the hot taps in the bathroom or shower room!

The boiler room was at one end of the house so he installed a hot water loop in the ceiling of the old schoolroom (which was going to be our sitting/dining room). Fortunately there was plenty of space for the loop because we would be lowering the ceiling to a better height for a home rather than a high ceiling schoolroom.

He installed a Grundfos COMFORT pump which is specifically designed for recirculating domestic hot water in pressurised systems. This is low wattage and pumps the water around the (well insulated) loop at preset times.

I turn the shower on and get almost instant hot water. Result!

Well worth thinking about if you are having long hot water runs and can install at an early stage.

Good luck with your project. Sounds exciting.
 
G

Gray0689

Seems that nobody has anything good to say about Hot Water Loops.

I live in a converted schoolhouse in France. The challenge I gave the plumber is that I do not like running cold water to waste while waiting for hot water to arrive at any of the hot taps in the bathroom or shower room!

The boiler room was at one end of the house so he installed a hot water loop in the ceiling of the old schoolroom (which was going to be our sitting/dining room). Fortunately there was plenty of space for the loop because we would be lowering the ceiling to a better height for a home rather than a high ceiling schoolroom.

He installed a Grundfos COMFORT pump which is specifically designed for recirculating domestic hot water in pressurised systems. This is low wattage and pumps the water around the (well insulated) loop at preset times.

I turn the shower on and get almost instant hot water. Result!

Well worth thinking about if you are having long hot water runs and can install at an early stage.

Good luck with your project. Sounds exciting.

Secondary returns are great in correct situation and used correctly
But very inefficient if fitted / used incorrectly
 

Worcester

Plumber
Messages
1,005
@Star Cruiser, let us know the feed back from ACV when you get it.

Your general spec looks a good one. We are seeing more and more larger properties run hot water circulation loops on thermal stores - it's a standard spec for large property new build or re-furbs. so it's not unusual. Tee off should be kept as shorter as possible, else the purpose is lost (they just become dead / stagnant ends even possibility of legionella..) make sure both the flows and returns are well insulated, else it becomes a secondary heating system :)

Properly sized thermal store should cope no problems, and they can be vented or unvented.

Your Solar thermal may be a bit undersized, if you've got the roof space you could consider going for the 30x58.

ImmerSun units are excellent - go for two x 3kW immersions, one high and one low and use the change over relay in the ImmerSun for when the top is hot (we recently did a 2500 ltre unvented thermal store with 3 ImmerSuns and 18kW of immersions :) )

Your hot water is then supplied either by a built in coil in the thermal store, or it can be done by an external plate heat exchanger (there are lots of advantages of that approach).

Make sure you've got plenty of connections to put heat into the thermal store - natural gas is a cheap way to heat, you may wish later on to add in say a wood burning back boiler stove or an air source or ground source heat pump. It doesn't cost a lot now to add in extra connections / coils and gives you options later.

Remember that as a self builder, you'll qualify for the RHI on certain elements as well :)

Sizing thermal stores is a complicated business!

To be done properly it needs to be based on full heat load and demand calcs (heating and hot water - it's not just how much, it's also when)- whoever has done the ufhs design should have full room by room power and energy requirements, - that will give you your peak power needed from the 'boiler' and thermal store - stores are often used to meet a very short term peak demand that can't be met by a heat pump - you can get 12 kW peak out of a 10kW heat pump with the right sized thermal store - it just depends how long you need that 12kW for :)

Make sure the boiler controls are suitable for interlocking with the solar thermal - you'll want to give that a chance to do some good before the boiler tries to over power it! Also make sure you've got weather compensation controls on the heating system as well as properly designed ufhs controls, a properly designed thermal store system will also help to ensure that the condensing gas boiler also actually condenses.

There are a few good people up in your neck of the woods that I know that would be interested in quoting for you - drop me a pm if interested.

Looks like a good starting spec, - Have Fun!

You've got the details for ACV, so here's another :: AKVA SOLAR

Couple of images attached illustrating sizing thermal stores:
ThermalStoreSize_01.jpgThermalStoreSize_02.jpg
 
S

Star Cruiser

Go for kingspan solar tubes
Varisol would be my recommendation for your set up as you can add on if you feel you want more in future

I already have the Navitron 2 x 10, 70mm Manifold fitted on my roof. Just need plumbed in (hard part!).
 
S

Star Cruiser

The thicker the insulation isn't the rule of thumb. If you increase insulation by 60mm u increase the external surface area of the outside of the tank a lot. There is a defined relationship for pipe lagging and cylinder insulation, as the cost in increased insulation doesn't offset the heat retained. But ACV are very good. They don't do poor. If your really concerned about heat losses build the thermal store into a compartment insulated well with celotex or.****** Move cylinder into house then any list heat will simply be heating and keep airing cupboard warm. Pipes will loose more heat than cylinder, kingspan kooltherm will stop that tho.

My understanding is the more insulation the better, but I understand the law of diminishing returns will be reached at a point. ACV Rep mentioned something like 4 degree tank loss over 12 hours, which seemed pretty wasteful to me. I will try and clarify with them.

I have a cupboard in the house which the tank would probably go in. ACV reckoned it would be difficult to plumb though due to all the associated Pipework. It might be an option though with the right plumber!
 
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Howsie

Plumber
Messages
5,232
Looks OK to me and you can have a secondary return on a thermal store.

Here's a pic of one, bit of a maze but you get your head around them in the end.

IMG_9289.jpg
 
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E

Ermintrude

4c yeh that's horrific. A traditional cylinder with a red jacket would only drop 50c in 12 seconds!
 
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