Electric unvented cylinder help.

[timmytank]

Hi I am hoping for some help please. I am newly qualified to unvented and did my g3 about 10 weeks ago. I am gas registered not that this matters.
I have corrected some issues with a rointe electric unvented cylinder in an apartment...sorted the balanced cold ,new expansion vessel sized correctly and I have piped up the d1 and d2 pipe in copper. It is 8.8 meters including 4 bends at 0.8. The fall is correct and 300mm between the tundish and bend. It terminates in to a metal hopper high level and building control have okayed this.
The problem is I was called today with a leak ..I watched in horror on a video he had taken as it disharged violently into the d2 and overflow the tundish. This would mean the d2 is not correct but it was within the 9 metres allowed. I have checked the that the main is 3 bar after the pressure reducing set and have checked the new expansion vessel is at the manufacturers 3bar. So the the temperature relief valve has gone off and rointe have been useless. The customer said a further 3 of these units in the block have done a similar think and they only use them for an hour a day . These unites have an anti leiganella programmer so they go up to 80 degrees once a day. The system has worked as it should since the alterations but the unit is 5 years old.
Any advice please would be helpful.

 

[lame plumber]

only needs to hit 60 degrees to control the risk so proably getting too hot

 

[timmytank]

Thanks lame plumber I suspect high limit stat has failed. My other worry was the d2 pipe...even though it was 22mm and less than 9 metres including the 0.8 allowed from each bend it spilled over. Have you ever heard of this...it came out with a massive force.

 

[Scott_D]

Does it spill when you manually test?

 

[timmytank]

No Scott_d definitely not. Appreciate your help. Not sure what to do.

 

[chris watkins]

It is not unusual for them to overflow / splash a bit when they discharge even if all the discharge pipework is correctly sized & installed.

It is the fact that it is discharging under temperature that needs your attention as you are no doubt aware the T&P is preset to discharge full bore if the water temp reaches 90-95degC & it is the last line of defence as it were so there must be a problem with the control & high limit stats.

If it has been regularly up to those high temps & you are in a hard water area then I would also be checking for scale build up on the sensors / probes or in the heater, as well as maybe replacing the stats.

 

[timmytank]

Great thanks . I have talked to the customer and we are going to replace the cylinder. I had a call today from someone in the same block who has this problem and will be looking to change there's aswell. There are a further 3 with the problem....the problem is as I am new to electric unvented what is a reliable brand and I need to find out if I can put a scale inhibitor on these appliances. Thanks.

 

[chris watkins]

Most are stainless steel & so long as the temperature is controlled at 60 - 65 there will not be a problem with scale.

What type of scale inhibitor ?

Megaflo are good but expensive

 

[Best]

Just be careful where you install the discharge pipe to that it can't back up. Check it all out. You said it goes to a hopper, but I know a gulley drain, if partly or fully blocked will cause the discharge pipe to be blocked, despite the regs asking for ideal situation of D2 terminating just below gulley grid.
Those tundishs are terrible for letting water splash out. Strange design

 

[timmytank]

Thanks Chris Watkins. I had thought maybe an electrolyte scale inhibitor on the cold feed . I would check with the manufacturer first but the main is well over 200 ppm. I put these on my combis regardless.
I will price up a mega flow. Out of interest have you heard of telford or rather are they any good?

 

[timmytank]

Thanks Best it's high level disharged into a metal hopper .. I had spoke to building control before doing this. It's definitely empty...I was just shocked how much spilled over.

 

[chris watkins]

Thanks Chris Watkins. I had thought maybe an electrolyte scale inhibitor on the cold feed . I would check with the manufacturer first but the main is well over 200 ppm. I put these on my combis regardless.
I will price up a mega flow. Out of interest have you heard of telford or rather are they any good?

IMHO those electrical or magnetic water conditioners are a waste of time & money, they may help a bit on your combi because of the slower water flows & instant use but not on an un-vented cylinder with the stored water & high surface temperatures of the immersions elements.

Scale will form on the element surface but break off & fall to the bottom of the cylinder due to the expansion & contraction. So long as it does not build up from the bottom & touch the element it will be fine, the key is the temperature is controlled to 60 - 65 Max.

Personally I would use Titanium Immersion Elements as these have proven to last 7+ years (in Megaflo's) working 365 for 4-5 hours/ night.

 

[chris watkins]

Just be careful where you install the discharge pipe to that it can't back up. Check it all out. You said it goes to a hopper, but I know a gulley drain, if partly or fully blocked will cause the discharge pipe to be blocked, despite the regs asking for ideal situation of D2 terminating just below gulley grid.
Those tundishs are terrible for letting water splash out. Strange design

I never understood that one either of discharging below the grating. I always suggested up to 50mm above, as it also give another point of warning if there is discharge guess it is the balance between splashing if it discharges full bore.

Also strange that the guidance for discharging at high level over a hopper (head) is that there should be an AA air gap between the down pointing D2 & overspill.

 

[Scott_D]

Any pics of the install?
Might help

 

[timmytank]

..
These are before and after...I havnt got a picture of the d2 termination because it was about 5 flights up. If really needed I could go back .
Thanks for your help Scott.

 

[Scott_D]

Lol at the before
If you have a longer section of straight pipe into the tundish it won't splash out so much. If space allows try ang get 150mm

 

[Best]

As above ^^^, I would try to always fit the combination valve as high as possible - ideally just above the height of unit (if that is suitable). That means the combination valve is easy to service without draining any of the unit in future.
It also means you have plenty of height from the pressure relief valve and you could install the tundish higher, giving a decent straight length of D1 pipe (but D1 still within 600mm) and as long as possible straight D2 pipe before it bends. The 300mm rule on D2 before first bend is a minimum length and I try to better it greatly

 

[timmytank]

Thanks alot. I will try and find the tap to the incoming main and move the combination valve up on the new install. Really helpful all of you.

 

[timmytank]

Hi everyone I am looking in to replacing this rointe cylinder. I have been looking at a megaflo eco 210 unvented direct cylinder. I have spoken to megaflo and they said it is ok to use as electric only. Comes as a pack and has an internal expansion section.
My question is how do I register this gas safe don't want to know because there isn't any gas involved .....building control havnt shown much interest. I don't want to fit a new appliance and be in a position were I can't register. Thanks for any advice.

 

[chris watkins]

Are you Gas Safe registered ? If not then you or the customer need to raise a Building Notice.
Unless you want to join another competent persons scheme.

 

[timmytank]

Yes I am gas registered . I spoke to my area gas safe inspector and he said I could register but as soon as I told him it was electric only he said that it wasn't possible. I logged on to gas safe register and couldn't find anything either.

 

[timmytank]

Lacb I think might be the only way unless anyone can recommend cps scheme I could join. What a pain haha.

 

[chris watkins]

How many of these do you do or think you will do a year?

 

[SimonG]

Should just be able to add it on to your gas safe same as I did with my oftec. You can join any cps that recognises your award. I wouldnt use megaflow, overpriced. If you want them then use the plumb center own brand made by same people. I like the rm's.

Sounds like you could be spending a bit of time in that block

 

[timmytank]

Honestly not many the way this is going...maybe 10. I will try and stick to the boilers but some times you get a job kind of pushed your way. What are your thoughts?