A bit o/t. Stratification in Thermal Stores

[Stereo]

Same old story I have had to sort the controls and some mechanical work on two large commercial boilers. New industry over here. If you want some direction what to do next some more info would help. I have asked some questions yesterday if you look back. Also is your stove piped direct or indirect. I can do some calculations for you but I need the information to work with.

 

Thanks for your help.

 

What sort of room temperatures are you running and where do you control it

 

Each room has a underfloor circuit and a room stat going back to a manifold. Stats are set to 20 degrees. This is warm I know but we have another issue in that the house is a barn conversion and building control made us fully tank the whole place in Vandex which has caused a mould issue as the walls can no longer breathe. So we have to have windows open and crank the heating. This keeps it at bay, sort of. It's an issue we need to remedy room by room by removing the tanking and going back to lime plaster. Ongoing project. If we run the house any colder, we get black mould everywhere.

 

 

What is the HW output of your stove and as already said dry wood?

 

The W23 is rated at 2.35KW max I think but there have been suggestions that this is optimistic and depends on a fully stoked firebox with very dry wood. I have a farm and source hazel, syc, ash, oak and lots of dead standing elm. It's seasoned for a year outside, usually in billets and then logged and a year in the shed. It's bone dry so that shouldn't be an issue.

 

 

Store temperature?

 

As mentioned, the gas boiler keeps the store at no less than 50 degrees at the control stat height (about half way up), I guess cooler below this.

 

 

Sounds like you have the heating on at night?

 

Yes, the stats just call for heat when needed. I was told that with underfloor, it's better to keep the slab warm than let it go cold and boost in the morning. Also, we need a constant temp ref. mould as mentioned before.

 

Have you good insulation under the under floor heating

 

100mm insulation sheets with pipes fitted into this on a concrete slab then a screed on top of this. It works very, very well and I'm happy that this is up to spec.

 

Have you checked for leaks ie constant topping up of the system?

 

No leaks at all.

 

 

No overflow running hot water to waste?

 

Nope. We did have a couple years ago but was sorted and I can't honestly recall what was causing it. A faulty valve or something minor.

[Stereo]

Fair play. Sometimes I find myself chasing companies / people for small amounts of money - where the principle is worth more than the time / money involved. I just don't like them to get away with it - maybe they'll think twice next time... Or maybe I'm just a petty bastard!

 

There is that. But given the time that has passed, I think a solicitor would advise that I am wasting my time. There's not much really to hang it on, it's just all a bit rubbish.

[cornish wood burner]

Are you sure about 2.25kw? ie less than 3

If that is right then its very low and not enough for the conditions you describe.

Edited October 27, 2014 by cornish wood burner

[Stereo]

Yes, that's what it says. The store has solar connectors as well so we were thinking we would get a solar water roof panel for the summer and some help in the winter and the Esse would also add what it could. I'm now thinking that the Esse is pulling the whole system down by circulating cold water or something?

[cornish wood burner]

Certainly you need a control to keep the stove water temperature high. Can you read the store temperature at a few points, ie top middle bottom. I was after the max temperature your store gets up to. How many hours a day do you run your stove and after this what has the tank warmed up to.

When you run it next try and get an approximate weight of wood/hour consumed when on full chat.

[cornish wood burner]

Without going any further I am certain with a solid walled vented house you need much more heat than your esse can produce.

The size of your thermal store is too small even if you had the energy to heat it. Enough to buffer an automatically fed wood burner starting up but pathetic as a store. You are not producing heat through the night so the store needed to be big enough to meet your demand. Only really suitable for dhw.

Your esse's 2kw would be fine for dhw only. Your problem is the heating is draining the system and you are getting cold water back to the stove.causing a cold spot adjacent to the back boiler.This in turn as I

am sure Alycidon would agree is bad for burning. You know the remedy for this.

I see three choices for you.

1. Fit a bigger boiler to your esse if available or bigger esse W35 I believe. Not looked at the figures for this,but something to investigate. You still would need to run your stove 24/7 to make any impact on your heating.

2 Accept you are going to burn a lot of gas to run your heating

3 Install a small wood chip or pellet boiler to run your heating.

I have no info on this but others might be able to tell you if you would be eligible for RHI. Do you need to have a well insulated property to qualify?

[Stereo]

Yeah, I think I'll have to go the ladomatt route and just take any input that the esse can make as a bonus. It's lovely as a cooker when it's not being killed by the heating and warms our main living area. Quite easy on logs too and burns efficiently when it's running right.

 

I feel that the store we have was under-specced for what we need and I'm a bit hacked off about that. I guess we need to stick with the gas until we can afford to install solar water and maybe ground source heat.

[cornish wood burner]

Yeah, I think I'll have to go the ladomatt route and just take any input that the esse can make as a bonus. It's lovely as a cooker when it's not being killed by the heating and warms our main living area. Quite easy on logs too and burns efficiently when it's running right.

 

I feel that the store we have was under-specced for what we need and I'm a bit hacked off about that. I guess we need to stick with the gas until we can afford to install solar water and maybe ground source heat.

Bottom line is you need a lot more heat.

Have a look at the HDG Navora gasification wood boiler 20kw 150 Ltr capacity fire box so one loading would last a long time. Your installer should be able to check what size you need from your gas usage. Should make your gas boiler almost redundant. Not cheap at

8k ish but I imagine your gas bill is not peanuts either.

[openspaceman]

SAlso is your stove piped direct or indirect. I can do some calculations for you but I need the information to work with.

 

Cornish WB has pointed to many of your problems but this last bit is significant to your original query. If it is direct then the turbulence from the return from the underfloor injection manifold will kill any stratification whereas a coil in tank will not.

 

Also if the woodburner is feeding the top of the tank without back end protection (e.g. ladomat) then this can also de stratify.

 

We installed a back up 25kW(t) pellet burner in a block of 12 highly insulated flats with under floor heating. The main heat source was supposed to be solar thermal panels. In fact the fluid logic and program were so badly implemented the pellet burner was held on almost permanently. The unmetered heat meant people in the flats tended to control temperature by opening windows and the constant call from the underfloor circuit wrecked strafication and kept buffer <50C so the pumps fro the DHW heat exchangers were inhibited. As the pellet heated burned in the early morning to get the buffer temperature up and there was little demand because the workers were at work the solar never cut in as the top of the buffer was hotter than solar could supply.

[cornish wood burner]

Spaceman , The occupants in your block of flats sound just like our foreign workers. All rad stats to max and windows open.

If I was looking at the right one that thermal store appears to have direct tappings for a wood burner so not much chance of stratification with Stereo's setup.

Any thoughts /opinion on the Navora and domestic RHI.

2.35 kw is not going to be much use for maintaing 20 deg with windows open.