Supplier fitted wrong boiler but saying it's ok

[smithfield11]

Just want a second opinion on a boiler offered by a fitter. Standard victorian terrace house with 1 bathroom but we’re putting in a second bathroom so will have 2 showers and 1 bath. I wanted to change the combi boiler for a new one that will be able to give a REALLY GOOD shower from a large rainfall type shower head. Fitter initially suggested a 35kw ideal logic + but when they’ve come to fit they’ve actually fitted a 30kw ideal logic +. I don’t mind if this is going to be ok for our requirement but if the 35 would’ve been quite a bit better at giving a shower I can play hard ball to get them to change it.

My cold water flow is high pressure (not measured it exactly)

Hot water flow rates:
30kw : 12.5l/m
35kw : 14.5l/m

 

[Agile]

In my view it would be mad for any installer to fit a combi without measuring the dynamic flow rate first. Did he convince you that it would supply both showers at the same time!

You need to compare the boiler output with the shower requirement.

Did you not have a written quotation specifying a 35 kW boiler that you signed as accepted?

You can see that a 35 kW has about 20% more hot water output. I expect most rain showers to use about 14 li/min but different ones will take different flow rates.

I never understand how anyone can come to a situation where they are quoted for one thing and have a lesser and cheaper boiler fitted.

Pretty obvious to me, you need the dynamic flow rate checked. If that is limited then you will not benefit from a 35 kW boiler anyway and should just have a reduction in the price.

Dynamic flow rate is not the same as an open pipe flow rate!

Tony

 

[smithfield11]

Thanks, Is this something I can test myself? Will the old "Time water out a few different taps and take an average" trick work?

He did say it should furnish both showers at the same time but obviously with a reduction in pressure. He's saying he just changed his mind over it and yes I do have a quote (haven't paid yet). My guess is he ordered the wrong one by accident for delivery to site and obviously the fitter (different guy) just fitted what turned up at the door. Now that it's fitted thought I should imagine it would be a big write off for him to swap it....

 

[Agile]

If you have one or two rain showers which need say 14 li/min each then you will not be happy with a dribble of 7 li/min if two are being used at the same time.

If you are paying for a 35 kW boiler then that is what you should have. And will need it for a rain shower.

It is not your mistake and you should not suffer from a disorganised installer who fits a combi without measuring the mains flow rate. Get him to fit the correct model!

You are describing measuring the open pipe flow rate. That is not the same as the dynamic flow rate which can be as little as half the open pipe figure depending on the static pressure.

Pressure and flow are not the same things.

Tony

 

[smithfield11]

Thanks for that. When you're spending a good chunk on 2 new bathrooms, saving £100 on a boiler because the installer messed up is pretty irrelevant I agree. Our existing shower with this new boiler is WAY better than it was with the older boiler but thats a very basic shower with small head. Sounds like I may have to play hard ball and say I want the 35 fitting. Presume that means he's got to write the whole job off though...

 

[muggles]

Don't pay him - he's not fulfilled his part of the contract between you. Insist that the 35kW be fitted as agreed, and tell him you won't be paying him until this is done. It'll still be fairly pitiful performance if you're trying to run both showers at the same time (with rain heads, unless they're specified as low-flow compatible, you may find that they dribble rather than rain with two running at once) but at least you'll be getting what you agreed to have installed, even if it still turns out to be slightly disappointing performance when it's done.

 

[smithfield11]

Thanks guys, just so I've got enough info to argue my point. Can you explain this water label to me. He's trying to tell me a shower I linked to would work fine at 5l/m and therefore the 30kw won't have an issue servicing two of them. I've gone on to the manufacturer and this is the "water label" If I'm reading this correctly it's basically saying the shower will perform better the higher the water flow, or am I misreading it?

http://www.bristan.com/epages/Bristan.sf/AU_en/?ObjectPath=/Shops/Bristan/Products/"PM2 SHCDIV C"

Also other showers I've looked at start at min pressure 0.5 bar, is there a rule for what this equates to in l/m?

 

[Twenty Four]

Surely the 'Water Label' is merely telling you at 6L/m you're being relatively green with your water usage and at above 13L/m you're being a greedy sòd. It has nothing to do with your boiler operation.

 

[smithfield11]

Ah ok, boilers seem to show their hot water stats in l/m but showers tell you a min/max pressure in bars. How do I convert (basically need to make sure I'm buying showers that will be decent with my flow rate)?

 

[Madrab]

The water label is like an energy efficiency label, is just give a visual representation of what is 'considered' to be acceptable water usage by the EU. The flow characteristics is what you need to look at, unless you will be restricting the shower flow to 5l/min! That 1 shower, without restriction, depending on delivery pressure, could flow up to and over 40l/min! Pressure and flow cannot be directly compared though so you need to have the pressure and flow rates of you mains checked first (static and dynamic), only way you'll know what can be achieved and confirm that the water delivery will be suitable for the showers you want.

This really should have been part of the system design and any recommendations coming from the installer IMO.

5l/min is not a very good shower and human nature suggests and what you alluded to is that most people will have as much as they can possible get as the shower experience gets better the higher the pressure and flow gets. Your plumbers suggestion about the 5l/min flow per shower etc sounds like he is now at the wriggling point if he knew what you were planning from the start

 

[Dan Robinson]

It's not as if it's a hard job to swap them over....gas pipe size not withstanding....

 

[ollski]

Um, if you bought a bmw330d and they delivered you a 316 saying it would still get from Birmingham to Manchester would you accept it?

 

[ianniann]

Um, if you bought a bmw330d and they delivered you a 316 saying it would still get from Birmingham to Manchester would you accept it?

That's pretty much it. Regardless of other valid questions relating to the suitability (flow rate, house heating requirements, etc.) he said it was going to be a 35kW and you got a less powerful boiler. You specifically mention the one issue where a combi boiler really needs high power, the shower that you have, so it seems pretty important. I'd suspect that a 30kW wouldn't work brilliantly with one of those showers, let alone two.

 

[smithfield11]

Cool thanks guys. Car analogy is the on I used too haha (I drive 330e though).

As we're on it, got any tips on a good shower for this then? I wouldve liked a straight drop rain type shower but if youre sceptical on this boiler I can stick to something more traditional. (I just want to get up in the morning and have great shower).

 

[ianniann]

Cool thanks guys. Car analogy is the on I used too haha (I drive 330e though).

As we're on it, got any tips on a good shower for this then? I wouldve liked a straight drop rain type shower but if youre sceptical on this boiler I can stick to something more traditional. (I just want to get up in the morning and have great shower).

Look up the specs for the shower head. It should mention a flow rate (litres/minute) possibly a range that it will work with. Then look up the flow rate your boiler (or the one you're hoping for) can supply. Bear in mind that rate is for a particular temperature increase, which might mean you get less in winter when it has to heat the water more. All 35 kW combi boilers will give something like 14-15 l/s for a 35 degree rise, which is plenty (temperature and water) for most showers, but won't supply the full experience with a rainfall head which may be able to use double that.