Vaillant Ecotec 428

[dumbrill]

I had planned to get an Ecotec 428 installed to replace an ageing conventional boiler. However having read many discussions yesterday on code S.53 I am having second thoughts.

It looks as if the problem is the 428 heat exchanger that creates a high pressure drop and so the minimum flow is often not reached. This means that my relatively new Selectric 15-50 pump will need replacing.

The system is Y plan with a conventional open vent cylinder.

I also planned to fit a VRC430f and VR65 with the VR10 installed on the cylinder.

Is this set-up going to be more trouble than it's worth?

 

[Tibbot]

I wouldn't use this boiler as a replacement for those reasons. You're better off with a more forgiving heat exchanger..

 

[DP]

I would suggest get the boiler fitted by an installer who takes pride in what he does and dreaded code will not be a problem.

Have fitted same boiler in various households, pumped by 15/50 grundfos without any problems. By the way, some of these installations even have microbore. Boiler operates without any difficulty.

In each case system was balanced for correct operation

Now am going to retire to my bunker

 

[dumbrill]

I wouldn't use this boiler as a replacement for those reasons. You're better off with a more forgiving heat exchanger..

I am tending towards a Remeha Aventa 24v and it has the added benefit of being Opentherm compliant. It's also closer to the heating requirement I've calculated for my house at around 19 to 20kW.

I assume that the Aventa 24v is more forgiving?

 

[DenG1]

I had one of these fitted into my home to replace an old back boiler nearly 3 years ago. It was a bit oversized but as we were planning an extension and new radiators we thought that was best. Providing your installer range rates it you should not get S53 code. (I know this as I was quite fascinated and altered the settings just to see!!) I soon altered it back!! It runs ok with a 15/50 pump but I do need it on setting 3.

 

[Agile]

You dont say if your system is sealed or open vented.

I dont see any problem with this boiler as long as it is range rated and not oversized compared with the heating load calculated by the whole house method.

Most of the problems you read about on here are when the boiler is seriously oversized and fitted to a dirty system. If they had used a competent installer they would not have needed to have posted about it here.

Generally its better to make the system sealed if its not already.

Tony

 

[dumbrill]

You dont say if your system is sealed or open vented.

I dont see any problem with this boiler as long as it is range rated and not oversized compared with the heating load calculated by the whole house method.

Most of the problems you read about on here are when the boiler is seriously oversized and fitted to a dirty system. If they had used a competent installer they would not have needed to have posted about it here.

Generally its better to make the system sealed if its not already.

Tony

The system is open vented with a Myson Aerjec installed about 50cm upstream of the pump. The system works very well at the moment (no air, no noise, etc) and so my initial thoughts were to change just the boiler.

I've used various methods to size the boiler and they come out at around 19 to 20kW. Unfortunately the cut off for lots of boiler sizes seems to be 18kW. Hence the switch to what seems a much larger size. In the case of the 428 it would end up being oversized.

 

[Tibbot]

I assume that the Aventa 24v is more forgiving?

You assume wrong, it has the same heat exchanger as the 428. So do the open vent boilers of Ariston, Alpha, Biasi, Dimplex and Glow-worm (Hxi).

 

[Agile]

A typical three bed semi is about 11-13 kW. Is your house significantly larger?

Whats the installed load of rads ( found by comparing sizes with current makers catalogues. ) ?

Did you add ( or the program allow ) 2 kW for hot water heating ?

I would still convert to a sealed system because the greater pressure raises the boiling point and reduces air entrainment and increases efficiency by about 2-3%. They are also less prone to faults.

Tony

 

[dumbrill]

A typical three bed semi is about 11-13 kW. Is your house significantly larger?

Whats the installed load of rads ( found by comparing sizes with current makers catalogues. ) ?

Did you add ( or the program allow ) 2 kW for hot water heating ?

I would still convert to a sealed system because the greater pressure raises the boiling point and reduces air entrainment and increases efficiency by about 2-3%. They are also less prone to faults.

Tony

The house is detached, four bedroomed, of 1955 construction and with limited roof insulation because it has a dormer roof.

I am going to do some more detailed calculations on heat loss. The existing boiler is a Glow-worm Hideaway 70B, but I don't know what output it has been set to, either 60, 65 or 70,000 btu/hr. In the depths of winter the house can be cold(ish), but that's probably more to do with the old and unfinned radiators.

My plan is to get the boiler upgraded and then replace radiators around the house as other work proceeds.

I will do some better calcs.

 

[Agile]

I would agree that 19 kW sounds about right as a boiler power requirement.

As there is not a boiler between that and 28 kW then the 428 would be an adequate choice and should not give any problems as long as you dont close off most of the rads and heat the house abnormally.

Tony

 

[Gasman77]

Op go for the Viessmann 100 19kw or 26kw, open vent. Much better than the vaillant IMO

 

[libby lou lou]

30,000 post's, well done tony!.

 

[Beerlover]

BTW the ecotec plus 428 should never be fitted with less than a 15/60 pump.

The pressure drop over the main heat excahnger is nearly 3.5 m

 

[dumbrill]

I would agree that 19 kW sounds about right as a boiler power requirement.

As there is not a boiler between that and 28 kW then the 428 would be an adequate choice and should not give any problems as long as you dont close off most of the rads and heat the house abnormally.

Tony

OK, well I've done some heat loss calcs and I get the following:

Using U values, room dimensions, etc I get a heat loss of 15kW (inc. 2kW for HW)
Using the IDHEE whole house calculator I get a boiler size of 20.4kW
Using the Energy Savings Trust whole house calculator I get a boiler size of 19.4kW (Basic Design Heat Loss of 15.1kW)

What factor should I apply to my basic calculated value of 15kW as a contingency? I would need to add 25% or more to get near to the two 'Whole House Calculators' that I have used.

The house isn't particularly large, approx 9m x 9m, with a poorly insulated dormer roof, small two story extension and located in the south.

Overall as you suggested I am still tending to go over the 18kW threshold, but it's annoying that the calcs don't give me a definitive answer.