Noisy return

[Little Clanger]

Recently, I've had to change our heating system. Previously, we had an indirect hot water cylinder, on the ground floor, near the Stanley solid fuel range that heated the water in the cylinder.

 

I've installed a new Economy 7 hot water cylinder upstairs for the DHW, and replaced the old, downstairs one with a 250l Economy 7 cylinder, to act as a thermal store. for the central heating circuit. As far as possible, I've left the existing pipework in place. This included the pump on the return, as fitted by the plumber about 40 years ago (he said something about putting it on the return to avoid 'over topping', which I assumed meant the risk of pumping the flow up into the F&E tank in the loft, via the swan neck expansion pipe).

 

It all seems to work OK with the exception of noise building up on the return. When the pump first turns on, its so quiet that I have to check it's running. After about 15 minutes, the return pipe near the pump starts to get noisy, sounding like - not surprisingly - gushing water. After a while the noise gets annoyingly loud. I didn't experience this with the previous set up. I've attached a video to give some idea.

 

So basically, all that is different with the new system is that now the water in the radiator circuit is being drawn from the thermal store, rather than from the Stanley - cylinder coil circuit. And that I've replaced the ancient Grundfoss pump with a new Trident one (I tried changing the pump back again, but it made no difference).

 

I had a mad theory that drawing the water form the thermal store is too demanding, and that the system is actually drawing air in from the F&E swan neck, as that is easier. Once I shake off this fluey cold, I'll get up in the loft and check. But in the meantime, has anybody any idea what is happening? Incidentally, if my mad theory is true, can I extend the swan neck down below the water level of the the F&E tank, with a non-return valve?

 

Thanks

 

 

 

[elite]

Not a plumber

 

Is there air in the system?

 

Does the pump have somewhere to pump from? e.g. are radiator valves / TRVs open?

[Little Clanger]

12 minutes ago, elite said:

Not a plumber

 

Is there air in the system?

 

Does the pump have somewhere to pump from? e.g. are radiator valves / TRVs open?

Thanks for your reply. I am assuming there is air somewhere.

 

I've bled the radiators and the pump a number of times.

 

One radiator is always open, the others have TRVs

 

I've just bled the pump again and was surprised that when I took the vent plug out (with the pump turned off!), water gushed out under pressure. I know that's not surprising, but I'm pretty sure that when I bled the old Grundfoss, water didn't gush out.

[ProDave]

Can we clarify:  Is it noisy all the time even if the stove is not lit and it is circulating cold water?  Or is it only noisy when the fire it lit?

[Little Clanger]

55 minutes ago, ProDave said:

Can we clarify:  Is it noisy all the time even if the stove is not lit and it is circulating cold water?  Or is it only noisy when the fire it lit?

Thanks for your reply.

 

The stove has gone, so the whole system is electric now, with the only heat source being the immersion heaters in the thermal store.

 

The water from the thermal store isn't very hot - about 60 degrees

[Little Clanger]

The weird thing is that each time the pump starts up, it's really quiet, only getting noisy after it's been running for a while.

 

Does that suggest that when it shuts down, the system purges itself of air, but then slowly draws air in when it's running?

[Nickfromwales]

As this is now an expensive way to heat the home, I'd defo consider converting to sealed and pressurised, and do away with the F&E arrangement for good. Then there's also no way for air to get in.

https://www.bes.co.uk/intafil-plus-24ltr-heating-vessel-and-sealed-system-kit-20246/ for example

[Little Clanger]

Thanks, Nick. That looks like a good idea.

Is DIY installation allowed?

[Little Clanger]

PS. We have a woodburner that provides most of our space heating (the heat seems to spread through our little house surprisingly well). The radiators are for top-up/background 

[Nickfromwales]

Just now, Little Clanger said:

Thanks, Nick. That looks like a good idea.

Is DIY installation allowed?

This may require a second G3 sign off, as you're then sealing up a pressurised cylinder which could go "bang" in the perfect storm. The thermal store type needs to be considered and whether or not it has a T&PRV relief valve or not, but a decent installer can talk you through this for feasibility before committing. It's just the thought of your heating costs via indirect immersions and then the losses of the F&E setup that make me think there's a better way perhaps.

It may require a new TS in the worst case, but if this is your heating solution for life, I'd even consider an electric inline boiler and do away with the TS altogether as that is a very convoluted and inefficient way of changing electricity into heat tbh.

[Nickfromwales]

4 minutes ago, Little Clanger said:

PS. We have a woodburner that provides most of our space heating (the heat seems to spread through our little house surprisingly well). The radiators are for top-up/background 

Just a 'not great' solution to be honest, the immersions into a TS, so these are my thoughts.

[ProDave]

What the OP has created is a DIY electric storage boiler.  Typically the commercial ones are quite large and have 3 or 4 immersion heaters. they work best on an Economy 10 tariff (not sure if that is available to new customers now) which meant the time they needed to store water between the 3 off peak times was not too great.

 

An Air Source heat pump is a far better idea though.

[Little Clanger]

Thank you both. I did consider an online boiler, but the thermal store gives us some of our heating on the overnight Economy 7 rate.

 

An air source heat pump would be ideal (although our neighbours are worried about the noise), but I was just attempting a shoestring system that used up bits and pieces that I already had hanging around. In

In fact I remember that I've got some Taco air separators in my shed. Perhaps one of those would help.

 

Thanks again 

 

[Nickfromwales]

3 minutes ago, ProDave said:

What the OP has created is a DIY electric storage boiler.

Just the worst possible one, in honesty.

2 minutes ago, Little Clanger said:

but the thermal store gives us some of our heating on the overnight Economy 7 rate.

Not unless it's massive. The losses will outweigh the gains I'm afraid, as, for one, the storage type and useful energy capture to then run these high temp emitters will be of negligible practical benefit in actuality, plus the accumulative losses and poor responsiveness will further add to the negative maths. The last TS I installed for space heating to rads was 2600L, and took up a 1/3 of a garage (for comparison). That stored at 85oC btw.

Driving this into a slab with UFH would work, but for rads I'm afraid it's a battle on a good day to suggest this is a 'good idea', sorry! 

[Nickfromwales]

Heat pump yes, but the demand will have to be known, and the temps won't be much or any better unless it's a high-temp split which will give a decent CoP at 60+oC. That leaves you heavily reliant on burning wood to keep the whole house 'warm' if the rest just adds background heat, but in bedrooms and other spaces away from the WBS I expect the rads are actually doing much more than you may first realise. Turn them off over winter and test this theory afaic, and then maybe readdress this in the new year when the UK warms back up a little.

[Little Clanger]

OK, Nick, thanks for your input. We have a small, rural cottage with pretty good insulation and, being a retired joiner, have pretty efficient doors and windows. And we are used to low temperatures. Even when we had the Stanley range, we only ever turned on the upstairs radiators on the coldest of winter days, so the demands on the CH is extremely low. We have an Everhot in the kitchen and there is an open staircase from the kitchen to the first floor. It's quite surprising how much it helps the general temps.

So a far from standard situation. I'll see how we get on this winter, as you suggested, and review things in the Spring. 

Thanks again for your input

[Little Clanger]

For now, emphasis is on sorting out the noisy return!