Drawbacks of sealed system?

[autolycus]

Hi,

Our heating system has a number of little problems, including:

- some rads get a bit warm when hot water (only) is selected on the controls

- a couple of rads do not get as warm as the others when CH is on

- air can be heard in the system (bubbling noise if you listen to flow/return pipes near boiler)

- lots of sludge in the system

- one rad that is on a separate loop of its own never comes on

- when we have CH on and HW off, we get pumping over (i.e. very hot water going into F&E tank

- there is a lot of pipework near the boiler which has obviously leaked a bit in the past (no current leaks though) as the joints are all covered in limescale.

I have had two plumbers quote to deal with all this.

Both said that the vent pipe and feed pipe are connected in the wrong place (they tee off in the airing cupboard rather than next to the boiler).

One plumber said that all my problems will be solved by replacing the motorised valves and converting to a sealed system for about £700.

The other plumber said that whatever I do I need a powerflush first of all. And that then I should stick with an open vented system and simply have some new pipework run from the boiler to the airing cupbaord so as the vent is coming off the system in the correct place (next to boiler).

He also said the pump needs upgrading as it is not big enough for our system. Current pump is a Grundfos UPS 15-50.

His price for all that is £1500.

So my question is: what are the drawbacks of the sealed system?

The £1500 guy said he wouldn't recommend a sealed system due to the potential for it showing up any defects in the existing pipework.

Is that the only drawback?

Is the powerflush worth having?

Would my best bet be to have a powerflush and then a sealed system - which would presumably cost somewhere between the £700 I've been quoted for the sealed system and the £1500 I have been quoted by the other guy?

If it makes any difference the system dates from the early 60s. However, some of the pipework will be newer than that because the boiler was moved from the kitchen to the garage at some point (I'd guess about 15-20 years ago).

The system has 10 double panel rads, one single panel, and three towel rail rads.

Thanks in advance.

Dave

 

[Rob]

Yes the leak thing is the only draw back.

Your system is probably not as bad as you make out as all of the faults are related and wouldnt take much to solve.

If its relativly easy to reconfugure the CF and OV to prevent the pumping over id go for that. along with a new pump and balancing is maybe all it needs.

Powerflush if system is still problematic. With certain rads not heating up

Cant see where the £1500 is going TBH how long did he say job would take.

 

[freeflow]

if the boiler is 15 to 20 years old it may not be suitable for a sealed system.

 

[autolycus]

Yes the leak thing is the only draw back.

Your system is probably not as bad as you make out as all of the faults are related and wouldnt take much to solve.

If its relativly easy to reconfugure the CF and OV to prevent the pumping over id go for that. along with a new pump and balancing is maybe all it needs.

That's the tricky bit. Due to the fact the boiler is in the garage and the existing CF and OV connections are in the airing cupboard, it is going to require a long and fiddly run of copper to get from one to the other.

Powerflush if system is still problematic. With certain rads not heating up

Cant see where the £1500 is going TBH how long did he say job would take.

Not spoken to him yet - only listened to a voicemail. Got the impression it was going to be at least 2 days, maybe 3. From personal experience, i know it takes a good 2-3 hours just to drain the system down at the start of the job.

 

[autolycus]

if the boiler is 15 to 20 years old it may not be suitable for a sealed system.

We're ok on that score. Boiler was replaced 8 years ago and both plumbers confirmed it is suitable for use in a sealed system.

 

[sambotc]

Sounds like at one point the hot water circ's were gravity fed and when changed over to fully pumped the vent and cold feed where never changed.

Could you move the pump into the house and get the CF&V in behind it rather than move them behind it's existing position?

Pressurising an old system can be problematic. If the engineer advised against pressurising i would have to ask why he recommends a powerflush also?

You could run a course of de-sludge yourself if you a familiar with draining down etc?

Sam

 

[Agile]

Wow, what prices!

But then I dont go round free to diagnose faults !

I cannot immagine that I would charge more than £450 whatever I did.

Tony

 

[autolycus]

Sounds like at one point the hot water circ's were gravity fed and when changed over to fully pumped the vent and cold feed where never changed.

Yes - that is what plumber #2 (the £1500 one) reckoned too.

Could you move the pump into the house and get the CF&V in behind it rather than move them behind it's existing position?

The option of moving the pump and the controls into the airing cupboard was talked about by plumber #2 while he was here but I think the reason that idea was dismissed was because all the pipework upstairs is 15mm rather than 22mm. Would that make sense?

Pressurising an old system can be problematic. If the engineer advised against pressurising i would have to ask why he recommends a powerflush also?

I shall ask him, but the impression that I got was that they now routinely powerflush before any major work - boiler changes etc.

You could run a course of de-sludge yourself if you a familiar with draining down etc?

Did that about 6 months ago. But judging by how much muck was in the 3 or 4 rads that i removed and manually flushed prior to doing the X400 desludge treatment, I suspect there is still a lot more that could be got out with a powerflush.


Sam

 

[simond]

I would be inclined to go for the sealed system option, but bear in mind I haven't seen your pipework, which is the $6M question.

With the sealed system the pumping over would be eliminated, and if the pipework is poorly dimensioned in parts, will help allocate more effort to reaching the furthest rads rather than pushing water over the open vent.

The warm up problem, assuming it hasn't always been there, will be a faulty MV so if the £1500 quote doesn't cover their replacement, you will still have it afterwards.

Regarding a Powerflush, I would want to see this before suggesting it might be necessary. Has a TDS reading been taken, or a chemical analysis of the water? I might be patronising you, so apologies if this is the case, but dirty black water is not to be confused with sludge, which is an oily mass the consistency of cowpats.

 

[autolycus]

If I went for the sealed system option, would it still be an good idea to upgrade the pump?

 

[Agile]

If I went for the sealed system option, would it still be an good idea to upgrade the pump?

If the system was installed and worked fine with that size then its probably OK.

The problem is that if the system is sludged up or just the inside of the pipes coared with oxide then that greatly increases the flow resistance. If that were cleaned ( as I would aim to do ) then its flow would be back to the original.

Merely increasing the pump pressure would improve the flow rate but would not solve the underlying problem.

Tony

 

[autolycus]

After having got a couple more quotes, I have decided to go for the sealed system.

Question now is whether I bother having a powerflush done at the same time (which will double the cost of the job from about £400 to about £800).

My current thinking is that I could do the sealed system installation to begin and see if it cures my problems. If it does, then great. If it does not, THEN the next step would be to try a powerflush.

How does that sound?

Would it be a good idea to install a Magnaclean when I do the conversion to the sealed system? That way I can get an idea of how much sludge is present and that could help me decide whether to do the powerflush or not.

David.

 

[Agile]

There are two types of dirt in a system, loose and being pumped round and fixed which coats the surfaces.

The latter is more problematic in a microbore.

I would want to remove both chemically.

Tony