Plumbing/heating advice

[57xx]

I have a question for the plumber/heating engineers on here. My radiators downstairs stopped getting hot a couple of weeks back. I did the usual checking for trapped air, nothing came out of the air bleed on either rad. Suspecting a sludge blockage, I pulled off the two rads and gave them a good flushing, there was some black sludge but not a lot. The rads filled up nicely and got hot for a day but then went back to being cold. I then wondered about an airlock so "burped" the system (lock off the rad, remove pressure, attached a hose to bung port and then open each valve in turn to burp air out), got a little bit of air gurgling through but not much. This made no difference though.

 

The pump in the boiler (Combi 80) is running, I can hear it. The boiler seems to cycle a lot, turns on for about a minute then goes off for a while, just leaving the pump running. The flow pipe from the boiler is very hot, but if following the main pipe upstairs soon after the heating is turned on, within about 6 m it gets cold. The upstairs rads do eventually get hot, but it's taking a lot longer than normal. My chief suspect is now the pump impeller, so whilst the pump might be heard to be running, I don't think it is pumping anything and the heat is just doing what heat does (flowing hot to cold), although the upstairs rads do get very toasty eventually.

 

Time to get the pro's in for a look at the boiler, but before I give anyone a call I just wanted it to run my theory past the chaps on here.

 

TIA!

Edited December 6, 2020 by 57xx
Clarity

[didcot]

Im not a plumber, but You might want to try balancing the system. Turn it on and when the down stairs rads get hot try winding the non trv valve down a turn. That's the one without the thermostat. Keep going until you reach a point where the radiator is still hot but with the non trv valve at its lowest point. It should then force more water into those upstairs.

I've just had to do it with our rads. I changed the position of our bedroom radiator and got a larger one. It wouldn't get warm.

You might want to make a note of the valve positions before you start.

 

[didcot]

https://www.bestheating.com/info/a-best-heating-guide-how-to-balance-radiators/

 

Here is a better way than described by me.

[57xx]

Thanks for responding Didcot. The system was already balanced a long while back. I have however since tried an experiment - closed off all the TRVs upstairs and wound the lockvalve shut on the bypass rad on the landing and I'm now getting hot water flowing down stairs. Seems the pump must be doing something, but not very efficiently.

[didcot]

No problem. You don't want to be cold this times of the year. 

[jcm@gwr]

I would suggest that either the pump is not at full efficiency (partial blockage,

damaged impellor, etc.), or an air-lock in the boiler.

I doubt that it's a balancing issue, the fact that the boiler is cycling so often,

and the pipes are very hot, suggests that the hot water is not being moved.

Your experiment might have shifted the air-lock, try opening the bypass rad,

then gradually add the other rads.

[The Stationmaster]

Have you bled the upstairs rads as well?

[57xx]

16 minutes ago, The Stationmaster said:

Have you bled the upstairs rads as well?

 

Yes, checked every single one, even if they were showing no signs of trapped air.

[57xx]

18 minutes ago, jcm@gwr said:

I would suggest that either the pump is not at full efficiency (partial blockage,

damaged impellor, etc.), or an air-lock in the boiler.

I doubt that it's a balancing issue, the fact that the boiler is cycling so often,

and the pipes are very hot, suggests that the hot water is not being moved.

Your experiment might have shifted the air-lock, try opening the bypass rad,

then gradually add the other rads.

 

BIB - that was the conclusion I came to as well. I'll give that a try with the bypass rad and see what happens.

[Enterprisingwestern]

 

Just because you can hear the pump running doesn't mean it's operating at full efficiency, it's only the motor you can hear spinning, how hot is the pump motor case getting?

If you feel up to it, isolate the flow and return and drain the boiler, undo the cap head bolts which hold the motor to the impeller block and check that the waterways are clear and that the impeller spins freely.

From experience, it's either the pump not at full capacity or there is a blockage in the pipework upstream of the boiler somewhere.

How old is the boiler and system, is it a conversion of an old system?

 

Mike.

[57xx]

Hi Mike, pump casing is getting very hot. unfortunately I can't isolate the boiler, the two valves are seized open. The plastic noggins on them are on the verge of breaking and I daren't attack with the adjustables in case they start to leak. I can isolate the downstairs and lock off the upstairs rads before draining down the main pipework though.

