I would be concerned about the residual heat in the pellet boiler in the event of a power cut. Read the installation instructions of the pellet boiler to see if any gravity flow is required to cater for residual heat, if yes then no NRV. And also ask the manufactures of their opinion.

I agree with you that a normally closed valve would be no better than a NRV (or even worse as electrically operated valves go wrong or stick more frequently than NRVs)

How is the circulating pump controlled now? And what causes the boiler to fire up?

How much gravity circulation are you getting now? The thing about gravity circulation is that there needs to be a heat loss or lower temperature above the heat source. When the TS is up to temp. then (providing the pipes are insulated) you should only get gravity circulation whilst the boiler temp. is higher than the TS temp. when the boiler temp. drops (e.g. due to the gravity circulation) I would expect the circulation to stop.

Is the boiler next to the TS and both within the heated envelope?

If the pipes to and fro the TS are well insulated I would expect them to stay hot for a good while. If they cool down eventually in advance of the TS cooling then You don't have much (any) gravity circulation.

How does the TS call for heat from the boiler? From your description it sounds like that the boiler will switch off when the DHW is up to temp.

What I would expect is that both the DHW tank and the TS would have a thermostat switch that could call for heat from the boiler so that either can start the boiler. When the DHW calls for heat the same signal would operate the MV so that DHW would have priority over the CH. I would expect the DHW thermostat to turn off the boiler and the MV leaving the TS thermostat to call for heat if needed. The pump should be operated by either the of the DHW thermostat or the TS thermostast calling for heat or perhaps an 'up to temperature' signal from the boiler (done to prevent the pump running if the boiler is out) (sorry about the alphabet spaghetti).

can't you just break into wire to the boiler's timeclock to get remote control?

If i understand your descrition in an earlier post, the system is set up to fire the boiler when the buffer/store has dropped to 60 degrees and shuts the boiler down when it reaches 75 degrees.
If this is correct and the buffer/ pipework (between boiler and buffer) is good, is there any great disadvantage to leaving the boiler switched on 24/7 (at least during the heating season). Effectively giving control via the central heating controls.
Notionally there may be a slight advantage in that, (again from my understanding) hot water usage may reduce the buffer temp between boiler/heating cycles.

It seems to me that the heating system is obviously incorrectly wired and/or plumbed. My first step would be to get full plumbing and wiring diagrams as designed, if you don't have them already, and compare them to the actual system to see whether they match. If not, find out why not. If they do match then ask the designer (who was that?) to explain how it is supposed to work, and specifically how it deals with the cases that have been discussed.

Was the promise of remote boiler control made in writing? What does the boiler manufacturer say about its non-delivery?

Posting the plumbing and wiring diagrams and the makes and models of the major components would be helpful.

Artiglio: It seems that this is the norm on the continent according to the boiler manufacturer (Ekopower) i.e. the boiler is on 24/7. I think this would be wasteful of pellets as our house is well insulated and we don’t need the heating on all day (and certainly not all night). During the heating season the boiler is programmed to come on for 3 hours in the morning (7-10am) and then again for 7 hours in the afternoon/evening (3 – 10pm).

Djh: the whole system is a problem indeed; unfortunately the full story is a long and boring one. If you can face it, here it is:

Originally there was just a thermal store with 3 coils, one for solar thermal input and the other two for other heat sources e.g. ASHP etc., together with an OPOP wood pellet boiler. This could be remotely started and was a very simple boiler with no frills (no fancy self cleaning features). There was no separate DHW tank. There was a weather compensator and a mixing valve, which blended the boiler flow and C/H return etc. We have an electrical diagram but not a drawing of the plumbing aspects. This combination did not work very well in that the thermal store being on the small side (300 litres) was not man enough to cope with C/H and producing DHW at the required temperature at the same time.

So we started to think about how we could incorporate a separate DHW tank. Unfortunately in the interim the company that designed and installed the original system had gone bust so we found another green energy company to modify the system for us. We then had a separate DHW tank installed upstairs and the pipework and some of the electrics were modified accordingly. We did not get a proper set of drawings for this, so we are not sure exactly what mods were made to the original system.

We then changed the boiler from the OPOP to the Ekopower as my wife was not amused at the idea of cleaning out the OPOP. The Ekopower is supposed to be self cleaning but this is a bit of a joke really – there is more to do with this boiler than there was with the OPOP! Part of the incentive to change was that we would qualify for RHI payments. (We bought the OPOP less than a year before the RHI cut off date – typical!).

We discovered that the entire heating system was set up as a direct system i.e. the water in the boiler, TS and C/H system was the same throughout and the two of the three TS coils were not used. I was getting a gassing problem in the C/H system so we decided to revamp the whole lot using one of the TS coils for boiler flow and the other for C/H. In this way each part of the system is separate and pressurised (no, more F&E tank) and can be dosed with inhibitor independently. The weather compensator has been disabled as well as the blending valve, so the plumbing is very simple now. However this has thrown up some additional issues as I have described in this thread!

There is still a mass of unidentified white cables running here, there, and everywhere and I will be checking these in due course and labelling appropriately. When this is all done I would then be in a position to do an electrical diagram and a plumbing diagram. This is something I need for my own sanity and for any new user in the event that I sell up and move and some point in the future. (No plans to do that but who knows what life can bring!).

P.S. Yes, the offer of the remote start upgrade is in writing. Maybe time to chase up the manufacturer and see where they are at with this.

Posted By: Peter_in_HungaryIt sounds to me as if the plumbing is OK in that when the boiler runs the TS heats up unless the DHW is calling for heat in which case the MV diverts the boiler output to the DHW.

Please reread the description of the plumbing more carefully. It isn't a standard setup.

