Thermal Store problem

[turnerroy1]

I have been called to investigate the following system (installed 2 years ago). South East facing roof. NRG Solar vacuum tube collectors 2x20 tube panels SP-20-1800HT system pressure all o/k. Newark thermal store tripal coil. 1770x400 open vented combination. Open vented central heating boiler with gravity feed hot water not giving any output to tank coil. Navitron TD3 TDC. Output 1 to solar pump. Output 2 to single 11'' immersion at bottom of tank set to 60 degrees, on timer between 19.00- 20.00 Hrs. Customer reports lots of hot water enough to fill bath 1/4 full after which water goes cold. 1 bath attempted per day. 1st question, can anyone suggest optimum settings for S1 S2 and S3 on TDC please. Are the factory settings deemed to be optimal. I can visualise this being protracted so all suggestions will be gratfully recieved. Thank you. Roy Turner.

[JohnS]

I don't want to be to provactive and if I appear so, apologies, but why are you asking us before, it appears, you have even had a look.

What are you qualifactions or experience to have accepted the invitation to investigate.

If we know what you know or don't know, we can be better at giving suggestions. 

Are you a professional or a gifted amateuer/keen diyer or a well meaning friend?

[Philip R]

Driving an immersion with the relay output of the navitron controller (Or any similar type) probably failed on the first few cycles of the mains. Is the supply isolator on, is a fuse fitted? If working, you should have best part of a tank of scolding water.

Gravity feed? do you mean gravity (Convection) circulation system?  The money send on the solar should have been initially investied in fitting a fully pumped heating system, decent boiler, some decent controls, as per the requirements of part L building regulations.

First, try to look at each heating mechanism on its own; electric immersion, central heating and the solar. Then look at their commonality, the controller sounds ominous. Report back to us the "As found settings."

PhilipR

[Sean]

I don't want to be to provactive and if I appear so, apologies, but why are you asking us before, it appears, you have even had a look.

What are you qualifactions or experience to have accepted the invitation to investigate.

If we know what you know or don't know, we can be better at giving suggestions. 

Are you a professional or a gifted amateuer/keen diyer or a well meaning friend?

does it really matter ?

are we all expected to state our professional qualifications before we can expect a response

[M]

I don't want to be to provactive and if I appear so, apologies, but why are you asking us before, it appears, you have even had a look.

What are you qualifactions or experience to have accepted the invitation to investigate.

If we know what you know or don't know, we can be better at giving suggestions. 

Are you a professional or a gifted amateuer/keen diyer or a well meaning friend?

does it really matter ?

are we all expected to state our professional qualifications before we can expect a response

I don't think offence was meant. I thought John was trying to be polite and helpful. He even included a caveat just in case he was misunderstood.

Stating experience in order to expect a 'suitable' response, sounds like a great idea. It would certainly help those who are themselves being asked to help. Why should they spend lots of time drafting a detailed response when a short, acronym filled one would do, or vice versa?

I'm running off on a tangent, but a simple traffic lights type system for asking questions might be useful right across the forum. Starting with those completely green to a new area, all the way up to a red warning - 'Stop, I know a lot about this, but need some expert specialism to solve this specific problem'.

Sorry to interfere.

Mart.

[turnerroy1]

Re your request for info on qualifictions I hold C&G 2380 C&G 2381 C&G 2391/2 C&G 2399 P.V. C&G 2399 Solar Thermal CORGI No 25474 Unvented No104987 WRAS No 041283/1 Member of institute for electrical engineers. If you require any further info please let me know.
The Navitron relay is powering an independent relay for the immersion. Only the top half of the store heats to 60 degrees. The owner of the system has been sold a pup. Whilst I agree that the most advetageous option would be to upgrade the heating system the owner does not have the funds after paying out for the solar which at this time is virtualy U.S. I will try adjusting the T.M.V to deliver water at 48 degrees and hope for an improved bath fill level. I do not like the hit and miss approach which was why I attempted to use the wealth of experience available on the forum. Plumber / Electrician of 40 years in the industry. 

[brackwell]

Roy, I am not as qualified as yourself but i do believe the standard controller settings are reasonable if they are like mine are.  My observations of your post are

1) Open vented central heating boiler with gravity feed hot water not giving any output to tank coil.
2) The system is using a thermal store which happens to be something i am not enthusiastic about. Providing a thermal store is fully heated up to the likes  75C it can deliver usable hot water up to about 60% the volume of the tank before it becomes unusable.  In this case neither of these criteria are being met and therefore it will run out of hot water as the client describes.

The client may have been led to believe that the solar panels would provide all the hot water but at this time of the year it is more like a preheater.   The solar plus 1 hr of immersion would quite probably give the results seen.  The solution is more energy required to raise the temperature - as simple as that.

Ken

[KLD]

Roy

Google-ing for the panels you mention brings up specs saying they are 58mm heat-pipe panels. Is that correct?
Newark doesn't offer (any more?) a 1770x400 combi thermal store, but a 1770x450. Is that the type? That'll be 210L volume. That combination (40x 58mm tubes into 210L) should work very nicely between early March and late October.  (FWIW, we've got the same TS, and "only" 40x 47mm tubes, and it served 95% of our DHW needs in that same period.)

