Pump Sizing

[Chester]

Hey guys long time since I have posted here but know some of you know your salt. I've got a job in a townhouse and currently the boiler sits on the second floor of a three story but I'm moving it to the ground floor as per client request, problem is, its got ridiculously high ceilings, I'm going to double check but suspect at the very least top floor rads are 7 meters up.. so I'm concerned about a standard 15/60 or whatever being man enough, I've been looking at the 25/80 as a viable alternative but I'll be honest I really don't have a great deal of experience in pump sizing, I'm usually just whacking in combis and forgetting about it 🥴 so I keep hearing that it'll make the system noisy and all these horror stories, just wondering if anyone could give me some advice basically. Current system is 22mm flow + return, currently open vented, 10 rads overall, I'm going to seal it and putting in a 180l unvented indirect. Also, client is a bit of an eco warrior so they want me to put in electric, electric boiler needs 12lpm minimum according to Mi's. Cheers

 

[SJB060685]

If they're off grid why not consider an oil boiler?

 

[Chester]

If they're off grid why not consider an oil boiler?

They're in the centre of a town

 

[SJB060685]

They're in the centre of a town

Oh, haha, my bad. Having said that we did use to have an elderly customer on oil in the town. He refused to switch over to gas lol.

 

[king of pipes]

If they're off grid why not consider an oil boiler?

Their not bud just don't want gas because they think it's polluting and harmful to the environment should watch seaspiracey on netflix see the harm countries are man are doing sickening. Kop

 

[Chester]

Oh, haha, my bad. Having said that we did use to have an elderly customer on oil in the town. He refused to switch over to gas lol.

its a combi job all day long, I know that, but I'm just following orders, I will quote them for unvented and heat only electric and see what they want to do

 

[IND_Nick]

I had a similar customer, who had done online research and thought electric would be a great idea to future proof the house. However once I went through the cost of install, running and the fact that most electric units are only carry a 2/3 year warranty he soon agreed to a replacement gas boiler.

 

[cjg]

just one more point do they cook on gas or leccy, power cut no heating or cooking.
yes i know ,,, no leccy no heating even if you use gas, but!!!!
thats my pennys worth now,..

 

[Chester]

just one more point do they cook on gas or leccy, power cut no heating or cooking.
yes i know ,,, no leccy no heating even if you use gas, but!!!!
thats my pennys worth now,..

no gas hob just the boiler

 

[Ben-gee]

Consider the personality of the customer, this job would be ringing alarm bells for me - remember sometimes a job is not worth doing from your point of view and it’s best to walk away.
If it’s a job you’d not wish your name to be associated with, for example when they start telling people that their bills have gone mad since you fitted the new boiler etc - just don’t do it.

 

[king of pipes]

Personally I don't think the power supply will be adequate for heating, hotwater, cooking , a kettle, computers TVs , gaming and to top that probably a charging point for a car or two if not now then in the future, I'd be getting a calculation done allowing for a -2- 3 degree temperature outside for a week or two and all these appliances loading it will be a mind blowing and a game changers I guarantee, take some Viessman boiler information with you these are designed for the changes coming to the Natural gas supply, the future is Hydrogen Natural gas mix the co2 produced from the combustion process is vastly reduced it's being trialled and tested in parts of the UK now that the future and the way I would be pushing this customer is this direction , or saying sorry I'm out . Kop

 

[king of pipes]

Maybe Murdoch should come in on this one ?? He knows his stuff on Electrics

 

[Chester]

Maybe Murdoch should come in on this one ?? He knows his stuff on Electrics

it'll be fine, its only 12kw, they have a 100amp supply, boiler has soft start and is modulating too which is nice.

 

[king of pipes]

it'll be fine, its only 12kw, they have a 100amp supply, boiler has soft start and is modulating too which is nice.

What you installing bud ??

 

[Chester]

What you installing bud ??

Potterton Gold electric

 

[king of pipes]

Only a years warranty and a D sebuk rating , I wish you well with it bud but alarm bells are ringing for me anyway. All the best kop

 

[ShaunCorbs]

Same as a slim Jim good units

 

[SJB060685]

Although I know quite a bit on electricity I'm by no means a qualified electrician. Is a 100 amp supply really going to be enough for a 12 kw boiler at full load and all other appliances running?

 

[ShaunCorbs]

Although I know quite a bit on electricity I'm by no means a qualified electrician. Is a 100 amp supply really going to be enough for a 12 kw boiler at full load and all other appliances running?

yes easily 12kw is 50amps provided he doesn’t run a big 20 plus amp cooker at the same time

also 12 kw is max load when the system warms up this could drop to around 6kw

 

[SJB060685]

yes easily 12kw is 50amps provided he doesn’t run a big 20 plus amp cooker at the same time

also 12 kw is max load when the system warms up this could drop to around 6kw

That's my point mate. Yes the boiler will modulate but what when it's -2°c outside, the boiler is at full output and then you switch on an electric cooker, plus your 1 or 2 32 amp ring mains and your lighting circuits etc etc. Admittedly this is an extreme situation scenario but like heating systems shouldn't all electrical systems be designed with max load in consideration?

 

[Ben-gee]

Actually no, they are not designed at maximum load - diversification is applied, don’t forget most heating elements actually cycle off/on to maintain a given temperature and pretty much anything that is not a heating element does not draw much current.
I’m over simplifying, but you get my drift.

 

[SJB060685]

Actually no, they are not designed at maximum load - diversification is applied, don’t forget most heating elements actually cycle off/on to maintain a given temperature and pretty much anything that is not a heating element does not draw much current.
I’m over simplifying, but you get my drift.

Thanks buddy. Yes I totally understand you and to be honest it's not something I knew. Many thanks 🙏.

 

[Chester]

Only a years warranty and a D sebuk rating , I wish you well with it bud but alarm bells are ringing for me anyway. All the best kop

Cheers, I spoke with them again today and laid it all out for them on the table, the potential bills from gas being 4 to 5x cheaper and whilst they were like yeah okay that's cool.. they still want electric. Honestly what more can I do? They don't want a gas boiler, period. There is no alternative. They asked what I would do, I said gas all day long, combi boiler, and bring gas in to cook on too. They're not interested, I think it also matters that these people are quite wealthy so the allure of saving money doesn't really grip them as much. What I'm going to do is arrange the system so in the event of a backfire (which I don't think will happen) I can just put a heat only gas boiler in with ease, I'm all out of ideas bar turning the job down.

 

[king of pipes]

Actually no, they are not designed at maximum load - diversification is applied, don’t forget most heating elements actually cycle off/on to maintain a given temperature and pretty much anything that is not a heating element does not draw much current.
I’m over simplifying, but you get my drift.

Agreed Ben- gee its the diversity factor if you take the full current loading of all the breakers in the fused board it could be way higher than 100 amps but each of of these circuits will not all be at full load so diversity is applied .

 

[ShaunCorbs]

That's my point mate. Yes the boiler will modulate but what when it's -2°c outside, the boiler is at full output and then you switch on an electric cooker, plus your 1 or 2 32 amp ring mains and your lighting circuits etc etc. Admittedly this is an extreme situation scenario but like heating systems shouldn't all electrical systems be designed with max load in consideration?

same as any normal house as

45 amps for a electric shower
32 amp ring
20 amp kitchen
32 amp cooker

you will find a normal house will run at 20-25 amps at peak

 

[king of pipes]

Same as a slim Jim good units

Here's one installed but as said very expensive to run did the job on a off grid holiday home added a nest for smart control on the heating side left the hot water on a Honeywell programmer