That's why I asked to see the diagrams; the problems will be more obvious.

Posted By: Jeff BI will be checking these in due course

Yes, the complicated history makes it even more imperative to get an accurate picture of the hydraulic and electric circuits before starting to diagnose the system and propose improvements, IMHO. So I would say that 'due course' starts tomorrow!

DJH wrote: "Yes, the complicated history makes it even more imperative to get an accurate picture of the hydraulic and electric circuits before starting to diagnose the system and propose improvements, IMHO. So I would say that 'due course' starts tomorrow!"

DJH - I absolutely agree! Unfortunately my time is rather stretched otherwise I would love to get stuck into this. At the moment it's a case of just keeping the whole system going whilst ensuring that pellet consumption is kept at a reasonable level. When I do get my head around how the system works I'll do some diagrams and update the thread.

Thank you, and Peter, and others, for your helpful inputs.

Meanwhile, in the words of the famous Antarctic explorer....I may be gone for some time!

Artiglio - thanks for your response. I have got the equivalent of your scenario (2) here, in as much as the boiler seems to modulate down to 5.5kW and then "coasts" along for what appears to be an indeterminate time before switching off. I don't have any equivalent to your scenario (1) with my boiler. As you rightly say, once the boiler has turned off it takes quite a while to get back up to temperature and when it does come back on, it burns extra pellets as it does so. However I'm not convinced that this represents an insignificant percentage of annual consumption in my case since we modified the system. I'll need much more data though to be sure. I keep a daily record of the amount of pellets we use, and have done so since we had the boiler (3 years).

We live in a 4 bedroom detached dormer bungalow in a fairly elevated, windy location near the coast in west Wales. I have put in a lot of extra insulation including IWI upstairs. I have 15 radiators with a total rated output of 18 kWh. The max boiler output is 25kW and we use 3 tonnes pellets p.a.

I admit that whilst the pipework is well insulated, the TS has only a minimal layer of insulating foam applied by the manufacturer (approx 25 mm) so I have added two layers of the trifoil type insulation which has helped - the cloakroom where it is situated is no longer suffocatingly hot! Nevertheless the foil still feels quite warm on the surface, so maybe I could add a few more layers.

I could add a thermostat to the TS and use it to operate a motorised valve to stop the flow from the boiler when the TS is up to temperature. In this way the boiler temperature would increase and the boiler stat would turn off the boiler. However the installer has indicated that this should not be done for safety reasons (or at least I should not install a non-return valve for the same reason but which in my opinion would be the same as having an MV?)

Artiglio - wow, you must have doubled the diameter of the store with all that insulation!

I have done a little bit more investigation into heat losses since I started this thread. The loop I put in plus the NRV have completely stopped thermo-syphoning into the C/H side of the system. I haven’t done anything with the boiler flow/return side as yet (still confused about MV’s vs NRV’s) but I have noticed that both the flow and return pipes are cold by the morning yet the TS is still holding its temperature pretty well (although see below). From this I conclude that thermo-syphoning back to the boiler is not an issue after all.

I have been monitoring the TS and have found that it drops about 6C overnight (from 10pm to about 7am) which is not brilliant I realise. I am not surprised as despite the extra insulation the surface is very warm to the touch. I do not have the room to add much more insulation as the TS is in a cloakroom. The room is 1000mm wide and the TS is currently 600mm wide! I need space to get around it as all the connections are on the back of the store but I could add some more of the foil faced bubble wrap. [I like the cling film idea!]. The TS is of course indoors, so the “lost” heat is going into the house anyway, rather than to outside. Since I have balanced the radiators properly I notice that the two in the hallway are not coming on at all, as this area, immediately outside the cloakroom, must be being heated by the TS. If I put a duct though the cloakroom wall with a fan I could create a mini warm air system!

Our TS has an F&E tank built in on top and this will be the difficult part to insulate really well.

What is the temperature of the water in your TS? Our’s is at about 72C.

Jeff

P.S. we are near St.Davids, Pembs. You must be near Towyn, so probably similar weather conditions to us.

Evening Jeff

The store has certainly increased in size, ours is in a barn room above the boiler across the farmyard from the house, so any lost heat is totally wasted, hence the overkill. Heat losses in the colder months when it was first installed were horrendous. Still room for improvement but certainly hit the point of diminishing returns.
The peak store temp is 80 degrees, the boiler is fired up once the store temp drops to 60 degrees. There are occasions of short cycling when the store is asked for just a little heat and gets a slug of cold water from the main connecting it to the house, this causes the boiler to fire unnecessarily as once the store restratifies the temp is often in excess of 60, this could be dealt with by adding a delay to the boiler firing , but in winter with a high heat demand this could result in the store losing too much heat, so system is staying as is.
We opted for a low tech system/boiler under the rhi scheme , so can't expect wonders. House is certainly more comfortable and heating more efficient than the old lpg boilers.

Thermal stores don't get any water from the mains, except when they are filled. That's their whole point.

<blockquote><cite>Posted By: djh</cite><blockquote><cite>Posted By: Jeff B</cite>Our TS has an F&E tank built in on top and this will be the difficult part to insulate really well.</blockquote>
Why can't it just be wrapped along with the thermal store itself?

I'd be tempted to stuff the whole space around the thermal store with insulation (recycled plastic wool is my favourite) to stop airflow and accept that you'll have to pull it out to access the connections if required.</blockquote>

Sorry not very well explained. The circumference of the F&E tank is insulated with the alu foil covered shrinkwrap but I don't want to bury the F&E as I would like to be able to inspect the contents from time to time. It has a circular aluminium lid which I have covered with polystyrene but there is just a 10mm lip which is exposed - I can live with that.