Thermal store nightmare

[Jjjk]

Sorry for a long post but we have a complicated thermal store situation

Over the summer we had a new solid fuel stovax back boiler installed and upgraded our hot water storage tank to a thermal store.

We have not had reliable hot water since. Initially we only used the emersion and after couple of hours we could run a shallow bath.

Now we can run a bath when the fire is on but even the morning after the fire has been on we can only get a small amount of water. If left to run more than a couple of mins the water soon cools down. If left we can then get another bout of hot water 2p mins or so later.

The engineer is completely stumped. We have replaced the mixer, the tank has been tested and is up to temperature. We have insulated all the pipes to ensure minimal heat loss.

The engineer thinks that perhaps the mixer valve is again faulty but the hot water pipe leaving the tank before the mixer does not feel overly warm.

I'm pretty convinced there must be a fault with the copper heat exchange coil. Maybe small holes with water leaking out or some reason for inefficient heat exchange. The engineer seems confident this isn't the case as we get good hot water when the fire is on.

In summary low volume and short bursts of demands on the store does not seem to be a problem (ie when the water has been sat in the coil for a length of time) but any higher volume demand, the water is soon cold. The tank itself seems to cool pretty quickly too.

It's gone on so long I'm thinking about getting rid of the thermal store and reinstalling the header tank to go back to a conventional system

 

[SimonG]

Is it only the stove feeding the thermal store, if so I wouldn't have gone with a thermal store.
But then I'm not a big fan of thermal stores.

Has it been installed correctly?

Any pics of the install?

 

[Jjjk]

It is just the stove and an emersion heater.
The install I think is ok. There are preexisting 15mm pipes under the bathroom floor from the fire to the store (just a short stretch otherwise its 30mm throughout) the thermal store does seem to heat up quickly and gets very hot so we had ruled this out as a possibility.

 

[centralheatking]

Sorry for a long post but we have a complicated thermal store situation

Over the summer we had a new solid fuel stovax back boiler installed and upgraded our hot water storage tank to a thermal store.

We have not had reliable hot water since. Initially we only used the emersion and after couple of hours we could run a shallow bath.

Now we can run a bath when the fire is on but even the morning after the fire has been on we can only get a small amount of water. If left to run more than a couple of mins the water soon cools down. If left we can then get another bout of hot water 2p mins or so later.

The engineer is completely stumped. We have replaced the mixer, the tank has been tested and is up to temperature. We have insulated all the pipes to ensure minimal heat loss.

The engineer thinks that perhaps the mixer valve is again faulty but the hot water pipe leaving the tank before the mixer does not feel overly warm.

I'm pretty convinced there must be a fault with the copper heat exchange coil. Maybe small holes with water leaking out or some reason for inefficient heat exchange. The engineer seems confident this isn't the case as we get good hot water when the fire is on.

In summary low volume and short bursts of demands on the store does not seem to be a problem (ie when the water has been sat in the coil for a length of time) but any higher volume demand, the water is soon cold. The tank itself seems to cool pretty quickly too.

It's gone on so long I'm thinking about getting rid of the thermal store and reinstalling the header tank to go back to a conventional system

In order to get the correct info. you will need to explain a few things
1. which Stovax by model
2. Which thermal store
3. maybe a diagram of what it was ...and how it is now.
I like conventional systems but others on PF will have their views, especially as you have already forked out ....let us know...loads of collective knowlege on PF ...Centralheatking

 

[snowhead]

As above, plus how long is the Stovax back boiler fire up, what fuel and what level of burn
e.g a couple logs cracking for a few hours or coal blazing away all day and evening long.

When the tank temperature was tested how was that done, just observing a guage at the top or ?

Who recommended the Thermal store, who designed the system?

 

[Jjjk]

Thank you so much for your help. I'm not sure on the name of the thermal store, I am getting that info as we speak. It has a copper coil that much I do know. It is a stovax 8hb we burn coal and wood.
I've attached my understanding of the system. (Not an artist, and I hope it is the info you need)
[automerge]1578843639[/automerge]

As above, plus how long is the Stovax back boiler fire up, what fuel and what level of burn
e.g a couple logs cracking for a few hours or coal blazing away all day and evening long.

When the tank temperature was tested how was that done, just observing a guage at the top or ?

Who recommended the Thermal store, who designed the system?

We mainly have coal blazing from about 5 until we go to bed about 11 and top it up before we go upstairs. We occasionally add a couple of logs if we have it burning longer on a cold day.
I'm not sure how he tested the temperature but there is no inbuilt temperature gauge. The system was in place when we moved in and we have just replaced the stove out of necessity and was recommended the thermal store by the heating engineer (heatas registered)
[automerge]1578848875[/automerge]
Also we have had the emersion and the fire on for several evenings in succession and the emersion turns off as it is up to temperature. Still the water is not hot in the morning

 

[Brambles]

For a Stovax HB, the only inputs you as a user can have to increase Hot Water Temperature / volume is the fuel (not enough or wrong type) and air control settings. Anything else is a design / sizing / installation issue - so I would get the installer back.

Most of the Stovax range ( other than the 14kw models) need to have the fire to be fully stacked most of the time to achieve the stated outputs. As the fire burns down, the contact area with the back boiler reduces - along with the output.

If you have any doubts about the fuel, run it for a week on anthracite - keeping it fully loaded - you won’t get an output any better than that.