Did Ken get it right that there is no boiler connection (what's the third coil connected to, then?)

If you want to have a bath full (say 120L) of 40°C water, and your cold mains come in at 15°C, then you need 3.5kWh of heat.
If your store is 210L, then 3.5kWh will raise the store temp by 15°C. For a decent flow rate at 40°C you probably want the store at a minimum of 50°C. So, heating the entire store to 65°C should yield plenty of HW for your customer's specs. If you heat only the top half, then you'd need proportionally higher temps there. Note also that the DHW coil spans the entire height of the TS, and if you only heat the top part of the store, then the heat exchange will be less efficient.

Klaus

[turnerroy1]

Thanks for the input. The T/m according to the paper work supplied is 170 Ltr. 1st lower coil solar. 2nd (center) coil boiler input. 3rd domestic hot water out. I am wondering if boiler input is air locked has any one any previous on this. Immersion is on bottom of cylinder so no reason for stat to come in before bottom of cylinder reaches 65 at lower level. I am thinking faulty stat on immersion or stat 2 on navitron? Regards.

[KLD]

Roy,

as Philip suggested earlier, let's try and look at the various in- and outputs separately first before checking the interplay.

I can't see why a 170L thermal store (TS) shouldn't be large enough to supply a full bath. Following on from my earlier calcs, 3.5kWh out of 170L means a delta T of 17°C now. Have you actually measured what the temperatures are at the bottom and top of the TS after the immersion had been on? What are the thermostat settings (on the immersion itself, the safety cutout, and the TDC settings)? If the TDC3 controls the immersion element, then what are the settings (hydraulic variant, temp settings for sensors 1, 2, and 3)? Where is sensor S3 mounted? Is there an additional time-programmer to limit when the immersion can come on (you mention one in your first post)?

The boiler loop: when you switch the boiler manually over to heat the TS, do the pipes get warm? What's the boiler flow temp when heating the store?

Klaus

[turnerroy1]

Hi Klaus
Thanks for your interest. S3 is mounted at  mid / top of T/S . Immersion at bottom of tank at 60 deg. Safety cut out normal at 90 deg. As previous, timer on immersion rod 1 Hr between 7 & 8 evening. Due to insulation I have avoided temp readings until all other possibilities resolved although as you suggest a faulty stat is probable. Thoughts on settings for TDC3 would be welcome. Boiler hot water and space heating one and the same, control ed by stat on boiler. Space heating pumped, water gravity, no other cotrolls.  No TRVs, room stat, tank stat. He was still sold and accepted Solar Thermal, not good for the industry or his family. Regards.

[KLD]

Roy,

We need the settings from the TDC3 now, especially TsetS3 and Hysteresis. Do you have the manual for the TDC? It can be downloaded from the Sorel web page.

On the boiler side: is there any valve (S-plan, Y-plan ...) selecting CH versus DHW? I still don't understand what you mean by 

water gravity

. Is the DHW coil supplied by/ from a cold water cistern, or is this "water" simply the F&E tank for the CH circuit?

Does your customer have enough solar-heaed HW during summer? In that case he's maybe not completely mis-sold into solar, since if he's able to switch off the boiler altogether in summer, that'll likely save a lot of energy? Whether it was cost-effective is another question ...


Klaus

[turnerroy1]

Klaus
      Boiler system has no valve controls at all. Space and water are one and the same. Space heating pumped. Potterton boiler in excess of 20 yrs old. I have Navitron TDC3 Install and op in front of me all parameters as per factory settings. I will call at customers house to verify tomorrow. Flow and return from boiler to coil (gravity) do not heat up even when I raise boiler stat to max. I am baffled but will persevere and report back when resolved. Regards.   

[dhaslam]

Looks like the  store is only being heated by some solar and the immersion which is  not on for long enough.  A 3 kW immersion will  only add about 15 degrees C   but probably does heat the top more and the bottom less.     It may just be an air lock on the boiler circuit.     No qualifications  by the way, just learn from mistakes.     

[Antman]

Roy

The 'old fashioned' gravity HW boiler loop would usually have had a non-return flap valve (not the sprung loaded type!) in the flow pipe from the boiler to prevent reverse circulation cooling the cylinder (store). It is possible this has furred-up and stuck closed - especially if there is no corrosion inhibitor in the system. If an airlock is not the problem then this could be the cause. If this is low down in the pipework i.e near the boiler, be aware that it holds back a 'head' of water in the pipework above when you remove it. It is surprising how far a couple of metres head of water sprays  

As a basic measure without going fully-pumped, it is possible to fit a 28mm 2-port zone valve (with changeover contact) on the DHW feed to the boiler coil with a stat to interlock the boiler. The cost would probably be saved in the first year!
But the valve must be between the expansion/boiler flow and coil - not so as to close the expansion pipe route.

Antman