Hi Hope you can help, my sister has a 3 bed 1 bath house, currently old fashioned heating and hot water system but boiler on way out. she has been advised Vaillant 937 with wireless room thermostat and weather outside sensor, she has spoken to Vaillant also who said although would not get full 15ltrs/min it would still be better than what she has and whilst the storage tanks are full it would be better than 12ltrs/min, also 2 bar pressure is way better than what she has now, any and all thoughts would be appreciated, she does like this type of boiler as she had one in her old flat and she wants the old hot tank gone, dunno why but she does , thanks in advance
12ltrs/min & 2 bar pressure, combi selected
- Thread starter cj33
- Start date
Go for 837 not 937 they not as reliable an have u seen the size of em! They hang on the wall like a freezer!
thanks for your reply, the size isn't a problem as the boiler is in a utility room, don't you think though that the tanks will benefit her if another hot tap in the house is opened whilst somebody is showering ? or is the 837 ok with that situation ?
Most Combi struggle if u wanna run more than one tap at a time prob best to go for unvented cylinder etc, the vaillants r the best but unfortunately the 937 has suffered with software probs, also they r a pig to repair if anything goes wrong with the back unit
The 937 is a good boiler within its context and can give over 15 li/min for a LIMITED time of about 10 minutes until the store is depleted when it reverts to its basic 13 li/min. Ideal for filling a bath quickly.
HOWEVER, to perform it needs an adequate mains supply. I would say a dynamic 20 li/min @ 1.5 Bar. Few properties in London have that. More disappointing is that most installers dont even know how to properly assess the mains supply and just measure the static pressure and the open pipe flow rate. Thats NOT whats required.
In spite of comments about their reliability, there are many providing good performance in thousands of homes. But to enable repairs to be done they do need about 200mm clear on either side and 600 mm in front in case any repairs are required. Its also better if they are not mounted very high up as if anything is wrong on the back store assembly the front unit has to be removed.
Not in my opinion a bad boiler although if space permits I would always recommend a boiler and cylinder.
Tony Glazier
HOWEVER, to perform it needs an adequate mains supply. I would say a dynamic 20 li/min @ 1.5 Bar. Few properties in London have that. More disappointing is that most installers dont even know how to properly assess the mains supply and just measure the static pressure and the open pipe flow rate. Thats NOT whats required.
In spite of comments about their reliability, there are many providing good performance in thousands of homes. But to enable repairs to be done they do need about 200mm clear on either side and 600 mm in front in case any repairs are required. Its also better if they are not mounted very high up as if anything is wrong on the back store assembly the front unit has to be removed.
Not in my opinion a bad boiler although if space permits I would always recommend a boiler and cylinder.
Tony Glazier
if you put 13l/min into a 937 you'll be lucky to get out 9 or 10. they're quite restrictive. Needs at least 20l/min to be a wirthwhile investement. you'll be wasting your money, and 824 would be more appropriate. Whoever suggested a 937 with that flow rate wants kicking into touch
Er... surely whatever you put in must equal whatever you get out on DHW.
As you say on the 937, like all plate HE combis, the DHW circuit is quite restrictive.
Thats why they need a supply giving 20 li @ 1.5 bar
Tony
yes 12ltrs/min, wouldn't the tanks help increase initially though whilst they are charged and only drop once they are depleted, thats what Vaillant have said or are they just trying to sell the expensive unit, it was the technical helpline and not sales
bullplop, they're talking nonsense.
I once went to a warranty call, complaint of poor performance on a 937. The customers cold flow rate was 14l/min. hot was 11 l/min from start. installers face was a picture ! silly boy.
If you think that tiger, back to college for you young man.
The 937 is a hybrid combi. Some of the water is stored at temperature, and then blended into the combi output to create a usefully higher hot water flowrate than you would get with a standard 37kW combi.
I say 'usefully' because we tend to use our HW in bursts, and 200 litres over 10 minutes is very good.
The trouble is, to discharge 200 litres in ten minutes requires a 20 litres per minute incoming supply. And you only have 12.
So, I'm afraid the advice you think you received from Vaillant is wrong. If you have just 12 litres/min coming up the garden path, that is the best any combi could deliver out of a tap. The two storage vessels on the back do not in any way boost the water supply, they are just heat storage, no more no less.
I say 'usefully' because we tend to use our HW in bursts, and 200 litres over 10 minutes is very good.
The trouble is, to discharge 200 litres in ten minutes requires a 20 litres per minute incoming supply. And you only have 12.
So, I'm afraid the advice you think you received from Vaillant is wrong. If you have just 12 litres/min coming up the garden path, that is the best any combi could deliver out of a tap. The two storage vessels on the back do not in any way boost the water supply, they are just heat storage, no more no less.
Its worse than that!
The 12 li/min open pipe as fas as we can see.
Through a combi the flow rate will be reduced even further.
Odd though that most installers above dont seem able to understand what a dynamic flow rate means.
The 12 li/min open pipe as fas as we can see.
Through a combi the flow rate will be reduced even further.
Odd though that most installers above dont seem able to understand what a dynamic flow rate means.
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