EXPERIENCED Plumber Question

[mattypants]

Hi all,

I have just had an old backboiler system replaced with a Vaillant Ecotec plus 837. Lovely!

It feeds 9 radiators. The largest is a 700x2000 single ( 7900 btu). Above the reccomended for the room size.

This is in the room where the remote thermostatic control is. I have the thermo set at 21 degrees. However, it takes around 3-4 hours for the thermo to display a room temp of that target (21 degrees).

This radiator is always the last one to warm up when the heating comes on and never gets red-hot all over. It has been off the wall on 3 occasions in the past and rinsed and de-sludged thoroughly. I have a Magclean on my system and the rad was de-sludged when the system was changed. ( 2 weeks ago.) The rad is a 1 year old Purmo with no trv.

MY QUESTION: Does this mean that my boiler is continually in overdrive to get this room up to the target temperature and is this uneconomical?

ALSO; Is it normal for some rads to take longer than others to heat up and not be totally consistent?

The boilers maximum radiator temp is 75 degrees. Should I have this set to maximum?

Your help will be hugely appreciated. Thank you, Matt

 

[Bahco]

I would balance the rads and set your thermo to 18. As long as you are comfortable there is no need to have it set at 21 unless you are loaded with cash.

Read no 2 here

 

[mattypants]

Well done on the no smoking. I did it 2 years ago. Best thing I did!

Thanks for the reply, please tell me, how do I balance the system?

 

[tamz]

You may have a 1 pipe system

 

[Bahco]

Read no 2 here

 

[mattypants]

No. I have a 2 pipe system though it is all 15mm. apart from the immediate pipe near the boiler.

 

[tamz]

15mm feeding 9 rads will be well undersized and will bnot be able to deliver the required amount of heat through it. As a rough guide 18000 btu max for 15mm.

 

[muggles]

Read Topic 5 in the FAQs

 

[mattypants]

WHAT??????????????

So how does that leave me with my new boiler and rads? Is balancing then a waste of time?

Where should the 22mm pipe begin and end and should I consider having it changed. My total btu output of the rads is about 48000!

 

[sambotc]

Hi,

15mm pipe, as a general rule of thumb, should be used to supply 15,000 btu's worth of heating. So your 1 large radiator is half of that.

Without sounding patronizing, are you sure it is a 2 pipe system? It does sound like typical symptom's of a 1 pipe system, and I have seen many 1 pipe back boiler systems run in 15mm through-out.

In short, you need a part or full re-pipe to take advantage of your new boiler, which you should have been made aware of by your installer at the time.

HTH Sam

 

[sambotc]

Also, just to add, do you have thermostatic radiator valves? That would explain the inconsistant heating, as they shut down it allows more flow to other radiators etc?

Balancing will have a very limited benefit.

Sam

 

[mattypants]

No, it's a 2 pipe system. Each radiator has each end going to 2 seperate pipes running along side eachother under the floor.

TRVs on every rad apart from the big one in the room where the thermstatic programmer is. What temp would you set to in a living room with a patheticly "I'm cold" mrs sitting in?

Will my boiler be on full burn untill the thermostat reaches the target?

 

[tamz]

Your installer should have noticed this and even if it wasn't priced for , still mentioned it to you.

At the minimum it should be changed to the first tees but the further you can take it (easily) the better. Generally 22 throughout system branching to 15mm and 15mm last 2 rads on run.

15mm will take over 20000btu at a push but pump speed will need setting high.

 

[sambotc]

The boiler will be circulating the closer rad's until the return temperature reaches what it is set to on the boiler. The rad's further away will not have reach a suitable temp by this time so you then wait until the return temp drop's enough for the boiler to kick in again and the process repeats itself.

Re-pipe is the only real solution, balancing may help, but you've spent the money on a nice new boiler, so put it onto a decent system to reap the rewards

Would also be good to check the boiler has been fitted on a large enough gas supply, presuming the hot water is very good?

What size gas pipe do you have and how far from the meter does it travel? Many elbow's or bends etc?

Sam

 

[mattypants]

Thank you all so much for your input so far.

The hot water is ok I suppose, but I wouldn't say it blasts out and if you turn on the cold, the hot flow reduces..

The gas supply was fitted new at 22mm. It travels under the floor for about 18 feet - 3 elbows then upstairs to the boiler at about 12 feet.

How big a job is it to change the pipework to 22mm. Am I to take it that ALL the pipe should be 22mm other than those little bits that attatch to the rad valves?