Vaillant Multipoint Water Heater

[fidom]

This is a long shot as this appliance probably does not exist in UK. I am staying at a house in Austria that has a 3 phase, 21 kW electric water heater, Vaillant model VED 21 H/6. I think the problem is with the flow sensing mechanism. The appliance feeds the shower mixer, kitchen sink and bathroom wash basin. With the filter fitted to the wash basin mixer the flow is not enough to activate the appliance so it always runs cold. With the filer removed it works OK. The shower is very sensitive to lever position, it tends to go from too hot straight to stone cold. Even at a constant lever position the heater sometimes shuts off for a few seconds and the water goes cold. I can find some technical info. online for this heater but only on PDF and only in German. I mainly wanted to know if there is any adjustment for the sensitivity of the flow switch?

 

[Agile]

Reading what you have said the problem seems to be a blocked filter.

The industry standard for water heaters and combi boilers is for them to be turned on with a flow rate of about 2.5 litres per minute.

I have seen Vaillant gas water heaters but not any electric ones. I am not sure about Vaillant, but in many cases with small volume selling appliances, another maker's unit is rebadged.

Tony

 

[fidom]

Thanks Tony. I checked the wash basin tap and it is flowing about 3 litres a minute with the filter fitted. Looking at the plumbing inside the heater it looks to be about 12mm copper and where it goes onto the cold feed coming out of the wall the pipe looks to be a bit deformed so I'm wondering if that is restricting the flow. I'm not sure if improving the flow at that point would help with the shower problem though. I don't really know how these single lever shower mixers work. As you move the lever from left to right is it turning the hot off as well as turning the cold on or staying at full flow of hot right up to the central position? This would mean you have full flow of hot and cold when central. I suppose even if it does work that way the cold side would be robbing the hot of flow so it could take it down below the point needed to activate the flow switch.

 

[polesapart]

The german manual isn't much cop. It states that you need minimum 3 litres/min flow rate, points you to the inlet filter or to decalcifying if that can't be acheived. "Spare parts see wholesaler."

 

[Agile]

You are there, I am not.

You tell me the flow rate at the tap with the filter on it.

But what is it without the filter???

What does the heater do with the 3 li and what dos it do with the ??? li without the filter?

Can you clean the filter?

Tony

 

[fidom]

With the filter removed the flow is about 6 litres a minute. I have tried to photograph the deformed inlet pipe and the tap filter but they were probably a bit too close for the flash so they are not too clear. I think you can get new filters but personally I would leave it out and just put the chrome bezel back on. I suppose it would be worth descaling the shower head as it is a hard water area.

 

[Agile]

So if you remove the restrictive filter what issues do you have?

Can you not clean the filter?

Tony

 

[Agile]

So if you remove the restrictive filter what issues do you have?

Can you not clean the filter?

It looks more like a flow restrictor to me. But obviously not needed to do that in your case.

Tony

 

[fidom]

Mention of the wash basin tap behaviour was just for information, it is the lack of proper control over the shower that is the problem. I have heard mention of low flow shower heads but when I asked about them in plumbers merchants they did not seem aware of the existance of such fittings. Although this property in Austria is not mine I would buy such a shower head to try it, as it would be useful to me for my place in Croatia. I have a gravity feed hot water system there and despite all the plumbing being done in new 22 mm pipe, the flow from the shower head is a mere trickle.

When I mention low flow shower heads I mean ones designed for use in systems such as gravity applications which offer limited flow output, not the sort designed to conserve water.