Discuss New CH system underpowered/ wrong layout? in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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Alex100

Hi all

I had a complete new CH system installed a few months back. I did some research, got multiple quotes, went with a guy with a few good references and checked he was Gas safe registered. He did work very fast though. Perhaps too fast.

It runs 9 radiators from a Greenstar 38 Cdi combi. It's a two storey end terrace house, with about 120 square metres of floor space. The carcass is 22mm copper, with 15mm branches to compact Stelrad radiators. The boiler is upstairs at the back of the house. Another plumber already told me the boiler is too big for this house and so inefficient - I did ask for good water heating power, so maybe that's why he chose that one.

Questions:
1. From installation I thought the rads are small, but the plumber told me that's because they are compact. Anyway, sure enough, it takes about 45-60 minutes per degree of room temp rise in the two living rooms, from when the radiators are really hot on a night, when outside is below about 7 degrees, and this is with the boiler at maximum CH heat setting. I think this is unacceptably slow, as if the heating comes on when the room is 16 degrees, takes 15 minutes to heat the rads, then I'm looking at 5 hours to get to 21 degrees, which is mad (and bedtime). I have checked this with an independent thermometer and it agrees with the thermostat on the rate of heating up the room. Needless to say, we're quite chilly with our brand new system.

The plumber is arguing that he's never had a problem with his BTU calculator and wants us to pay for the bigger radiators we need. I don't care about BTU calcs, as every house is unique and they are only a guide. I want to be sure this is an under-powered set of rads, based on how long it takes to heat up, before putting my foot down on who pays. Underpowered?

2. THE BIGGER QUESTION
With the above and other teething issues, it got me thinking to take a look at the piping. Now I realise that rather than take the flow and return to the front of the house upstairs, for the front and middle bedrooms (which are the lion's share of the upstairs floor space), he has instead taken a long two-pipe branch from the flow and return in the study at the back of house, where the boiler is, all the way to the farthest front room (8-10 metre), and also teed off this for the middle room. So two pipes emerge from study and run 8-10 metres along corridor into the master bedroom, one pipe into one end of a rad and one into the other. Near their beginning, outside the study, a tee is taken from each pipe to go 2-3 metres into and out of the middle bedroom's radiator. The pipework starts as 22mm and reduces to 15mm about 1metre from each radiator.

Is this just lazy but no great issue (the rads do heat up). I do have an attic conversion above the front bedroom, and the plumber knows I want to put a rad in there one day, but that means teeing off what is already an 8 metre branch.

3. The system used to creak terribly and woke us up in morning and kept us awake until fully cooled down at night. It's clearly the pipes touching joists and boards. We did manage to get the plumber back, grumbling somewhat that we're fussy, to put felting in the worst places. He said he's never had to put felt around joist notches for anyone before, but I find that odd, having read how common it is. Am I fussy or is felting standard? (better still, he could have cut floorboards so his pipes aren't touching them where they emerge). It still creaks a lot downstairs.

4. I don't know much about heating systems (obvious huh?). However, does the above indicate I should get a different plumber out to check the system?
If so, what are my rights? I paid about £7k for the system (No VAT, as he's not VAT registered).

Many thanks for any input.
Alex
 
just somthing to throw into the mix. how many other gas appliances do you have in the house ? and did the other plumber who came round to have a look at your issues did he check the gas pipe size to the boiler ? have him check the boiler commisioning report.
but please for your own safety dont touch the boiler yourself.
 
just somthing to throw into the mix. how many other gas appliances do you have in the house ? and did the other plumber who came round to have a look at your issues did he check the gas pipe size to the boiler ? have him check the boiler commisioning report.
but please for your own safety dont touch the boiler yourself.

Thanks 1967skyblue



Two small gas fires downstairs. But the boiler is run off a separate, dedicated new main supply from the meter. Not had someone come and look on site yet. What should I be getting them to look for? Does system sound in need of checking over for general competence?
 
unfortunatly i can only say that your gas safe installer would understand what i was saying and might explain this to you in person, sorry.
 
Another plumber already told me the boiler is too big for this house and so inefficient
Is the boiler continually turning on and off while the house is heating up?

Did the installer measure the incoming cold water flow rate and dynamic pressure before recommending a 38kW boiler?
 
QUOTE: The plumber is arguing that he's never had a problem with his BTU calculator and wants us to pay for the bigger radiators we need. I don't care about BTU calcs, as every house is unique and they are only a guide. I want to be sure this is an under-powered set of rads, based on how long it takes to heat up, before putting my foot down on who pays. Underpowered?

BTU calculator? Hope he calculated the whole house heat loss method as well?
 
Best plan is for you to measure the rooms width/length and height, post this on here with each room named and state no of windows, outside walls also.

Then measure the rad size installed in the room - and state wether its a single,
double, or 3x with fins or not - type radiator.

We (on here ) can work out what rads we would have supplied.

centralheatking
 
Simple ask him to provide the design & heatloss calculations he used to size & then select the rads, as you believe they are undersized & this is the cause of the system (product) you have paid a lot of money for not working correctly, give him a few days to provide these & the chance to correct the problem otherwise you will have to go see trading standards & the court. You may need to get another engineer in to prepare a report on the installation to back up your claim. (see CIPHE)

As others have said it could also be the boiler heating output is to large for the load but most likely it is the rad's.
 
As others have said it could also be the boiler heating output is to large for the load but most likely it is the rad's.
The OP has a boiler which modulates between 9.4kW and 30kW. He has 9 rads, which at, say, 1.5kW each is 13.5kW total load. Even if they were 2kw, which is doubtful, that would still be only 18kW. So whichever way you look at it the boiler is oversized for the heating load.

There's a good chance that the flow water temperature rises to 75, or whatever is set, but the return temperature keeps on rising, meaning the boiler then cuts out, waits and then restarts. So the mean water temperature is well below the required value, which means the rads are not giving off the correct amount of heat.

The OP should use Whole House Boiler Size Calculator to find out the heating requirement and Stelrad Elite Catalogue, first table to estimate the output of his radiators.
 
The OP has a boiler which modulates between 9.4kW and 30kW. He has 9 rads, which at, say, 1.5kW each is 13.5kW total load. Even if they were 2kw, which is doubtful, that would still be only 18kW. So whichever way you look at it the boiler is oversized for the heating load.

There's a good chance that the flow water temperature rises to 75, or whatever is set, but the return temperature keeps on rising, meaning the boiler then cuts out, waits and then restarts. So the mean water temperature is well below the required value, which means the rads are not giving off the correct amount of heat.

The OP should use Whole House Boiler Size Calculator to find out the heating requirement and Stelrad Elite Catalogue, first table to estimate the output of his radiators.
I agree totally with you on the technical bits above & asking the installer for his design criteria (or lack off) would provide proof of poor design practice be it the rads or boiler.
Is it not possible with these to down rate or limit the heating output to say 15-18kW, as with the Vaillants ?

Not so sure the OP should have to do any calculations to confirm one way or the other, there are to many variables, all they should have to point out is that it has been cold & the new heating was not heating the house to a normal standard.
 
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