Boiler is coming up for 20 years old, it was a complete brand new install, there was no CH in the house when I got it. Pump head was replaced ~10 years ago.

 

With consensus on it being a potential pump issue I thought I realised I hadn't actually had a go at bleeding it. I managed to get a hiss of air from it before the water came out. Also checked the automatic vent at the top of the boiler and think it may have been blocked as after cleaning up the screw cap, I was getting a steady ticking noise from it as it started to release air, so hoping it might just have been an air lock in the boiler itself stopping the pump working efficiently. So far I have got one rad upstairs and one downstairs working together so will persevere! Thanks for all the replies so far.

[Mallard60022]

Only thing I can add is that we had our New Boiler Fitted two years back (old one had been in the house from new in 1998) and the old Immersion Heater taken out from the Airing Cupboard where the Pump was situated. So the system had been in for just over 20 years. The Boiler was actually OK but spares were getting scarce and I wanted the Header Tanks taken out of the loft. 

Fortunately the Plumber, who was a local, we chose was really excellent and checked the pipe system in several places where he knew there may be issues with pipes getting choked from our hard water, despite the system having had special fluid installed. Good job he did as there were several places where the pipes were in an absolutely fatal heart attack blockage situation. When he showed me I was shocked that the existing system had even worked! If the pipes were 10mm then the space was around 1mm in several sections near the Immersion Tank.

Just saying this as your system is about the age ours was on changing (20 years?) and you may be in a 'hard' water area? The Pump could be desperately trying to pump through a blockage or blockages? I have no expertise at all so apologies if this is b0llocks. 

Phil

[jcm@gwr]

Firstly, it sounds like you are making progress, removing air from the pump

and boiler can only improve the situation. But don't forget to keep checking

the radiators for air as well.

Secondly, if Phil is right, the problem could return, but you won't know when.

If the heating system settles down you might be alright, if not, then you will

have to get someone to flush the system (unless you feel confident enough

to do it yourself)

If you go for a Power-flush, get your local heating engineer to do it (Gas-Safe)

not British Gas, I've heard of quotes in excess of £800 from them!

[Enterprisingwestern]

12 hours ago, 57xx said:

Boiler is coming up for 20 years old

 

You've done well, the theoretical age for white goods is 7 years, but then that is the manufacturers recommendation, bonne surprise!

Perhaps a new boiler beckons if it turns out not to be the system, peace of mind and all that?

 

Mike.

[Nearholmer]

May not be relevant here, but another thing to look for when faced with bits of the system not heating-up is stuck TRVs. 
 

I don’t mean the ‘head’ not working, although they do die eventually, but the sprung-return valve that it drives getting stuck after ages in one position.

 

I spent ages thinking we had an airlock or blockage that was affecting one leg of our system, but eventually traced the problem to two TRVs that had stuck in the ‘off’ position after months set to ‘off’. I took the heads off, and both valves freed-up after I pulled the drive-needle up and down a few times using snipe-nosed pliers.

[jcm@gwr]

4 minutes ago, Nearholmer said:

May not be relevant here, but another thing to look for when faced with bits of the system not heating-up is stuck TRVs. 
 

I don’t mean the ‘head’ not working, although they do die eventually, but the sprung-return valve that it drives getting stuck after ages in one position.

 

I spent ages thinking we had an airlock or blockage that was affecting one leg of our system, but eventually traced the problem to two TRVs that had stuck in the ‘off’ position after months set to ‘off’. I took the heads off, and both valves freed-up after I pulled the drive-needle up and down a few times using snipe-nosed pliers.

 

Sometimes they need a little 'encouragement', normally with a small hammer!

[Enterprisingwestern]

10 minutes ago, jcm@gwr said:

 

Sometimes they need a little 'encouragement', normally with a small hammer!

 

Usually a nice earner, 10 minutes, 2 blows, £40, thank you very much!

 

Mike.

[jcm@gwr]

9 minutes ago, Enterprisingwestern said:

 

Usually a nice earner, 10 minutes, 2 blows, £40, thank you very much!

 

Mike.

