Plumbing Problems – Hot Water Loop

[Star Cruiser]

Hello UKPF. I'm a new member, in the process of trying to self-build a house. I hope I have come to right place for some good advice and help. I have a potential problem with my first fix plumbing hot water loop. I’ve since fell out with the plumber (long story) who undertook this and it looks to me that he maybe didn't know what he was doing in terms of my request for a hot water loop.

It’s not easy to describe, but here goes. Instead of plumbing a continuous loop to all the hot water points and then having a single return pipe, he has Teed off where needed with both a Hot Water Feed (22mm) and Hot Water Return pipe (15mm). Some of these Tees are a good few metres in length and I wonder if this method will work or not? I’m wondering if this will balance out ok?

I've drawn up a crude sketch of what I think is going on:

https://www.dropbox.com/s/mssw7i02msu0309/Photo 03-09-2013 10 46 24.jpg

I don’t want the original plumber back, so I need to confirm if this will work or not or whether I need to alter.

Thanks in advance for any advice or help.

 

[stevetheplumber]

you learn some thing every day i would have said it wasnt possible but seen like that its obvious

 

[Chalked]

hw return with a thermal store is possible, it's whether you need it.

Secondary Return Schematic

who makes a a heat exchanger like that? Interesting way to do it tho.

 

[chris watkins]

What you are proposing to install is IMHO over engineered for your requirements, you need to sit down with an experienced plumber who can run you through all the options. They will not be to enamoured if you ask them to start second fixing onto somebody else's 1st fix, they will charge you a premium for the aggro.
If of course you want to DIY then would strongly recommend you pay for pro advice there are still good people out there, it will be cheaper in the long run take our word on it.
Good Luck

 

[Ermintrude]

On page 6 of this document (under Installation) is a schematic which looks useful to my installation. (Apologies but I haven't got the software to cut and paste directly at the moment). I would obviously only need 1 boiler!

http://www.bssindustrial.co.uk/uploads/docs/666.pdf

BSS industrial? School, hospital, offices. You could generate steam and fit a few flash heaters if site is big enough .

What did you want the system to achieve ? - it's a straight up question write down what you want and what you would like, it's a design brief for fitter,helps a lot. You can evaluate financial and mechanical merits / pitfalls. ACV tech could help u once u have a brief.

 

[Star Cruiser]

What you are proposing to install is IMHO over engineered for your requirements, you need to sit down with an experienced plumber who can run you through all the options. They will not be to enamoured if you ask them to start second fixing onto somebody else's 1st fix, they will charge you a premium for the aggro.
If of course you want to DIY then would strongly recommend you pay for pro advice there are still good people out there, it will be cheaper in the long run take our word on it.
Good Luck

Chris, that's exactly my thinking re a plumber picking up a "botched" part first fix installation.... DIY is maybe an option, but I definitely need to find someone to help me on the design side. Any recommendations of where to start for that advice?

 

[Star Cruiser]

BSS industrial? School, hospital, offices. You could generate steam and fit a few flash heaters if site is big enough .

What did you want the system to achieve ? - it's a straight up question write down what you want and what you would like, it's a design brief for fitter,helps a lot. You can evaluate financial and mechanical merits / pitfalls. ACV tech could help u once u have a brief.

Thanks for your advice. The BSS industrial stuff is obviously a large installation. I thought it might be useful for my requirements albeit on a smaller scale?

I will write a bit of background and design requirements paper and I'll post later to see what people think.

 

[Star Cruiser]

I've drafted up this design brief. What have I missed off that will be needed?

Domestic Plumbing System:

Background
A timber frame, 3 storey, 5-6 bedroom house in the course of construction, currently at first fix stage. The house is located in the North East, near the North Pennines, high up at 300 metres (1,000 ft). It gets quite cold and windy and there are periods when the electric is out. The fabric will be well insulated, U-Value wise:

Walls 0.12 w/m2K
Roof 0.15
Ground Floor 0.12
Windows 1.4-1.7

SAP Assessment
A desktop SAP calculation has predicted:

Final SAP Rating of 89 (Band B)
Space Heating 21,568 kWh/year
Hot Water 2,677 kWh/year

It just misses out on Band A as it is marked down for having a MHRV system. If we didn’t install that and just fitted normal extractors, it would be Band A. That’s how stupid SAP is.

Heating
Water underfloor heating on the ground floor only within a flow screed and ceramic tile finish.

