all. I don't know if this is normal for a grant, but its not normal as far as I'd expect. An LLH if used should be AFTER the diverter for the CH/DHW. So DHW flow should not be through the LLH.

If only one pipe into a component that has multiple pipes in and out is hot, that can be heat moving by convection currents. which is slow, but it will move heat. A pipe somewhere upstream (follow the heat) is hot, but the water isn't flowing.  looking at your system pics, there is a vertical pipe with a red pump in it connected to the top left, which being vertical is capable of easily transmitting convection, follow the heat down that pipe and see where its coming from. It could be pulling heat from the hot water tank. 

So no change in heating over night.

seems the 3am-4am hot water run worked as that’s sitting at 45c 3.5 hours later. So least we have that.

zones aren’t up to temperature. Downstairs 18c, upstairs 18.5c, underfloor 20c (but that’s floor temp, a digital thermostat says it’s around 18-18.5c).

too right pipe to LLH hot, too left slightly warmer than yesterday but not much. Bottom left and bottom right hard to tell if in same range as that.

i remembered we have a temperature gun for children’s temps. Obviously woefully inaccurate for surface temps but it’s pretty consistent when repeating so might indicate a differential over actuals

Too right - 28c (feels a lot hotter than that)

top left - 25.3c

bottom left - 23.4c

bottom right - 25c

the bottom right is of interest to me. That seems to indicate flow of heat is maybe mixing in the LLH and going back outside? Or it’s per diagram shared earlier that we’re getting out flow mixing in with top left which goes to the heating system. This is only seemingly happening when on the heating zones. Soon as it flips to hot water the top left gets hot.

basically my setup the flow is reverse of that diagram - right to left (hence me talking about top right being hottest as that’s from the ASHP).

if my primary flow is deficient though, and it’s getting outweighed by the secondary. I think only flow there is coming from the ASHP itself

I’m sorry I can’t provide anything helpful, but I’m mighty glad I didn’t need a header or buffer in my install. It seems like a nightmare.

Yeah I don’t see it being useful at this point lol. Especially as the ASHP is running at 50c and I’m not getting that through. Cost to heat ratio is horrific atm. Be glad once this is all sorted but will keep posting what’s done incase happens to someone else and there’s potential solutions amongst our prolonged chilly house.

I’m thinking back through the last couple months. If a valve closure could cause this issue of flow being insufficient or its primary flow v secondary.

Plumbers had issues with some rad supply deliveries. So at some points rads were isolated from the system so that upon install they didn’t have to drain the entire system. Could that be a precursor to this?

@crimson, sadly this a design issue, and we have two rads at the far end of the house, right at the end of the circuit that struggle to come to temperature when it drops below 3C outside. We’ve had the installers back countless times and we now have four distribution pumps installed and there’s still insufficient feed to those rooms. This is something I’ve raised with other installers and the thought process is that the buffer tank is the root of this issue.

Hi @crimson, probably time to bite the bullet and get the system checked over by Grant. The installation manual from Grant has suggested circuits for typical heating and hot water system ASHP installs. Your system should be based closely on one of them, with additions such as your water softener. It is possible to install without buffer tanks or low loss headers, but that requires very accurate hydraulic calculations & sizing, and an experienced engineer to get it right. With your primary flow being so low, and way out of spec, something is fundamentally wrong. Until that is rectified there’s no point trying to balance anything else up such as the low loss header. 

GRANT.IE "https://grant.ie/media/1590/grant-aerona-installer-irl-doc0001-rev-10-july-2019.pdf"

Posted by: @hughf

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I’m sorry I can’t provide anything helpful, but I’m mighty glad I didn’t need a header or buffer in my install. It seems like a nightmare.

You’ve smashed the nail on the head. Most of the issues we see with inefficient heat pump installations involve systems with buffer tanks, and it’s one if the main questions I urge homeowners to ask installers. By default, installers go down down the buffer route. 

As I explain in Bodge Buster, there is a common but incorrect belief that buffer tanks substantially aid heat pumps in balancing their workload. However, the actual impact of a buffer tank on load management is quite small. For example, a buffer tank with a 100-litre capacity (which is what we have) can only store around 1.17kW of energy when the temperature is 10C above the necessary level. In a system requiring 10kW, this amounts to a mere 7 minutes of extra operating time, which isn't considerable. Additionally, reaching this additional 10C can lead to a rise in energy costs of as much as 25%.

It’s all rather frustrating. Far as I know Grant specifiy the use of a LLH.

Thankfully I’m in a ‘fortunate’ unfortunate position. The contract for the project is the plumbing firm design the heat system which they’ve consulted Grant on - who reccomended the ASHP size etc after checking calcs. And we haven’t handed over/completed. So fortunately it’s on the plumbing firm to resolve it all (I don’t have to pay the Grant fee for a visit) as architect who’s functioning as the project design manager won’t certify plumber’s fee payment until the system runs as expected.

Plumber said he’ll be contacting Grant so let’s see how next week goes.

in a way in quite thankful we moved in and haven’t completed during winter period as this could have been a horrible surprise.

In terms of rads. None are warm now, no zone is getting much heat which would reflect simply barely any heat going through the LLH. 

Posted by: @crimson

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It’s all rather frustrating. Far as I know Grant specifiy the use of a LLH.

All manufacturers do, and it's becoming an increasingly divisive topic among installers.

@heacol has not been on the forums for a while but he's leading the charge on the issue trying to show the short fallings of systems with LLHs, and he now has a lot of data and evidence to show how much more efficient systems can be without a buffer. I'll see if I can convince him to pop onto the forums again so that we can share some of his insights.

@crimson So far as I understand it, before the plumber started fixing things (i.e. when you had the blown DHW controller) most of the CH zones were working ... you now seem to be in a worse position.

The things that strike me are:

1. There is probably a blockage on the primary side (the flow regulator broken?) or a closed valve to account for the low flow rate

2. The DHW might be working, as the HP generates a much higher LWT than when on CH, and there's a much shorter pipework path to the cylinder

3. The fact that the secondary pump comes before the DHW cylinder is unusual but seems in keeping with Grant's installation for UFH (see Installation Pack B schematic)

4. Given there was a blowing DHW controller, could there be other issues with the EP001 wiring? Maybe the DHW opening (which should enable the zone controllers to send open requests to the zone valves) isn't switching the load correctly?

5. A lack of heat on the secondary side (your left hand side) implies the flow on the primary side is much higher; yet this completely contradicts the observed value on the flow regulator. But varying the flow on the secondary side helps out slightly supports that. It's confusing.

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I'm not sure any observation is useful, apart from (1).

To verify (4) you should see the lights on the zone valves (at least the 2 with lights on them) be lit (orange) when CH is on; and the one on the DHW circuit not lit. And the opposite during DHW cycle. But I think your earlier pics confirm that anyway, unless things have changed.

As you say, thankfully down to the plumber to sort. Or Grant. You shouldn't be having to do the fault finding or fixing.

@mikefl 

thanks Mike. Can confirm 4 works as expected. Only 2 of the 3 zones have lights on the valves but when hot water mode comes on can see the two zone lights off and hot water water zone light kicks in.

does seem like something has gone wrong since the last towel rad went in and cap left off the LLH. I was always moaning rads not warm all the time before then but now never feel them warm. Today outside is quite a bit warmer than it has been and nothings improved so it’s not like it’s struggling in colder weather. Just nothing of note really passing into the system. ATM am tempted to dial back the weather curve as the ASHP is running at a high temp and we’re not gaining form it (just thinking cost per day right now till it’s resolved) but will leave so it’s consistent.