 

That all depends on how nice your customer is!

[Free At Last]

 

Quote

the theoretical age for white goods is 7 years

 

I installed my Baxi Bermuda back boiler in 1985. Only fault I've had with it was in the early '90s when a coil in the gas valve thermocouple circuit went o/c. The coil itself not being available as a spare I managed to repair it. Still giving sterling service.

[Mallard60022]

Whilst we are on this I heard on the steam radio a few days back that there are large grants for gas replacement systems. Ground or Air somethings. Most places in Towns' houses are unsuitable for Ground heat things it seems. Also SWMBO tells me all new builds from whenever will have to have an alternative to Gas Boilers and maybe even Cookers. I shall have to get the Butler to look into a replacement for the mighty Arga thing that seems to produce hot food somehow. Never seen or used it myself, or even been in the Servants' Quarters for that matter.

A. N. Arse

[Bernard Lamb]

16 hours ago, 57xx said:

Hi Mike, pump casing is getting very hot. unfortunately I can't isolate the boiler, the two valves are seized open. The plastic noggins on them are on the verge of breaking and I daren't attack with the adjustables in case they start to leak. I can isolate the downstairs and lock off the upstairs rads before draining down the main pipework though.

Boiler is coming up for 20 years old, it was a complete brand new install, there was no CH in the house when I got it. Pump head was replaced ~10 years ago.

 

With consensus on it being a potential pump issue I thought I realised I hadn't actually had a go at bleeding it. I managed to get a hiss of air from it before the water came out. Also checked the automatic vent at the top of the boiler and think it may have been blocked as after cleaning up the screw cap, I was getting a steady ticking noise from it as it started to release air, so hoping it might just have been an air lock in the boiler itself stopping the pump working efficiently. So far I have got one rad upstairs and one downstairs working together so will persevere! Thanks for all the replies so far.

If the system is that old then I would think that a power flush would be worthwhile even if you manage to get everything working. I had mine done back in March and  I am now feeling the benefit. There are some people who will give a very cheap quote but beware that in an old system it will find out if there are any weak spots. I had two very old radiators replaced just in case  before the work was done and with each room checked and adjusted afterwards it was a very worthwhile improvement. There are of course various standards for power flushing and costs will vary greatly.  Check exactly what they are offering to do before you sign up. 

Bernard

[Enterprisingwestern]

1 hour ago, Free At Last said:

 

 

I installed my Baxi Bermuda back boiler in 1985. Only fault I've had with it was in the early '90s when a coil in the gas valve thermocouple circuit went o/c. The coil itself not being available as a spare I managed to repair it. Still giving sterling service.

 

The Morris Minor of the boiler world, less moving/electrical parts = less to go wrong and simpler to repair.

 

Mike.

[57xx]

On 07/12/2020 at 08:37, Nearholmer said:

May not be relevant here, but another thing to look for when faced with bits of the system not heating-up is stuck TRVs.

 

One of the rads is lockvalves only, all the others have relatively new TRV valves. They all got replaced with new ones when I put my Honeywell Evohome in.

 

As a general progress report, I'm pretty sure there is air in the boiler, each time you turn it off/on you can hear it gurgling as the pump stops and starts. I'm not sure how well the air bleed is working, so for the sake of £8 I ordered a new one. I'll fit that when I drain it down at the weekend to check out the pump as Mike suggested earlier. Thanks goodness for "old tech" my gas fire in the front room has been keeping me nice and warm downstairs.

[57xx]

On 07/12/2020 at 12:29, Enterprisingwestern said:

 

The Morris Minor of the boiler world, less moving/electrical parts = less to go wrong and simpler to repair.

 

 

I had a Corvec Britony in the bathroom when I bought the house. NO electrics to go wrong and the only moving part was the knob to control the flow rate/heat.

[Enterprisingwestern]

9 hours ago, 57xx said:

 

I had a Corvec Britony in the bathroom when I bought the house. NO electrics to go wrong and the only moving part was the knob to control the flow rate/heat.

 

Pedantically, (sorry!), there were the moving parts in the diaphragm assembly, push rod etc, but, your theory holds good, less moving parts equals less chance of problems equals happy customer, a yearly service and away you go.

 

Mike.