A whole house Mechanical Heat Recovery ventilation System (MHRV) has been fitted as part of the first fix – solid spiral ducted. This is a [DLMURL="http://www.allergyplus.co.uk/wp-content/uploads/2011/01/KWLC-650-Install.pdf"]Helios KWLC 650/WW[/DLMURL] with a water battery heater fitted. This will top-up the incoming supply air if the heat exchanger cannot fully heat.

Bathroom Towel Rails
These have been first fix plumbed in 15mm copper. These will provide the heat needed in the bathrooms to replace the air extraction side and also balance some heat around the rest of the house via the MHRV.

Hot Water Supply
Required to:

Ground Floor Kitchen, Utility and Cloakroom WC
First Floor Main Bathroom and En-suite
Second Floor Bathroom

Some of the runs are 15-20 metres, so thinking was to have a hot water loop to minimise draw off waste.

Solar Thermal and PV
2 x 10 Navitron 70mm solar thermal tubes fitted to south west roof @ 38 degree pitch. To be plumbed in.

4kW solar PV panels fitted to south west roof @ 38 degree pitch. Immersun unit to be fitted to divert excess generation to thermal store immersion.

Proposal
Natural gas is available, although not fitted as yet.

Thermal store (size tbc) to be installed in garage and to take solar inputs and feed all hot water needs. Gas boiler will top-up if needed, although it is hoped the store can feed most needs with 2-3 days of stored reserve to see us through the cold snaps or when solar feeds are poor.

Thermal Store Inputs:
1. Solar Thermal (2 x 10 Navitron 70mm tubes)
2. Excess Solar PV via electric Immersion.

Thermal Store Needs to Feed (via boiler booster if needed):
1. Hot Water Loop to all tap outlets.
2. MHRV Water Heater Battery.
3. Underfloor Heating System.
4. Bathroom Towel Rails

Gas Boiler
This will top-up the thermal store (if needed) and see us through cold periods. The Rinnai booster boilers, which only heat up water supplied via thermal store if needed, are of interest. Would prefer a tried and tested boiler if this can fit in with the system design.

 

[Ermintrude]

Pretty comprehensive pack. Send to ACV as they have good thermal stores , the will spec system for you.

 

[Star Cruiser]

Pretty comprehensive pack. Send to ACV as they have good thermal stores , the will spec system for you.

I have just spoken with ACV. They are getting my local rep to contact me and he will visit site and look over. Hopefully this is a good start as he's bound to know local Engineers who can help.

 

[Star Cruiser]

Very little feedback on my Design Brief? Please let me know if I have missed anything or if there are some good thermal store / boiler suppliers I can approach.

Ermintrude, thanks for your feedback and suggestion. I have a site meeting with ACV Rep next week.

 

[Ermintrude]

Very little feedback on my Design Brief? Please let me know if I have missed anything or if there are some good thermal store / boiler suppliers I can approach.

Ermintrude, thanks for your feedback and suggestion. I have a site meeting with ACV Rep next week.

Still don't like your idea of pumped DHW. Move cylinder into upstairs cupboard. Centrally located less dead legs.

Solar seems possibly abit small especially if u want ufh as well from thermal store??? Have u looked at ground heat pumps? Excess solar PV could work at 4:1 ? Better than immersion ??

Get a few mfrs out, see what u can learn. Just make sure u have a bowl (not pinch) of salt.

 

[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.

 

[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

 

[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.

 

[Gray0689]

Agree with above
And acv you really can't go wrong there the best imho

 

[Frelon]

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.

 

[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]

@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:

 

[AlanWright]

Ho****erRecirculationFinal - YouTube

http://www.youtube.com/watch?v=m4rioTu10AM

I have posted links to 2 Youtube videos.

The first is fully installed and working in a large food factory (March Foods - Nr Peterborough)

The Second was fitted in my own home (3 years ago)

The pump is the showerpowerbooster

 

[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!).

 

[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!

 

[Howsie]

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.

 

[Ermintrude]

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

 

[Star Cruiser]

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

i just want get a good level of system specification and hopefully, I'll have no regrets!

Maybe, I need to speak with an independent body:

http://www.greenspec.co.uk/files/energy/storesperformance.pdf

 

[Ermintrude]

Speak to other mfrs . They will make u weep. Some may claim 5c drop over 12 hours ( but that's the mean water temp at 45c and ambient at 21c. Heat transfer is driven by temp difference. The bigger the difference the more readily the heat transferred. That's why some (cheaper ) companies may show an apparent better performance. Radiators work in the opposite maker. (Cheap ones use bigger temp difference. )